 Hello everyone. In the previous lecture, I discussed about the two nuclear integrate techniques namely RBS and ERDA which are based on a charge particle beam bombarding the target and we are measuring either the backscattered particle like in RBS or the forward imitated recoils in ERDA. Now, I will discuss two techniques which are based on the measurement of the gamma rays that are emitted when a projectile reacts with the target. So, they are called nuclear reaction analysis NRA and particle induced gamma emission PE. In fact, in particle induced gamma emission mostly we use proton as a projectile and it can also be called as proton induced gamma emission, but there are other piggy reactions where the deuterium beam also can be used or even other beams can be used alpha can be used and so on. So, first let me discuss the NRA nuclear reaction. So, there is a distinction between what NRA techniques I am discussing basically they are based on the resonance in the nuclear reaction cross-section. So, those techniques which are based on the resonances in the nuclear reaction cross-sections we will call NRA and other techniques. So, NRA and piggy basically you have nuclear reactions emission of gamma ray, but those techniques where there is an enhancement in the cross-section at particular energy of projectile that means there is a resonance we are clubbing as NRA as the historical it has been used as NRA. So, resonant nuclear reaction means at a particular energy of the projectile there is a significant enhancement in the cross-section of the reaction. The two most commonly used nuclear reactions are projectile is 1915 you take note of it projectiles during 19 normally you know proton will be used as a prototype here nitrogen 15 or fluorine 19 is the projectile and we also study hydrogen in the material. So, hydrogen is a target. So, nitrogen 15 plus proton carbon 12 plus helium plus a gamma ray is emitted. Now, the gamma ray is 4.43 amide and the ER means the resonance energy this is resonance energy the energy of nitrogen 15 at which resonance occurs. So, I will elaborate this using this graph what we have here is the cross-section versus the energy of the projectile nitrogen 15 and corresponding energy of proton also is used suppose you want to detect nitrogen 15 using proton B that also you can do but applications are more with regard to hydrogen determination using nitrogen 15. So, what I am showing here that the cross-section is going here and then there is a see this is log scale. So, here the cross-section is 100 200 and here it is 2 lakh. So, 200 to 2 lakh 200,000. So, there is a 300 3 3 orders of magnitude increase in the cross-section 1000 time the cross-section is rising. So, there is one more resonance at so this is at 6.405 amide of nitrogen 15 this is at 13.38 amide of nitrogen 15 and there are more resonances but we focus on the first resonance 6.43 405 amides. So, that means what if you bombard a material containing hydrogen at the surface and at 6.405 amide of nitrogen 15 you will get very high increase in the gamma ray yield. And so that the moment the energy of nitrogen agrees with the resonance energy then there will be 3 4 increase in the gamma ray yield 3 orders of increase in the gamma ray. Another reaction is chlorine 90 plus proton or hydrogen option 60 60 plus alpha and the gamma ray of 6 amide is emitted and this happens again at 2 energies 6 amide and 3.3 again we use the 6 amide gamma energy of the chlorine 90. So, essentially you are using making you the resonance. So, if the energy of the projectile is matching with the the resonance energy there will be significant enhancement of the gamma ray yields. So, how do you get the information yield at the resonance energy gamma ray yield gamma ray yield a resonance energy gives you the concentration of the hydrogen. So, when you are starting with the resonance energy 6.4 amide for nitrogen 15 resonance condition this resonance condition is met at the surface. So, you are probing the surface hydrogen then you increase the energy of nitrogen 15 in steps of 0.1 10 K e b and so on. So, you are gradually increasing the energy of projectile the resonance condition is met in the depth of the. So, you understand this point if we suppose this is the target and you start with the first 6.4 amide you will see the hydrogen here. If you want to see the hydrogen here you have to have higher energy maybe 6.5 6.6 or so because the projectile will lose energy in this. So, as if you want to probe hydrogen at different depths you required to have iron at projectile energy and you can calculate from the energy at which the resonance is achieved you can calculate what is the depth of that condition. So, that is the yield at higher energy gives you the bulk hydrogen. So, that means at high energy you are in the bulk resonance condition in the bulk and what is that depth the e minus here. So, e minus e r upon d e by dx we give you dx. So, if you know the resonance you know the resonance energy the energy of projectile at which the resonance occurs we divided by d e by dx is known you can find out the depth at fixed depth and does not was probed. So, this is the principle of resonance nuclear reaction or NRA. So, how do you get the depth profiling? As I already discussed you measure the gamma ray yield as a function of nitrogen 15 B minutes me projectile B minutes. So, you can see here the nitrogen 15 B energy is increasing from 6.4 or you can go slightly low 6.3 or so that is for 6.35. So, you can see here each point you know here the point will be 6.5, 6.6. So, under t you can go even lower smaller steps and so, the experiment involves bombardment of that target. In fact, I forgot to tell you about the experimental arrangement here that this projectile beam is passing in a vacuum and the you can one can divide the target depending upon you have a target that like a rotating wheel circular wheel and you have the targets at different. So, we can have 4, 6 targets at a time one of the target will come in the beam path and up when you bombard simultaneously you will measure the gamma energy and intensity energy is known intensity with a sodium iodide thallium. So, you do not need to have a high high HPG because you are not interested in the energy measurement. So, you can have multiple targets and measure the gamma intensity using sodium iodide thallium. And so, you can see this spectrum this 6.4 MeV yield of hydrogen corresponds to surface because that is the resonance condition initial beam energy and as you increase the beam energy you are covering the bulk hydrogen. So, this target actually they have implanted hydrogen in the sample at a particular energy and then you are proving whether this is like a demonstration of the profiling of hydrogen. Okay. So, the yield the gamma rate yield depends upon some factor which is depends upon the cross sectional detection efficiency the stopping power and the how many counts you get per micro coulomb that you choose the hydrogen concentration. So, counts versus energy gives you concentration versus depth as I mentioned just now and depth profile gives coming from the E minus ER energy of the incident energy minus resonance energy upon stopping power B by gates. For this silicon carbon this is a nitrogen 15 bombardment of hydrogen resonance know whatever resonance we saw in the previous slide resonance width was only 8 kV and that width determines the depth resolution because that gamma rate yield if you vary by less than 8 kV it will not make a difference. So, when you vary by 20 kV 30 kV you will see the hydrogen at different depths. So, up to 10 kV you will see it is only same as that you are proving by varying by 8 to 10 kV. So, the steps of nitrogen beam energy will be 20 to 30 kV and so on. So, this width of the resonance gives you the depth resolution 8 kV WHM upon the stopping power of nitrogen 15 in that matrix and that happens to be 46 nanometer in silicon will stopping power of nitrogen 15 in silicon can be obtained is known and 8 upon that stopping power gives you depth resolution. So, you can imagine at a nanometer scale you can prove the hydrogen. So, you will find there are not many techniques whereby you can prove hydrogen in the normally you know you will see that you can you can detect hot vacuum extraction and hydropole mass spectrometry for low jet hydrogen isotopes you you you hold the hydrogen by heating it and then you evaluate them by mass spectrometry. But if you can do it non-destructive thing like that. So, NRA is a unique technique to prove hydrogen because hydrogen is invisible in many other non-destructive techniques. What are the other like Newton activation analysis? You cannot do NAA of hydrogen by NAA by RBS. Therefore, by scattering spectrometry you cannot do because this is sensitive to heavier jet only. Then X-ray and OJ electron based spectrum X-ray fluorescence ahead of the X-ray very very small you know. So, most analytical nuclear analytical techniques hydrogen is invisible and therefore NRA in fact the the growth of NRA technique was basically because of its potential to determine hydrogen in materials. And also you will find technologically there are many materials which you know they may have hydrogen may have dramatic effects on their physical chemical, electro electrical properties and so it is important to know if there is a hydrogen impurity into this material. Particularly you know in nuclear technology the the hydrogen diffusion in zircal oil you are using water as a pool and hydrogen is generated it may diffuse into the zirconium and zirconium hydride will lead to stress corrosion cracking. Similarly the steel is prone to embrittlement by hydrogen and so in many technologically important materials hydrogen induced embrittlement or corrosion is a big problem and so if you have a non-destructive technique this will be the best to determine hydrogen and it is depth profiling in these materials. So, mostly NRA is used for hydrogen depth profiling in technologically important materials. Okay so I will just give you a couple of examples of hydrogen determination in technologically important material. One of the examples was you know the glass the Bodo-silicate glass is used for beautification of high level waste. This high level waste is the waste material in nuclear technology now it is not called a waste because it contains lot of important radioisotopes which are good food. So, when you irradiate uranium in the reactor to produce electricity and you get plutonium also and many present products are produced. You want to recycle the uranium and plutonium in the subsequent reactors and therefore what you do is you separate uranium plutonium from this spent nuclear fuel and then the ravinate of that's reprocessing is you can you have condensed to make what is called as the high level radioactive waste. This high level waste is a big problem to know how to manage it. So, what they do they electrify immobilize in a glass matrix and the glass matrix should retain this radioactive isotopes for a time period of hundreds of thousands of years because it shouldn't come out and therefore the chemical durability the leach rate of the glass is determined as a function of radiation doses people are studying radiation damage and so it can even the glass can be attacked by water and therefore how the leach rate will depend upon the if therefore you dip the glass in water then there could be leaching of sodium. Sodium is in the glass the sodium bolusical glass. So, sodium is taken as a marker for leach rate determination. So, when you put a glass in the water sodium will come out in the solution and the hydrogen will ingest into the glass. So, that study was done what is the mechanism of leaching of sodium from glass into the water and you can see here depth of by this reaction. So, nitrogen 15 beam energy is increased. So, they have directly put in terms of the depth in microns. So, 0.1 to 1 micron thick 1 micron thick glass sample and the depth profile of hydrogen is here and depth profile of sodium is here. So, for sodium sodium 23 p gamma magnesium 24 was used which is giving you 1.3 to m e d gamma a. So, you can do sodium depth profile. So, it also has got as a resonance at a particular energy of proton. So, what they see that from the surface sodium is coming out depth means this is a surface. So, from the bulk sodium is coming out into the water and hydrogen is getting into the bulk on the surface. So, surface is in touch with the water high hydrogen and gradually water is ingressing into the. So, you can find out the rate at which the exchange is taking place and another important thing that water H plus is not coming at plus, but H3O plus in rated hydrogen from the ratio from the ratio of the signal due to hydrogen and sodium in the NRA spectrum you can find out what is the form in which hydrogen is getting into the glass. So, this was a very important study way back in 1979 it was studied and it in fact led to the understanding the mechanism of inter diffusion between the alkali metal and the glass and hydrogen in the water. Another study was the hydrogen adsorption by palladium nanoparticles. This paper was published in Anguarte Kimi you can imagine the kind of studies people are doing because the kind of information that you get from these techniques are unique. It is not a routine analysis, but it is a very important technique very very useful information you get from. So, let me try to explain this what is happening that this the palladium nanoparticles are used as a catalyst for agglomeration of alkenes. So, they wanted to study whether it is the hydrogen is getting adsorbed on the surface of nanoparticles or the volume though there will be some hydrogen in the work of the nanoparticles. So, what is the role of surface adsorbed hydrogen or and volume adsorbed adsorbed hydrogen. So, what they found that by this technique NRA one could distinguish between the surface adsorbed hydrogen and volume adsorbed hydrogen and you can see here the depth provides at a different function of the hydrogen pressure they studied temper minus 7 millibar to 2 minus 5 millibar and the surface adsorbed hydrogen and the volume bulk hydrogen could be distinguished in you can deconvolve this their profile of hydrogen and then as a function of the hydrogen pressure they found that the surface adsorbed hydrogen plays a role only at low pressure high pressure the bulk hydrogen also starts playing its role. So, I will not go into the details the point I wanted to emphasize was that you can study the role of surface and bulk hydrogen in understanding the particular chemical reactions that are taking place. This is the kind of study people are doing. Now, I have come to the another technique of nuclear reaction analysis called the particle induced gamma emission where some of our colleagues have done a lot of work in this area. So, at the Bavarian Research Center we have an accelerator called FOTIA Holded Tandem Ion Accelerator. It is a 6 million volt terminal tandem accelerator and so you produce you can have 6 into 2 12 we have 6 million volt terminal then you can have 6 plus 1 1 plus 1 into 6 12 MeV proton beam but normally you get 5 MeV 6 and MeV proton beam and you can have higher beams also carbon and oxygen and so on. So, this is a the photograph of the setup we have a scattering chamber here 50 centimeters scattering chamber and for particle induced gamma ray you have a HPEG detector at 90 degree and you have the ladder target ladder you can bring different targets in the position of the beam by raising and lowering this target holder and this chamber is at vacuum because you may require to have suppose you are doing IBS you are determining the charge particles. So, there are different nuclear reactions with loaded elements induced by mostly protons but there can be reactions by Duteron like sodium D Duteron can be done. And so, what is important is then you should have a suitable gamma ray in the range 100 to 1000 Tv or so. So, for low jet materials you will find lithium, boron, fluorine, sodium, magnesium, aluminum, silicon, phosphorus, sulphur all of them have suitable nuclear reactions with their isotopes and the gamma energy are also well resolved. So, if you irradiate a sample with the proton beam of the order of 2 MeV and detect the gamma ray emitted by this reaction using a gemini detector you can do the determination of concentration of the elements present in a target. So, mostly this nuclear see once you go to higher target isotopes let us say you want to do for carp iron, cobalt, nickel or so what happens first of all you have to cross the coulomb barrier you have to have higher energy. Once you have the high energy for proton beam then you that the compound nucleus will be formed with the ethyl energy high energy and so it will evaporate neutrons. So, you will not have one reaction you will have multiple reactions Pn, P2n, P3n and also you may have P, P, P, P alpha and so on with lighter ones and so for higher in mass nuclei the gamma spectra will be very complicated. Whereas for low mass nuclei there are only simple reasons these are like you know inelastic scattering or low line states are involved in the nuclear reaction. So, gamma ray spectra are not very complex. So, P is a very simple technique you are not going to pour depth profiling because you are using protons. So, the stopping power is not very high you have a very low so resolution is not good as I mentioned in the IBS of that experiment for 4MV proton beam depth resolution was 1 micron. So, normally you know you would look for a nanometer scale depth resolution to do that profile. So, this is one of the experiments we did at Potia Quality Assurance of Nuclear Materials. So, as I mentioned know these are not meant for routine analysis you would just want to determine concentrations and then. So, this is a specific application there are certain rods they have they contain boron certain rods they do not contain. So, you want to quantify qualify them whether they use they do mixing. So, you want to know whether this rod contains boron or not. And so, you use the nuclear reaction boron 10 P alpha lithium 7 and there is a 429 kV gamma ray is emitted and that is that is measured using this germanium detector and the target actually target is very long. So, you cannot keep it inside the chamber because chamber height is only one one or two feet. So, what you do you take out the proton beam in air by isolating the vacuum with a tantalum file and proton beam is a proton with not much energy in air. So, you can put this big sample at the surface and then determine the gamma ray that are limited in the nuclear reaction. So, you can see here the 429 kV for the sample which contain boron and the without boron you do not see a peak. So, this is a kind of experiment where you do quality experiments means you want to ensure the people who have the manufacturer of the rods want to assure the user that this does not contain boron or this contains boron. You have to provide a certificate of 2A that this is not this is the meeting the requirement. So, that is the kind of experiment people do in the using proton induced gamma emission. This is another important work for piggy of glasses used for verification of high level based. So, again let me try to give you some background to this study as I was discussing in the previous one also that borositic glass is used to verify the high level based. The high level based is generated during the reprocessing of the spent in nuclear fuel and there will be different types of fuels and one of the fuels now for the future is thorium based fuels and that will contain THO2. Now, when you dissolved thorium in particularly sintered thorium it is very difficult to dissolve. And so, to dissolve thorium they may be use of hydrofluoric acid HF HF is very reactive acid and so, when you do reprocessing ultimately some fluorine may get into the glass matrix when you are immobilizing the they are supposed to remove fluorine. But suppose some fluorine is left then this fluorine in the glass matrix may lead to appearance of the spline faces some fluorides calciferide or some it may precipitate out because some like rare fluoride may precipitate out and so, you want to know what is the tolerance of fluorine in your glass. Even the fluoride can perfect the chemical durability of the glass because it may start to enhance the leach rate and so, for the long term performance of that this glass will retain the fish and products and actinides it is important to again ensure that whatever content of fluorine is there in the glass it is a safely it is within the tolerance. Therefore, every time you know dissolution of glass is when you can determine fluorine by ion selective electrodes very very simple, but then you have to dissolve the glass and do the study. So, that is a very tedious and you suppose you have multiple samples. Here is a very simple technique, you take the glass as it is non-destructively just bombard with the proton beam for a few seconds, few minutes and the gamma spectrum tells you what is the fluorine content. So, again the same reactions I have shown for the consequence of the glass you can have sodium borosilicate it will have sodium, aluminum, silicon, moron. So, there may be some extent of alumina also and if there is the fluorine then you will get this 110 kV gamma ray. So, in the one shot all the constituent of the glass will give you the gamma spectrum 110 again there is one more reaction of fluorine with the proton EP gamma you have 197 kV sodium 440 kV there is your 511 kV gamma ray also. So, by 2.4 kV proton beam you can determine the concentration of not only the constituent of the glass like silicon, aluminum, sodium, boron you can also determine the fluorine content and thereby qualify that the fluorine concept. So, there is a threshold of 1 percent you cannot have more than 1 percent fluorine in the glass you can quickly do the experiments and find out what the content of fluorine is glass. So, I just give you some of the examples of NRA and PIGI due to lack of time I could not give more examples, but the point I wanted to emphasize was that these nuclear electrical techniques are not meant for routine analysis they are meant for a very specific application in high technology areas and so, what has to which is not the only technique we will be using there can be a combination of other techniques and to understand the process to understand the what are with the mechanism also to qualify the high technology magic. So, there are there are many other examples, but I do not have time to describe, but I hope the I am able to bring the point that ion beams the charge flow energy ion beams can be used in current and slope materials which are being used in many many applications. So, that is all I have to say thank you very much.