 Thank you everyone. All right, so my name is Fredrik Tobeson. I'm with Los Alamos National Lab So this is Los Alamos is a fairly large government laboratory in the US I'm sure you're all familiar with Los Alamos in New Mexico and can point it out on a map If you can't just go and look it up afterwards So, you know, I'm glad I came here early this week and saw some of the talks that that represented. So you already seen several talks that had to do with So the general topics of fission and different nuclear reactions So I was going to focus these two lectures this morning on Just going over the different experimental programs for nuclear data that we have at Los Alamos So I'm not really going to go into a general discussion on the nuclear reactions or The general physics topics, but try to focus on capabilities and instruments both on the Neutron production side and also the instruments we use for nuclear data measurements We have two times one and a half hours, so feel free to interrupt me and ask questions as we go I'm going to not only bore you over these three hours, but I'm going to bore myself if I'm the only one speaking in here So please ask me questions And this is not going to work. All right, so I'll just kind of give you a sort of an introduction and talk about why we do nuclear data measurements at Los Alamos and What are our strengths and what are some of the weaknesses with our program? And then I'm going to talk about the lands facility Los Alamos Neutron Science Center Which is where we do our research and we actually have well, we have several facilities out at lands But the two that are a neutron Facilities are the Luan Center which traditionally has been used for material science research and we have the weapons neutron research facility where we make fast neutrons and do more of the traditional nuclear science or nuclear data measurements Although we also use the Luan Center and especially recently we use that facility for nuclear science measurements as well And then much of our recent program is focused on fishing in different ways So I'm going to spend a lot of time talking about our fishing work I'm going to start with cross-section measurements. That's What I've started with when I came to Los Alamos And then talk about another project where we look at the Prompt Fish and Neutron spectrum for the plutonium in this case And then fishing product yields is another big business and something that we've started up and a little work on in the last sort of three to five years Total kinetic energy release in fishing is another Recent topic and then I'm going to talk about some of the other capabilities neutron capture measurements and Neutron induced like charged particle reactions and that's something we were just developing the capability But there's been some measurements that are actually starting up In the last few weeks I'm also going to mention some things that aren't really nuclear data that we do at lands Towards the very end here Okay, so you had almost two weeks now on nuclear data, so you know why you want to measure nuclear data One good reason is for nuclear energy technology and I really like nuclear power. I think that's a great energy source. So I Think it's worthwhile measuring the nuclear data we need for reactor applications And if you want to do new and advanced reactor technology You need a new type of nuclear data. So with new reactors, you need higher precision and If you do a fast reactor, for example, you care about the different neutron energy range than you would do in a thermal system And you can also save money by improving the data You can lower your safety margins if you know better the different nuclear Cross-sections and nuclear data that goes into simulating the system There's the global security aspect We use nuclear data to look at different schemes for Nucleopharynx for example, so that's another Basic motivation for us and nuclear nonproliferation And then okay, of course fundamental science Nucleus we do nuclear structure research in a group and there is a strong nuclear astrophysics Program and we go after capture cross-sections and other nuclear data in order to better understand the origin of the heavy elements in the universe so Why do those measurements at Lannell? Some of those measurements at Lannell So first of all our institution It's part of our mission as part of our mission. We're supposed to measure nuclear data It impacts our global security missions and our energy security missions Now one of the nice Things about being at Los Alamos is that we bring it together Very many very different types of expertise in this field So we do experiments, but we also have a strong theory and evaluation group In fact, a lot of the people that do the export or sorry the NDF evaluation files are at Los Alamos and Do at least in the in the fast-range a lot of cross-section and capture evaluations We also have our colleagues that work on the benchmarking of the data and we have the users of the data the people that actually take our data and use that in calculations so When you do measurements or do experiments at Los Alamos You have a chance to actually go up to the next building and talk to some of the people that do the evaluation And that's usually how you convince them that your measurement is better than the other guys Measurements and they take your your data and weight that differently in the evaluation I'm not saying it should work that way, but that's actually how it how it usually is When I was a graduate student and measured a cross-section I think it took five years before it showed up in an X4 and when you're since I came to Los Alamos when we do a measurement that usually shows up in the library the next few months or so So our measurement program Has the advantage of having a rather nice neutron source the Lens facility And I'll show you some some detail about that facility It's I think one of three explanation neutron sources That do where you do nuclear science in the world. So there's Los Alamos there's end-of-of-course that we hear about this afternoon and PMPI in Russia and I think those are the only places we really do nuclear science With spallation sources all the other spallation sources are used for material science We have the ability to handle radioactive samples Plutonium and heavier Samples something you cannot always do at a university Ent-of-of-course now have the capability to do plutonium target, which is very nice so we can do Comparisons and some of the measurements there We've also invested heavily in new instruments Some of the types of instruments that were previously mostly used in high-end physics We're now applying to nuclear physics programs And we have a long tradition of doing measurements. So you have You know your fellow Scientists that I've been there since the 40s or so. So there's a lot of expertise to pull from I Thought I should mention just because there's some misconceptions out there We do like to collaborate so you can actually come to Los Alamos and do experiments and Collaborate with us for some reason some people think that it's prohibited because of security concerns or so and then that's not true So Lance is actually a user facility. We have a lot of hundreds of users coming in every year to do experiments there Both from universities national laboratories and from industry and I'll actually show you a little bit at the end of this about the industry program that we have Almost all of the projects we do are in collaboration with other institutions. So Almost all of the experiments. I'm going to talk about We do together with some some universities in the US or international collaborations the CA in France all kinds of places And we do have both Domestic and international collaborators. All right, so here's an overview of Lance So Los Alamos is sitting up on these so-called Mesa tops in New Mexico So first of all, it's not the desert. That's what I thought when I came there and it's not we're actually a really good skiing there So the southern part of the state is a desert, but this is kind of a green area So if you see the aerial overview of Lance there, that's one of these Mesa tops of plateaus And so the town of Los Alamos and all the areas around there are up on this Plateaus they were kind of nice when they build the lab there because it was very difficult to get there And so you just have to close off one road and then you're protected against access from from people getting to the lab So this is the the Lance facility here is the 800 mv proton accelerator So we have an 800 mv linak And that drives a few different facilities We have isotope production for medical isotopes. So that happens at the sort of pre-excerration stage of the accelerator We have an ultra cold neutron experiment facility Proton radiography where you actually image things using protons Things that happens very quickly and you need a fast Camera to to image them But what I'm going to talk about are the WNR and Luan center facility where we make neutrons So at both of those facilities we use the spallation process With tungsten targets and make neutrons So what happens is that the so here's the the red here is the proton beam You know protons are red and neutrons are blue, right? So this is the proton beam Here is the Luan center At the Luan center you have the proton beam coming in And being bent down so the proton beam comes in from the top and You have these two tungsten targets where the proton beam goes through both of them without stopping so you make neutrons there and then That target assembly is surrounded by different types of moderators. So you get different types of moderated spectrums So this facility you have some flight path that are very short. It's kind of difficult to see here probably So back here you have flight paths that have sort of 8 to 10 meter flight path and then on this side you have stations that are more like 20 25 30 meters flight path lengths There's something like 20 flight paths or so Available there and up until about a year ago almost all of them were running material science instrument neutron scattering experiments and Three were dedicated to nuclear science so we had some Changes over the last year the the neutron scattering program lost much of its funding And that's because the Oak Ridge facility is not doing most of the neutron scattering work in the US So this year we actually just started running this facility a few weeks ago and now we have three Material science flight paths and three nuclear science flight path so that that place has really changed quite a bit And then over at WNR we so as I said, this is a moderated target and then at WNR We just have a bear spolation target. So it's it's a very simple target. You have a can of tungsten Wolfram and It's just cooled with water and we make high-induced pollution neutrons and you get a spectrum from Well, you get a spectrum from from low energies up all the way to hundreds of MEV Because of the pulse structure and you can only use certain energies So at the Luan Center, you get 20 Hertz reputation repetition rates So you have plenty of time to measure neutron time of light between pulses So you can go down to thermal or sub thermal energies And that's because we take the proton beam and Compressed it in a storage ring So you bunch up several pulses and then you get this long term between between pulses at WNR You actually deliver beam with 100 Hertz repetition rate, but each Pulse has a microstructure pulse structure So what you do is you measure time of flight over 1.8 microseconds between these pulses So with that pulse structure, you can only go down to sort of hundred KV roughly and then Going up you go to hundreds of MEV of neutron energy So this is the neutron spectrum for those two facilities So this part here is the Luan Center one of the flight paths, of course it depends on which flight path you're on because they have different moderators This is flight path 12. We would do it's kind of like a general use nuclear science flight path and The thermal bump there is reduced because we had a dead acquisition system That's couldn't handle the fission. This is for a fission experiment when couldn't handle the rate at thermals We only took some of the pulses So this is actually a count rate estimate for one of our experiments But yeah, so there you get in a large thermal bump and then you can do measurements out to 200 300 KV or so and at that point you really start losing resolution The the pulse that gets delivered to WNR is 250. I'm sorry to Luan Center is 250 nanoseconds So by the time you're out to hundreds of KV, you have very poor resolution So that's a major difference compared to ENTO for example We have this excellent resolution in the KV hundreds of KV region And then if you move over to the WNR facility, this is a spectrum there Again, you go down to sort of 100 or 200 KV and there's a small overlap region So if you want to do a measurement and cover this whole energy range You do one measurement at Luan one at WNR You have a small overlap region and you get a continuous cross-section from low to very high energies and We've used that for many of our patient cross-section measurements Again at the end top you can do that without having to do it in two facilities You just do one measurement from thermal up to hundreds of MEV and we do not have that capability Okay, so we have several different instruments that we use for nuclear science research And I'm going to talk about many of these We have the time projection chamber the TPC Which is the fancy ionization chamber that we use for efficient cross-section measurements I think there's an expression in Swedish about shooting elephants with a Shooting mosquitoes with an elephant gun or something like that. It's kind of overkeeled to have a TPC to measure cross-sections So we do some other fun physics studies with this instrument as well Can you which is the? neutron Array where we measure the prompt fish and neutron spectrum And that's an ongoing project as well The dance array which is at the Luan Center. We will look at neutron capture measurements using a color calorimeter detector Genie which is actually now decommissioned but that was used for Things like measuring the end to end cross-section in plutonium. So looking at gamma rays from different reactions spider, which is a 2e2v instrument kind of like the cozy fantoti spectrometer that existed at the ELL back in the 80s So Stefan talked a little about these types of techniques Yesterday and this is for measuring fish and product yields And then Apollo is actually an instrument that is not being used for experiments at Los Alamos But it's something that been developed for doing immerse kinematics measurements At the AFRIB facility when that comes online One of the directions that we want to go in is to direct measurements at Los Alamos and do Heavy ion beam type of experiments in the future at AFRIB And if you combine those two types of techniques, you can learn much more about the nuclear data and Nuclear structure. All right. So you heard all about fishing yesterday. So I don't have to repeat much of this All I was going to just point out is, you know, if you look at this cartoon of the fishing process There's a lot of things we can learn using different techniques So in nuclear fishing you have a neutron pinching on a heavy target And you might want to measure the cross-section of that reaction. So that's what we do with the TPC instrument You create some heavy fishing fragments Fishing products and that's what we want to measure with the spider Instruments and look at the mass and charge and kinetic energy so the fragments And then you have the de-excitation of the fishing fragments with neutron emission and gamma ray emission With CanU we measure the neutron outgoing neutrons With the dance detector we also done some work where you tag on fishing and you measure the fishing gamma rays multiplicities spectrum and so on and Again, I think Stefan showed some of that in yesterday about gamma ray emission in fishing Okay, so I'm just going to start with the cross-section work Now of course cross-sections are important in nuclear technology When it comes to the minor actinides there are several cases where there's a lack in the data and I saw some good posters Where that's being addressed yesterday Things like plutonium 240 and 242 Are produced in in fast reactors and you want to know the cross-sections of those I think it's for plutonium 240 where there was a real weird discrepancy in the cross-section up to a few years ago where people had done the measurements for a sort of energies below 100 kV and then other measurements in the fast region up in the MEV region And since there were discrepancies between those data sets there was a place in the cross-section There was just a step a very unphysical step So those are the types of things you want to address with the minor actinides If you do a fast reactor system In the traditional thermal system you cared about the thermal region cross-sections and the fast fishing spectrum cross-sections For a fast reactor you care about the sort of kV to MEV Regions you want to improve the accuracy of the cross-sections there Of course if you build an ADS, then you have you want to know some of the very high energy cross-sections And then we have the alternative fuels if you do the thorium fuel cycle for example Then you care about other reactions or other cross-sections that you otherwise don't care about so When I first came to Los Alamos we did some of the more traditional fishing cross-section measurements using parallel plate line Dainization chambers So this is the type of chambers that were used back in the 40s already Very simple design. So you have a gas field dainization chamber You have some samples in there of your actinide deposits So you just have your your deposit and then an anode plate opposite that you apply a field Fish and fragments to induce fishing with neutrons Fish and fragments are emitted and ionizes the gas and you read out a signal. So pretty straightforward And in this case you have thick backings you only measure one of the fishing fragments not both of the ones that you can otherwise get to So we did neutron time-of-flight measurements with these instruments At Los Alamos and we always did them relative to the uranium 235 standards. That's a common technique The uranium 235 fishing cross-section is thought to be known very precisely from Sort of half an MEV up to I think it's now standard up to 200 MEV So at least up to 20 MEV people claim that it's known to about 1% so that's a reference reaction you can use So Back in in the last 10 years or so. We did a bunch of measurements using perl plate ionization chambers and I'm just showing some of the Cross-sections that we measured we did an attunement 237 and then several of the uranium plutonium isotopes as well as some of the emerysium isotopes So here you see the uranium series and the plutonium series and this has been published in the past In most cases this has been measured fairly well In this energy range, so you agree well with the EMDF evaluation But to some certain precision right so it depends on how well you want to know this cross-section And it turns out that for those measurements the uncertainties Depends on who you ask I would say typically you have at least a 3% uncertainty In in these measurements People have claimed 1% in the past and 1% it's very difficult to get to I think 2 to 3 at least percent is more reasonable So this is just a list of some of the uncertainties that goes into into the measurement When you do a ratio measurement you're in 235 The standard reaction adds about a 1% uncertainty by itself And then some of the major ones are Knowing what your beam profile is how uniform your deposit is All of those things add quite a bit of uncertainty to the measurements. So 3% is pretty common for the ones type of measurements that I just showed you So in order to improve on that we started a project Together with Livermore Seven years ago or so the Time Projection Chamber project So that's a Reynac-Cleanrath one of my graduate students with the TPC and This is a project where the goal is to reach 1% accuracy in fishing cross-section measurements And the basic idea is to use particle tracking to reduce many of the systematic uncertainties This technology has become the TPC technology has become less expensive In the last decade or so so that made it easier to do to make this project or have this project It's still a pretty expensive detector. So it required a major investment This is something instrument with 6,000 channels and in the past it would be a very expensive instrument to build TPCs were developed in the late 70s for high energy physics experiments So typically they are the size of big rooms and this is a very small detector as you can see here So here's some some mechanical drawings of the of the TPC So it consists of an inner volume of about two liters. So again, it's a gas detector and You have a central cathode where you place your actinide target right there And for most of the measurements we use thin backings carbon thin carbon films that we have there are deposits on So in fact you get both of the fishing fragments out of your sample and you measure There's two volumes here. So you can get both fragments in coincidence So yeah, so this inner part is about the size of a coffee can and then we use micro magas for the for the readout so on each side here is a micro magas plane and This is how it's pixelated. So it has 3,000 pixels roughly on each side and then Each segment here is the corresponds to 32 segments. So that's being read out by one of our electronics cards So this is a custom digital electronic system. So this is the readout cards There's about 200 of those cards to read out all the 6,000 Channels or pixels And it consists of 32 amplifiers 32 digitizers and then an FPGA card to do the signal processing So you can imagine with six thousands and thousands channels and you're sampling At about 10 nanosecond samples Data rates becomes kind of difficult to handle. So we do at least zero suppression with the FPGA technology on board Originally the plan was to do some more fancy single processing to do pulse site Calculations and determine the timing of the pulse and so on And in fact right now we just use the zero suppression and that's sufficient for the data rates It's still a bit tricky. So when we have plutonium in the TPC, we have very high trigger rates This is a self triggering system So one of the problems we had recently was just to keep up writing to disk So we've had to come up with some ping-ponging system to to write the data to disk Some of the other requirements was that Eventually we want to do measurements with the TPC and a normalized hydrogen scattering That's a better standard than the uranium 235 standard and the uncertainty is there again, it depends on who you ask but the Uncertainties on that cross-section is more like a third of a percent or so. I think it's the first statement so in order to do efficient fragment measurements and do and Hydrogen scatterings you have to have a very nice large dynamic range of the instruments those and other design requirements So there is a publication out from last year on that gives you the technical details of the TPC Mike Hefner at Livermore led the development of the TPC and Los Alamos is doing the beam experiments So we're actually up and running right now Okay, so this is what the online data looks like When you run with the TPC. So as I said there the basic idea is to use Particle tracking to reduce systematic uncertainties So if you have so this is our online viewer when you have efficient fragments emitted from Here is the sample and There's the 3d particle track that we get from a fishing fragment And this case it's ah in this case. It's not actually a fishing fragment. I'm sure you call caught that right? It's a alpha particle which is why there's more ionization at the end of the track So so we get the full particle tracking But you also get the brag peak or the brag curve of the particle So you see the specific energy loss along the track And that helps you distinguish between fishing fragments and the alpha particles for example that causes background in the measurements So in the past you only had the total amount of charge deposited and now we can look at the brag curve As a way of doing particle ID So the TPC part. So like I said, we have this segmented or pixelated readouts that gives you XY position of the particle track and then you look at the drift time That's a time projection part of the TPC to get the C components we get to get the 3d track So that's what this is trying to show So these are all the individual waveforms for the different pixels that got hit in one event And you look at the relative timing of those to get the third component Of the particle track Okay, so the as I said the goal is to measure fishing cross sections with sort of 1% accuracy. Yeah, go ahead Yeah, it was funny. We didn't figure that out until after we sort of build the TPC So so what happens is that so you know So you have a data acquisition system that is fairly slow with samples that sort of I think it's 10 nanosecond samples So that's enough time to get good spatial resolution of the 3d tracks But to do the neutron timer flight you need more like one or two nanosecond timing So we read out the cathode for that so that we have the micro mega street out that gives us the track And then we have a trigger from the cathode signal that is faster And we use the same system, but we sample the same signal 10 times with individual delays And then you get the one or a few nanosecond timing. So that gives you the neutron time of light resolution Yeah Sure, that's right So the idea is that here you so in the past, you know, there were always uncertainties because you didn't know how your Sample how uniform your sample was and how your beam prive profile looked like and if you overlay those two you can have uncertainties right in the event rates Here we measure with the TPC we measure both those things So so you have the neutron beam going through the TPC you ionize the gas from recoils and You image that and then you actually measure the beam profile as you do your cross-second measurement Then you turn off the beam and you look at the alpha decay and that gives you a map of the uniformity of the sample Sounds easy. It was very hard and now in the third year of running this we're starting We actually are getting that that data Yeah the what The crosstalk that's right So, I mean, there's not much direct crosstalk, but you have I mean the electron cloud is fairly large for for efficient fragment so you when we do simulations of the detector response we take that into account and sort of Look at the diffusion of the electron cloud and see what the how that affects our signal But it's actually not much of a problem. I mean we have more of a problem of channels dying The electronics is somewhat susceptible to the neutron damage and One of the big questions there were several questions when we started this one is what happens if you shoot a neutron beam through a TPC So people hadn't really done that before very much And that worked okay, so we don't really See, you know any large backgrounds because of that and the other question is what happens with a highly ionizing thing like efficient fragment that goes through a TPC and the answer is that we can Track those particles quite well, although there's been some weird effects that we had to work out with You're very sensitive to non-uniformities in the field and TPC and things like that Yes, alright, so right so exactly so so what we hope to reduce are the uncertainties associated with the normalization beam profile and Sample uniformity This will basically know dead time in the system, which is nice if you see in the star TPC You can do thousands of particle tracks in one interaction. So dead time is not much of an issue And we do better on the fission identification So in the past you would have these Overlapped in the decision chamber measurements. You have an overlap between low energy fission fragments and pile up alphas For example, and now we can much better distinguish between fission fragments and alpha particles Ah and then for the normalization We want to use hydrogen the hydrogen standards ago that brings down that uncertainties is more like a third Of the uncertainty of the uranium 235 standard Okay, so, you know, it's not very sexy to measure cross sections with the TPC So we do other physics Studies and this is the work by rena clean right that was in the picture here before So she's looked at angular distributions of fission fragments with this instrument So it's actually one of the things I hadn't really thought about when we started I wanted to do ternary particle ternary fission studies with the TPC and I'm sure we'll get to that point eventually But for now we have a measurement of the uranium 235 Fission fragment anisotropy so if you look from 100 kve up to 100 MeV you will see that there is a change in the anisotropy of the fission fragments. So For low energies you have isotropic emission and then as you increase the excitation energy You get relatively more fragment forward peaked fragments So we measure that change and compare that to some previous measurements. That was some really good work done already in the 50s on this But we extended the energy range. They only did this up to 10 maybe even standard nutrient genes now we're going higher and There is also some work from end of on fragment anisotropies and like We have looked we have done some comparisons, but I think that's not published yet So so I didn't want to show it on this spot just yet okay, so that was the TPC and that was the cross sections and The same time where we started this work on improving cross-section accuracies We also started the prompt fish and neutron spectrum project with the can you a And Those two types of measurements kind of go together if you have a critical system you want to know the cross section for fission But that cross section changes as a function of incident nutrient energy as you just saw So you also want to know the spectrum of of the neutrons emitted that keeps the chain reaction going So you measure one and you want to measure the other as well So to know the neutron spectrum in a critical environment You need to know so the material there that that affects the spectrum But you of course have to know the initial Prompt fish and neutron spectrum as is for your starting point So there's been a lot of work done in the past to measure these things, but there are certain issues with the old measurements It is something that's very difficult to measure. So in some cases there are large uncertainties and large discrepancies in old measurements And sometimes people have underestimated the uncertainties in their measurements and we actually found Some cases of that as we started working on this problem and did simulations and You want to know how the prompt fish and neutron spectrum changes as a function of incident neutron energy So there's been some measurements at thermal for example and some measurements at fast and we wanted to do measurements to map that out better from Both in the thermal range, but then from one MV up to at least 20 MV or so and So I'll talk about the experiment we do these measurements and I don't I think I don't have slide unfortunately But there's also been some advanced modeling and simulation To reproduce old experiments and better figure out whether the backgrounds that they were ignoring mattered or not and we found that in some previous measurements that people used they were underestimating the effect of room return In their measurements were able to Actually correct in some cases old measurements So here's a picture of the prompt fish and neutron spectrum for you in 235 And it's shown as a ratio to mix maxillian just to put this on a on the easy to read scale So here are all the data knitter Staples are some of them well-known measurements. I was done in the past that a few different energies So they did these are the energies incident neutral energies in these cases So most of the data is Where the peak of the spectrum is so in a few MV and and up to maybe 8 MV or so But it gets very tricky to measure the spectrum for the lower neutron energies and for the very high neutron energies so high neutron energies you just run out of statistics every few neutrons out there and At the lower part, you know your detector might not be very sensitive to low-energy neutrons depending on what neutron detector you're using So there's been and you're also sensitive to background back here. So There's been little questions on whether The spectrum goes up again at low energies or goes down and according to the valuation. It sort of stays flat. So one of the things we want to address was those two extremes of the spectrum and These are sort of the target accuracies That was set out as they started the can you project So these measurements are done with the kai new array I think the kai new part comes from the name of the Matrix of in going versus out going neutron And in fact, it's two different detector arrays So some detectors are better for high-energy neutrons. Some are better for low-energy neutrons So there's an array of liquid scintillator detectors that does the high-energy neutrons well But has sort of a threshold on the lower side Where it's difficult to measure below half an MV or a few hundred KV and Then there's an array of lithium glass detectors that covers the lower energy part of the spectrum So this is sort of being done as as two measurement campaigns to cover the whole spectrum Bob hate that Los Alamos is the lead for the can you project At least for the next two months, then it's going to retire and Matt Devlin will be the new main contact for this And it just does the TPC. This is a collaboration with live more in this case Los Alamos is the lead But live more is providing the fission tagger Detector that is being used in the measurements Okay, so So the measurements are done at WNR So you have incident neutron engines from half an MV and you want to go up at least to 30 MV or higher And as I said, we have this neutron detector rays and then you have the live more developed P-pack that is your fission trigger. So you put your plutonium targets in a P-pack You trigger on fission. So you have an incoming neutron time of light You measure the time difference between the accelerator and the P-pack that gives you the incident neutron time of light And then time difference between the P-pack and the neutron detector gives you the outgoing neutron time of light It's a double time of light measurement We actually it was kind of lucky So we were building a new building for where this experiment is going to be located and people looked at the background issues If you're trying to measure fission neutrons, you also have and you have a neutron beam coming in You have a bunch of scattered neutrons all over the place so in order to Reduce that background we moved shielding as far away as possible It's always difficult to move the floor away. It's kind of is where it is So they build and they happen to be building a new building. So we build a large swimming pool in that building so you take a nice concrete floor and you have a big hole or a pit where the ticker sits and then you have a false floor so actually that instrument is now sitting on a false floor and you have less room return from from the floor under you So this is a multi-year project. That's a fiscal year 17 and of course, you know, we're not exactly on track. So I think this party is going to go to 18 or 19 or so So the the motivation is for is not for nuclear energy in this case So I mentioned how many of the measurements were done at certain energies for thermal incident neutral energies or certain fast Incident neutral is this plot is trying to show that so so there's littered data in the thermal region and Then there are different measurements at different energies between a few hundred KV and a few Mev And so that's that's in select places in this measurement. We're going to completely cover The fast range from half an mev up to 30 mev. So that will give you a sort of a continuous spectrum in that range Here are some preliminary results Uranium 235 in this case So the goal is to do plutonium 239, but 235 is what we know better So it makes sense to measure that first to show that you know what you're doing So again, this is a ratio to mix will end but it's going to show us the kind new data compared to some of the previous Experiments and that was our milestone for last year and This year so the uranium 235 measurements, I think are completed now and they're moving over to to plutonium measurements And as I mentioned, it's going to be this two campaigns where first the high energy array and then the low energy array measurements and At some point I'm going to upload this slide So here are all the references if you're interested in reading up on the topic and as I mentioned it is a collaboration so we have people at Los Alamos, but also at Livermore and Several university people people Xinjiang is from Livermore I'm sure there's some university people in there, but I'm not sure which ones they are and then I was gonna switch over to fish and product yield measurements so So Stefan again talked about fishing yesterday and study fish and fragment properties There are different reasons why you want to do that. One reason is that In nuclear technology, you can use the presence of fishing products to figure things out So if you have a nuclear device and you find a certain number of fishing products You need in 147 for example, you know, you calculate back how many fishing occurred in that device and So we've done really good measurements of fishing product yields but the relative yield for different fishing products changes as a function of incident neutron energy and that is not well understood So there is large uncertainties in certain regions for example, if you do 14 MeV neutrons The yields have really large uncertainties again up to 30 MeV or so So you can address that problem two ways or several ways, but at least two ways You can use ionization chambers With low mass resolution to look how the fashion look at how the mass yield changes in fishing as a function of incident Neutron energy and I'll show you some of that and then we Also worked on a 2e2v instrument where you get high mass resolution Measurements and measure the same thing but then with lower efficiency. So you have lower count rates Okay, so here's a measurement from I'm assuming Gale Peters-Hillebeck's Of plutonium 239 showing the mass distribution in fishing of plutonium 239 I think that's for incident energy of half an MeV or so So I'm assuming that the line is the England and rider evaluation of fishing product yields And the points there is data from an ionization chamber and these measurements are usually quoted as having a four or five Mass unit resolution. So that's why you don't really see the same structure in the data as you have in the evaluation So and then you might care about one specific fishing product You didn't in 147. So that's located somewhere here on the heavy side And if you take that yield and plot it as a function of incident neutron energy where we know that the mass distribution changes You can look at the data. So there's some data in the FUMEV The FUMEV region and there's data out at 14 MEV and basically nothing in between So the big question is is and as some people here with the posters were showing yesterday You want to know how that yield changes in the region in between? And if you measure that You will also have more confidence in the data out at 14 MEV So here's some Some predictions and of course every person who makes a prediction are convinced that they are right. So I Mark Mark Shadwick has made some some fits to this data and he's convinced that he knows the slope of How this yield changes and then for some reason it drops over at 14 MEV and then one of his colleagues at Los Alamos to another prediction and is equally convinced that it's Completely flat that there's no change in the FUMEV region So that's a good reason to actually go out and measure this and figure out what it really is It's also some good theoretical calculations So that's another reason why we want to measure efficient product yields because we're getting to a point where people can Hopefully at some point will be able to predict those yields for systems that we cannot measure This is from a publication from Peter Moller back in 2001 I believe where he's done some of the most advanced studies to date on how the potential energy Of a fishing nucleus changes as it's being deformed and undergo fishing So by taking those kinds of potential energy calculations and combining them with other methods to look at the dynamic aspects of fishing you can actually predict the mass split in fishing so These plots here are from Arnie's Cirque at Los Alamos where he's comparing the amount of total kinetic energy release as a function of Fragment mass for example and comparing that to some of the measurements we've done with ionization chambers And it's also predicted mass yields and get actually very good Results and good comparison to experimental data and how the data changes as a function of the incident neutron energy So it's kind of a promising time where Fishing modeling and theory is getting better. So it's kind of nice to do measurements and try to support that effort okay, so ionization chambers is the low mass resolution high efficiency approach to The mass yields so very simple chamber and again, I think Stefan Scholl is yesterday Central cathode with a thin Deposits you can you get both the fragments out into the detector and then you have Frisch grids and anodes on each side And you just measure the kinetic energy of both fragments and if you do that and You apply the 2e method You can take go from to From two energies and translate that into mass yields the mass of the two fragments using momentum and nuclear on conservation and if you do that and you do a measurement where you have a Neutron time of light so you can look at different incident neutron energies. This is for your aim 235 So this is the black point series and measurement a recent measurement from Los Alamos Actually, the student to do this is defending her thesis in two weeks or next week next week So these are different incident neutron energies, so it goes So sort of 2mv 5mv 9 and then up to 14mv And then you can nicely map out the changes in yields going at higher to higher energies So for low incident neutron energies, you have almost no symmetric components You just have very asymmetric peaks and as you increase the excitation energy you start filling in the valley here and you get this Symmetric component and that's exactly the type of information that you can use when you model the fission process and improve your theory and If you plot that different wave in this case for urine 235 So in this case is again mass distributions and the incident neutron energy going this way So again, you see this sort of valley filling in here And you can map out those trends Well, so what you measure in nice in the timescale of a nice asian chamber what you measure are the fragments kinetic energy after Neutron emission, but before radioactive decay So you have to make certain corrections you have to make some assumptions about the number of neutrons that were emitted per fragment for example But is that what you're asking? It's a question of the timescale, right? So you you measure I mean if you ever met a stable state, I mean the decay happens after your measurements, so it doesn't really enter into the Technique in this case you can talk about it afterwards So so even if you do a low mass resolution measurement, you can still study these trends as I mentioned I mean you might not give get the change here of a very specific yield But then on and you can get the overall trends and use that to try to understand individual yields So here we plot the difference in yield between Low energy in this case, I think one and a half mev compared to 14 mev and what you see is that some of the yields are lower at 14 mev and other yields are higher especially in the symmetric region you get an enhancement of the yields so Some of the work by Mark Machalvic for example He made a lot of fits like that to try to figure out which exactly which fishing products would increase with the incident neutral energy and which would decrease So this is certainly valuable information and and again even with lower mass resolution measurements You get really a nice comparison to the evaluation. So this is the England and rider evaluations for 14 mev So, you know even even with this lower mass resolution we compare very very well to the England and rider Evaluation which kind of the gold standard when it comes to fishing yields. So then With the fishing chamber measurements another thing we wanted to look at is the correlation between mass and kinetic energy and that's mostly driven by the modeling and theory Work being done by our colleagues in particular Patrick Talu is doing some work trying to use a Monte Carlo technique to Simulate the de-excitation aspect of fishing fragments And that code actually starts by sampling from a mass and TKE distribution So this is what you see here. So here on this axis is the TKE energy release in fishing And here is the mass of the fragments This in this 2d plot I know if I always refer to this as a lung x-ray or if that was for some of the gale people that came up with that but either way So what this shows you is that for the more asymmetric fishing events you have a lower total keg energy release and When you go to more symmetric Fragments you get more TKE and this Data is being used to sample from as a starting point when you try to figure out Neutron and Gamma ray emission fishing in fishing in certain models And again and then in Arnie Cirque's work he calculated this TKE versus mass distributions and again we use this data to try to Compare to his results, right? So I think I'm going to stop here for the first lecture and then after the break I'm going to go into this spider or the higher mass resolution measurements So if you have any questions feel free to ask them. It's pretty straightforward. So Why not So when I say so when I showed oh So when I show the Lewand center, it's actually a count rate from an experiment. So it's actually the flux Folded with a fishing cross section And the dips you see at that at hundred of KV or so is actually Absorption absorption resonances and some of our windows and so on so typically you don't well. I mean easy Again, I think this was probably because it was a count rate So you're probably seeing the fishing resonances showing up at those energies