 Εντάξει, το γαμμάριο εμμείτες από έναν εξαιρετικό νεοκλαιούς, μπορείς να βοηθήσεις, μπορείς να δεις τι είναι το νεοκλαιούς που είσαι. Για παράδειγμα, αν έχω ένα παράδειγμα, και μπορώ να βοηθήσω αυτό με πρότονες από 3MV, δηλαδή. Και τότε διδείξω ένα 440KV γαμμάριο. Αυτό το 440KV γαμμάριο έρχεται από σώδιο. Ξέρουμε ότι βρίσκω σώδιο, ότι το σώδιο μου έχει σώδιο. Και αυτή η ιδέα της πίγερας. Θα διδείξω γαμμάριο. Με το νεοκλαιούς της γαμμάριος μπορώ να δεις τι είναι το σώδιο, τι είναι το νεοκλαιούς, τι είναι οι αιζοτώπες που το σώδιο έχει μέσα. Και από το νεοκλαιούς που διδείξω, μπορώ να βρεις πόσο. Για παράδειγμα, αν ξέρουμε ότι το σώδιο δίνει 100 γαμμάριο 440KV, και αν θέλω να δω 200 γαμμάριο, αυτό δηλαδή έχω δύο πιο. Και αυτό είναι ποιο η ιδέα της πίγερας, πιο χρόνος που χρησιμοποιούμε στάντας. Λοιπόν έχεις το νεοκλαιούς της γαμμάρις, έχεις το νεοκλαιούς της γαμμάρις, έχεις το νεοκλαιού που διδείξει, δηλαδή, για παράδειγμα, 5% καλύτερα. Είδατε το νεοκλαιού της γαμμάρις που έχετε εδώ, το μυαλικό you put your unknown symbol, you measure the same γαμμάρί, the number of them you just did use. You need some corrections about stopping power and things like that. But then, you have your result. And this is what the gami array is for. Let say the simple gama array. So, you have your reaction. You make what we call a compound nucleus, an excited nucleus. That the excites and it gives you a gama array. We measure these gama arrays and from these gama arrays δηλαδή μπορώ να βοηθήσω ό,τι μου βοηθήσω. Για παράδειγμα, το σωδιό μου δίνει αυτή η καρακτηριστή γαμμαραία 440, για μπωρον είχα 2002 μμεβ, έχεις μπιρίδιο, μπορείς να δεις φλοράιν, όπως είχα πένει, μπορείς να χρησιμοποιήσεις και για χειδρογέν, αλλά δεν είναι για όλες λευκότητες. Για παράδειγμα, αν χρησιμοποιήσεις πίγε, δεν μπορείς να δεις καρβόν. Γιατί, γιατί η πρώτη εξαιρετική στιγμή της καρβόν είναι 4,4 μμεβ, πολύ, πολύ δύσκολο και με very little probability. Παρακολουθείτε, ό,τι είπαμε στον Κουστινό, η καρβόντητα που έχω για την δυνατότητα είναι η δυνατότητα. Πολλοί είναι να έχουν αυτή τη δυνατότητα. Οπότε η δυνατότητα της πρότασης με καρβόν, είναι δυνατότητα, δηλαδή δυνατότητα, δεν είναι πολύ δύσκολο, και όσο η γαμμαραία που δίνει, είναι πολύ, πολύ δύσκολο. Γιατί να αντιμετωπίσω αυτή η γαμμαραία, πρέπει να χρησιμοποιήσω πρότασης με 6 μμεβ. Δεν είναι εύκολο να βρεις πρότασης με 6 μμεβ σε καρβόν εξαιρετικούς. Η δυνατότητα είναι δύσκολο για οξιγέντρα. Λοιπόν, πρέπει να κοιμηθώ, ότι για καρβόν και για οξιγέντρα, στις τώρα δεν έχω τίποτα να δούμε. Οπότε, δεν μπορώ να δούμε με πιξέ, δεν μπορώ να δούμε με πιγέντρα. Πρέπει να δούμε κάτι άλλο. Είναι κάτι τελευταία και κάτι καρακτηριστικό τελευταία που είμαστε αναλειάζονται με πιγέντρα. Για παράδειγμα, εδώ έχουμε κάποια γλώσσια, που were used, as I told you, πιγέντρα, αυτοί τα τρεις είναι έξιχνοι με πιξέ. Είμαστε πιγέντρα για τα πιγέντρα, αυτοί τα πιγέντρα για τα λακά. Αυτό είναι ένα γαμμαρόσπιγό. Υπάρχει εδώ, as you can see, I can see the 400 kV, so I know that I have sodium, I integrate that, and I know how much sodium I have. Those two lines come from aluminum, so I can detect also aluminum, this also comes from sodium, this comes from silicon. This is another example. One question. Of course. Those spectra were taken with the same current, the same current, but the same flow as the same. I'm not sure, to be honest. I wanted to compare. If you want to compare the standard with the sample, you have to keep the same fluence, of course. No, but I mean, if for a sample, let's say you have a sample with 50% cooper and 50% something that you can see, aluminum or something that you can see with πιγέντρα, are you going to take more or less the same count on both detectors or are very different those summers? No, normally you want to have both detectors the same current most of the time. Most of the time you do the same measurement, the same experiment, so you keep the same fluence until you see, if you can see what you want to see. Because maybe you have, let's say, let's take sodium. Maybe you have something like 0.01% of sodium. This peak will never get out of the background, whatever you do. So there is sodium, but unfortunately it's under your low detection limits, so you can't really see that. This is another example. Okay, it's an analysis of an Indian pigment. Galstone, so here you have the pixel detector and the piquet detector. Here you can see that you have all the heavy elements. You have bromium, zinc, copper, iron, chromium, titanium, things like that. And you use the piquet detector for the light ones, aluminum, sodium, magnesium. Sorry, this is a nice example. This is something I like very much. This is a painting that was somehow and somewhere restored. This means that it was destroyed in some places and the conservators go there and just filled in the gaps. Now, the thing is that this, the original painting had some blue. In that time, when they wanted to produce blue paint, they were using this semi-precious lapis lazuli. So in order, in that time, to make the paints, they had lapis lazuli, they were breaking it, they were making the blue paint and they were using that over here. The conservators that they conserved that at the 20th century, they used, let's say, the same paint, the same color, but of course now this is artificial. In nowadays, we don't use lapis lazuli in order to make the same color. It is purely artificial. So the guys over there, they wanted to see which parts were restored and which were the original ones. Now the trick with lapis lazuli is that lapis lazuli has sodium inside by itself, while modern paints don't have sodium. So they said, let's do the same trick. Let's hit at some areas and see if we have sodium or not. If we have sodium, this means this is an original paint, this is the original part of the painting, while if I don't see any sodium, this means that this was restored in some time. And as you can see, these are the two spectra. Here you can't see anything at 440 kV, so you conclude that this was a restored area. While here you can see this nice peak at 440 kV, this means that this region where you hit is an original one made with paints made from lapis lazuli. And here you can see again that they used, of course we have a painting, you can put the painting at the vacuum, so you used the external beam setup. Now let's go, of course. Since you are going to RBS, can I ask one or two questions about piggy? Of course. So, would you comment on the comparison of Pixie and piggy, taking into account that Pixie actually has more or less quite smooth cross sections for excitation, while piggy, in my understanding, has very... Resonances. It has resonances, so, I mean there are two problems. One is the resonances, another one is that for different elements you have different resonances. So, is it really possible to say, okay, I'll, for TIG target, or even for TIG target, I want to use piggy for every light element. Or you have to be really strict and focused. No, strict, you don't have to be strict, absolutely strict. What does it mean? You want just to see one element, first of all. Let's take things one by one. As it's complementary with Pixie, most of the times you fix your energy according to Pixie. Most of the times. Okay, so piggy follows Pixie. Let's say now that you don't have Pixie and you want just to do piggy, so just piggy. If you have just piggy and you want to see one element, then you will go, let's say, to an energy that is high with a good cross-section and then you're finished. If you want to see two, three, or four, or five light elements, then you will go at an energy the highest for all the elements. If you can, you want to take all the resonances into this region. So normally you don't have any problem using Pigie. If you refer what we call resonant Pigie, how you use Pigie specifically just for one isotope in order to do depth profile, this is another question and I have it later on. But normally you can see everything. If you have a high energy, it's very good. Quantification with Pigie is very good because you have two ways of doing quantification. One is with standards and one is by using cross-sections. By using cross-sections because we don't have a lot of cross-sections, it's not very good. You will have an error around 10% to 15%. If you use standards and if your standard is well chosen, this means that your standard, the matrix of your standard is almost the same as the matrix of the sample that you are looking at, then you go down to 7%. So Pigie is very good. I don't know if I answered your question. In general, yes, although what I understood we never did, but always it was quite focused on very few elements and then one used to find this smooth, more or less cross-section. It's not necessary to be at the smooth part. You can take... But this is the same case for almost everything. You need to have somewhere to... For Pigie you have well-known cross-sections. That's the difference. You have well-known cross-sections. A smooth. In Pigie, if you had the same degree of precision in cross-sections, even if they have inside them resonances, you don't care. It's the same because if you have, let's say, a very sharp resonance, this sharp resonance, when it reacts with your sample, it will broaden. Because of the struggling it will broaden. So you don't really care if it's sharp resonance or not. The only thing that you have to know is to know well the cross-section, to know very well the resonance, how high it goes. And in Pigie, nuclear physics, it isn't simple to measure resonance because you always compensate with the thickness of the target that you are going to use. It's convoluted with the thickness. That's the problem and also the ripple of your machine. It's more difficult. This one. This is Pigie and Pigie under the same conditions. It's in the same time. So you have two detectors, one Pigie detector and one Pigie detector, looking at your sample. Everything else is the same. And this is the trick. You use Pigie for heavy elements and you use Pigie for light elements. No, you use the same energy. For example, most commonly for Pigie you will use 3 MeV protons. Some of the protons will ionize your sample, your atoms, so you will have pixels, you have x-rays. Some of them will fix, will make the new compound nucleus, they will excite the nucleus and then you will have Pigie. Of course, if you are using a proton of 3 MeV, it's very difficult to see gamma rays above 3 MeV because this is the energy you have. So you don't expect that by throwing protons of 3 MeV you will see a gamma ray of 6 MeV. You can, you will see, but you don't expect something like that. As you saw before, all the gamma rays I gave you, it's below 3 MeV. It's very rare, it's very, very rare to find two nuclei emitting the same gamma ray. Exactly the same gamma ray. There is the possibility, but it's very, very, very, very rare. I can give you an example. Is this, no, for example, if I remember well, if your sample has aluminum and silicon inside, it's aluminum and silicon, I'm not sure, but you may do a PP-prime gamma reaction on lithium, sorry, on silicon and P-alpha gamma reaction on aluminum. They make the same compound nucleus, which the excites with one gamma, but you don't know how you really produce this. You produce it by hitting protons on aluminum or by hitting protons on silicon. So in some cases, really you have problem. The good thing is that most of these reactions that you can see, for example, aluminum, they don't just give you one gamma ray. They give you two or three gamma rays. So if you know that one gamma ray is problematic, you throw it out and you use the other two or the other one. But it's very rare to find the same gamma ray, exactly the same gamma ray from two different nuclei. From the thickness of the sample, because it's not going to be out-absorbed as it happens in pixie. I mean, the gamma rays have a much higher energy. Yeah, if you are talking about attenuation of gamma rays, no, you don't really care, because look here. You are at 1mV of gamma rays. 1mV gamma rays in a 1mm sample thick, or 1cm thick, it will be attenuated by 2% or 3%. So there is no really problem, attenuation of gamma rays into your sample. You may have attenuation of the gamma rays because of your chamber. You may also have attenuation because of your detector or something you have in front of your detector. But there you don't care, because as we were talking in the afternoon, when you are doing an efficiency calibration, if you put your source in the place of the target, on the place of the sample, then you compensate, you measure, and you take into account these attenuation factors. And attenuation into the sample, if you want to see it, then you have to go and use very low energies of 100-something kV, which is not very common in pixie. You can use either high-purity German detectors, it's better, or you can use sodium iodide. Natural background is almost nothing. Okay, the natural background comes most of the time from potassium 40, that gives you one... I have it somewhere here. Yes. It's over here. Oh, sorry. A. It's over here. You see background. This is natural potassium. Most of the time, if you have a problem from the background, it's not from that, it's from 511. This gives you a problem sometimes. And especially if it's a beta-plus emitter, if you produce something that is a beta-plus emitter, and it doesn't give you only 511, the problem also is the Comton that this one gives you. This may be elevated. So if you are looking at fluorine, for example, and fluorine can give you one gamma-ray at 110 kV, which is good. It gives you one at 197 kV. This sits onto the Comton of the 511 background, and normally you don't use that. Because it's bad. Yes. But there can be some gamma lines that can interfere and cannot be resolved by even HPG, right? Of course, it depends, but the normal resolution you have at a high purity germanium detector is around 2.0 kV at 132. So if your gamma rays are apart more than 2 kV, you are perfect. If your matrix is complicated with a lot of gamma rays, then yes, there you must have this problem. And this problem is bigger if you are using a sodium iodide, because a worse resolution, and they are doing bigger with that, it's much more difficult. While with jelly or with a high purity germanium detector, you have the resolution to see one. So for example, look here. Here if you watch, you can see that there are two lines over here. It may happen. I don't say that it never happens. It may happen. But most of the time you have ways of compensating with that. But instead of taking that gamma ray, you take another gamma ray. Magnesium, you always rely on the lower one. This one. For the aluminum, it seems to be overlapping. The second and the third one. You are talking here? Yes, this one and there is another one. These are, I said before, the aluminum and silicon. It wasn't aluminum and silicon, it was aluminum and magnesium. You do a P-alpha, if I remember well, at magnesium and PP-prime at aluminum. You go with both ways. You end up to the same nucleus, which will give you these things. But here you have also magnesium, as you can see here, which is clean. It doesn't have any aluminum inside. Sorry? Yes, but magnesium here is clean. So you can use this one in order to do your quantification. And if you wait, you can use, for example, this aluminum. This one is 10,014 kV, which is clean with no interference. This one is 844, which can be given from aluminum and from magnesium. Should we continue? Are we ready to continue with RBS? Why are you laughing? So, RBS, rather for backscattering. This is a very nice technique. First let's define where it works better. RBS, it's best when you want to identify and quantify heavy elements that exist in lighter substrates on lighter matrices. So, RBS, it's ideal, for example, if you have gold onto or into glass. Heavy element, light substrate, silicon oxide. If you have, for example, let's say, tantalum onto aluminum. It's perfect, very heavy, very light. The problem comes with RBS, as you will see, and you will hopefully understand why there is a problem. If you go vice versa, for example, if you want to see carbon into gold with RBS, forget it. You will never see it. If you want to see silicon that is, for example, diffused into tungsten, forget it. You will never see it with RBS. So, what's the idea of RBS? RBS, it's like pool, like billiards. I have my sample over here. I throw ions. These ions are elastically scattered from the nucleus of the sample. Let me take the elastically scattered ions and I have the information about the nucleus that I found in my way, the quantification of them, and as you will see, I also take information about their depth profiling, how they go, how the concentration changes as I go deeper. Identification of material, very simple. Physics. Elastic scattering. You know the mass and the energy very well of what you throw. You know the mass and the energy of what you detect. You don't know the mass over here, but you know its energy. You assume that this energy is zero. Okay, there is some thermal movement, but let's say zero. So, if you solve the conservation of energy and momentum, you can find the mass over here. If you find the mass, you know the element. It's so simple. It's very, very simple. Easy physics. This you can see here. For example, if you assume that A that I have this sample and I have nucleus A and nucleus B, A is heavier than B, the protons or the ions that will come back from the heavier A will come back with a bigger energy than the ones that will come from B. So, I measure the energy over here. I measure the energy over here. I solve these equations, and then I have my identification. How do I quantify? This is the formula I showed you the first day. It's the cross-section. I just solved from the point of view of the unknown number of target elements. This is what I searched. Okay, how many of the nucleus, of the nuclei, sorry, I found in my way. This is the number of the detected ions. No, I measure them. I have my detector over there. I measure it. Of course I know it. Ω, the solid angle of the detector. I know it. I put the detector there. I can measure it. Number of incident particles, number of beams particles. I know it. I produce the beam. I throw them. I measure with the current. I know it. And here comes the cross-section. Now, the problem with the cross-section is the following. That in nuclear physics, the only analytical form I know for cross-section is rather for cross-section. Άγγλιο Άγγλιο Άγγλιο has solved this cross-section many, many years ago. It's over here. Well known. So, if I'm obeying rather for slow, I put here the rather for cross-section. I have everything known. I can find that. Perfect. It's very, very easy. What is my problem in rather for backscattering? The problem in rather for backscattering is that this formula over here doesn't hold for all the situations. It mainly, you can mainly use rather for cross-section where you are using. Like Heavy elements with heavy elements. When the COOLOB barrier or includes COOLOB interaction is big. In order to have that, if you use light elements, you need for your target to have heavy elements on your target and low energies, 1.5 or 2 MeV. Or if you are using heavy elements here, you need again heavy elements here but for example, if you use protons of 5 MeV onto aluminum, this doesn't hold, you throw it out. You can't use RBS. If you use protons on lithium, light with light, this doesn't hold, you throw it out. So this is the restriction of RBS. This is the beams we usually use, protons from 05 to 3 MeV, you can use for RBS heavier ions like carbon or oxygen or even heavier. We talked about that. You use normally surface barrier detectors. These are our chambers where you can do RBS. The beam comes over here. These are surface barrier detectors. You mount your target over here. So you have elastically backscattered and you can detect that over here. Or this is another chamber where you can mount your targets. The beam comes from this direction. Your detector is somewhere over here. So again, you backscattered. Why you backscattered? This is very simple. Because if your target is thick, your beam stops there, nothing exits. So you can't do forward scattering. This is the first reason. The second reason is that if you look at the radar for backscattering, it goes here with theta. So this holds when you are looking at large angles. 170 degrees, 160 degrees. If you go to 30 degrees forward scattering, this doesn't hold. So you have problems of quantifying. And here, let's see some conceptual examples. The reason of putting this example is to understand how I can... Did use, how I can calculate the depth profile using RBS. So this something symbol. I have red nuclei, I have blue nuclei, blue nuclei are heavier than red nuclei. I use the same E1 nucleus over here. So what do I expect? The energy when I scatter from light elements will give me something over here. If I go and scatter to heavier elements, I will go back with an E2 larger than this E2. So I'll take a peak over here. OK, something very easy. So from the energy of the backscatter ions, I can find the mass of what I hit. Of course, the first problem is that if I combine these two in one layer, you will have E2-scamming scattered from the blue nuclei. So you will take this peak. And I will have also E2-scamming from this nuclei. So I will take also this peak. Now let's make things more complicated. Instead of having just one layer of red nucleus, I have two layers of red nucleus. So what will happen? As I throw my ions over here with energy E1, some of them will scatter in the first layer and will go back with an E2. So I will have this peak over here. Some of my ions will pass through the first layer. They won't interact with my first layer. As they pass from the first layer, they will lose energy. Remember what we said on Tuesday? Energy loss. So they will find the second layer, not with an energy of E1, but with an energy of E1-prime. So they will scatter from that and will go back with an energy of E2-prime, which will be a little less than E2. So instead of having only this black line over here, I will have also the red line. The red line is the superposition, think of a Gaussian black line from the first layer and another one from the second layer. If you superimpose that, you will take the red one. If I put a third layer, then you will have the blue line. And if I continue my game, you have the superposition of Gaussians like that, and this is what you will take as a spectrum, until my energy stops in there. So I will begin from the energy of the first layer and go back down to zero. This is what I call a thick target or an infinite target spectrum. When I'm talking about an infinite target spectrum, I mean that I have a target that my beam stops inside. Why it goes up and it's not like a straight line? This is because of Rutherford's law. If you look at the Rutherford's law, the lowest the energy, it goes up. So as I go to lower energies, as I go deeper in my sample, I have lower energies, bigger probability of interaction, and this is what I take. This is the example I show you, and now let's play some tricks. What I do here? I take the red nucleus and I put them behind the blue ones. Okay, so what will happen? This is the spectrum I will take from here, but here as I have the red nucleus behind the blue nucleus and I lose energy as I will find them. Instead of having the black line over here, my line is over here a little to the left with lower energy. And why? Because my ions lost energy in order to pass the first layer. This is the first indication that I can deduce information about depth profiling from RBS. If I look that the energy comes in a lower position that I expected that, this means that it's not on the surface, but it's deeper inside. Of course, this gives you also the first problem in RBS. If you look at this energy, forget the black line, and look only the red one, this can mean two things. Either that I have the red species behind something else, or that I have a lighter element than the red one on the surface. It could be both. Okay, so this is the first problem, because I only rely on the energy for RBS. It doesn't mean that I have only one solution. Many times I can find different matrices giving me the same spectrum. Just keep that in mind that this is the first problem. The same game over here, so I have a thick target here with blue and red dots. So what we will have? The red line over here stands for the blue heavy elements. The blue line stands for the light elements, and what I will see will be this step over here, which is the superposition of two thick targets. Here I have no problem because I can see it. If I can see the step, everything is perfect. I can quantify. Here I have put more red nuclei, light nuclei, than thick. What I will have? This one drops because I have less quantity. This one goes up because I have more quantity. So the step is more pronounced. Perfect. Remember what I told you in the beginning, that RBS is perfect if I have heavy elements into a light matrix on a light substrate. We have this thing over here. If you do the vice versa, you are lost. So here I have a lot of blue heavy nuclei with little red ones. This is what you will take. This comes from the heavy nuclei, and here start having the step from the light nuclei. You won't see it, never ever. You can't see it, you can't analyze it. Then you are lost. RBS is useless if you have this situation. On the other hand, if you have just a heavy layer, or let's say thickness of layers, onto a light substrate, from the light substrate you will take this infinite spectrum, while from the light ones just this one's peak. As I don't have infinite thickness for the blue nuclei, I have just one peak. This is perfect, this is textbook case for RBS analysis. These are some samples, let's say some examples. Here I have a layer of gold onto silicon dioxide. So this is silicon, this is oxygen, and this is gold. This is a thin layer of gold onto silicon dioxide. This was taken with 2 MeV helium beam. This is another trick that you can see how the profile works. I have a layer of gold, a layer of glass, layer of gold, layer of glass, layer of gold, infinite glass. Okay, so I have a tri layer. This comes from the first layer of gold. Then my beam meets oxygen dioxide. It will give you this trick over here. Then it meets again gold, then again silicon dioxide. This will give you this trick over here. Again gold, again silicon dioxide. So from that you can see layers of gold onto these samples with RBS. Okay, this is something, let's say, difficult, so the lime glass with RBS, infinite thickness, so each step corresponds to one of the elements. These are real examples, if you want. This was an experiment we did. We had some gypsum where it was dissolved into lead and they wanted to see how its lead is absorbed into gypsum. So this is the RBS spectrum from clean gypsum. While this one over here is from a gypsum that absorbed lead. So if you magnify here you will see this peak over here, this peak corresponds to the lead and if you look at the form, the form corresponds to the depth profile of lead. If you had the lead only on the surface you should have only a Gaussian over here, but if you look over here you have a tail. This tail means that my lead has gone into depth. Other examples with proton beam, this is nice, this is a spectrum from an external beam, it's an RBS spectrum from external beam of a glass. Here you can see the peak of helium. This is because in external beams many times we use helium between your sample and your detectors in order to throw away air. So you can see that again you can see the elements. This was done in comparison between some clean glasses and some corroded glasses. So for example here you should have sodium and you see that in the clean one you have sodium while in the corroded one you don't have any sodium. So this means that sodium has been depleted. Again this was used in external beam. You can see oxygen, carbon, copper, gold over here. Another example lead, silver, silicon, oxygen. And this is let's say what is new in RBS. As my problem in RBS is how to distinguish between energies. This is what we call high resolution RBS. So what you do is you use your incident beam but instead of putting here your detector and detect your backscatter ions you use a magnet so depending on the energy you divert to different positions and here instead of having a silicon surface barrier detector you have a position such as a detector and from the end of the position of your ion over here you can identify the species. More resolution that's why it's high resolution. Your surface barrier detector has a resolution of 15 to 20 kV. So you can distinguish between two peaks between 15 and 20 kV. With this trick over here you go to high resolution you go down to 3 kV. So you can see better layers, layer structure and things like that. What is it? I believe in this situation they used also some timing signal. It was with a pulsed beam and they were using also a pulsed... If you're using a timing signal in my knowledge... You don't need the position sensitive. This is somewhere... This is this one what you are talking about. It's this tough RBS where they use... I don't know why in this situation they used both of them. I really don't know but you are talking about this tough RBS where here you are using again the time of light how much time from the recalls will take to reach your detector in order again to distinguish masses. This system, this time of light, whenever you hear time of light it's very good for mass resolution. And for example here you can see that for gallium you can distinguish between two different isotopes of gallium. 71 and 69. In normal RBS you will never, never, never, never see this distinction of isotopes. They are there but because of the resolution of your detector they are super opposed and you have one signal just from gallium. By using this tough RBS you can also distinguish isotopes. But these are special cases for example. It's much less. Yeah, because of the distance it's much less the efficiency. That's true. No, no, in the ion beam analysis in most of the times you don't damage your target. You don't have that problem because you are using a beam of 10 to the... 10 particles per second for example and if you do some damage here could be only by thermal deposition. Not from sputtering because here you are not doing any sputtering. You can just scatter on them. So normally you don't have problems here but because of the solid angle you are absolutely right. The efficiency of this system is less than normal RBS. That's true. Because here your problem is that the distance until you find something is much, much bigger you see it's half a meter. So the solid angle is very small. If you had only one detector you would put the detector over here in 30 centimeters covering a bigger solid angle. So what the number of ions that you detect is much, much, much bigger than the ions that you detect over here. Yeah, you have better resolution. You have better resolution. Where's efficiency? In life you can't have both. You can't have good efficiency, a good resolution. So you use this trick over here you have better resolution but lower efficiency. You have to wait a lot in order to see that, a lot of time. While if you use your surface barrier detector over here you will do half the time, one third of the time but you will never distinguish that. So depending on what you want to do you have to choose what you are going to do. No, it should go down. This is because of electronics. You cut it. If you look at physics, if you look at physics it would go up. Rather it would say that it would go up. I don't know if it's, for example, look over here. It goes up. Why it goes down? It goes down because of my electronics. If I leave that up I will have a lot of counts over here that are useless but this will give me the time. It will slow my system. So I use a threshold and I cut them. It's going like that. You have multiple things. You have multiple scattering also that plays a role over here. You are in lower energy so you have also multiple scattering that plays a role over here. You have struggling but normally this doesn't matter. You don't use that. It should be the same. It should be the same. The form should be the same. Both should go up. At least when we are doing experiments with protons it always goes up. It always goes up and we cut it with discriminators because it's annoying. I don't know if I have a sample of flowers here. Okay, this is simulations. If I have a real spectrum. This is a real spectrum but here we have cut it because here it starts going up if you see. It has to tend to go up but here we have put a discriminator just not to count a lot. But from whatever I have seen it's the same. Protons and alphas. And carbon also. We used also carbon. It gives you the same effect. And oxygen gives you the same effect. If you go to low energies it goes up. For example, look here. This is the normal thing. Okay, it's with alphas but this is the normal thing you should have going up. Should we continue or you have other questions? Okay, this is a dream. Let's say it's, I believe it's a Chinese company that sells that. It's called its Bench of RBS. So this is a compact accelerator because as I told you the biggest problem with human analysis techniques is that they are not portable. They have the accelerator so the samples must come to the laboratory. You can't take your laboratory to the sample. So this was the idea of having a portable, let's say accelerator installed within chamber and then RBS detector. It goes up to 500 kV. So this is the accelerator. Here you have your chamber. Okay, and you do your analysis. I don't know how good this thing works. I've never used that. And let's proceed. Okay, it's two meters. I don't know. It should be something 150 kilos, something like that. But it's the best idea I have for portability. So move on on elastic backscattering, EBS or nuclear elastic backscattering. This is just a joke, elastic EBS. Normally EBS is RBS. It's absolutely the same thing. What's the only difference? That instead of using the Rutherford formula, you use cross sections that are measured by someone else. Remember that in the beginning I told you blah, blah, blah. I need to know the cross section in order to quantify. If it's not Rutherford, but somebody else has measured that and gives me the cross section, I don't care. I have the cross section. If I have the cross section, I can do my job again. And this is EBS. The only thing is that in some cases, as you will see, for example, in carbon, the actual cross section is much bigger than the Rutherford. This is the cross section. And this is the ratio of the cross section of this reaction elastic scattering onto carbon 12 over the Rutherford. So if you look at 101.7 MeV, you will see that the actual cross section is 90 times bigger than the Rutherford one. So I do my Rutherford experiment. But if this reaction obeyed the Rutherford, I would see the black line over here, impossible to analyze, forget it. You have to throw it out. But because of the cross section that goes 90 times higher, you will see the red line. So you see something like a peak. But in order to perform EBS or RBS, you have to have a well-known cross section, first of all, and second of all, this cross section should be higher enough, much higher than the Rutherford one. OK, these are some examples of EBS. But this is applicable, as I told you, only for specific combinations of beam and target. Because of the cross section that has to be high. And for example, this cross section, again for PP, PP prime at boron 11, you can see here that I have this resonance that I can use. The same thing, an example, they used that in order to detect carbon into these swords. They were able to see carbon, not very well, as you can see, but they could see carbon using this exact reaction at this energy, taking advantage of the resonance. But in most cases, when I want to see carbon, I use nuclear reaction analysis. What is nuclear reaction analysis? It's much like RBS. The only difference is that now I'm not using elastically scattering, but I'm doing reactions. So instead of throwing protons and recording detecting protons, I throw, for example, neutrons and I detect protons. Or I use neutrons and I detect alphas. Or I use protons and I detect alphas. Or I throw alphas and I detect protons. These are all nuclear reactions. When you have a nuclear reaction, your nuclear reaction can be either elastic. So I have preservation of kinetic energy. It may be what we call esothermic. This means that I have to give energy in order that to happen. Or it can be exothermic, like let's say chemical reaction. This means that when I do the reaction, I have a surplus of energy that the reaction gives me. It doesn't know what to do with this energy. And it gives that energy as kinetic. One, two, the products. The way I measure my reaction, how exothermic or exothermic is, is the Q-value. If I have a Q-value that is very, very positive, this means that I have a surplus, a big surplus of energy. For example, let's take carbon to make myself understand. So let's say that I want to detect carbon. Instead of using protons, I use deutrons. What we will have? Some of the deutrons will elastically scatter from carbon. So I will have this situation over here. Okay, I have the big background of gold and a very small peak of elastically backscattered deutrons for carbon. On the same time, some of the deutrons may react with proton, do this DP reaction. So they react with carbon. And instead of having back deutrons, I take back protons. Because this reaction, the DP reaction on carbon, has a high Q-value, it's positive plus 2.7 MeV. This means that my system has a surplus of 2.7 MeV. That somehow has to give them back to me. So what it does? It gives them back to me as a kinetic energy of protons. So instead, if I use a deutrons of 1.2 MeV, I will take back protons of 3 MeV. It's almost 1.2 MeV, the energy I'm throwing, the Q-value 2.7. Is this good for me? It's very good because all the elastically scattering things will come from 1.2 MeV and less. Okay, it's elastically scattering. So whatever I have as much as it will go less than that. And my reaction will come in a free, in a background free region, over here, at 3 MeV. It will give me a very nice peak that I can analyze because I have no background. It's easy. My reaction here belongs to this reaction. Do I have some nice examples? Okay, let's take that as an example. I use deutrons on a sample. This is what we called before RBS. Okay, so you have zirconium, iron, calcium, aluminum, sodium, oxygen. All these steps. Oxygen here is very difficult to analyze. You see, it's not a real peak. On the same time that I take this measurement and with the elastic scattering deutrons, I also have reactions on oxygen. So I have the DP reaction, so I throw deutrons and I take back protons. I have the DP1 reaction, again deutrons, but I take protons of lower energy. And look what happens here. My RBS spectrum starts at 200 while this starts at 500. So this, if you extend, is somewhere over here. In this region, it's background free and from the form of this one, if I know the cross-section, I can take, I can first quantify and second, I can also find the depth profiling of oxygen into that sample, which in this case is absolutely impossible. Is it clear what nuclear reaction analysis is? What is the trick? Instead of looking elastic ones, I look at inelastic channels, I look at inelastic particles, other kind of particles, that if I have a proper cross-section for this reaction, I can find them into a background free environment. Nuclear reaction analysis is ideal. If you want to look at carbon because of this DP reaction, oxygen, it's perfect for oxygen, it's good, sorry, it's perfect for nitrogen. You can see easily nitrogen with nuclear reaction analysis. It's not good, it's good for beryllium, it's not good for fluorine, it's not good for sodium, why? There is no such reaction with a positive Q value. We don't have any exothermic reactions for sodium, so I can't use nuclear reaction analysis for sodium. This is another example, again you see, I have here, this is protons coming from carbon, this is protons coming from oxygen and this for example, protons coming back from nitrogen, it's not very clear over here, but this is nice spectrum and we go to finish with, do I have time or have exhausted my time? You just missed time for 7 minutes. Do I have some time for Erda? It will go fast. What's elastic recoil detection analysis? The trick is the following, this is what I do in RBS. I use a light element and I detect the backscatter from the elements. In Erda, which is perfect for light elements, if you want to see light elements into a sample, what you do is you take your sample, you turn it at around 15 degrees, you bombard it with heavy ions like silicon chloride and you throw out the light ones. So it's something like sputtering. You have your sample here, but instead of throwing and detecting, this is RBS, you tilt it, you have heavy elements, you hit under an angle and you kick out light elements. You detect all the light elements by throwing them out from your sample. The problem in Erda is that some of these heavy elements, heavy nuclei, sorry, some of the beam will scatter elastically and will come also into your detector. This has two problems. First of all, it will kill your detector. The second one is that it will mess with your signal over here. So somehow you have to get rid of your elastically scattered beam. In most of the cases what you do, you put a foil here, an absorber, let's say, that will permit light elements to pass while it will stop due to the high stopping power, the heavy elements. This is what we call normal Erda. So here is the sample. We use Erda, most of the time it's for hydrogen. This is the RBS spectra. You can see here. And this is the profile of hydrogen. Detected in forward angles. These are detected backward angles. So you have your sample like RBS. While you're here, you throw hydrogen from the surface backwards. And again, from this shape, you can also depth profile your hydrogen. This was what I saw you here. It was, let's say, the old way of doing Erda. The new way is this one. It's what we call TOFERDA, time of light, elastically called direction analysis. Again, your sample is over here. Your beam comes from this direction. Your sample is tilted. But as you hit your target, you throw outside light elements. Because the problem is that if you use just a surface body detector, again you have only the energy in order to detect and to distinguish between different species of light elements. With TOFERDA, you are using the time of light of the elements in order to distinguish between masses. So you have a timing detector over here, a timing detector over here, and an energy detector over here. You measure timing between the two detectors and you construct this kind of matrices, what we call energy over time of light. And you have these nice bananas. Each banana corresponds to one mass. So what you do over here? You select the mass you want. For example, I want to see what's happened to oxygen. And you project that over energy. And you take something like that. If you want to see what's happening with hydrogen, you select the banana from the hydrogen over here. You project that to the energy. You take something like that and you analyze. So the trick with TOFERDA is that you are using the time of light in order to have a better mass separation than using just an energy detector. And this is what most of the laboratories nowadays use instead of normal ERDA. I'm skipping all of that, going to the last transparencies. As I told you, in most of the times, if you take care, you can't destroy your sample. These are some tests that were done to see how I affect my sample by using different fluences. So this is a glass. And as you can see, as it was irradiated, this is what you take with some normal fluence. And as you increase your fluence, it's getting worse, worse, worse, worse. The same was done also onto a canvas. Okay, here you see that you start having bubbles. This is because of thermal deposition. And this is again the same thing with the microbeam. If you stick to 10 micro coulombs per centimeter square, you can't see really anything that you have damaged anything. If you go four times the fluence, you start seeing things. You start destroying your canvas. If you go to 80, it's clear, you can see also the movement of the beam, how it moves. Why should I go from 10 to 80? The only reason is detection limits. If you want, for example, to see sodium, and you go to 10 micro coulombs per centimeter square and you don't take the signal, you may say, okay, let's wait. Let's wait, let's wait until I see it. If you wait until you see it, you may destroy your delicate artefact. So you have always to take into your mind that they are not distracted by the beam analysis if you are careful. In this case, what I should do was saying that, okay, I have two choices. Either destroy your artefact and give you an answer or not destroy your artefact and you stay without an answer. What do you prefer? Okay, most of the people would say, okay, don't destroy my artefact. And this is just to close up. So rather for bascattering, it's depth profiling and it gives you results, as we said, most of the times when you want to detect heavy elements into light matrices. Elasticity goal detection is for light elements wherever you are, z less than 17. PIXE is best from sodium and up. PIGE is best from silicon and lower, but these are the cases that mostly I use it, lithium, boron, fluorine, sodium, magnesium. Nuclear reaction analysis is very good for carbon, nitrogen, oxygen and I also didn't talk to you about steam and ion or luminescence. So that was all. Do you have questions before going to it? Sorry, I couldn't hear you. Tell me. Yes, yes, oxygen is easy. With nuclear reaction analysis, not with RBS. No, with RBS it will be difficult to see it. You will take, sorry? Yes, but depending on the thickness of the layer, maybe it's separated. So if your thickness is low, sorry, it's small, maybe the two signals should be reposed and you will have only one signal. If it's thick enough, maybe you have the first signal for the layer and the second signal. But this I can't tell you without doing any simulations, real simulations. Maybe you have to adjust your beam also, the energy of your beam in order to see them, to see the difference. What I can tell you is that if it's less than 10 nanometers, you will never see it as too different. You will never see it. No, we'll never. You need RBS in very low energies. You need what we call in our days medium energy maze, medium energy... You need very low energies. With normal RBS it's very thin, so you will never see it as a signal. You need medium energy ion scattering, which is exactly like RBS, but in energies lower than 400 kV. So you use very low energies and there you have a very good mass resolution. There you can see it. It's very good for nanometer scale. RBS is starting getting better... It starts working from 100 nanometers and higher. But it always depends on the sample you have. But in your case I believe you need maze, lower energies. It's a big discussion. RBS and channeling is... It's a big discussion. It can really mess your signal. If you want to do what we do... What we do in these situations... If we are not care about the channels, we don't want to know the channels... Can you do anything? Yes, you can. This is what we call channel, but you need a special goniometer for that. You need a goniometer that can change your crystal in various samples, sorry, in various positions. We have this channel device. If you look somewhere in the beginning, over here. This is a motorized sample holder that can give you five movements. It can go like that. It can go four movements up and down, but it can also tilt like that and it can tilt like that. So by playing like that and looking at RBS, you can turn in various angles your crystal until you find the channel. It is possible, yes. It is a technique we are calling channeling. So if you look at your RBS signal, you will see that in a random position you will go like that and when you go into your channel, you go down. But you need something like that. With RBS, you can do it. We have played with silicon crystals, we have played with germanium crystals, and really you can find your channel. But you need that device that is not common. The sample, I am moving the sample. Here this is the sample holder. The chamber stays like that. The detector stays like that. But here I am moving the sample. I am moving the sample in various... No, no, no. I am moving the sample. It is a sample holder. But it is not very common, I believe. I believe in... You have it? Because I know... If you apply, for example, the CRP... Because I know that most of the laboratories have these movements. Maybe also rotation. But they don't have also this rotation most of the laboratories. Because when you are doing a normal RBS what you want is to mount a lot of samples in your target. So you just need this movement and this movement. Magnitude slower measurement. Of course. 0.9°C. But it's done. We have done sonic measurements. Other questions? For detectors. You don't need for detectors. For RBS we don't need for detectors. You just need one. Okay, in the best case if you want to be perfect you want two detectors. As if you remember I told you that in some cases you can't distinguish if the peak you have comes from an element in depth or from a lighter element onto the surface. If you have two detectors at different angles you can distinguish between them. Because you have two equations and two parameters. So you can solve the equation. This here was done for a nuclear physics measurement not for RBS but when I took the photo it was another setup. Normally for RBS what you need is only the guy over here. Okay, either this one either this one at 170°C the other you throw it, you don't care. And in this chamber this is what we have. We have just one detector over here. But it's just one detector. You don't need more than that. Always. If we increase the energy of incident peak it transmits the absorber. And we don't reach the depth profile. If we decrease the energy for prevent the transmission of absorber we lost depth of sample. Can we solve it? If you are using an absorber you can play also with the thickness of the absorber. But you can't solve all the cases. One of the problems with ERDA is that you are much more surfacial than RBS. You are using heavy ions so you stick more to the surface and also you are tilted. So you are even more surfacial. If you increase your energy in order to go deeper then in order to cut that you need a thicker absorber but then you will lose also some light elements. You will cut some elements. The only solution to that is using a toferda. You can do magic. It's physics. When you gain something you always lose something. There is no win-win situation. It's the same thing in physics. You can't solve all the problems but in your case the only solution I would think was a toferda system because they are the only absorber if you can call it absorber you have is the carbon foil of the detector. This is the limitation and also of course the electronics but the only limitation. Polluting no polluting because the number of particles that you are ejecting is very low. So polluting your chamber I wouldn't say that. Not more if you want from doing I don't know normal RBS but the amount of particles you are producing it's very very low. So it's if you are lucky you will take something like let's say 4000 or 6000 counts it's nothing no no no no no it's the same like ion beam analysis you can't do everything with ion beam analysis also ERDA has some limitations depending on your sample I can tell you if you can do it or not if you have metals for example it's easy easily done sorry I never tried putting soil into vacuum to be honest I have never tried that because ok I believe it can be done but there you must take a lot of time for sample preparation so you have somehow to dry soil you have to make a pellet and if you dry it and make a pellet that can withstand vacuum yes you can use that then also you can do that we are missing time yeah I finished but I just answered questions yeah but I am just saying that this is already half another but this is can I stop? yeah yeah of course so really leave me your IBA stick you want it