WEBVTT 1 00:00:04.290 --> 00:00:04.980 Mark Kushner: Okay, so. 2 00:00:06.299 --> 00:00:11.849 Mark Kushner: Okay, so like to introduce Joe agent from uc Berkeley. 3 00:00:15.240 --> 00:00:26.070 Mark Kushner: Exactly make a couple personal notes so you're running a little late okay so Joe received his PhD and also bachelor's degree from MIT. 4 00:00:27.120 --> 00:00:38.670 Mark Kushner: Is not this is work was pretty much on lasers, they took a postdoc at university of San Diego and they were going to last. 5 00:00:42.090 --> 00:00:44.910 Mark Kushner: US for trapping invite and. 6 00:00:46.320 --> 00:00:59.730 Mark Kushner: After that postdoc he went to Berkeley became fax number there and then got involved with the project and that's what he's going to give us a presentation on about the combine the. 7 00:01:00.870 --> 00:01:01.530 Mark Kushner: Hydrogen. 8 00:01:02.670 --> 00:01:05.940 Mark Kushner: Trapped and personal so i've known for. 9 00:01:07.650 --> 00:01:08.340 Mark Kushner: Something like that. 10 00:01:09.840 --> 00:01:14.220 Mark Kushner: told me about his anti hydrogen we're real excited because i'm interested in. 11 00:01:15.330 --> 00:01:18.450 Mark Kushner: Knowing about is the ultimate social. 12 00:01:19.920 --> 00:01:33.390 Mark Kushner: Selling through cold water my excitement about his work on making is inside tells you how much effort, it will take to make the entire to travel with your star. 13 00:01:36.750 --> 00:01:39.180 Mark Kushner: Please ask this question at the top, you. 14 00:01:40.350 --> 00:02:01.110 Mark Kushner: Know 111 other quick things certain work that they're doing that the Alpha collaboration is groundbreaking and and Nobel Prize may come out of it, and so we have something for you, Joe that's rare than the Nobel Prize, and that is. 15 00:02:02.550 --> 00:02:06.390 Mark Kushner: This about so you can put this, along with your Nobel Prize. 16 00:02:10.110 --> 00:02:11.640 Mark Kushner: I think it's going to be a while. 17 00:02:12.690 --> 00:02:15.630 Mark Kushner: Oh yeah you don't you can take off okay fine. 18 00:02:19.380 --> 00:02:24.750 Mark Kushner: I see, for some reason my wife is on this zoom in a board meeting that's going to be strange. 19 00:02:25.890 --> 00:02:28.170 Mark Kushner: I don't really know why but nevermind that. 20 00:02:29.310 --> 00:02:37.860 Mark Kushner: Thank you for inviting me here I don't quite know how this has happened, but this is actually the first time i've ever been to Ann arbor in my life. 21 00:02:38.460 --> 00:02:46.170 Mark Kushner: Obviously, a mistake also it was some some steak to come in wintertime I should have come in the summer, but nevermind all that. 22 00:02:46.560 --> 00:02:58.500 Mark Kushner: i'm going to be talking about anti hydrogen atoms and what we can do with them and how we make them with classes today and people have been interested in anti hydrogen, for a very long time. 23 00:03:01.680 --> 00:03:12.900 Mark Kushner: At least some since about the 1980s, or so and the interest in at the hydrogen stems essentially from three different so two different objectives. 24 00:03:14.040 --> 00:03:25.650 Mark Kushner: But they all are in fundamental physics, one is to study charge parody times are cpt and variance which comes down to the question is the spectrum event I hydrogen, the same as the spectrum of hydrogen. 25 00:03:26.310 --> 00:03:36.810 Mark Kushner: And the second question we'd like to address is the week equivalence principal or web does anti-matter gravitate in exactly the same fashion as normal matter will gravitate. 26 00:03:37.830 --> 00:03:38.250 Mark Kushner: and 27 00:03:39.540 --> 00:03:54.900 Mark Kushner: Both cpt and the week equivalence principle are very, very likely to hold they're very well established, but there are some problems with anti-matter and there's there's excuse me that went wrong. 28 00:03:57.990 --> 00:03:58.320 Mark Kushner: well. 29 00:04:01.020 --> 00:04:10.530 Mark Kushner: Sorry okay physicists have been wrong about these matters before about parody conservation thanks for instance of Parity Conference in. 30 00:04:12.090 --> 00:04:23.880 Mark Kushner: Conservation Wolfgang pauli once wrote, I do not believe that the Lord is a week left hander and will be willing to bet a very high some that parity well that experiments will give symmetric results. 31 00:04:24.900 --> 00:04:37.230 Mark Kushner: I don't know if paulie actually ever made that bet, but I do know that Richard fineman made a $50 bet that parents would be concerned $50 being quite a son back in the days when he actually made that bet. 32 00:04:38.070 --> 00:04:52.050 Mark Kushner: Of course parody conservation was very quickly fixed up by adding charge to it, so, then we had CP conservation, this was work done by live Lando who wrote CP is violated, I will hang myself. 33 00:04:53.820 --> 00:04:54.210 Mark Kushner: So. 34 00:04:55.350 --> 00:04:58.590 Mark Kushner: Look, none of us are in the League of these guys right. 35 00:04:59.850 --> 00:05:11.640 Mark Kushner: But they were they were brilliant physicists they were wrong, we now know cpt is much, much better tested than P or CP wherever tested at this point would they made those statements. 36 00:05:12.420 --> 00:05:20.040 Mark Kushner: So almost surely CP will not cpt will not be violated, but it is a warning that one to keep in mind and. 37 00:05:21.030 --> 00:05:27.480 Mark Kushner: There are hints that something's wrong here and the wind tense come from the back what's called the barrier genesis problem. 38 00:05:27.810 --> 00:05:40.230 Mark Kushner: Namely, why is there, so little matter antimatter in the universe, the universe, is entirely matter as far as we can tell, and it shouldn't be because the big bang should have made equal amounts of matter and antimatter In fact there should be nothing. 39 00:05:40.710 --> 00:05:59.610 Mark Kushner: Left, because it should involve mutually annihilated and yet that's not true, and nobody knows the reason for this, so both cpt and wet violation could solve the barrier genesis problem and there are some other problems that you could possibly solve people. 40 00:06:01.530 --> 00:06:08.760 Mark Kushner: And we're really I hesitate here because they're crackpots in this field and we're getting shortly into crackpot. 41 00:06:09.420 --> 00:06:24.930 Mark Kushner: territory here, but there are people that believe the problem with dark matter the embarrassment that dark matter is because, since I was most of your age people have been looking for it rather run successfully that would go away if you were able to find some strange things about. 42 00:06:26.040 --> 00:06:28.650 Mark Kushner: about anti hydrogen and anti matter in general. 43 00:06:29.400 --> 00:06:39.120 Mark Kushner: So what about the history event to hydrogen research well, of course, it started with a series of papers by direct and 1928 who predicted the existence of the positron. 44 00:06:39.510 --> 00:06:54.660 Mark Kushner: And then, just a few years later, Carl Anderson at caltech was able to actually see positive trends and balloon experiments the anti-proton was discovered at Berkeley i'm pleased to say, by a group late led by Chamberlain said grey. 45 00:06:55.380 --> 00:07:04.470 Mark Kushner: And there as far as empty hydrogen was the field rested for a long time, but in 1996 first at CERN and then it fermilab. 46 00:07:04.980 --> 00:07:08.220 Mark Kushner: People were able to make anta hydrogen and at. 47 00:07:08.640 --> 00:07:26.430 Mark Kushner: accelerator scale energies, this was not very useful because he couldn't really study these atoms if they're up the TV type energies so progress relied on some way to reduce the energy of the anti protons and that came about in 2000 where the. 48 00:07:27.420 --> 00:07:42.960 Mark Kushner: The CERN deployed the anti-proton decelerate or facility, the Ad which took the anti-proton stand from gv levels down to about 5.3 MTV and, since then, progress has been relatively rapid in. 49 00:07:44.160 --> 00:07:50.550 Mark Kushner: First, the Athena collaboration and then shortly thereafter the a trap collaboration made low skill. 50 00:07:51.030 --> 00:08:02.370 Mark Kushner: And a hydrogen atom that means low low energy scale means ED type and a hydrogen atoms and since then hundreds I should really update this maybe even billions of anti Adams have been made today. 51 00:08:03.060 --> 00:08:08.100 Mark Kushner: But once you know how to do it, it turns out to be relatively easy to make anti hydrogen atoms. 52 00:08:09.150 --> 00:08:14.580 Mark Kushner: takes a lot to know how to do it, but nonetheless, but the problem with these anti hydrogen atom says that they were untracked. 53 00:08:14.880 --> 00:08:24.150 Mark Kushner: They were made in an apparatus, they would be created with an ev er so of energy and then just go screaming off into the walls, where they would annihilate. 54 00:08:24.510 --> 00:08:33.630 Mark Kushner: and be destroyed, not everybody agrees with the statement, but at least many researchers in my group believes that you really can't study the antioxidants until they're trapped. 55 00:08:35.010 --> 00:08:49.710 Mark Kushner: And so we we tried to we began an experiment, the Alpha caught experiment, to try and track the anti hydrogen and in 2010 we were able to trap 38 and a hydrogen atoms over the entire here. 56 00:08:50.160 --> 00:08:56.520 Mark Kushner: Here are some of the original experimental data I don't have time really to go into it, but. 57 00:08:57.060 --> 00:09:11.340 Mark Kushner: we've been making good progress since then the next year we trapped 500 that's a specter of 10 and we held some of those atoms for as long as 1000 seconds there's no lifetime actually we just got bored after 1000 seconds. 58 00:09:12.090 --> 00:09:26.940 Mark Kushner: And in 2017 we trapped over 70,000 anti atoms now just to give you a summary of some of the tech the improvements that we've made this is a graph this year versus. 59 00:09:27.390 --> 00:09:37.560 Mark Kushner: The number of trapped per hour, if you will, and all of this trapping we lies, and these improvements and trapping relies on improvements in class with techniques. 60 00:09:39.150 --> 00:09:44.190 Mark Kushner: The spokesman of our collaboration keeps on saying that this is not a plasma physics experiment in fact. 61 00:09:44.430 --> 00:09:51.450 Mark Kushner: For most of these years had very definitely was the plasma physics experiments and i'll tell you in a few minutes, have the platforms come into these things. 62 00:09:52.020 --> 00:10:01.980 Mark Kushner: But we started out in 2008 in 2008 we actually over the entire year in retrospect, were able to trap six. 63 00:10:02.790 --> 00:10:08.100 Mark Kushner: Anti atoms That was one in every 35 attempts to trap anti-church anatomy that is. 64 00:10:08.610 --> 00:10:17.700 Mark Kushner: A very dismayingly low number it's almost impossible to work with because 35 attempts would take several days, so we were trapping one. 65 00:10:18.150 --> 00:10:29.910 Mark Kushner: In retrospect every several days and we're always fiddling and sometimes we would probably fiddle the experiment away from workable correct parameters and then we would fill it back to workable parameters. 66 00:10:30.540 --> 00:10:43.290 Mark Kushner: And the problem is you can't optimize that because the statistical fluctuations are so large just in one in 35 that you never know whether or not you did something to experiment was drifting faster than our data rate. 67 00:10:43.830 --> 00:10:54.390 Mark Kushner: Which is why we didn't publish anything that year, but as we improved our plasma techniques, and these are all different classes of techniques, we were able to increase the number and. 68 00:10:54.900 --> 00:11:03.810 Mark Kushner: I am not going to go into this in any great detail, I just want to get to the top here str AVC was a plasma. 69 00:11:04.680 --> 00:11:09.270 Mark Kushner: stabilization technique that was developed by my graduate students Celeste truth. 70 00:11:09.690 --> 00:11:17.070 Mark Kushner: And what it meant is our classes became much more stable, which immediately led to some advances in plasma physics as well. 71 00:11:17.430 --> 00:11:29.010 Mark Kushner: That led to us getting 20 anti atoms per trial, but more importantly, we also well just as importantly, we also developed this technique of static stacking where we would make 20 of them. 72 00:11:29.460 --> 00:11:43.710 Mark Kushner: keep them in the trap and then make 20 more of them with a new set of antique protons and positive trends and add them to the ones that we had previously, so what we can't get 1000 simultaneously, we can stack up 1000 of them and. 73 00:11:45.840 --> 00:11:49.110 Mark Kushner: That says more or less where we, we are today. 74 00:11:50.250 --> 00:11:50.670 Mark Kushner: and 75 00:11:52.470 --> 00:12:03.330 Mark Kushner: You might wonder why this graph starts in 2000 stops you 2018 that's because in 2019 the CERN shut down for four and a. 76 00:12:04.080 --> 00:12:17.280 Mark Kushner: big improvement that they called the long shut down to and we haven't had any data until very briefly, last year we had a short experimental run, but the new run is starting in March and we better be prepared for that, and then the case. 77 00:12:19.020 --> 00:12:21.720 Mark Kushner: You can read that we're not prepared, but never mind that. 78 00:12:24.180 --> 00:12:34.260 Mark Kushner: What did plasmids have to do with this well these the way you may get a hydrogen is true plasma physics, what you do is you create an anti-proton plasma. 79 00:12:34.680 --> 00:12:47.490 Mark Kushner: And a positron plasma, these are charged plasmas they're pure so just anti protons just positrons you store them in something called the pending Magdeburg trap which uses a strong Axial magnetic field. 80 00:12:48.120 --> 00:12:54.480 Mark Kushner: To provide radio confinement and then electrostatic wells, to provide Axial confinement. 81 00:12:55.200 --> 00:13:01.950 Mark Kushner: These traps work, really, really well, we can keep the passwords in here for very long periods of times actually. 82 00:13:02.580 --> 00:13:09.000 Mark Kushner: Essentially forever, you might wonder about the fact that, since these are charged particles and just. 83 00:13:09.480 --> 00:13:21.900 Mark Kushner: A neutralized charged particles they make big electric fields, so you might wonder why the electric fields just don't cause the plasma to explode in all directions through to self propulsion they don't. 84 00:13:22.920 --> 00:13:30.480 Mark Kushner: What they actually do is they rotate on their access, so they spin something like this, due to the east coast be forces that are involved here. 85 00:13:30.900 --> 00:13:39.330 Mark Kushner: it's not particularly germane to the rest of the talk, but it is important, and one of the things that makes all of this hard. 86 00:13:40.050 --> 00:13:47.010 Mark Kushner: Is that we have to be able to make very difficult to achieve plasma parameters. 87 00:13:47.520 --> 00:13:57.210 Mark Kushner: The positrons come from radioactive decay in a circle style positron accumulator a fascinating device that I really can't get into but, once we get the positrons. 88 00:13:57.480 --> 00:14:12.570 Mark Kushner: We make need to make this positron plasma and it needs about 20 million positrons in it, it has a length of about a centimeter and a radius of about one centimeter so it's a small needle like object inside of our machine. 89 00:14:13.050 --> 00:14:22.050 Mark Kushner: The density is about 10 to the eighth per cubic centimeter but the hard parameter to achieve is that we need to get the temperature down to about 10 kelvin. 90 00:14:22.710 --> 00:14:30.360 Mark Kushner: and improving this temperature is really been the most important thing that we've done in the experiment over the years. 91 00:14:31.350 --> 00:14:42.150 Mark Kushner: The anti protons don't need to be quite as good We only need about 20,000 of them, they have the same shape basically still need a like but their temperature need only get down to about 100 kelvin. 92 00:14:43.440 --> 00:14:50.880 Mark Kushner: And once we've got these parameters, you might wonder what we do with them well, we have these separate plasmas which are separated electrostatic Lee. 93 00:14:51.300 --> 00:14:56.940 Mark Kushner: And then we just tip them not like this, but with electrostatic so we tip them into each other. 94 00:14:57.330 --> 00:15:05.820 Mark Kushner: Through three body recombination they make anti hydrogen atoms these anti hydrogen atoms just go to the wall and annihilate because they're charged neutral. 95 00:15:06.780 --> 00:15:12.330 Mark Kushner: And so the electric field and the magnetic fields that we have inside of the trap aren't going to confine them in one place. 96 00:15:12.900 --> 00:15:23.640 Mark Kushner: So we need to do something, additionally, to keep them in one place, and remember you guys should be asking the questions, what we do to keep to trap them. 97 00:15:24.270 --> 00:15:33.240 Mark Kushner: Is we take advantage of the fact that anti hydrogen has a small magnetic moment it looks like a bar magnet and some simplistic picture and. 98 00:15:34.380 --> 00:15:41.100 Mark Kushner: It can be confined in what's called a yoffie Pritchard track and and magnetic minimum if you can make a field which is a minimum. 99 00:15:41.670 --> 00:15:52.410 Mark Kushner: In the Center and increasing in all directions you'll get confinement and we can use mirror coils to create an axiom minimum and we can use an okta pole or. 100 00:15:53.490 --> 00:15:58.920 Mark Kushner: We could use a quadruple but an octopus turns out to work much better from a plasma physics perspective. 101 00:15:59.910 --> 00:16:07.380 Mark Kushner: To create a radio minimum, so this is a picture of what our magnet system looks like obviously doesn't rotate in the real experiment. 102 00:16:07.800 --> 00:16:13.350 Mark Kushner: But what it does do is it makes a bath tub where, if this is the Center of the trap. 103 00:16:14.040 --> 00:16:22.860 Mark Kushner: To get out, you have to climb the walls in all directions, so long as the spin of the anti hydrogen doesn't slip and indeed doesn't flip. 104 00:16:23.310 --> 00:16:37.830 Mark Kushner: Half of the anti hydrogen atoms will be low field seeking and the hydrogen atoms and they'll be stuck in the Center they won't be able to escape out the velocity of the 10 Calvin protons and can I come to that in quite a long time. 105 00:16:40.650 --> 00:16:51.450 Mark Kushner: So they're going to stick inside of this trap okay now half of them are going to be highfield seekers and they're going to be lost something that will become important later on in this talk. 106 00:16:53.220 --> 00:17:12.810 Mark Kushner: We use a state of the art superconducting magnet which is fabricated at brookhaven to do this and it produces a strong field that one and a half tesla, the problem is that that field nonetheless it's very shallow in terms of confinement and to confine the anti atoms in that field requires. 107 00:17:13.860 --> 00:17:24.660 Mark Kushner: Well, it generates a well depth of only about half a Calvin or 40 micro electron volts So why is this a plot problem but remember our plasmas are charged. 108 00:17:25.170 --> 00:17:31.500 Mark Kushner: And there's a potential drop across her plasmas which is on the order of one volt so the natural energy scale in this. 109 00:17:31.950 --> 00:17:41.340 Mark Kushner: In this problem is the potential across the plasma one volt to trap things we have to mix these things which have natural energy scales of about one volt. 110 00:17:41.640 --> 00:17:58.890 Mark Kushner: We need to mix them in such a fashion that the net energy for the created and the hydrogen atoms is something like 10,000 times less than their natural energy scale, this is really, really tough to do, and most of our time has been spent learning to do this, this is an early graph. 111 00:18:00.150 --> 00:18:13.770 Mark Kushner: Early data that we had, but you can see, when the positron temperature was high, namely around 71 Calvin we were trapping only about one in every 30 attempts and yet if we lowered it down to 40 Calvin. 112 00:18:14.280 --> 00:18:20.370 Mark Kushner: Just a factor of two and also lowered the anti-proton temperature, we could get the trapping rate to almost one. 113 00:18:20.970 --> 00:18:28.470 Mark Kushner: And then, if we further go down to about 10 Calvin, which is where we are today, this was at the time prediction. 114 00:18:28.980 --> 00:18:38.670 Mark Kushner: and actually we've done better than this, instead of getting about four per attempt we get about 20 per attempt it's so rare case and plasma physics, where things work out better than you had expected. 115 00:18:39.660 --> 00:18:47.970 Mark Kushner: So the whole secret, then, is to get this positron temperature to be really, really low, so you might wonder how we cool the positrons. 116 00:18:48.330 --> 00:18:57.030 Mark Kushner: We take advantage of Cyclotron cooling the positrons our might and they're in a strong magnetic field so there's Cyclotron rating at their energy away. 117 00:18:57.480 --> 00:19:06.240 Mark Kushner: And did about three tests at one tesla I should say the cooling time is about every four seconds their energy will drop by a factor of one over he. 118 00:19:08.970 --> 00:19:18.660 Mark Kushner: This is a graph of that phenomenon at three tesla so they're going to drop the temperature is going to drop you from faster, but you can see there's an exponential decay in the temperature. 119 00:19:19.260 --> 00:19:25.230 Mark Kushner: And it goes, all the way down to the wall temperature the bath in which it's surrounded except that it doesn't. 120 00:19:26.040 --> 00:19:41.490 Mark Kushner: You would expect them to cool all the way down to the temperature of the surroundings, which is a little bit lower than 10 Calvin Calvin, but in fact it gets hung up at about 100 kelvin we don't really understand the details, why it gets hung up here and. 121 00:19:44.730 --> 00:19:54.630 Mark Kushner: Getting hung up has been observed across multiple experiments at multiple institutions It just seems to be a very generic problem to these sorts of devices. 122 00:19:54.930 --> 00:20:00.300 Mark Kushner: There are a number of mechanisms that you could think of that would keep this thing hung up at this temperature. 123 00:20:00.960 --> 00:20:10.260 Mark Kushner: One of them is electrode amplifier noise, another is that we could have high temperature radiation leaking in from the outside, we have. 124 00:20:10.620 --> 00:20:20.130 Mark Kushner: A more or less eight kelvin Chamber but it's got open ends, which are open to the to the outside, which is a 300 kelvin and some radiation is going to. 125 00:20:20.430 --> 00:20:26.640 Mark Kushner: come pouring down there as well as gas molecules actually going to be coming down here, and the other thing that's. 126 00:20:27.480 --> 00:20:38.220 Mark Kushner: A standard explanation not proven explanation is that the plasma is expand normally, you would think that if plasmas expand when things expanded cool. 127 00:20:38.790 --> 00:20:46.920 Mark Kushner: But in this case the plasma is actually doing work against itself converting potential into kinetic energy and the plasma is actually heat up when they expand. 128 00:20:47.340 --> 00:20:57.450 Mark Kushner: So we don't really know which of these mechanisms are some completely different mechanism is causing them to get hung up but we can't stay there, because 100 kelvin wouldn't work at all for us. 129 00:20:58.020 --> 00:21:00.930 Mark Kushner: So we use something called positron evaporates with cooling. 130 00:21:01.560 --> 00:21:11.010 Mark Kushner: To get them below 100 kelvin here's a graph of the electrostatic potential that's holding our positrons their positively charged so negative potentials will hold it in actually. 131 00:21:11.340 --> 00:21:18.030 Mark Kushner: And what we do is we lower one of the side barriers just enough to allow some of the hottest positrons to escape. 132 00:21:19.830 --> 00:21:31.500 Mark Kushner: And, as with any evaporate of process when things escape when things evaporate what's left behind gets colder and this works well enough to get us down to about 10 Calvin. 133 00:21:32.040 --> 00:21:43.560 Mark Kushner: Unfortunately it's a temporary effect so as soon as we finish the evaporated process the plasma quickly warms up and you can see here some data we got it down to about 10 kelvin. 134 00:21:43.860 --> 00:21:49.290 Mark Kushner: But within just three or four seconds it's above 2012 and it's headed up towards 100 kelvin. 135 00:21:49.890 --> 00:22:01.200 Mark Kushner: What this means is that, whatever mixing process we use to make tea and the hydrogen that mixing process, perhaps can only occur within the first, second or so of the end of our evaporates of cooling. 136 00:22:01.980 --> 00:22:11.610 Mark Kushner: Before from mysterious possible reasons the things start to heat up backup yeah temperatures ISO traveling or isn't dependent direction with. 137 00:22:13.170 --> 00:22:16.920 Mark Kushner: The temperature could be isotopic because there's actually. 138 00:22:18.630 --> 00:22:31.770 Mark Kushner: there's a separation, as you may know, due to work by Tom and Neil, and that says that you can get different parallel and perpendicular temperatures, however, the collision rate here is still probably about a killer hurts, so it probably is I. 139 00:22:33.390 --> 00:22:34.140 Mark Kushner: isotopic. 140 00:22:37.020 --> 00:22:37.440 Mark Kushner: Okay. 141 00:22:40.290 --> 00:22:47.370 Mark Kushner: So what could we do to do better than this well I don't really have time to go into this in any detail but at Berkeley. 142 00:22:48.330 --> 00:22:57.150 Mark Kushner: My graduate student Eric hunter did some wonderful experiments exploring cavity cooling it's been a well known effect due to purcell that if you put a single. 143 00:22:57.570 --> 00:23:08.130 Mark Kushner: charged particle like a single electron inside of a cavity the cooling the Cyclotron cooling can be dramatically enhanced and the it will cool much, much faster. 144 00:23:08.820 --> 00:23:17.850 Mark Kushner: But that was never shown to work for a collection of interacting particles, the effect isn't so it isn't as great. 145 00:23:18.240 --> 00:23:26.730 Mark Kushner: For collection of particles, as it is for one single particle nonetheless and I don't have time to really go into this data nonetheless. 146 00:23:27.540 --> 00:23:39.780 Mark Kushner: He was able to demonstrate about 10 times faster cooling, maybe 20 times faster cooling when we put these plasmids into a cavity and it's something that we might be able to employ in the future. 147 00:23:43.110 --> 00:23:44.790 Mark Kushner: But moving on from that, I that. 148 00:23:45.600 --> 00:23:56.730 Mark Kushner: I really could spend the entire lecture talking about how we make counter hydrogen and inner plasma things, but what i'd like to do is talk about some of the things we can do with that I had to Jen i'm going to discuss, I hope, three topics today. 149 00:23:57.480 --> 00:24:02.820 Mark Kushner: are two of them are really closely motivated by plasma physics and nonlinear dynamics sorts of stuff. 150 00:24:03.060 --> 00:24:12.300 Mark Kushner: And one of them really isn't but is one of the more important things that we actually do what i'd like to start out by is discussing how we measure the anti hydrogen charge. 151 00:24:12.750 --> 00:24:20.010 Mark Kushner: Now normal mattered atoms are known to be charged neutral to what is the 10th of minus 21 times the unit charge. 152 00:24:20.370 --> 00:24:28.590 Mark Kushner: In other words, they're neutral as best we can measure them to be that's not a surprise, but we would really like to do that for an anti hydrogen atom. 153 00:24:29.160 --> 00:24:41.610 Mark Kushner: So cpt and quantum anomaly can can solution demand that anti hydrogen be charged neutral to a similar level but it's this actually so where, at least, is it so experimentally. 154 00:24:42.360 --> 00:24:57.180 Mark Kushner: How well do we actually know the charge Well, unfortunately, the techniques that we would use that are used to make this measurement just aren't applicable for anti hydrogen atoms because they require a macroscopic quantity of atoms. 155 00:24:58.050 --> 00:25:09.870 Mark Kushner: And we don't have anything close to a macroscopic quantity of atoms Moreover, if we did have a macroscopic quantity of atoms I certainly wouldn't want to be in the same lab, not even in the same country. 156 00:25:11.010 --> 00:25:16.890 Mark Kushner: As that much anti-matter, so we need to come up with something else, so what else could we use. 157 00:25:17.460 --> 00:25:33.570 Mark Kushner: The only prior limit, which was known from the accelerator scale experiments was about 10 to the minus two times a so you could think about using superposition to to put a limit of bound on the charge of an anti hydrogen atom and. 158 00:25:34.650 --> 00:25:42.060 Mark Kushner: The charge of the anti-proton is known through laser spectroscopy experiments to be about seven times 10 to the minus 10. 159 00:25:42.540 --> 00:25:56.820 Mark Kushner: call it a little bit better than one part per billion, curiously, the charge of the positron is less well known and that's really something of surprising to me, to this day, but it's only known to about 25 parts per billion. 160 00:25:58.170 --> 00:26:07.230 Mark Kushner: So if you want to use superposition to put a bound on the charge of an anti hydrogen atom you would come up with this limit of about 25 parts per billion. 161 00:26:08.340 --> 00:26:17.220 Mark Kushner: But you know i'm from a field where it's permissible at some level to consider that and to hydrogen might fall upwards. 162 00:26:18.420 --> 00:26:24.960 Mark Kushner: So in that kind of field it's permissible to think that maybe superposition isn't correct. 163 00:26:26.310 --> 00:26:29.190 Mark Kushner: I mean, I have no idea how but. 164 00:26:30.270 --> 00:26:34.230 Mark Kushner: You could consider that, so therefore measuring the charge event I hydrogen. 165 00:26:34.500 --> 00:26:46.470 Mark Kushner: is a really good test and novel test of a fundamental physics, so how can you do that well the obvious thing to do is to put the hydrogen in a strong electric field and see if its effects to one side, and we did do that. 166 00:26:46.920 --> 00:26:56.640 Mark Kushner: And that experiment works, but it doesn't work, as well as doing something that's a bit closer to plasma physics and non linear dynamics, which is to take advantage. 167 00:26:57.000 --> 00:27:09.030 Mark Kushner: Of stochastic acceleration stochastic acceleration or Fermi acceleration is the process of applying if you ever charged particle he applies to caustically varying electric fields which randomly kick. 168 00:27:09.390 --> 00:27:17.550 Mark Kushner: Your object back and forth Okay, and as a random process it's going to random walk and energy, space gradually gaining energy. 169 00:27:18.300 --> 00:27:24.690 Mark Kushner: And it could get enough energy, so that it escapes your trap so here's a cartoon of this going on. 170 00:27:25.320 --> 00:27:31.020 Mark Kushner: What I have is an Anti hydrogen atom over here and i'm kicking it with these this potential. 171 00:27:31.440 --> 00:27:36.960 Mark Kushner: Which is just kicking it its energy is fluctuating slightly it's trapped between these two mirror walls over here. 172 00:27:37.350 --> 00:27:47.490 Mark Kushner: And the energy stays down and flux doesn't do anything much of interest for a while, but eventually it starts to pick up some energy and gets close to the point of escaping but doesn't. 173 00:27:48.780 --> 00:28:02.730 Mark Kushner: And then on the neck go through it actually has just enough energy to escape out of the system, so we could use something similar to this, but if you don't believe this example is to cast acceleration here's Another example is to tax to cast acceleration. 174 00:28:03.450 --> 00:28:05.970 Mark Kushner: The beach ball is our anti hydrogen particle. 175 00:28:07.230 --> 00:28:15.510 Mark Kushner: And it's obvious that it's subject to random kicks if it wasn't for air friction, this would beach ball with eventually leave the stadium. 176 00:28:16.350 --> 00:28:28.560 Mark Kushner: And float free so that's basically what we're doing you can set this up as a physics experiment for anti-matter Adams, you can set a bound on the charge for the charge to escape, it has to exceed. 177 00:28:29.340 --> 00:28:39.690 Mark Kushner: Well, the well depth obviously that's a mirror well depth on either side, and if you kick it end times you can get this back of the envelope formula. 178 00:28:40.410 --> 00:28:56.370 Mark Kushner: For how much charge, it would have to have to escape the one other thing that you need to know is whether the size of the potential fluctuations that you're using to kick the atom back and forth, and we did this, and we did that, because. 179 00:28:57.690 --> 00:29:04.860 Mark Kushner: Well, this is really motivated by stochastic eating and plasmas I mean that's where I first heard about this kind of technique. 180 00:29:05.520 --> 00:29:11.190 Mark Kushner: We did this and here's our experimental data we weren't that good at trapping onto hydrogen atoms at the time. 181 00:29:11.490 --> 00:29:20.160 Mark Kushner: But we did two two trials and stochastic trials, we applied the the oscillating electric fields we did 10 trials and we observed 12 the end. 182 00:29:20.640 --> 00:29:27.510 Mark Kushner: And then we did no trials, where we also did 10 trials and we observed 12 at the very end. 183 00:29:28.350 --> 00:29:34.440 Mark Kushner: i'm sure it's a statistical coincidence that we got 12 in each case, but the point of this experiment. 184 00:29:34.800 --> 00:29:43.350 Mark Kushner: Is that obviously applying the level of fields that we were applying didn't do very much to the number of particles that that survived. 185 00:29:43.650 --> 00:29:53.970 Mark Kushner: So, then you start getting people who know more about statistics and I do who do careful computer simulations of how many would survive and then they imply careful. 186 00:29:54.450 --> 00:30:06.150 Mark Kushner: Statistics, and they do basically analysis, because they're they're based in people not frequencies, which I tend to agree with, by the way, not knowing very much about the subject, but in any case. 187 00:30:06.660 --> 00:30:15.900 Mark Kushner: What we found is that the bound on the charge with the anti anti hydrogen atoms has to be less than about Point six parts per billion. 188 00:30:16.320 --> 00:30:25.290 Mark Kushner: But that's without considering statistical effects if you systematic errors, I should say, if you include that you get a band of about Point seven. 189 00:30:25.800 --> 00:30:35.850 Mark Kushner: So that is the the best known charge of an anti hydrogen atom I have an undergraduate doing simulations now we can probably get better by about a factor of 100. 190 00:30:36.720 --> 00:30:47.400 Mark Kushner: If we went back and did this experiment again but let's become enter the re enter the real world and believe in superposition again if you believe in superposition. 191 00:30:47.850 --> 00:30:57.270 Mark Kushner: That means that you can set a new limit on the charge with the positive trends and you can improve the chart the known charge of positron by a similar factor of about 25. 192 00:30:58.530 --> 00:31:08.370 Mark Kushner: So that is also the best known limit on the charge of anti pride to proton now alpha stands for something something laser apparatus. 193 00:31:08.820 --> 00:31:22.890 Mark Kushner: And our primary goal was to do laser spectroscopy to test cpt on this experiment so i'm going to spend a few minutes talking about how we do that it's complicated because if we start with ground state anti hydrogen. 194 00:31:24.120 --> 00:31:41.190 Mark Kushner: The linemen serious serious, which is this series over here the least energetic transition is the one ESTA Tu es transition which is at 121 nanometers it's a forbidden transition, but it can be excited by to 243 nanometers photons. 195 00:31:43.200 --> 00:32:00.390 Mark Kushner: This requires a lot of power, because any forbid and transition requires a great deal of power and it's a very difficult wavelength, but it does have the advantage that it stopped for free, which gets rid of one of the main systematic effects so to do this, we need to. 196 00:32:02.310 --> 00:32:07.320 Mark Kushner: get up to a very high power, how do we do that well. 197 00:32:08.610 --> 00:32:16.380 Mark Kushner: What we do is use a cavity so we have some laser light coming in and a mirror over here and another mirror over here. 198 00:32:16.920 --> 00:32:22.590 Mark Kushner: And the laser light bounces back and forth inside of our trap, this is where the anti hydrogen atoms are. 199 00:32:23.460 --> 00:32:31.410 Mark Kushner: And it builds up within the cavity, this is a miserably difficult cavity to build and fortunately. 200 00:32:32.340 --> 00:32:38.760 Mark Kushner: But for the success of the project and because it's just miserable to try and do it, I had nothing to do with building that cavity. 201 00:32:39.750 --> 00:32:45.450 Mark Kushner: The problems are that the mirrors are very far apart they're almost a meter apart. 202 00:32:46.290 --> 00:32:57.060 Mark Kushner: And they're not on an optical table So how do you get rid of vibrations in this kind of system, there are cryogenic temperatures there in vacuum. 203 00:32:57.990 --> 00:33:08.880 Mark Kushner: which really limits your your choice of material materials and even at room temperature normal mirrors at 243 nanometers the mirrors are not lossless. 204 00:33:09.210 --> 00:33:14.370 Mark Kushner: So it was real feet on the part of the laser people in our collaboration to get this to work. 205 00:33:15.030 --> 00:33:19.920 Mark Kushner: And they use the complicated laser system i'm not going to go into any detail here because. 206 00:33:20.400 --> 00:33:26.640 Mark Kushner: it's really not what I do and understand, but it basically starts off with the topical laser which produces 150. 207 00:33:27.060 --> 00:33:42.600 Mark Kushner: milliwatts of light at 243 nanometers goes into this cavity where it's bouncing back and forth and and beats up to about one to one and a half Watts of circulating power inside of the cavity with all sorts of fancy. 208 00:33:43.740 --> 00:33:48.660 Mark Kushner: cavity stuff to get it to to to do that so. 209 00:33:50.550 --> 00:33:57.780 Mark Kushner: Before going further, we really have to spend a little bit of time talking about the empty Adam states, the anti hydrogen states. 210 00:33:58.950 --> 00:34:06.600 Mark Kushner: were in the ground states so it's a one s level but they're actually for one s levels, having to do with the positron and the elect anti-proton spin. 211 00:34:07.710 --> 00:34:18.870 Mark Kushner: To have those levels are not tropical they've got the wrong positron spins so they're going to be highfield seekers and leave our trap immediately, two of them are tropical split by the anti-proton spin. 212 00:34:19.230 --> 00:34:30.600 Mark Kushner: And they're split by about 600 megahertz with this two photon transition, we can knock them up to the two F state over here, which is also split but but by quite a bit less so i'm not trying to draw here. 213 00:34:31.590 --> 00:34:39.420 Mark Kushner: And that's what we wanted to measure and detect is this this transition okay So how do we go about doing that. 214 00:34:40.200 --> 00:34:47.100 Mark Kushner: Well, the obvious way to go about doing that is to wait for it to tk back down, and then we can measure. 215 00:34:47.580 --> 00:34:55.530 Mark Kushner: We can find the photons but that's almost impossible to do we do have some plans for thinking about it but it's really, really hard. 216 00:34:55.800 --> 00:35:09.240 Mark Kushner: The reason is that the nearest detectors would be about out where the mirrors are maybe they could be a little bit closer but they're very far out, so the solid angle that the detectors would be detecting of the photons is really very, very low. 217 00:35:10.710 --> 00:35:29.490 Mark Kushner: And it's just not that many photons in 600 seconds, which is our typical exposure every atom admits once basically so if we have 1000 atoms were most getting about 1000 photons total couple that with the solid angle, and you have a really hard measurement problem to do. 218 00:35:30.870 --> 00:35:36.690 Mark Kushner: And then there's a very amusing problem which is, we want to measure anti hydrogen not hydrogen. 219 00:35:38.010 --> 00:35:51.510 Mark Kushner: So what if it happened to be the case that there is any atomic hydrogen in the system we would measure those photons, how do we tell the difference between a hydrogen photon and an Anti hydrogen photon. 220 00:35:52.230 --> 00:36:09.870 Mark Kushner: Particularly since there's not supposed to be any difference there's no way to tell the difference now hydrogen atomic hydrogen is not supposed to exist in a cryogenic vacuum, at least I can't find any references that say that it doesn't exist, on the other hand, I can't find. 221 00:36:11.010 --> 00:36:15.390 Mark Kushner: i'm sorry that it does exist, but I can't find any references to say it doesn't exist. 222 00:36:16.140 --> 00:36:24.870 Mark Kushner: So it's undoubtably very, very low, but the volume here is big enough so that there are millions and maybe 10s of millions of. 223 00:36:25.230 --> 00:36:42.630 Mark Kushner: atoms neutral atoms inside of here, so if a very tiny fraction of them happened to be atomic hydrogen, we would be we'd be do not be able to do this experiment, so we need a signature that wouldn't be set off by Anna hydrogen and also is detectable. 224 00:36:43.980 --> 00:37:01.980 Mark Kushner: The only signature that we have is annihilation normal matter I hydrogen does not annihilate right, so if we can do something to the atoms that causes an eye on elation, then we can reliably measure that because we can measure annihilation, with about 50% efficiency. 225 00:37:04.200 --> 00:37:13.560 Mark Kushner: So it's worth spending a little bit of time going over this it's atomic physics, I guess, but we start out in the one so trapped state down here. 226 00:37:13.920 --> 00:37:22.890 Mark Kushner: We have two photons pick it up to the state, and then you can ask what happens to the two F state it's a forbidden transition so it's a long live state. 227 00:37:24.240 --> 00:37:35.820 Mark Kushner: And there are three routes that the anti hydrogen atom can take away from the to escape to have those roots roots that you'll see in a moment, lead to annihilation of the anti data. 228 00:37:36.990 --> 00:37:46.800 Mark Kushner: So what's the first group well there are strong magnetic fields around and that causes effectively an electric field that's called a motivational electric field. 229 00:37:47.430 --> 00:37:54.480 Mark Kushner: From the Cross be force as the particle as the anti atom moves through the strong Tesco level magnetic fields. 230 00:37:55.260 --> 00:38:05.130 Mark Kushner: that's effectively and electric field, you could you could think of this is it's a stark shift whatever, but in any case, what it does, is it miss mixes the two s than the two piece dates. 231 00:38:05.400 --> 00:38:17.820 Mark Kushner: So there's some mixture of to pee here the two P, is not a forbidden state for a decay and about half of it will decay down into the untracked one State and annihilate on the wall. 232 00:38:18.900 --> 00:38:36.960 Mark Kushner: So that's one route to annihilation another route to annihilation comes from ionization so if you're up in the to F state the lifetime of that state, given the one tesla magnetic field is about 60 milliseconds during that 60 milliseconds it can absorb another photon. 233 00:38:38.130 --> 00:38:46.290 Mark Kushner: And if it does, that it actually kicks it actually Ionized as the other photonic goes so we're left with a bear anti-proton. 234 00:38:47.520 --> 00:38:48.030 Mark Kushner: and 235 00:38:50.520 --> 00:38:58.860 Mark Kushner: If it does absorb what we're left with this parent, I felt a proton again and it turns out that while we do a good job of trapping. 236 00:39:00.000 --> 00:39:10.800 Mark Kushner: plasmas that are anti protons for various and complicated reasons single anti-proton inside of our trap did not last any length of time at all, they they decay away. 237 00:39:11.130 --> 00:39:12.450 Mark Kushner: They can carry out in. 238 00:39:12.510 --> 00:39:23.730 Mark Kushner: In in milliseconds Okay, this is actually a big mystery until a few years ago, when I had an undergraduate at CERN a stunningly brilliant undergraduate. 239 00:39:24.210 --> 00:39:32.580 Mark Kushner: And he figured out the reason why they escaped within one know a second that has to do with touch potentials if you know what that is, if you don't and happy to discuss it. 240 00:39:33.090 --> 00:39:38.160 Mark Kushner: Afterwards he's now my graduate students I wasn't going to let him go and. 241 00:39:38.790 --> 00:39:48.600 Mark Kushner: we're about to publish a paper on this, but he really did figure it out, while he was an undergraduate something that the rest of the 50 other on people here did not figure out. 242 00:39:49.200 --> 00:40:02.010 Mark Kushner: But in any case so that's also leads to annihilation, and then of course there's what before I go there, you might think a three photon process is going to be incredibly rare but it's not. 243 00:40:03.210 --> 00:40:04.230 Mark Kushner: Because. 244 00:40:05.730 --> 00:40:19.110 Mark Kushner: The second photon the ionizing photon doesn't have to be simultaneous with the two photons and in fact the Cross section for the ionization is far, far higher than the Cross section for the initial expectation up to the two s level. 245 00:40:19.530 --> 00:40:33.240 Mark Kushner: So it's really a two plus one photon transition, not a three photon transistor and the third transition comes for free, because we have this powerful bath of photons doing the one to two s thing, and you just pick up another photon. 246 00:40:34.620 --> 00:40:49.680 Mark Kushner: So that's just going to happen and then what I starting to say is there's a third well a third, and a fourth route, if you will, it can do the forbidden transition back to a trap state or the two piece date can come back to a trap state instead of two and i'm trapped state. 247 00:40:51.000 --> 00:40:54.180 Mark Kushner: That would just recycle the atom and we get to try it again. 248 00:40:55.350 --> 00:41:07.110 Mark Kushner: But in any case computer simulation suggest that most of the time we actually get the sign ization route that's the most common root of things that happens, once we kick it up to the two so rude. 249 00:41:07.530 --> 00:41:18.570 Mark Kushner: And it's, this is the signal that we use to to to measure our spectrum, because only when we put in precisely the right wavelength of 243 nanometers what we see in annihilation. 250 00:41:19.410 --> 00:41:34.350 Mark Kushner: Using that we were able to do an on off experiments in 2017 it wasn't very accurate 200 parts per trillion, but a year or so later, we were able to actually measure the spectrum event to hydrogen, which is. 251 00:41:35.580 --> 00:41:51.570 Mark Kushner: shown over here and the the line Center is accurate to about two parts per trillion which, not surprisingly, reduced without of hydrogen now of course in any experiment like this, you have to systematic consider the systematic I didn't do that. 252 00:41:53.460 --> 00:42:00.210 Mark Kushner: And i'm not going to go into it, but So what is this a good cpt test and. 253 00:42:01.380 --> 00:42:15.570 Mark Kushner: There are many, many ways many, many cpt tests and many, many ways of measuring how good the cpt test is everybody has their favorite way of measuring how good their particular cpt test is. 254 00:42:15.960 --> 00:42:26.580 Mark Kushner: And naturally everybody's way of measuring how good cpt tests just coincidentally happens to be the way that favors their test the most. 255 00:42:27.240 --> 00:42:39.720 Mark Kushner: So i'm picking this method, because it favors our test the most, but the generally accepted best way is to look at the mass of the case CEO and the anti K zero. 256 00:42:40.680 --> 00:42:46.890 Mark Kushner: system and they're equal to each other and that's the cpt test that on a mass scale gets you somewhere over here. 257 00:42:47.370 --> 00:43:02.400 Mark Kushner: Our one s two s measurement is over here, we plan to be able to get it to here without too much trouble we've also done a hyper fine measurement i'm not going to talk about it today, but that's also on this particular scale better than the case zero test. 258 00:43:03.900 --> 00:43:24.330 Mark Kushner: But there's something more going on here, which is, you cannot measure, a phenomenon to 10th and minus 10 in an accelerator accelerator based environment you just can't what you can do is have a model of how one s i'm sorry have a model of how cpt might be broken. 259 00:43:25.650 --> 00:43:27.870 Mark Kushner: And then you can test within that model. 260 00:43:29.310 --> 00:43:41.610 Mark Kushner: To very high precision and that's what this test is but, again, our measurements are model independent, so we have a much more general measurement and the K zero measurement actually is. 261 00:43:43.230 --> 00:43:53.100 Mark Kushner: Okay, the final topic i'd like to get to and i'm really getting out of time is gravity will anti-matter fall under gravity, the same way that normal matter false. 262 00:43:53.790 --> 00:44:05.220 Mark Kushner: Okay, and everybody knows apples full towards earth and everybody believes an Anti apple would fall towards an Anti earth, the question here is how does an Anti apple fall towards our current Earth. 263 00:44:05.790 --> 00:44:16.380 Mark Kushner: There were lots of people have thought about this thing and in the the week equivalent principal asserts that it will fall in exactly the same matter as a normal Adam. 264 00:44:17.130 --> 00:44:26.490 Mark Kushner: will fall and there are many, many theoretical arguments that support this contention that there's nothing interesting going on there, based on energy conservation quantum field theory. 265 00:44:26.820 --> 00:44:35.340 Mark Kushner: CP violation, there are lots and lots of these measurements there's also a lot of experimental indirect experimental. 266 00:44:36.390 --> 00:44:51.450 Mark Kushner: observations and support this contention up in Seattle they've done a lot of measurements of the influence of G with isotope number, you can do can oscillations you can do anti proton and positron Cyclotron frequency measurements here. 267 00:44:52.560 --> 00:44:58.200 Mark Kushner: In fact, there was a really good measurement that just came out a week and a half ago from the base collaboration at CERN. 268 00:44:59.220 --> 00:45:03.420 Mark Kushner: But it's still an indirect measurement as our neutrino arrival times from. 269 00:45:04.350 --> 00:45:15.030 Mark Kushner: snl 97 eight and then finally there's a classic experiment that the old timers here may well have heard of by with a burden and fairfax fairfax was at. 270 00:45:15.570 --> 00:45:29.010 Mark Kushner: Stanford, in which he dropped positrons and that seems to have conclusively answered the question accepted it doesn't even though it's very, very well established lore that fair banks drop positrons he actually didn't. 271 00:45:30.060 --> 00:45:31.410 Mark Kushner: He dropped electrons. 272 00:45:32.550 --> 00:45:39.030 Mark Kushner: He was going to drop positrons but he dropped electrons from the top of the tube and measured how fast, they would fall. 273 00:45:40.800 --> 00:45:42.000 Mark Kushner: And they didn't fall at all. 274 00:45:43.890 --> 00:45:55.620 Mark Kushner: They just stayed there, and that was an anomalous experiment which has been argued about its cause ever since people think they know why the electrons didn't fall and i'm happy to answer that question. 275 00:45:57.030 --> 00:45:59.250 Mark Kushner: Afterwards, and the questions why they don't fall. 276 00:46:00.630 --> 00:46:03.480 Mark Kushner: So that's not a measurement So what are we left with. 277 00:46:04.530 --> 00:46:23.880 Mark Kushner: All of these experiment tests have have some issues assumptions, which were talked about in a paper this paper over here, for instance, the invariance of G with isotope numbers makes the assumption that that virtual and real particles gravitate in exactly the same fashion. 278 00:46:25.170 --> 00:46:31.200 Mark Kushner: Which is very reasonable, but not, it says, an assumption that has never been directly tested unless you consider this is a test of that. 279 00:46:32.400 --> 00:46:34.980 Mark Kushner: Which is going around in circles, a little bit. 280 00:46:36.600 --> 00:46:47.640 Mark Kushner: So, until recently, there were no freefall tests, we did a test which had gave us very, very crude answers, but now i'm going to come to your question about how fast, are they moving. 281 00:46:48.180 --> 00:47:09.180 Mark Kushner: On our the average energy of the anti Adams is about 300 Noah kelvin all right and that corresponds to a velocity of about 90 meters per second anybody know what would happen if I threw a baseball and it frictionless world up at 90 meters per second how high it would rise. 282 00:47:10.740 --> 00:47:17.520 Mark Kushner: Okay, you can all do this calculation, but perhaps not in your head under pressure, it would rise to about 400 meters. 283 00:47:19.200 --> 00:47:19.680 Mark Kushner: and 284 00:47:21.600 --> 00:47:23.910 Mark Kushner: That makes making a fountain impossible. 285 00:47:24.930 --> 00:47:37.620 Mark Kushner: All right, I have looked around and I have yet to find the funding agency that's willing to build me a superconducting ultra high vacuum tower that is 410 meters tall, so I can't do it this way. 286 00:47:38.700 --> 00:47:45.000 Mark Kushner: So what are we going to do about that there are three collaboration at CERN which are trying to do this direct measurement. 287 00:47:46.170 --> 00:47:53.850 Mark Kushner: And one of them, they all rely on miracles, including our experiment, but one of them is the G bark collaboration. 288 00:47:54.330 --> 00:48:05.370 Mark Kushner: What they they're not satisfied with making anti-church and what they want to do is make anti hydrogen Plus, which is the equivalent of a minus, in other words, put two positrons on one anti-proton. 289 00:48:06.420 --> 00:48:14.880 Mark Kushner: And what they have to do is then they claim they can pull these Apps down to well sub Calvin temperatures, good luck with that. 290 00:48:15.420 --> 00:48:25.860 Mark Kushner: And then they would strip the ions which would be much lower energy and make a fountain this is really hard, these are really good people a lot of them are my friends. 291 00:48:26.970 --> 00:48:30.300 Mark Kushner: And I wish them luck, but it requires several miracles. 292 00:48:32.730 --> 00:48:50.520 Mark Kushner: Another experiment is to make a beam event to hedge an atom so you make a horizontal beam event a hydrogen atoms you propagate it from meter and then they have a fancy detection scheme, which is supposedly going to detect that they deflected downwards and gravity. 293 00:48:51.690 --> 00:49:13.260 Mark Kushner: And this would be millimeters or less I mean well less, and they have a complicated scheme for making it, which involves nevermind what it involves it's complicated they haven't yet made an Anti hydrogen being at all, really, and so there are a lot of miracles, here too, so what's our skin. 294 00:49:14.490 --> 00:49:25.170 Mark Kushner: well remember what we do we use mirror coils to trap are anti hydrogen atom so if we were to turn this experiment on the side what we would have is. 295 00:49:26.220 --> 00:49:29.640 Mark Kushner: An anti hydrogen, which is trapped in the Center and it would bounce up and down. 296 00:49:30.750 --> 00:49:37.890 Mark Kushner: Being deflected reflected by these miracles, but if we lower the strength of the miracles so that. 297 00:49:39.480 --> 00:49:42.360 Mark Kushner: The atom is going to take a larger excursion. 298 00:49:45.240 --> 00:49:54.270 Mark Kushner: lower the strength sorry that wasn't working so it's going to take a lower and lower excursion in the fields right it's fine to continue to bounce up and down. 299 00:49:54.810 --> 00:50:06.780 Mark Kushner: So what we've in fact made is a balance by lowering the field so that they're just just getting reflected back inside and, as you probably know, as soon as you make a balance experiment. 300 00:50:07.290 --> 00:50:16.140 Mark Kushner: You can do make very high precision measurements that's what a balanced scale is doing is making very, very high i'm good aren't I never mind. 301 00:50:18.390 --> 00:50:18.900 Mark Kushner: So. 302 00:50:20.490 --> 00:50:31.110 Mark Kushner: The idea is that if we've got a magnet a precise magnetic balance, then a little tiny effect from gravity, will be able to push things over the corner. 303 00:50:31.410 --> 00:50:43.290 Mark Kushner: And a little bit of Mount of gravity will push them over the edge if gravity is pointing downwards for these atoms are going to fall downwards if gravity is pointing upwards, they would fall out at the top of the trap. 304 00:50:43.680 --> 00:50:47.130 Mark Kushner: And we would be able to detect which side of the track they fell out of. 305 00:50:49.020 --> 00:50:49.410 Mark Kushner: So. 306 00:50:51.210 --> 00:51:04.890 Mark Kushner: We can we can our previous measurement was plus or minus 100 G OK and it's really, really crude that's hardly a limit on gravity at all, not 150 or 100 g. 307 00:51:06.630 --> 00:51:09.240 Mark Kushner: So, but if it is the only. 308 00:51:11.100 --> 00:51:17.730 Mark Kushner: leaning tower of PISA type measurement of gravity today with this new apparatus that we're building to do this. 309 00:51:18.690 --> 00:51:32.190 Mark Kushner: We hope to be able to get down to about a hundredth of g to make a measurement to the acceleration but that's really, really tough our miracle is that we require controls of the magnetic fields. 310 00:51:33.000 --> 00:51:44.400 Mark Kushner: To about a 10th of the gas level and one test with background, and this is just hard in fact we don't really know how to measure the electric to them, they did I say electric fields, if I did, I meant magnetic field, obviously. 311 00:51:45.750 --> 00:51:55.230 Mark Kushner: We don't even know how to measure the magnetic field to this level, the best we can do so far as to use a plasma technique electron Cyclotron resonance magnetometer. 312 00:51:55.650 --> 00:52:00.960 Mark Kushner: i'm sure you all know here what the car is what you do is you send in microwaves into a plasma that. 313 00:52:01.200 --> 00:52:09.810 Mark Kushner: When you hit just the Cyclotron frequency that hits the plasma, you can measure that heating, so you look for overheating peak and that gives you the Cyclotron frequency. 314 00:52:10.770 --> 00:52:18.090 Mark Kushner: sounds straightforward, but it isn't, and the reason why it isn't is that there are many peaks where did these people come from well. 315 00:52:18.600 --> 00:52:28.980 Mark Kushner: here's one of our atoms or i'm sorry the electron bouncing back inside our fourth inside of the trap okay this bounce motion effects where the peaks are. 316 00:52:29.730 --> 00:52:40.680 Mark Kushner: And if we make the bounce motion faster by making the trap shorter that will spread the peaks out and that's what you're observing here, these are spectra at different bounce frequencies. 317 00:52:41.040 --> 00:52:49.170 Mark Kushner: And you can see that the side bands are moving outwards as as we increase the bounce frequency. 318 00:52:50.010 --> 00:53:05.730 Mark Kushner: Well here's our peak that right that's the that's the Cyclotron frequency, except that it isn't because if you take a closer look at that peak you could discover that it's fairly broad and it is got peaks within it itself okay. 319 00:53:07.020 --> 00:53:18.270 Mark Kushner: And these peaks are coming these sub peaks are coming from the rotation of a password remember, I mentioned the plasma rotate So these are rotational peaks. 320 00:53:18.930 --> 00:53:34.680 Mark Kushner: That are splitting it again, and there is one peak that doesn't move the Cyclotron frequency peak right over here that's what we want to measure but it's it's a mess, because if you look at it carefully that's, not even the highest amplitude peak. 321 00:53:35.790 --> 00:53:45.360 Mark Kushner: Nonetheless, it's the one that stationary so it's got to be the Cyclotron frequency, at least we hope Cyclotron frequency and using this technique, we can get to the accuracy, you need. 322 00:53:45.720 --> 00:53:49.470 Mark Kushner: We can measure the location of that peak to about one part per million. 323 00:53:50.280 --> 00:53:57.000 Mark Kushner: This is plasma physics experiment, remember, there are very few plus experiments that measure things on the part per million scale. 324 00:53:57.390 --> 00:54:03.810 Mark Kushner: And we can make relative measurements down to about 30 parts per billion, this is more than good enough so. 325 00:54:04.710 --> 00:54:15.270 Mark Kushner: I need to come to a conclusion here here's our new apparatus that we're building to to gravity, it has an incredibly complicated magnet with about 30 coils. 326 00:54:15.630 --> 00:54:28.230 Mark Kushner: This is that magnet being about to be lower down into the door over here, if you want to talk about a hair raising moment that several million dollars on a crane right there. 327 00:54:29.370 --> 00:54:36.240 Mark Kushner: But eventually it got in and a large number of people are responsible for this i'm grateful for all of them. 328 00:54:36.480 --> 00:54:49.620 Mark Kushner: they've been a joy to work for a lot of them are undergraduates I don't know if there are any undergraduates here but here's my plug for doing undergraduate research, all of these people were undergraduates working on the project, and then there were some graduate students of mine. 329 00:54:50.670 --> 00:54:57.810 Mark Kushner: I should say, these are all my students at once i've highlighted their mind students than there were some graduate students in another Professor. 330 00:54:58.860 --> 00:54:59.310 Mark Kushner: So. 331 00:55:01.830 --> 00:55:12.690 Mark Kushner: To summarize, since 2010 we really improved our ability to trap and hydrogen atoms and currently we can trap about 20 add an Anti Adams per. 332 00:55:13.110 --> 00:55:19.950 Mark Kushner: per attempt, we can get about 1000 in the machine and we can store them for upwards of 1000 seconds. 333 00:55:20.670 --> 00:55:28.590 Mark Kushner: and doing this we've made all sorts of physics measurements we've measured the microwave spin foot frequency we've done a really crude measurement of g. 334 00:55:28.980 --> 00:55:36.510 Mark Kushner: we've been able to bound the charge event I had written to one parts per billion we've measured, the one s to s transition to two parts per trillion. 335 00:55:37.140 --> 00:55:46.170 Mark Kushner: We measured the hyper find structure to about a killer hurts for so we've been able to excite the one as to pee lineman alpha transition. 336 00:55:46.620 --> 00:56:02.220 Mark Kushner: And the latest thing we've done is laser cooling, this is our region, this is an original temperature spectrum and then, if you laser cool the atoms you get a much narrower spectrum this over here, and this is certainly the direction that we want to be going. 337 00:56:03.480 --> 00:56:06.210 Mark Kushner: So what to make of all of this. 338 00:56:07.380 --> 00:56:13.830 Mark Kushner: The chance that we'll we'll find something interesting is really, really small I mean let's face it. 339 00:56:16.110 --> 00:56:17.130 Mark Kushner: Essentially zero. 340 00:56:18.390 --> 00:56:36.810 Mark Kushner: The importance of US finding something is enormous, it would totally revolutionize fundamental physics, if we were to discover anything in these experiments So what do you think about the worth of doing these things, the problem of course is that that zero times infinity. 341 00:56:38.250 --> 00:56:47.700 Mark Kushner: Is whatever you choose it to be right and different people make different decisions about what they choose this type of research to be I happen to think there are a lot of fun. 342 00:56:48.210 --> 00:56:57.480 Mark Kushner: And i'm happy to be doing this other people can think this is a complete waste of time Why did I bother to come to the seminar etc and that's fine too. 343 00:56:58.140 --> 00:57:06.750 Mark Kushner: But if you're in the first group, you might eventually contact me because we are looking for postdocs on the system, so thank you very much i'm sorry I kind of ran out of time here. 344 00:57:07.890 --> 00:57:09.270 Mark Kushner: And i'm happy to take questions. 345 00:57:17.610 --> 00:57:20.250 Mark Kushner: Thank you very much, other questions. 346 00:57:22.710 --> 00:57:26.580 Mark Kushner: What is the efficiency of turning and anti-proton a hydrogen atom. 347 00:57:28.620 --> 00:57:29.100 Mark Kushner: factory. 348 00:57:32.010 --> 00:57:32.640 Mark Kushner: well. 349 00:57:34.290 --> 00:57:39.540 Mark Kushner: Certain gives us I forget about 10 million anti-proton okay. 350 00:57:40.740 --> 00:57:59.460 Mark Kushner: And in every shot every time they deliver us centric protons they give us 10 million of those 10 million, we can trap 1010 to 100,000 of them inside of our experiment of that 10 to 100,000 we can turn about half of them into anti hydrogen atoms. 351 00:58:01.080 --> 00:58:03.570 Mark Kushner: And we trapped 20 it's not good. 352 00:58:05.970 --> 00:58:16.020 Mark Kushner: Remember, I was talking about the time when we were trapping one in every 35 attempts just the little bit of a deviation on there and you're back to zero really quickly. 353 00:58:19.200 --> 00:58:25.170 Mark Kushner: This is why anti-matter collection schemes are futile there's well. 354 00:58:26.400 --> 00:58:35.040 Mark Kushner: Okay, and it's very, very inefficient, to make the answer protons in the first place I should have said really very inefficient just for basic physics reasons not technique reasons. 355 00:58:36.780 --> 00:58:41.970 Mark Kushner: So we're happy to have gotten the thousand simultaneously that's that's about. 356 00:58:43.320 --> 00:58:54.750 Mark Kushner: 500 more than we ever expected to be able to get simultaneously in fact what this gravity experiment I all the initial simulations were done, I assume that we were just going to have one in the trap. 357 00:58:55.380 --> 00:58:59.610 Mark Kushner: And we'd have to do it over and over and over again, and now we can do the whole experiment in one shot. 358 00:59:00.690 --> 00:59:01.080 Mark Kushner: Maybe. 359 00:59:03.720 --> 00:59:04.740 Mark Kushner: Yes, yes. 360 00:59:05.970 --> 00:59:12.750 Mark Kushner: It is just a follow up question, so there is enough from these types of experiments are you. 361 00:59:14.460 --> 00:59:15.150 Mark Kushner: Pushing out. 362 00:59:17.970 --> 00:59:26.880 Mark Kushner: Okay, so to collect 10,000 takes us about half a day to cool them, you know some of you must. 363 00:59:28.080 --> 00:59:33.750 Mark Kushner: have done laser cooling experiments anybody here how long does it take to cool your sample sample. 364 00:59:36.780 --> 00:59:43.170 Mark Kushner: yeah on the order of milliseconds right that's because you have nice transitions and powerful lasers to do this cooling. 365 00:59:44.400 --> 00:59:45.900 Mark Kushner: takes about five hours. 366 00:59:47.400 --> 00:59:56.940 Mark Kushner: Okay, so all together you're about it, you know you're half a day to about a day to us as thousand anti atoms so you have to but. 367 00:59:57.450 --> 01:00:11.790 Mark Kushner: We could use more anti atoms, certainly if we had them would use them, we could track more of them, but then you know, certainly has power on a regular basis right you, you lose patience somebody gets lazy. 368 01:00:12.900 --> 01:00:20.130 Mark Kushner: kills the magnet we are magnets quench so we have to balance, how long we're willing to to accumulate them. 369 01:00:21.630 --> 01:00:34.920 Mark Kushner: Against the the risk that we lose them all, for one reason or another interesting point follow what is the gas pressure inside those experiments all try to the minus 12 now. 370 01:00:37.470 --> 01:00:39.300 Mark Kushner: 10 minutes minus 15 oh. 371 01:00:40.740 --> 01:00:47.370 Mark Kushner: So it's a cryogenic vacuum system we are doing these experiments in the middle of a cryo pump yeah and. 372 01:00:48.750 --> 01:00:54.240 Mark Kushner: How do you even measure those pressures, the best way to measure those pressures is to look at the anti-proton lifetime. 373 01:00:55.620 --> 01:01:04.500 Mark Kushner: And that's a difficult thing to do, because the Cross sections for annihilation of anti protons at these temperatures with gas at this temperature is not well known. 374 01:01:05.760 --> 01:01:09.300 Mark Kushner: So somewhere around 10 to minus 15 we normally. 375 01:01:10.230 --> 01:01:18.720 Mark Kushner: We have to warm the experiment up every now and then because eventually the vacuum poisons and the way we noticed this is our anti-proton start having lifetimes that are measurable. 376 01:01:19.110 --> 01:01:27.630 Mark Kushner: But when the experiment is clean The anti protons don't have a measurable lifetime in the amount of patients that were willing to do, which is about 12 hours. 377 01:01:29.820 --> 01:01:30.090 Mark Kushner: Yes. 378 01:01:31.710 --> 01:01:41.910 Mark Kushner: too big things that you put into this one is magnetic field and the other one maybe the laser for the magnetic field, what is the main constraint on the noise induced. 379 01:01:43.020 --> 01:01:43.500 magnetic. 380 01:01:45.090 --> 01:01:48.150 Mark Kushner: It was one of your key points so. 381 01:01:51.330 --> 01:02:00.240 Mark Kushner: brookhaven is really good at making specialty magnets they have a unique process for making crazy shape magnetic fields. 382 01:02:01.650 --> 01:02:16.860 Mark Kushner: But nonetheless they do not lay the wire down precisely where you think they're going to lay the wire down Okay, especially uniformity, is the issue you're talking about so that's one of the issues that we're going, we need to talk about the other issue is. 383 01:02:19.680 --> 01:02:31.110 Mark Kushner: I was talking about this a little bit earlier in the day, you would think if you just take a simplest superconducting magnet a solenoid right, you would think that if you take the current leads to the solenoid. 384 01:02:32.040 --> 01:02:41.220 Mark Kushner: And you stop all the current in the solenoid so you have zero you genuinely have zero current running to the solenoid you would expect that the magnetic field inside this own it would drop to zero. 385 01:02:42.570 --> 01:02:46.950 Mark Kushner: It was a shock to me when I learned that it doesn't. 386 01:02:49.050 --> 01:02:57.390 Mark Kushner: So why is that this has to do with a phenomenon called residual fields, if you take a superconducting wire here's a long. 387 01:03:02.610 --> 01:03:03.120 Mark Kushner: How many. 388 01:03:04.260 --> 01:03:17.730 Mark Kushner: All right, that'll do if you take a superconducting what am I oh yeah that's super ducting wire, this would actually been in helix if it was in the solenoid but let's ignore that okay and you're running current this way right. 389 01:03:19.590 --> 01:03:25.290 Mark Kushner: So, you would think that's the only current, but in fact it's not the only current within the superconducting filament itself. 390 01:03:26.760 --> 01:03:43.890 Mark Kushner: Which this might be only a millimeter actually it might be a lot thinner than a millimeter, you will know, nonetheless, get current loops which are totally contained within one wire within the wire and these current loops add up substantial fields 10 gauss maybe sometimes. 391 01:03:45.120 --> 01:03:54.060 Mark Kushner: And you can't control them because it has current loops are not going to the outside, the only way, you can truly get rid of them is to warm the magnet up. 392 01:03:55.350 --> 01:03:58.140 Mark Kushner: And let them become non superconductors. 393 01:03:59.520 --> 01:04:20.940 Mark Kushner: But on the other hand, they do decay and they decay because, while the resistance along this path is essentially zero because it's a superconductor the conductance which is proportional to the area of the path is also very near to zero, so the decay time ranges from one second to. 394 01:04:22.260 --> 01:04:27.000 Mark Kushner: lot of them decay within an hour, almost all of them are decay within a couple of days. 395 01:04:28.710 --> 01:04:33.660 Mark Kushner: So this is a huge source of error for us that's beyond the mechanical construction. 396 01:04:34.890 --> 01:04:46.410 Mark Kushner: Of the wire one saving grace of this is that it's repeatable if you take the magnet through the same cycles over and over again, you get the same fields over and over again. 397 01:04:47.730 --> 01:04:53.520 Mark Kushner: Okay, I won't be Armor htc know they're they're just standard superconducting wire. 398 01:04:55.380 --> 01:04:56.880 Mark Kushner: And there are things you can do. 399 01:04:58.590 --> 01:05:05.550 Mark Kushner: We learnt this message this lesson the hard way it didn't really matter, it was just a big puzzle, but for this gravity experiment. 400 01:05:05.850 --> 01:05:12.570 Mark Kushner: We have special wire that instead of having large size filaments I don't know if you know this, but superconducting wire. 401 01:05:13.080 --> 01:05:18.810 Mark Kushner: Is a set of filaments embedded in a copper matrix the copper is to take the current if there's a clinch. 402 01:05:19.800 --> 01:05:27.390 Mark Kushner: Okay, and tip the wire that we tend to have before had maybe 20 filaments the wire that we now have has. 403 01:05:28.050 --> 01:05:42.900 Mark Kushner: 640 filaments if I remember correctly, each of the filaments is much, much smaller What that means is that the indications of each individual filament is much, much smaller, and so they were hoping that this means that a lot of fields, will decay away faster. 404 01:05:44.460 --> 01:05:51.210 Mark Kushner: So we don't have to worry about them, but that's why we need the ECR technique to measure what the field is because. 405 01:05:52.350 --> 01:06:02.670 Mark Kushner: We can try to be as careful as we want construction, but we still got this problem, which is only can be determined by measurements and this dominates our power supply noise. 406 01:06:04.230 --> 01:06:08.850 Mark Kushner: I mean it helps you the high inducted to the magnet helps us. 407 01:06:10.320 --> 01:06:19.470 Mark Kushner: power supply noise is a big problem if you're trying to have two coils which have exactly the same current we have dcc to do you know what those are. 408 01:06:20.340 --> 01:06:34.320 Mark Kushner: Okay DC cities are magic it stands for direct current current transformers transformers that work at DC don't even ask every time I look up and try and understand how they work general relativity undoubtedly. 409 01:06:36.090 --> 01:06:41.640 Mark Kushner: Nonetheless, they're fantastically accurate, they are accurate, they can measure currents to one part per million. 410 01:06:42.960 --> 01:06:51.150 Mark Kushner: they're also fantastically expensive they're about $10,000 apiece we have about 30 of them, sadly, on our experiment by now. 411 01:06:51.720 --> 01:06:56.820 Mark Kushner: And we can feed back their measurements to the power supply so that gets rid of some of the noise. 412 01:06:57.210 --> 01:07:07.140 Mark Kushner: But fundamentally in the end, if we want to do a balance experiment, what we need to do is to run the same current through both coils that are doing the balance like this. 413 01:07:07.560 --> 01:07:13.470 Mark Kushner: And then, if we want to shift the balance, a little bit what will run is a typical supply that powers, only one of them. 414 01:07:14.340 --> 01:07:27.150 Mark Kushner: which can be a small say 10 Apps applies as opposed to the hundred Apps or so that we would normally be using and that way we can get around most of the power supply noise because it's common to the balance experiment. 415 01:07:33.000 --> 01:07:33.840 questions. 416 01:07:35.700 --> 01:07:51.330 Mark Kushner: two to two quick ones, so what what is so far early temperature Father just wondering how is that psycho psycho could you comment on how much energy and time to take to be microscopic. 417 01:07:54.120 --> 01:08:05.760 Mark Kushner: Let me deal with what we deal with the first question first it has anybody had the misfortune to have either read the book or seen the movie angels and demons. 418 01:08:08.790 --> 01:08:09.330 Mark Kushner: yeah. 419 01:08:10.710 --> 01:08:27.360 Mark Kushner: sorry about that that book was based on the Athena experiment, the predecessor to this experiment in which they have, I think, nine seven grams of macroscopic material people at CERN have calculated that it would take. 420 01:08:29.700 --> 01:08:38.790 Mark Kushner: Roughly the entire world's energy production for roughly 1000 to a million years to make that much antimatter. 421 01:08:39.840 --> 01:08:42.480 Mark Kushner: it's really not a prospect. 422 01:08:43.530 --> 01:08:51.240 Mark Kushner: As for how we measure the temperature there a fair number of complications here, but we can put our plasma in a trap. 423 01:08:53.850 --> 01:09:05.070 Mark Kushner: like this Okay, and this is grounded say and let's deal with positrons because it's easier, just to think about this so positrons might make this plus plus. 424 01:09:06.210 --> 01:09:16.980 Mark Kushner: I don't know 10 volts or something like that maybe 20 volts and then we can take this potential and what we can do is as a function of time we can lower it from. 425 01:09:17.400 --> 01:09:23.220 Mark Kushner: Starting at some point, it was at plus 10 volts and we can lower it slowly down to ground. 426 01:09:24.000 --> 01:09:30.900 Mark Kushner: Okay, as we do that eventually particles will start to evaporate the hot particles will start to evaporate first. 427 01:09:31.410 --> 01:09:49.230 Mark Kushner: And from measuring the time history, or more precisely the voltage history of the voltage and the number that get out, we can measure the temperature, this is easy to do at 1000 Calvin okay to do it 100 kelvin and very, very difficult to measure at 10 Calvin because, for reasons I. 428 01:09:50.970 --> 01:09:57.450 Mark Kushner: It would take me a bit to get into fewer and fewer of the positrons contain temperature information. 429 01:09:57.840 --> 01:10:17.670 Mark Kushner: As the plasma gets colder and colder electrostatic information becomes more important and temperature information with called plasmas so to measure, a 10 kelvin plasma, you have to do it the measurement on something like 100 300 positrons, and that is noisy to measure. 430 01:10:18.780 --> 01:10:35.130 Mark Kushner: that's it is, it is Maxwell and when you do that distribution what comes out is basically as an arrow function what comes out with a complicated argument, the beginning of what comes out is exponentially increasing. 431 01:10:36.240 --> 01:10:47.250 Mark Kushner: So we look for that exponential increase in measure the the gamma in the to the gamma V whatever, and that gives us that's proportional to the temperature. 432 01:10:52.740 --> 01:10:55.740 Mark Kushner: Okay, one last question why didn't be electron phone. 433 01:10:59.850 --> 01:11:06.960 Mark Kushner: Okay, this is just speculation on the part of many people and it's not my speculation, though, it sounds pretty reasonable. 434 01:11:09.450 --> 01:11:11.310 Mark Kushner: It was completely unexpected. 435 01:11:13.710 --> 01:11:18.090 Mark Kushner: But what fair banks was doing is he had a big tube I will draw the tube. 436 01:11:19.140 --> 01:11:20.640 Mark Kushner: I will attempt to. 437 01:11:23.190 --> 01:11:24.150 Mark Kushner: i'm just going to draw. 438 01:11:25.380 --> 01:11:29.550 Mark Kushner: A half section of the tube okay so here is his tube right. 439 01:11:39.300 --> 01:11:42.660 Mark Kushner: So this is some magnetic material, maybe copper. 440 01:11:45.360 --> 01:11:46.800 Mark Kushner: Maybe it's gold plated copper. 441 01:11:49.500 --> 01:11:50.310 Mark Kushner: And he put. 442 01:11:51.480 --> 01:11:52.530 Mark Kushner: An electron here. 443 01:11:53.580 --> 01:11:56.310 Mark Kushner: and gravity port pointed upwards right. 444 01:11:58.710 --> 01:12:00.000 Mark Kushner: Anything else going on there. 445 01:12:01.980 --> 01:12:07.950 Mark Kushner: Any I guess i'm sorry very charming, yes, there is a mirror charge but beyond the mirror charge. 446 01:12:11.610 --> 01:12:16.230 Mark Kushner: Well simplest model for metal as there's an electron gas. 447 01:12:18.270 --> 01:12:26.820 Mark Kushner: The electronic gas is influenced by gravity right So what does the electronic gas do it tends to congregate at the bottom. 448 01:12:33.180 --> 01:12:36.450 Mark Kushner: Right When does it stop congregating at the bottom. 449 01:12:37.560 --> 01:12:39.450 Mark Kushner: When it generates an electric field. 450 01:12:42.330 --> 01:12:42.750 Which is. 451 01:12:44.550 --> 01:12:45.900 Mark Kushner: An electric field which is. 452 01:12:47.340 --> 01:12:54.690 Mark Kushner: Pointing well downwards, but that is a force that is pointing upwards right and you'll reach a balance. 453 01:12:55.980 --> 01:13:03.630 Mark Kushner: And, as he know if you have a cylinder like this just if you have an electric field in the wall you're trying to have an identical electric field. 454 01:13:05.670 --> 01:13:18.720 Mark Kushner: Inside the cylinder and it is by design because it's coming from electrons it is by design exactly what you need to cancel gravity on the electron in the Center. 455 01:13:22.230 --> 01:13:27.060 Mark Kushner: So Okay, this seems simple right, you can measure that you can take your multi meter. 456 01:13:31.410 --> 01:13:32.040 Mark Kushner: multimedia meter. 457 01:13:33.090 --> 01:13:38.130 Mark Kushner: Okay, and you can put one lead over here and one lead down here, and you can measure the potential right. 458 01:13:42.180 --> 01:13:57.120 Mark Kushner: There yeah you're going to get exactly the same effect inside the wires of the Multi meter, the only way to measure this effect is to drop an electron and see it fall if you did drop the positron What would you expect to see. 459 01:13:59.580 --> 01:14:02.430 Mark Kushner: It would fall twice as fast as you would expect it to fall. 460 01:14:05.880 --> 01:14:09.540 Mark Kushner: Anyway, it's speculation, he never did do the positron. 461 01:14:13.560 --> 01:14:16.380 Mark Kushner: mean it's really well established legend that he did, but he didn't. 462 01:14:17.730 --> 01:14:24.450 Mark Kushner: At least I can't find any record of it in the literature and that's what everybody looked into it, the reason he didn't do it. 463 01:14:26.760 --> 01:14:28.380 Mark Kushner: it's one of the reasons why. 464 01:14:29.430 --> 01:14:44.310 Mark Kushner: Most people think that you need to use neutral matter to do a gravity experiment, because otherwise electrostatic forces are are too large, but i'll tell you another reason why this is a really difficult experiment to do. 465 01:14:45.600 --> 01:14:46.110 Mark Kushner: You think. 466 01:14:47.550 --> 01:14:57.030 Mark Kushner: A conductor right everybody knows what a conductor is conductor, is something that doesn't sustain any electric fields inside internal electric fields right. 467 01:14:58.110 --> 01:14:58.860 Mark Kushner: That is wrong. 468 01:15:00.090 --> 01:15:00.780 Mark Kushner: As the. 469 01:15:01.800 --> 01:15:18.660 Mark Kushner: Atomic physicists people have difficulty people doing quantum computing these days are finding out much to their dismay they're actually very large if you just take a copper they're very large and large electric fields on the surface of that copper. 470 01:15:19.710 --> 01:15:23.910 Mark Kushner: There are fields on the order of one vote per centimeter. 471 01:15:26.220 --> 01:15:26.550 Mark Kushner: and 472 01:15:27.570 --> 01:15:37.620 Mark Kushner: it's really confusing to me where these forces come from, but some of it comes from grain boundaries and the crystal structure of the copper that's inside, if you have a grain down to you. 473 01:15:38.340 --> 01:15:46.290 Mark Kushner: I can say some fancy words which I don't know what they mean you have a chemical potential due to the grain battery that is causing electric fields. 474 01:15:47.460 --> 01:15:49.410 Mark Kushner: To test all right. 475 01:15:51.390 --> 01:15:51.930 Mark Kushner: and 476 01:15:53.160 --> 01:15:55.950 Mark Kushner: Other things could be could be. 477 01:15:57.780 --> 01:15:58.800 Mark Kushner: layers of. 478 01:16:01.230 --> 01:16:12.810 Mark Kushner: oxides on the surface, whatever you have very strong electric fields, they may not be quite as large you can an old the old people here will have heard of aqua dog. 479 01:16:13.830 --> 01:16:27.540 Mark Kushner: Right it's a carbon code is a spray on carbon coding aqueduct tends to reduce these fields substantially and it's used in a lot of these traps now, but not only do you get these these traps at the Center. 480 01:16:28.230 --> 01:16:35.730 Mark Kushner: i'm sorry the wall, you also get these electric fields in the Center, and that makes it really, really difficult to do a gravity experiment, because the electric. 481 01:16:36.030 --> 01:16:48.570 Mark Kushner: forces are so much greater than gravitational forces and, by the way these patch potential fields are what causes are anti-proton so single anti protons to leave so quickly, this is what my undergraduate Andrew realized. 482 01:16:49.680 --> 01:16:52.410 Mark Kushner: And can now measure the size of the potentials. 483 01:16:56.400 --> 01:16:57.450 Mark Kushner: Thank you so much for.