 Now, in the beginning I said that accelerator is nothing but a microscope and why it is so and what kind of things are required. For example, here it is given on the left hand side that the resolution is inversely proportional to the momentum and which is inversely proportional to the root e at low energies and at high energies it is proportional to 1 by e. Now, if you so that means, if it is high energy you can get better resolution and therefore, you can you will be able to study much smaller dimensions. For example, these are some of the things which are given here that if you want to study this kind of dimensions. For example, if you want to study 1 millimeter kind of things then you need an energy kinetic energy of the particle which is of the other 10 to the power minus 4 electron volts that is good enough and if you want to study the you want to have resolutions of micron size then you have to go to about 0.1 electron volts. Similarly, if you want to have the resolution of 10 to the power minus 18 meters then the energy required is energy of the particle required is 10 to the power 11 electron volts and which is about roughly about 100 G e V and for particles of 10 to the power minus 20 meter that will be minus state 18 centimeter you will need this kind of energy and which are of the order of 10 T e V and therefore, if you want to find out what is the sub structure of quarks then you will need energy which are higher than this and these are shown here. Even to study the quarks you can see which are the dimensions of this type and the energy required will be in T e V several G e V energies and that is why when the quarks were discovered the energy of the energy of the electrons one of the order of 30 to 40 G e V kind of things. Now, where we have gone it is you can say these quarks actually they are what are the properties and there are six types of quarks which have been discovered and they are called up, down, charm, strange, top and bottom these are the six quarks up, down and they come in pair up, down, charm and strange so these two come in together and this charm and strange come together and top and bottom. Now, these are some of the parameters now you see here this is very interesting that up quark is 2 by 3 plus of electron here you can see that they are fractional charges and down is minus 1 3 1 by 3 so you can see here. So, if you put these things then proton consists of u u d because proton has charge 1 unit 1 and therefore u u d you can have 2 by 3 plus 2 by 3 minus is here and that is why you get 1 neutrons are neutral and therefore charges 0 net charge is 0 and therefore they are made up of u d d and that is equal to 2 by 3 that means there is one up quark that is 2 by 3 minus 1 by 3 that is d and minus 1 so that becomes a neutral particle so proton is having a positive charge is a positive charge and charges plus 1 while the neutron is neutral that the charge is 0 and that is why they are made up of these up up and quarks like this so these are some and this top quark is the heavy assist you can see the mass is is heavy assist 172 gv and this was discovered at Fermi lab accelerator Tevatron when the proton with anti proton been provided and the mass was measured to be about 172 gv this is a heaviest particle now this now you will be wondering can of course now the technology has developed and therefore you can have high energy particles but what was happening earlier earlier also a lot of good physics was done and even without these high energy accelerators so what were the sources of high energy particles so you can see that although theoretically in the right in the beginning of 19th 1905 the Einstein gave this equation and Dirac actually predicted antimatter and pi mesons were predicted in 1935 but the source of studies for particle physics or doing the experiment was that time it was cosmic rays and cosmic rays have the energies right from very small energy electron volt to up to TV they are all available particles and there are different kind of particles are available for example in 1932 itself the positron which is an anti particle of electron was discovered and later on pi mesons were discovered in 1937 so people were able to get all these information using the cosmic rays ions and in cosmic rays the particles of all energies are available now here I have talked about anti protons and pi mesons so one question obviously will come is that can you produce or can you get accelerated anti protons in the lab of course of course the answer is yes but you have to accelerate particles to appropriate energies and appropriate particle then only you can do for example if you collide two protons like in lab in the in the LSE then the then the you cannot simply make it's not possible to support two you two protons interact with each other then you cannot simply make one anti proton and one this is not allowed this is not allowed and the reason being that for example if you take the charge then charge is one here so it is one so it becomes two and charge of this is anti proton is minus one so it becomes zero so the charge is not conserved so that reaction is not allowed so that is why we have two protons collisions and we have p plus p and then this now if you want to have these four particles then the energy conservation says that you need higher energy that is why this anti protons p bar is created at a minimum energy of about 5.3 g and that is how this so this is not allowed you have to have this reaction and that will be possible only at higher energy so one needs highly energetic beam of particles to break the nucleus and instant the constituents that is a fundamental things that high energy new particles can be produced and that comes from the Einstein equation mc square and this has been done at for example large head on colliders which is in Geneva Switzerland where two protons of mass one g v is collide interact with each other and even the particles like Higgs bosons were produced which has a very large mass so you can see that accelerators can do what does and in different fields now let me just talk about little bit of physics of these accelerators so when the when the any charged particle is either traveling or through this electromagnetic force is electromagnetic fields then there will be force acting on it and both electric and magnetic field will be applying some force on that in the electric field force part will be in the same direction while the magnetic force this will be v cross v that means the force will perpendicular to both velocity as well as magnetic field and that is this is the principle this is the force which is used in cyclotons and synchro cyclotrons and so you can get this and you can get details of this for example the rate at which the work can be done on the ion is given by here and sorry this has to be only this portion as this is zero and only this force will be there first one which is e times so here again we have classified accelerators in different categories earlier based on type of ions and and and the whether the particle is heavier or not and things like that there is another category whether the acceleration is is due to electric field or it is because of magnetic field as well for example rate of change of magnetic field can be used for accelerating charged particles particularly electrons in the case of betaton accelerators so if it is a static magnetic field then it will not be accelerating it will only be deflecting the particles but if the v is changing with time then you will find that that can accelerate the particles also because there will be gradient accelerating gradient will be so basically then you can see that there are two categories one is that there is a static field which is given here and the second term will be zero here in this case and the acceleration by dc accelerates the and dc voltages will be done and there are different types of accelerators in this category which is as i said that for nuclear low energy nuclear physics experiment is the most useful one and they can be seen here that they are in the initially in the early late 20s the first one which came was a corporate walton type of multiplier which will which will convert into accelerators then later on the things for technology was improved and the vending graph electrostatic generators were developed and then further improvement led to building of tandem and paletron accelerators they all have different characteristics which i will be discussing and of course the dynamitrons and they are basically all electrostatic accelerators so in this case category i have said that if if the rate of change of magnetic field is used for accelerator acceleration then that accelerator is called betaton and if you are using changing electrostatic then they are called resonating because you have to resonate the particles with the actual frequency and the phase etc and they are called cyclotrons in this category these accelerators come into picture they are they are the one switcher so this is basic background for the accelerators and i have told you that why accelerators are important and why they are required what they can do and what we can gain from them and now let us see that how useful are these dc accelerators they are normally low energy accelerators but their their energy resolutions are much better than the other ones and therefore the for certain kind of studies they are much better than the in this category let me just talk about how the they they are functioning or how their work principle is involved and in this category there are three kind of accelerators which have been used and the first one is let's say this just i explained the how it is working suppose this in the beginning also i have explained that suppose there are two plates and i connect a battery here which is this portion is positive and this is negative that means this plate is negative and this is positive and then you inject a positive ion which is having a charge of q plus then they will be this these ions positive ions will be attracted by this second plate which is at ground potential these particles reach to the second plate the energy gain will be q times voltage so this is the basic principle of this so but the improvement of that is a cockroach walton so this act also like a like a capacitor so if you if you can have several capacitors and you have instead of this dc voltage you can have ac voltage and you use a another circuit which is called which has both capacitors and diode then the voltage can be much higher and you can see here that using this techniques people were able to go to higher voltages and one to about 1.5 million volt could be achieved with this now this cockroach walton type they were all open air open air type and therefore if you try to go to higher voltage there will be breakdowns and we will not able to go to higher voltages while this could be this problem could be overcome in the vendicraft type of accelerators where this whole accelerator is enclosed in a in a pressure vessel and that is a insulating gas is put inside that pressure vessel at higher pressures which could which improve the dielectric constant and therefore we were able to extend the higher voltage on the on the terminal or the point of high voltages which could which was different from the other ones here for example in the case of cockroach walton you are using condensers or capacitors directly while in the case of vendicraft and pelotons the capacitor is made by the electrodes by so they are made there itself so high voltage terminal acts as a capacitor in that case so that has to be charged so it is technology is slightly different now coming back to these accelerators what are the what are the components involved basically now we are talking about this I have explained earlier but the few components which are required of course is a source of charged particles then there has to be accelerating tube because inside which we have to accelerate the particle so and if we don't have a very high vacuum inside the accelerating tube then these particles will collide with the all the gas particles in the tube and they will lose the energy so not only the energy will be lost but also the also the resolution of the beam will be because then there will be a spectrum of energy rather than one energy single energy and therefore you have to have a very high vacuum in this one to avoid the energy loss etc now this this source has to be isolated from the other this source and this and that is what is done by the high voltage column section or the accelerating tube across which we maintain the electric field and that provides the force to accelerate them to the high energy so the beam which is coming at this point is accelerated beam and of course as I mentioned earlier that many times sometimes it is focused beam but many times it is a defocused beam and that has to be focused so here you have to put the beam help handling components like focusing devices and so on ultimately we want to take the beam to the target chamber where the experiments will be are done and therefore that is the ultimate now what is the criteria see ultimately and actually I was mentioning that in the cockroach Walton type you can go maximum up to 1.5 million volts what is that is there any study and Kilpratik studied these phenomena very nicely and he came with a criteria and that is that tells us that at what voltage the breakdown will take place what maximum voltage you can go which of course voltage means the gradient and that is more important than so the Kilpratik he gave the criteria after the empirical criteria based on lot of his studies and above that voltage he gave that at what voltage the breakdown will take place above that voltage the plasma will form or the discharge will form and voltage will not be able to go so in all these accelerators there is a limit to which the voltage can go above that there will be discharge and in these kind of accelerators for example normally normally the safe limit to for operation of these accelerators is about 1 million volt per meter of course in open air it is much smaller but by using very efficient insulating gas like SF6 which has a dielectric constant of about 2.5 times that of air at the same pressure you can go to higher present and still you are able to go to 1 million volt per meter so for example if you take 14 million volt peloton then the length of that accelerator is almost like 14 meters so the gradient is limited to safe gradient is limited to about 1 million volt or something like that now any accelerator which you develop has to have applications and they have to be used and one of the excellent one of the most fruitful application of even the small accelerators like occult valton was to generate the neutrons and there what you do is that you accelerate neutrons bombard on another neutron target it could be the target could be gas or it could be different kind of targets so if you do that then you have to see that to what voltage you have to achieve what we have voltage you have to achieve and the what is the energy required and that will be defined by the q value so if the q value is positive then the even at very low energies the neutrons will be produced for example if you take this dt reaction then the you are able to get two mvb beams two mvb neutron beams and that is because the q value of this is 2.7 mvb and this 2 mvb 2.7 mvb will be distributed on these particles as per the mass and the other other reaction which is very popular even today is dt reaction and in dt reaction when deutone beam of about let us say few hundred keb to up to one mvb or even higher yeah is bombarded on tritium target then helium is produced and a newton will come out of it and that newton will be 14 mvb because the q value 17.67 mvb and that will be distributed to this as per the kinematics between these two particles so the energy of this helium kinetic energy of helium 4 will be 1 by 5 and of the neutrons it will be 4 by 5 so that is why you get 14 mvb and this is one of the best ways to produce one of the unique ways to produce 14 mvb mono energetic neutrons which are even today so even these new these particles they are these accelerated accelerated particles from any of these dc accelerators even cockroach valton type of things are used for many many applications some of them are listed here and they are used in solid state physics ion beam modification of materials atomic physics ion beam analysis of materials like the other code that is that particle induced x-ray emission is called pixie particle induced gamma ray emission is called pig nuclear reaction analysis and elastic recoil detection astrophysics is very useful for this this astrophysics and nowadays they are finding very great uses in ecological research also thank you so this is the end of this lecture