 Okay, let's let's go ahead and get started. So I'd like to welcome everybody to the last department speaker series event of the fall term the winter colloquium. And I don't have any announcements so I'm just going to go ahead and turn things over to the host for today's speaker Professor Jody Cooley who'll make introduction. It's a great pleasure for me to introduce Dr. Dave Nygren today. Dr. Nygren Dave was one of the professors are guess not really I guess you were a doctor not professor at lbnl, but certainly one of the most senior people that I worked with. When I was a graduate student working on an experiment at the South Pole called Amanda, which is now the predecessor experiment is something called ice cube. I don't know if you'll talk about that today but it is a really interesting experiment. We should get a talk here about it sometime. So Dave is the presidential distinguished professor in the University of Texas at Arlington, his research interests have ranged from electron positron colliding beams. Key violation in neutral chaos, the astrophysics of neutrinos medical imaging to most recently an intersection of nuclear physics neutrinos cosmology and biochemistry in the search for neutrinos double beta decay. Within his span of research he has always been focused on improving experimental techniques. He's the inventor of the time projection chamber currently a preferred choice for searches for dark matter and neutrinos double beta decay. He has received his bachelor of arts and mathematics and physics with honors from Whitman College and a PhD from the University of Washington in Seattle. He held postdoctoral and assistant professor appointments at Columbia University, before accepting a position at Lawrence Berkeley laboratory. He remained at lbnl for several decades, decades rising to distinguish scientists. He's now currently a professor at UT Arlington, of course, he's a member of the National Academy of Sciences, a fellow of the National Academy of inventors, and a fellow of the American physical society. He has numerous awards that have spanned his entire career. Starting with the Department of Energy E. O. Lawrence Award in 1985, to most recently, the IEEE Marie Curry Award in 2018. He was a recipient of the breakthrough prize award. And just a number of others and I'm not going to list them all but he is really a distinguished scientist, and we're very fortunate to have him here today to tell us a little bit about the history of experiments in particle physics. Thank you, Jody. I guess the microphone's on. I'm really delighted to be here and tell you a little bit about something that we don't often hear about. So, my history for you today is pretty selective and biased. There's really too much history to get into the whole thing we've got almost a century to cover today. I want to emphasize opportunities and found in this because my comments are mainly addressed to students who are learning how to do things, the faculty already know how to do everything. So maybe I can give you some hints that will be helpful. I wish I could talk about everything, but a lot of things are not going to get much attention. And of course I've stolen slides from people who may know this field better than I do. I want to give acknowledgement to that. So I see a value in kind of segmenting this into four distinct epochs, the Bronze Age where people were finally figuring out there are particles and the way this was generally found is that many particles would induce a visible signal together. The next epoch was what you might call the Age of Discovery where single particles were found either in an imaging way or by an electronic way. And then finally we reached the Golden Age where we have the ability to reconstruct and understand extremely complex events. And the present era which I think money particle physicists in the audience would agree with is the megalithic era where we have huge everything, huge amounts of data, huge systems, huge detectors, huge networks, everything is huge. So again, we might even usefully distinguish between imaging techniques and more logic techniques. This is actually the title of a book going over many of these things by a Harvard professor. The imaging techniques were the ones that first got us into this field. We'll look at those first. But even from the early times, electronic schemes emerged as well. And eventually today, almost all things are done with electronic techniques. Here's a complicated plot. I'm going to stand a little bit aside to try to illustrate. The story begins just before the turn of the century with the discovery of x-rays, radioactivity and electrons. And leading to the discovery of atomic nucleus, isotopes, the discovery of quantum mechanics and working it all out. There was also the discovery of QED, the discovery of the muon by Anderson and the positron by Anderson, the discovery of elementary particles, pions and cairns, and so on. This is a steady march of discoveries up here. My story ends right around here because there's just too much, there was an explosive set of advances then and that's really another lecture, but we'll see what we can do. And the bottom side of the chart are those techniques that emerged. First, there was the idea that you could actually see single particles just by looking for what they do and something that makes light. The cloud chamber was developed in around 1910 or 11 by CTR Wilson. The Geiger-Mueller counter is an interesting story. I'm going to talk about that. The coincidence circuit is an interesting side story. I'll talk about that. A device that detects single photons, the photo multiply was developed in the 30s, which remains a mainstay of particle physics and medical imaging. Another technique is the nuclear emulsion, which had a longer life than one might have thought. The bubble chamber was invented possibly due to watching a glass of beer with bubbles, but that story was never confirmed in all of my years at Berkeley. I never found anybody who said, yes, that's the way Glazer really invented it. Some other semi-electronic techniques, spark chambers, the multi-wire proportional chamber was a revolution, and that led to some other inventions here. And then unfortunately, I will run out of time or you'll all go out for dinner before I get to the next part. So in physics, we want to measure things like energy, the momentum of a particle, its speed, which is connected to these two, where it's going. What kind of particle it was? Does it have electric charge? What sign? What are the patterns that groups of particles generate? What happens before something else? And of course, when did something happen? But our signals are something that are really quite disconnected from these directly. We can measure ionization when particles liberate charge. We can measure light when particles excite atoms to emit light. Cherenkov radiation, transition radiation, which is a weak effect liberating x-rays at dielectric transitions. When a magnetic monopole passes through a circuit, you can see a signal that way if monopoles exist and so on. Finally, there's just simple vibrations in lattices, the phonons, acoustic signals, or heat. So that's it. How do we connect all these with the various areas to get the information? A common principle in doing so typically is that there's some gain mechanism. The signals are so tiny by themselves, individual particles just can't be seen unless we have some other way to turn that into a signal we can see. There are also common enemies, noise, or backgrounds, particularly in the search for dark matter or rare events. Backgrounds typically from radioactivity are the Bet Noir, the thing that can kill or make a search successful. So this is the challenge we've faced since the turn of the century, how to connect the left and right half of this plot. Now, probably the first one of interest is the spin theroscope. William Crook spilled some expensive radium salt accidentally on a zinc sulfide screen. How strange is that? An accident, he tries to recover it, so he looks at the screen under a microscope and he sees flashes of light coming from the zinc sulfide, which is a kind of simulator. He invented this thing called the spin theroscope from the Greek word spark. Interestingly, when I was a kid, I could see those alpha particles in my glow-in-the-dark wish spot. I'd stay at night looking at it and boom, there they'd come in that hand would light up and then fade away. It was great. I don't know if that contributed to cataracts or not, but it was great. Now, turning to other kinds of chambers. People were interested in what causes clouds, and they saw that steam engines also caused condensation in the lab. And so people started with a dust chamber because they saw the droplets of water formed around dust particles. What's going on? So this is a form of amplification. A dust particle is a creaking, something that then you can see it, perhaps more clearly. So this Scottish meteorologist, C.T. R. Wilson, built a cloud chamber before the turn of the century to try to study the influence of electricity and ions on the formation of water droplets. And he knew that the air showed slight natural conductivity. That was of course due to cosmic rays, which nobody had any idea about. So he was trying to understand things like the Brock inspector, which is this kind of picture here. He found, whoops, sorry. What happened here? Oh, that was interesting. Just pretend you didn't see that. So the cloud chambers actually, oh, I know what I'm doing, sorry. Cloud chambers stayed productive for a long time, but they're really gone now. So what's going on here? I'm not sure, but I think this is a vacuum vessel that was allowed to reduce the pressure suddenly in this little chamber up here. And this is where the vapor would become super saturated and the particle tracks would appear. This is what stuff look like back in those days. These are pictures of tracks in a cloud chamber. This is not an artist paintbrush. These are alpha particles emanating from a common source because they all had the same energy. They would all go pretty much the same distance. Now, some of you may have noticed that is that a hair that got away or something like that. That's the decay from an excited state where the alpha particle got all of the energy instead of the gamma ray that normally would have carried off that extra energy. On the left, we see really scraggly tracks from electrons, which scatter a lot in the gas. And then what happens after a while is the tracks just kind of fade away just like the Cheshire cat. This was a very powerful tool to visualize single particles. And the amplification factor was the condensation around a single ion. Turning more to the physics, Arthur Compton explored the scattering of x-rays on electrons, which is now known as the Compton effect. A gamma ray comes in or an x-ray hits an electron, knocks it out. The new gamma ray or x-ray goes in some other direction with different energy and it can also interact producing a second event. And if you know some of the energies and the angles here, then you can reconstruct what happened. And here's an image of a collision which produced a little track here and an angle could be more or less measured there. And then subsequently another track would appear with a related angle not quite accurately measured. And from that, he deduced that this was a process that existed in nature. I've never been able to figure out what's really going on here. Now, this is a famous, the most famous picture of a cloud chamber. It shows a lead plate in the middle and a particle is clearly going through it. Does anybody know what's going on here? What's the difference between the top and the bottom? Let's take a moment and ask, is there a visible difference between the top and the bottom half of this picture? So, everybody agree with that comment? The curvature is greater in the top than... Well, that can only be because this particle lost some energy here. And so the curvature could be greater here because lower energy particles bend more at greater curvature. So, the particle had to be coming from below rather than what you might have thought in the cosmic rays coming from the top. Well, such things can happen. But because they knew the direction of the magnetic field coming in or out of the picture here, they could tell that that had to be a positively charged particle. This was the invention of the positron. Carl Anderson was credited with that discovery. It's said that it was his editor that named the positron, not Carl Anderson. Also, the positron had been discovered, but these guys did not publish. So, Anderson got credit for the discovery and got the Nobel Prize. There was an even earlier discovery nobody's ever heard of. So, this is an interesting commentary on how credit is given. It's not always necessarily to the first, but some will really make the discovery most clearly or most definitively. Now, also in the 30s, Marietta Blau and her colleague pioneered the nuclear emulsion technique. These are basically just very fat photographic films that could also be developed and produce images of what was going on. In these films, spectacular events such as this one could be found and where somehow a nucleus exploded into constituent fragments. This was the first proof that nuclei probably weren't really immutable. And it showed at the level of precision, a few microns, that it was a single particle doing this. And so this was a big discovery. And here the amplification effect is the development process which takes a grain of silver or whatever it is, and it amplifies during the chemical process to turn into a grain that can be seen. This was a major advance and the emotions were critical for that. Quickly, Cecil Powell discovered the pion in cosmic physics using nuclear emotions, and later the kion was discovered by Rochester. So here comes a pion, this is just a snipped out part of an image, and it stops in the case and the muon goes a certain distance and then it decays into an electron. So they found that this is a very common pattern that the pion would stop, and the muon, the particle of kion, always had a fixed range. And that showed it was a two-body decay of the pion going to a muon and then the neutrino in the opposite direction. Here's an example of a k-mison coming in, the emotion, decaying into three pions as shown here. Well, Marietta Blau was written out of the story. Her part was critical later. She had a very difficult career driven out from Vienna by the Nazis. Erwin Schrodinger eventually got her admitted to the Austrian Academy of Sciences, but it's one of those stories of how women were badly treated in those times. Now in 1952, about that time, Donald Glazer invented the bubble chamber, and this led to a tremendous development of these devices. Here's one based on heavy liquids in which muon neutrinos came in and produced electrons. This is known as a neutral current event. This neutrino did not turn into a muon, turned into an electron, which is visible by the amount of scattering it did. And these things became very large. This is what the heavy liquid bubble chamber of Gargamel. The biggest one was the one built in CERN, the big European bubble chamber. Here's the piston that allowed it to go from an unsaturated to a super saturated one that would produce the bubbles. One hopes that the young lady here isn't pushing too hard on that because it looks like it's about to fall over. Probably it was held up, but it looks kind of scary. You can see the tremendous quality of the images, even though there's a lot of noise. There's a particle that comes in and makes a very complicated event, as you can see. If the bubble chambers are filled with something simpler and lighter like hydrogen, the scattering is much less. Here's a kaon coming in, decaying into a pion, which then decays here into a muon and loses energy and produces this gorgeous spiral. Sorry, this is an electron from a conversion of a photon. The higher energy one went straight. The muon is here decaying into this electron. So you can see that the quality of these was lovely and a lot of physics was learned with the bubble chamber. This is the most famous image ever made by a bubble chamber. This one taken by the 80-inch bubble chamber at Brookhaven. Berkeley had a 72-inch bubble chamber. Everybody was competing. Fermilab had a big bubble chamber, too. K Meson comes in here and produces an omega minus. The crowning achievement of the quark model was revealed in this event. A strangeness minus 3 particle, which then goes on to have a complicated decay, which could be completely reconstructed in this event. They could only be made sensitive, maybe a few per second, or the big ones, even less. Thousands of kilometers of film had to be looked at by humans. Machines were built to scan and turn the images into measurements, but then suddenly they almost died off when electronics reached an unexpected but completely transformational point. They're back, though, now in a very restrictive way because they can be made insensitive to gamma rays so that they can be sensitive only to nuclear recoils and they can reject gamma rays. So this is a really interesting aspect that some detection techniques really never die off if they have special qualities. Oh, I should mention nuclear emulsions had a renaissance, too, looking for the oscillation of a muon neutrino into a tau neutrino, the third lepton. And they sent beams of neutrinos through Europe to Italy, and they're a huge stack of bricks that were consisting of sheets of lead and nuclear emulsions, plus other detectors that could see the events and point back to a particular brick, and then looking in the brick with automated scanning machines, you can see how tedious this might be. You could find out what happened, and this could show that there might be an interaction of interest. So this is an example of that at a fairly large scale. This is the beam side view zooming in. You can see this little track here. That's the tau particle itself. And then the beam direction is this way. You can barely see the little kink in the track here of the daughter. So that would prove that the tau neutrino exists as well. I'm going to switch gears now to the next side of things. These names that are very familiar to us, Ernest Rutherford and Hans Geiger, single ionizing events using electrical techniques in 1908. These papers are really fun to read. They're charming. They have the flavor of a letter to friends that you might dash off. The apparatus was a reservoir of radon with a stopcock. They could let some radon into this little chamber. A tiny window allowed a few alpha particles from the radon decay to get into this cylindrical vessel with a thin wire down the middle with voltages applied across here. A signal could be generated here in the wire. And I'll talk more about that. So you'll find language like this. It has been recognized for several years that it should be possible by refined methods to detect a single alpha particle by measuring the ionization it produces in its path. And they went on to describe how they did it. They mentioned this fellow Townsend, and I'm going to get back to him as well. They used this technique of producing avalanche amplification of a single particle or a few particles to produce a viable signal. So the way of detecting it was to look for a deflection in the mirror so a light beam came in from one direction and they'd watch for the spot of light on the opposite side to deflect just a little. So the part of their apparatus was somebody watching that spot of light. But it worked. Now, moving ahead to 1928, Hans Steiger and Walter Mueller. I'm sorry for the complexity of the slide, which I stole, but it's still a very good one. You can imagine a cylindrical container a tube with a wire down the middle that's much, much smaller than in this drawing with a voltage across it so that the electrons are attracted to the wire and ionizing particles through will see the electrons move toward that wire. Because of the one over our field. At some point they will get to an energy between collisions that they can actually ionize other atoms in the gas or molecules, and you can get similar you can produce simulations like this where one particle comes in and produces a large number that arrive here, producing an electrical signal. The difference between the proportional counter that brother Fred was using is that the avalanche is stuck to a small region on the wire was in the Geiger Mueller tube it spreads along the wire. And that produces a much larger signal. The Geiger tubes are filled with something like neon or helium or argon plus some kind of organic paper. I don't have time to go into all of the interesting details, but I want to take a moment to tell you how the Geiger Mueller counter was really invented just by the greatest chance I happened to meet the granddaughter of Walter Mueller. And she gave me this piece of an old newspaper which discussed how it was actually discovered. So it started out with Mueller giving an old brass tube by Geiger and brother Fred was asked him to look at what's going on so it was known to produce some kind of signals. And he discovered when he had it all set up that it was behaving strangely and would sometimes produce pulses on its own but the rate was highly variable paced around the room under unable to understand what was going on. And he realized that when he was standing in one position, the rate was greatly reduced effect was reproducible a good scientist he did the experiment several times. He turned around and open the door to the room behind him anybody have an idea what might have been in that room behind. Yes, and radium next door. And so he realized that his body was shielding his special spark counter. So, he told that to Geiger and Geiger think we're the only people who know this wonderful instrument we shall make it known and a host of physicists, very biblical somehow and but they appreciated the importance of the discovery. So in a sense the Geiger Mueller tube was discovered more than it was invented but I don't want to take anything away from them. They didn't seek a patent and the device is still used today. I recently had a nuclear medicine test, in which I absorbed 20 millicures of technician 199. And so when the kids brought up their tiger counter now I really saturated it. So, it was even useful today for that purpose. I don't think I have time to discuss this too much but what goes on in the molecular gaseous electronics is interesting. The alcohol is particularly important because the argon produces an ultraviolet that travels a certain distance some of those go along the wire. They ionize the alcohol and then they can spread this way at a certain speed along the entire length of the wire, the only way I can stop it is to reduce the voltage on the wire. It's clever but there's even more interesting physics that I probably don't have time to talk about. Also in the 30s, a very interesting vacuum tube development came called the photo multiplier to this is a tube. Here's a piece of scintillator that produces light ionizing radiation can produce light some of that hits the surface and just on the inside of this high vacuum region and produces a photo electron. You can get the Compton effect but you have very low energy by accelerating that photo electron toward a very thin structure here. More electrons come out and arrived maybe a factor of three by repeating this a few times you can get three to the nth and finally you get a large number of electrons arriving at the anode. And you can see it. Modern photo tubes don't work this way. And here you can see how one was built like that in the old days. You can even have silicon photo multiplier tubes in which each of the little pieces of silicon is filled with tiny dots that support a Geiger mode avalanche within the silicon. And so these have also become an important part of the arsenal of particle physics techniques. Here's one that is particularly interesting. Walter both have received a Nobel Prize in 1954 for the coincidence circuit. I'm old enough to know exactly what's going on in the circuit of two signals come in here at the same time to short signals. It will raise the potential, make the more positive on these two grids, the electrons can then get to the plate here. Also known as the anode and produce a signal here. But if only one of those signals is present, the other grid will prevent the electrons from going to two signals have to be present at the same time. Now, the idea of a coincidence circuit is conceptually identical to the answer to which every student of computer science knows from day one, it occupies a tiny spec inside some piece of silicon. So how things have changed. Something that seems so obvious today was not obvious then. And it was a big advance in being able to sense, for example, got a row of detectors up here. And another one here and you require coincidence between this one and now you had a good chance that some particle went through something called a, for example. Interesting. I saw that the proportional counter was even sort of around in 1912 or 19 eight. There are many other different kinds of one sees in the 30s and 40s. Here's one with several wires and a thin window to let particles get in other geometries, circular ones. Many wires between plates. And we're all connected to a single circuit because the electronics to produce a signal from all of that with about the size of a lunchbox. And there was a limit to how many lunchboxes you could probably put in your circuit in your experiment. I should take a little detour to talk about spark chambers that you developed in the 60s. There's a kind of stage photo of male Schwartz in front of an experiment of Brookhaven, looking for particles. What do neutrinos do when they pass through steel and then they interact. They made a nuance they didn't make electrons because almost all of the neutrinos were made from nuance. There was a very popular detector for a while. You had to know when the particle came through here's a plastic scintillator producing a fast signal. Another one, here's the coincidence circuit. And then you put a fast pulse, you can cause sparks to form where the ionization trail occurred. And these could be made as large as that table, or even larger as large as that blackboard. And so these were very popular for a while. The spark chambers disappeared except for display units. And what happened, it was the invention of the multiwire proportional chamber. A joy shark back at Surin in 68. Now what he did is he said, okay, I'll make a plate here just like the other proportional count is this might be two centimeters apart. But he put the wires very close together in a common gas, just like you'd seen before. These are only about two or three millimeters apart now. What made it possible was that he had integrated electronics to actually put individual signal circuits on each of those wires. There's an old picture of Sharpaq with Fabio Saleh and the super technician John Claude Santiago. And so he's one of my heroes not only because of his contribution to physics but as a humanist. And of course he was recognized with the Nobel Prize in 1992. And we see again that the ideas that were kind of around there were parallel plates with lots of wires, but nobody before Sharpaq it thought, well, I can put a circuit on each one of those wires I don't have to gain them all together. Seems obvious now, but it wasn't then it struck everybody as a bolt from the blue. So many of these large systems were built. There's a set of six chambers they maybe they only measure the vertical position the wires are horizontal to get a very good measurement of the tracks in this plane. You could put more chambers with the wires vertically and get the other to get the XY position of the particle track. These are very powerful and many systems were built. There's a problem if you have more than one particle. Suppose you have n particles going through here's a n when particles went through my detector with six vertical coordinates and six horizontal time. You have 100 you have 36 possible combinations of those independent x and y graph. And you only have six correct one so you can see that this gets to be kind of a nightmare, particularly if the chambers are not fully efficient. You can put chambers at various angles to try to resolve okay there's one was out here that could be another one, but the anguish rises quickly and you really can't keep this up for very complicated events. So about this time. Another variant on this theme was invented by Volenta Heizer and shoreline a drift chamber again if you know when something happened, and the particle left to the ionization child, you could measure the time relative to that signal. To when you see a signal at the end of then you could drift maybe several centimeters this way. You could measure that timing and that's why it's called a drift chamber. The problem with this is that typically the magnetic field would be out of the plane of the screen give curvature to the track to measure its momentum. You can also feel that E cross be effect, and they tend to curl around, and there's a distortion of the tracks, and it complicates the interpretation of time and distance. And again at about the same time, Wade Allison at Oxford developed something called equal ISIS identification of secondaries by ionization sampling. He wanted to know what kind of particle is, and by measuring the ionization density, along with momentum information, you have a good chance of figuring out what kind of particle this. So here's an image where drifting in this direction say either down or up I don't know which way. There's some bad circuits here. It's drawn to the eye these are not I'll just draw it's lots of other particles particles in the picture here as well. But this is clearly an impressive device. And he put this behind the big European bubble chamber to try to get some particle information. He did pretty well, 7% to get some clear definition between slow moving particles. It's starting to look like a bubble chamber and it gave pretty crisp two dimensional images. So now I'm going to take the liberty to what time is it. Okay. I want to give you a little personal story because I think it has value for the young people who may worry that maybe it's all been figured out. Let's see. So I was trying to conceive a detector for a new electron positron collider and slack but I couldn't figure out anything. And I eventually had to abandon all the ideas that we knew that I just told you. And then I recalled that when I was a graduate student, we had an experiment in which there was a spark chamber inside a very high field magnet. And the electric field of the spark chamber just happened to be parallel, because that's how you had to read it out parallel to the magnetic field. And then when the magnetic field was on those sparks suddenly became very narrow and very bright. And when the people in that experiment were analyzing the data, oh, this is great. That makes it all easier. And everybody forgot about it. But somehow that stuck in my mind and that day and Berkeley. I thought, well, maybe the diffusion of the electrons, transverse to the electric and the magnetic field can be suppressed. And that means that the electrons are forced to execute cyclotron orbits, and they can't really deviate until they hit something and then maybe they can move a little bit further out. So that's the way that diffusion could be suppressed by having a magnetic field parallel to the drift field. So while the electrons are drifting along the electric field, they can't get away because the magnetic field was keeping them. So I went down to the library and I found this thin little book by Townsend. Here he is again. And on page 20, I saw this formula. This is the diffusion constant. That's the main collision path and mean free time mean distance between collision to speed. And here's this denominator with omega squared t squared. And it's clear that if you can make the product of the two things large enough. You have reduced the diffusion. This was published in 1948. So how could it be that I was the first guy to figure this out this book was sitting in the library on page 20 there it was. But it's worse than that. He actually published all this in 1912 in the proceedings of the Royal Academy. And you can get that and there it is again, copied it out. So it's really remarkable that something so simple and so useful could have been ignored by so many for so long. But I'm okay, I got there first. So, Omega is the cyclotron frequencies is kind of like 10 to the 11th radians per second for Tesla. And so if tau can be long, this dimensionless number of time times frequency can be larger than one. If you can do that then you can basically transport information over a long distance without losing information, at least in the transverse which is the important direction where the magnetic curvature is allowing you to measure momentum. But then I discovered that Wow, and these two gases are gone and nothing is a deep minimum in the cross section around two tenths or a quarter of an electron volt. This is a very old plot, the modern versions of this are even steeper. This is known as the Rams our towns in effect. And it turns out that even if you run the detectors, we did an eight and a half atmospheres, we still have this very large product of Omega tell. So now you could have now I should mention this is just quantum mechanics in action. It turns out that in the in the quantum well that that of the argon and method, the electron can only scatter in the forward direction scattering to another angle is is just canceled out. So this is aware quantum mechanics and in the laboratory really helps. And then the next challenge was to produce a developer readout plane, I could get the XY information, and also measure the time information, the time of arrival so that you could project back. And voila, you could have a time projection chamber of the sort, you can get three dimensional information directly from the detector. So we built this little thing which is about six inches high, an alpha particle source here with a pinhole allowed single electrons to go down this little field cage. And there's a knife edge slot here, and we could map out the arrival in position by using the micrometer, put that in a magnet and twisted it around, and we reproduced what towns that it all worked out in 1912. So we built actually built this thing was two meters long meter and radius. So the electrons drift down to these wire planes here that are schematically indicated. Eventually, after much agony. We had one nanosecond resolution in the drift time which is really impressive. And the resolution in XY was 100 microns, and the energy loss information has never been surpassed, because we had this eight and a half bars. And we didn't have a, it was really kind of a Wild West scene that we were. We didn't have a real criterion how to accept the pressure. We were seeing the Fellini movie eight and a half I thought well you know that's a good number so we did that rather than some more obvious number like 10. That's a true story. So this is what one of those sectors look like it's a work of art, 192 wires measured the particle energy loss information for particle ID. 14 of these wires had little pad roads underneath where we could tell where did that avalanche occur along the wire by looking at the induced signals on the pad, and you just do a kind of center of gravity. And so these, these things were real works of art. And there's one now in UTA and in front of the Science Hall, you all come on down and take a look. So these were these things were just great. So today you've probably seen these iconic images on coffee table books they even grace reports of the DOA. Thousands of particles seen in 2D of course, have been fully reconstructed. Even more frightening is when you turn on the magnetic field such as this picture by the least caliber detector at CERN. Another event is production of a star at Brookhaven, an anti hyper triton and anti hydrogen with a strange port followed by decayed anti helium three. Now the story gets even more complicated I don't have time but people figured out ways that if you take a piece of capton with copper on each side drill holes in it, put a voltage across, you can get amplification here too. Some of those electrons will land on some detector that you can read the signal out, or you can use screens to do that instead of the capton. Lots of variations on the steam of micro structures. Perhaps the smallest one is built by Harry Grand vanderaan in the Netherlands this is an integrated circuit, you fabricate little posts and then this grid is then etched on top. So particle track then one standard TPC ionization goes down gets multiplied and you see a signal there. So the mass there is about a hundredth of a gram for one of these postage stamp size TPCs they produce beautiful images. I don't have the movie today. On the other hand, you can have a liquid argon TPC with 10 kilotons. It's interesting that the ratio of them these two is 10 to the 12 so I think the TPC takes the price for having the largest range and active masses. I shouldn't go on with that. So we kind of come toward the milestone here that there have been punctuated equilibria where something happens it's useful for a while and then something else happens that replaces that or augments it. Now in the present era, where everything is huge let's take a just a little look. One of them is the was a observatory in Argentina. Many water tanks that are sensitive to Churenko flight for cosmic shower that comes down and imaging detector actually looks for the original track before the shower develops. These are standalone devices run by solar power and communicate by cell phones. Very impressive. And it has seen energy and cosmic rays up to 10 to the 20th electron volts. Another mega left is the ice cube detector at the South Pole. This consists of 88 strings of photon detectors, very deep in the ice. They look for about one and a half kilometers down they start, and they look for neutrinos that come up through the earth, interact occasionally they do and produce a visible track. The interesting here is that this is made possible, I think by a digital optical module that can capture all of the dynamic range and all of the wavelength information and just send up the packets of digitized waveforms. Made this transformation possible. That was developed by an engineer at Berkeley not for this purpose, but just happened to be just the thing we needed to capture rapid transits that happen almost never. We have lots of time to digitize it and do what you need. That was a, that required a lot of electronics to be buried in the ice. And it was a $250 million bet that we won because everything is working very well. And this is this Dune detector, which has intended to have for 10,000 ton liquid argon TPCs where neutrinos come from Fermilab interact in the volume and drift over to planes that can detect the tracks that are produced trying to see if CP violation is made manifest in these events. Here's another mega left the Atlas detector for I don't need to tell the faculty or students here what that looks like. You can get an idea from the size of the student here, worker. And I think that's about enough. Let's just go back and take a look at this plot. There's been a few of these major advances the cloud chamber, the nuclear motions, the photo multiplier should have drawn a bubble around that the bubble chamber, even spark chambers for a while but especially the multiplier proportional chamber and the derivatives that came from them. And equally interesting story is all of the high tech stuff that happened after that based on silicon, both in integrated circuits, and in silicon detectors themselves. So, looking at all this we can say that our progress in the understanding of our universe at the most infinitesimal scale is beyond imagination. And over the century, there have been steady, but an even advances in the art of experiment. And while some of these came by surprise. Probably more often they came by making connections between seemingly disparate avenues of inquiry, like in the TPC the impact of magnetic fields and electric fields and gaseous electronics worked out by Thompson who had no idea about particle physics. So the pressing questions of today are deeply fundamental what is dark matter. Whoops. Sorry. What is dark matter what is dark energy. Why is there an asymmetry between matter and anti matter of interest to me is why is there is a neutrino its own antiparticle or not the standard model is I silent on that. Is there an energy scale beyond standard model physics that we can reach. And are there of course more fundamental principles to be found. In all of these I think it's clear that we need more advances in the art of experiment. Thank you. Okay. Okay, let me get this thing. All right. All right, so let's start with into the q amp a session here. So folks online if you want to ask a question, you can raise your hand and I'll cycle through you when you have a question anybody in the room have a comment or a question. Yeah. It's amusing when you were talking about the positron and people who had done work before Anderson. It seems like it's another example of Stigler's law of a pond me which says that the original discover for discovery, the original discovers name is never attributed to it Haley's comet. Oh, Haley didn't discover the comet vagarous is theorem known to the agent Bob of Babylonians the church or even Newton's laws he only gets the third one the other two thirds he took from somebody else so. There's a principle here. Yeah. I know it's wise to remember that names don't apply origins always right. Please. Our next question will take from keeping she who's connected online keeping you can just go ahead and unmute and ask your question. Thank you. Thank you David for this last journey for us especially for young people. Well, to get the old times so how we discovered this made this great discovery and I want to ask about for the future. Since we discovered these things that are to say, but when we go back to the to say, compare with the old time like the formula of 10 times. It seems that for the equipment technology seems to know. I mean, I don't know how to weather the correct world, but it seems that all this equipment technology is the formula of time. But the many many coming from electronics or some data issue, etc. But but this give us a sense to the future. How can we improve our technology or what we need for the future discovery with some we see something. You can. I think I understood your question. What do we really need for the future right now there's a tremendous interest in a super fast time resolution. Right. Technology is going to the high luminosity are in which there's a much is 100 collisions at once for beam crossing. And this could be these could be separated if we knew the timing to some fraction of a nanosecond. Now, I have to admit I'm not too optimistic, but I could be, I hope to be wrong, because to get that kind of time resolution typically requires a lot of electrical power. That's certainly something we need in there could be maybe some new technique to get ultra fast time resolution without dissipating a lot of electric power in circuits as we know them. So, I think that's the main thing the other thing of course is spatial resolution. Now there's no reason why we can't get spatial resolution like two microns and principle, where a particle goes. That's been too hard, except in highly specialized devices like pixel detectors. So I think what we need is what we see at least for the had run colliders extremely good spatial resolution and extremely and track their separation extremely good time resolution. Now I don't know how to do that. I did I'd certainly be working on that's the kind of thing we need. And I think it's up to the young people who are going to make those connections and see how to do this. More comments or questions from the room. Okay, Ryan, do you want to go ahead and ask your question online. Hi Dr. Niagara. It's nice to see you even though it's it's virtually again it I don't know if you remember but I used to work with you and Dr. Jones back at UTA in 2019. And I just wanted to ask and feel free if you're not to not divulge anything if you're not allowed at this point but how is the the next ton experiment going is it making pretty good progress are we expecting it to be up and running pretty soon. Yeah, what Brian is referring as to a project, among many, searching for this putative process of neutrino list double beta decay. This can only happen if the neutrino is its own anti particle and it has to have mass. We know that it has mass as demonstrated by the neutrino oscillation experiment. The main point is, the standard model doesn't tell us anything about the nature of the neutrino, it could be a direct it could be my Iran. If it's my Iran, I'm getting into a long discussion here but if it's my Iran or that could have been forced by heavy neutrinos, among other mechanisms, right at the moment of the big bang. So to search for this decay we need to get huge amounts of material and look for a long time so that kind of half lives are looking for is like 10 to the 27 10 to the 28 years, a trillion times the age of the universe. If we do see this decay. We have learned something about possibly learn something about the first trillion to the trillion to the second of the universe so this is tantalizing. It's a play of really big numbers and really big small, small numbers. Now our project is behind in a sense, but we could leap ahead. What we do is to detect the decay of a particular isotope of xenon which is an attractive candidate for double beta day xenon 136. When it undergoes double beta decay which it can emitting to nutrients. It becomes barium. Now no gamma ray which is our main background can convert xenon into barium that just doesn't happen. So, we're using biochemistry techniques called single molecule fluorescent emitting in which a molecule grabs the very mind which just to the cathode becomes fluorescent. We have already shown we can see single molecules with two nanometer resolution. If we do that then our concerns about gamma rays is the background disappears. This may be too hard. We don't quite know how we're going to do it. We saw some of the problem, not all. We're moving toward 100 kilogram experiment that won't have what we call barium tagging at the beginning. So this is a long term enterprise, we're making lots of progress toward 100 kilogram experiment, and the Spanish are Spanish colleagues intend to build a ton scale detector in Spain. We hope also to build a companion module here in the US, probably at surf, and we are working in lock step together one collaboration to see where this might go. Tune in in the next few years and we'll tell you how we're doing. That's an excellent tease. All right, we have time for one more comment or question from the room. All right, well I'll ask it then. So riffing off of exactly what you just said. Next uses time projection chamber technology right so this is a battle tested technology but what challenges did you face or do you still face in doing that kind of precision measurement of an ultra rare process what's what is what is a unique challenge that you didn't have in the sort of particle collider era. So in the absence of effective and efficient, pardon me, barium tagging we have to get rid of all the radiation. This is really heroic to try to get background molecules that are key part of the decay chains of thorium and uranium out of your detector. It's really heroic and that's what all the other experiments are trying to do one way or another. It's a challenge now to try to build in this technique which involves biochemistry. By the way, three physicists were awarded the Nobel Prize in chemistry for working out the single molecule. So it's a, we have a really a systems problem. We have to be able to see the event because the two electrons produce a very distinctive topology in the gas and maybe they go about 20 centimeters in the gas. They work for lobs at the end like a little brag peak that says other two electrons that came out. That's one way to get rid of background. If we get the barium tagging working them. Most of the background will be going anyway. So it's a really a systems problem at the imaging, you get the purity of the gas, and to get the mechanical engineering right. The problems are in principle soluble, but our main problem is to be able to transport the ion to these detectors that can see the single ions. The detectors are tiny we're looking at RF carpets that can actually levitate ions and bring them to a particular spot. It's tough, but you know this is a Nobel class experiment and it's white knuckle physics in the sense that you put your experiment together you don't know if it's really going to work until you've done so. But you know, it's the best physics I think we can do. Okay, well that it's hard to beat that kind of high note at the end so let's thank dr nigran one more time and close the event.