1 00:00:26,760 --> 00:00:31,150 so welcome back what we are going to discuss today is the next to the non invasive velocity 2 00:00:31,150 --> 00:00:35,000 measurement technique and the technique name is radioactive particle tracking technique 3 00:00:35,000 --> 00:00:39,989 now as the name suggests that we are going to use a radioactive particle and we are going 4 00:00:39,989 --> 00:00:46,410 to track the motion of that radioactive particle to get the velocity field now this technique 5 00:00:46,410 --> 00:00:51,129 is actually very versatile technique and has been implemented on many multi phase flow 6 00:00:51,129 --> 00:00:57,530 reactors and the major advantage of this technique is the use of the gamma ray and unlike pepped 7 00:00:57,530 --> 00:01:03,710 ah positron emission particle tracking here the we use actually the gamma ray source itself 8 00:01:03,710 --> 00:01:09,590 it means what it gives the luxury to use your source strength as well as source energy as 9 00:01:09,590 --> 00:01:11,360 per the application 10 00:01:11,360 --> 00:01:18,530 so if suppose i have a this column which the column diameter is very small then i can use 11 00:01:18,530 --> 00:01:24,600 a source which can have a very low activity now activity as i said has been defined is 12 00:01:24,600 --> 00:01:30,960 the disintegration ok ah per second so number of gamma rays disintegration per second so 13 00:01:30,960 --> 00:01:36,190 suppose if i am talking about activity of one curie it gives three point seven into 14 00:01:36,190 --> 00:01:41,180 ten to power ten disintegration per second it means it is three into three point seven 15 00:01:41,180 --> 00:01:46,800 into tens power ten gamma rays will be emitted per second by the particle 16 00:01:46,800 --> 00:01:52,930 so i can unit kind of i can choose a source of different energy i can choose a source 17 00:01:52,930 --> 00:01:59,130 of different activity or strength and therefore i can use this thing or this technique for 18 00:01:59,130 --> 00:02:05,060 any kind of system whether the system is transparent its opie its a smaller diameter its a bigger 19 00:02:05,060 --> 00:02:10,700 diameter what you need to do you need to prepare the tracer particle accordingly in that we 20 00:02:10,700 --> 00:02:15,150 will discuss so what we do in this technique the major advantage as i said is the technique 21 00:02:15,150 --> 00:02:20,030 is there is a very versatile technique it can be used for any system whether its a gas 22 00:02:20,030 --> 00:02:25,970 solid its a gas liquid any phase fraction doesnt matter that whether the discrete phase 23 00:02:25,970 --> 00:02:31,590 fraction is five percent ten percent thirty percent forty percent fifty percent any discrete 24 00:02:31,590 --> 00:02:37,239 phase fraction we can use this technique we can use this technique for opaque system because 25 00:02:37,239 --> 00:02:42,530 i am using the gamma ray so it can penetrate almost anything i can use it for the gas solid 26 00:02:42,530 --> 00:02:47,499 system because what i am doing i am just preparing a um tracer particle which is going to track 27 00:02:47,499 --> 00:02:53,269 the motion of the phase of interest so let me elaborate about this technique now 28 00:02:53,269 --> 00:02:57,400 with the advantages which i have discussed and i will also discuss the disadvantage at 29 00:02:57,400 --> 00:03:02,930 the end of this technique so what i said its a radioactive particle tracking technique 30 00:03:02,930 --> 00:03:08,209 in which i will use a single radioactive particle and this is very critical that we use a single 31 00:03:08,209 --> 00:03:14,890 radioactive particle as a marker of the phase whose velocity i need to map so suppose if 32 00:03:14,890 --> 00:03:20,779 i have to map a velocity of a solid present in a flow in a say gas solid fluidize bed 33 00:03:20,779 --> 00:03:27,379 or liquid solid fluidize bed i will take the tracer particle this radioactive tracer particle 34 00:03:27,379 --> 00:03:34,219 exactly of the same shape size and density so it means i am choosing one of the identical 35 00:03:34,219 --> 00:03:39,730 particle one of the particle and making it radioactive by doping some radioactive element 36 00:03:39,730 --> 00:03:45,239 and then after doping that i am keeping the density of the particle shape of the particle 37 00:03:45,239 --> 00:03:49,329 size of the particle exactly same as of the other particles project 38 00:03:49,329 --> 00:03:54,579 so my tracer particle is none but one of the billion of the particles of several particles 39 00:03:54,579 --> 00:03:59,590 which are present in the column of interest now because these are radioactive particle 40 00:03:59,590 --> 00:04:03,930 what it will be happen in the case of the movement suppose in the gas solid fluidize 41 00:04:03,930 --> 00:04:08,180 bit once the solid will move with the other solid this solid will also move because it 42 00:04:08,180 --> 00:04:15,459 has a exactly same property now during its path what it gamma ray does gamma resource 43 00:04:15,459 --> 00:04:21,250 does it emits ah photons or gamma rays ok depending on their its strength so we know 44 00:04:21,250 --> 00:04:25,900 that strength and if i know the strength i know that this much gamma emission it will 45 00:04:25,900 --> 00:04:29,889 do per second now we place some scintillation detectors 46 00:04:29,889 --> 00:04:33,300 and we will discuss about the functioning of the director later on but these are the 47 00:04:33,300 --> 00:04:39,050 scintillation detectors available which as specialise detectors to adsorb this photon 48 00:04:39,050 --> 00:04:44,180 counts which is emitted by the source now suppose the particle is here it will emit 49 00:04:44,180 --> 00:04:49,270 the gamma rays and all the detective place detectors around the column of interest and 50 00:04:49,270 --> 00:04:54,580 all the detectors acquires the gamma ray or the acquires the photons at the same time 51 00:04:54,580 --> 00:04:59,090 so it means all the detectors are fired at the same time so they are acquiring the gamma 52 00:04:59,090 --> 00:05:04,010 rays at the same time so what will happen we prepare a identical particle marker of 53 00:05:04,010 --> 00:05:08,470 the phase and thats why i am say marker of the phase in case of the solid the size shape 54 00:05:08,470 --> 00:05:13,580 and density of this tracer particle will be exactly same as of the solid present in the 55 00:05:13,580 --> 00:05:18,660 flow in case if you want to do the liquid tracking the particle which you present should 56 00:05:18,660 --> 00:05:24,480 be very small in size and the density of the particle should be equal to the density of 57 00:05:24,480 --> 00:05:27,520 the fluid it means you have to prepare a particle which is neutrally buoyant 58 00:05:27,520 --> 00:05:32,550 now if the particle is neutrally buoyant if their size is very less then what will happen 59 00:05:32,550 --> 00:05:38,040 it will actually follow the path of the fluid if the stokes number is less than one ok so 60 00:05:38,040 --> 00:05:42,190 in that case it will just keep on following the path of the fluid and you will track the 61 00:05:42,190 --> 00:05:47,650 motion of the fluid so this is the technique which gives you the advantage to track the 62 00:05:47,650 --> 00:05:53,720 motion of solid motion of liquid everything now with the part once the pressure particle 63 00:05:53,720 --> 00:05:59,260 will move inside suppose in this case whatever i have drawn for the gas liquid and this tracer 64 00:05:59,260 --> 00:06:03,360 particle is neutrally buoyant with the liquid whatever i have shown here and once it will 65 00:06:03,360 --> 00:06:09,200 move it will emit some gamma rays now those gamma rays will be actually adsorb by the 66 00:06:09,200 --> 00:06:14,650 detectors which are being placed around the column of interest all around at all the location 67 00:06:14,650 --> 00:06:18,930 to cover your phase of interest and zone of interest 68 00:06:18,930 --> 00:06:24,420 now what will happen each detector will record a photon count time series history so i will 69 00:06:24,420 --> 00:06:35,430 just say that its a count time series history so what does it mean say each detector what 70 00:06:35,430 --> 00:06:40,240 it will be happen suppose i will get a graph where the y axis will be count i am denoting 71 00:06:40,240 --> 00:06:47,490 it with the c x axis will be time and you will see that how the counts emitted a photon 72 00:06:47,490 --> 00:06:53,811 counts when the once i say count photon count is changing with the time on each detector 73 00:06:53,811 --> 00:06:58,800 so you will get a photon count time series history for each detectors with the particle 74 00:06:58,800 --> 00:07:03,870 movement now i am using single particle i want a whole velocity field so what i need 75 00:07:03,870 --> 00:07:10,220 to do i need to perform the experiment for sufficiently long time so that the particle 76 00:07:10,220 --> 00:07:15,500 covers approximately all the places inside the vessel of interest or column of interest 77 00:07:15,500 --> 00:07:20,400 and not only one time its a travel several time to the same location so that i can also 78 00:07:20,400 --> 00:07:24,590 get the mean velocity so what will happen we will discuss all those things so what will 79 00:07:24,590 --> 00:07:29,900 happen you will get the photon count time series history on all detector with the time 80 00:07:29,900 --> 00:07:36,620 now we know that by using beer lamberts law that i equal to i naught e raise to the power 81 00:07:36,620 --> 00:07:42,890 minus mu into l where mu is the attenuation coefficient of the medium l is the distance 82 00:07:42,890 --> 00:07:49,350 between the source and the detector so that will be there so what i need if i have some 83 00:07:49,350 --> 00:07:55,300 calibration position i naught values already existing then what i can do i can find it 84 00:07:55,300 --> 00:08:01,950 out the distance from each detector so by using beer lamberts law it says that the photon 85 00:08:01,950 --> 00:08:07,340 counts will be higher on those detectors where the distance is less it means this l is less 86 00:08:07,340 --> 00:08:12,990 it means if suppose the particle is placed at this location the photon counts on these 87 00:08:12,990 --> 00:08:18,740 detectors will be higher i will say even say lets include these detectors will be higher 88 00:08:18,740 --> 00:08:25,060 compared to these detectors compare to these detectors so what will happen i will get that 89 00:08:25,060 --> 00:08:29,160 what is the approximate location of the particle depending upon the photon count time series 90 00:08:29,160 --> 00:08:33,979 history and by using the beer lamberts law and we will discuss the reconstruction algorithm 91 00:08:33,979 --> 00:08:38,750 later on but lets understand in a very simple language by using beer lamberts law what i 92 00:08:38,750 --> 00:08:43,320 will get i will get the distance if i know that attenuation distribution and this is 93 00:08:43,320 --> 00:08:49,320 code that if i know that attenuation distribution then i will know the distance from each of 94 00:08:49,320 --> 00:08:54,320 the detectors of this particle so what will happen if i have four such lines 95 00:08:54,320 --> 00:08:59,590 or four such distances then what will happen i will get this and i will get that what is 96 00:08:59,590 --> 00:09:04,880 the location of the particle so ideally what i need i need the three detectors because 97 00:09:04,880 --> 00:09:10,420 each detector will give me a certain distance they was wherever they will cut ok i will 98 00:09:10,420 --> 00:09:15,050 know that where is the location of the particle and because this is changing with the time 99 00:09:15,050 --> 00:09:19,200 i need the four detector to cover the time coordinate so three detector will cover the 100 00:09:19,200 --> 00:09:24,279 x y z coordinate and four detector will cover the time coordinates so i need four detector 101 00:09:24,279 --> 00:09:29,410 to reconstruct the position of the tracer particle but what i have right now i have 102 00:09:29,410 --> 00:09:35,100 several detectors so each detector is going to give me a distance that how far this particle 103 00:09:35,100 --> 00:09:41,040 is and by solving all this distance or all these count time series together i will get 104 00:09:41,040 --> 00:09:46,560 the exact location of the tracer particle and when i am acquiring the photon counts 105 00:09:46,560 --> 00:09:51,200 with the time with the time what i can do i can find it out how the tracer particle 106 00:09:51,200 --> 00:09:57,300 position is changing with the time it means this i can convert in terms of the position 107 00:09:57,300 --> 00:10:02,410 so i can get the lagrangian position time series of the particle and from their lagrangian 108 00:10:02,410 --> 00:10:07,640 position times series once i have i can find it out the local velocity of the particle 109 00:10:07,640 --> 00:10:12,820 or local velocity of the tracer particle by using just simple delta x by delta t is equal 110 00:10:12,820 --> 00:10:17,190 to velocity so i am getting position with the time i will get velocity will the time 111 00:10:17,190 --> 00:10:21,260 or i will say that lagrangian velocity of the tracer particle because i am moving with 112 00:10:21,260 --> 00:10:25,980 the particle with the time so i will have lagrangian position of the 113 00:10:25,980 --> 00:10:30,310 particle lagrangian position of the particle i will have lagrangian velocity a local velocity 114 00:10:30,310 --> 00:10:35,510 of the particle now as i said we are performing the experiment for sufficiently long time 115 00:10:35,510 --> 00:10:41,540 what will happen the particle will move each location several times and then by doing the 116 00:10:41,540 --> 00:10:47,020 ensembled average of all those the put point all those times was the particle comes to 117 00:10:47,020 --> 00:10:52,790 a fixed location we can calculate the mean velocity of that position and by subtracting 118 00:10:52,790 --> 00:10:58,720 the mean velocity to the instantaneous velocity we can get the fluctuations and once you have 119 00:10:58,720 --> 00:11:03,600 a fluctuation you can calculate many turbulent quantities like reynolds stress r m s kinetic 120 00:11:03,600 --> 00:11:08,600 energy we will discuss about all those but you can calculate lot of turbulent quantities 121 00:11:08,600 --> 00:11:12,680 so that is the beauty of the technique and the principle of the technique which is very 122 00:11:12,680 --> 00:11:17,710 simple that we are tracking the motion of a single particle for sufficiently long time 123 00:11:17,710 --> 00:11:22,600 these are the gamma rays particles so which emits the photons with what you will happen 124 00:11:22,600 --> 00:11:27,970 is the particle will move with the this with the time what will happen you will get that 125 00:11:27,970 --> 00:11:33,290 how the count photon count is changing on each detector with the time from there if 126 00:11:33,290 --> 00:11:37,540 we solve all the detectors photon count time series history simultaneously by using the 127 00:11:37,540 --> 00:11:42,690 suitable reconstruction algorithm then we will get the position of the particle so what 128 00:11:42,690 --> 00:11:46,779 you will get is the position time series and from there you can get the velocity 129 00:11:46,779 --> 00:11:52,790 so this is the basic principle of this technique the technique basic looks very simple but 130 00:11:52,790 --> 00:11:57,300 it has many challenges and we will discuss some of those challenges in this course to 131 00:11:57,300 --> 00:12:03,339 understand that what is the benefit how difficult or how easy it is to implement the technique 132 00:12:03,339 --> 00:12:08,590 how it is how difficult or easy it is to reconstruct the particle position and calculate the post 133 00:12:08,590 --> 00:12:13,510 process a post process that data so as i said that what you are going to have 134 00:12:13,510 --> 00:12:18,320 we are going to suppose have a system this is a typical liquid solid system diagram where 135 00:12:18,320 --> 00:12:27,990 these are the scintillation detectors we call it scintillation detector which are placed 136 00:12:27,990 --> 00:12:32,940 around the column of interest so if you see that i place the detectors all around the 137 00:12:32,940 --> 00:12:38,090 column and then these detectors are connected actually to a data acquisition system which 138 00:12:38,090 --> 00:12:44,380 records how the photon count time series history will change on each detector with the time 139 00:12:44,380 --> 00:12:48,860 like suppose this are the eight detectors i have placed around the vessel of interest 140 00:12:48,860 --> 00:12:54,980 then these if you see is the photon count time series history for each detectors 141 00:12:54,980 --> 00:12:59,500 so each graph shows actually the photon count time series history for the three detectors 142 00:12:59,500 --> 00:13:05,740 so if you see this is for detector number one graph is red two green and three is blue 143 00:13:05,740 --> 00:13:11,180 similarly for all the three boxes this is for four five six seven eight ok so because 144 00:13:11,180 --> 00:13:15,190 i have eight detectors used in this experiment i am getting the photon count time series 145 00:13:15,190 --> 00:13:21,170 history with ah for all the eight detectors here x axis is the number of event if you 146 00:13:21,170 --> 00:13:26,290 multiply it with the data acquisition time you will get that time unit and y axis is 147 00:13:26,290 --> 00:13:30,930 the photon count photon count now you can see that if i track any line whether 148 00:13:30,930 --> 00:13:35,540 the red color or green color you see that how it is moving it is increasing then count 149 00:13:35,540 --> 00:13:40,779 is reducing then again increasing then reducing then increasing it means what the tracer particle 150 00:13:40,779 --> 00:13:46,110 is actually circulating inside the system suppose this is the system this is the detector 151 00:13:46,110 --> 00:13:50,740 because in the liquid solid fluidise bed the solids are in batch then what will happen 152 00:13:50,740 --> 00:13:55,850 the tracer particle will be keep on the circulating it will be keep on the circulating inside 153 00:13:55,850 --> 00:14:00,440 so what will happen once it will be far the detector count will be on the detector will 154 00:14:00,440 --> 00:14:04,660 be low once it will come close the count on the detector will be increasing 155 00:14:04,660 --> 00:14:09,550 so thats what we are seeing that increasing and decreasing count pattern for all the detectors 156 00:14:09,550 --> 00:14:15,570 ok so what we have now we have a photon count time series history of the tracer particle 157 00:14:15,570 --> 00:14:21,370 from there by using the suitable reconstruction algorithm i calculate the position of the 158 00:14:21,370 --> 00:14:25,790 particle we will discuss about the reconstruction algorithm so suppose this is the initial position 159 00:14:25,790 --> 00:14:31,200 of the particle and its so that how the particle position is changing with the time so how 160 00:14:31,200 --> 00:14:35,470 my tracer particle is actually moving with the time so this is the photon count time 161 00:14:35,470 --> 00:14:39,490 series history which shows that how the tracer particle moving with the time so what you 162 00:14:39,490 --> 00:14:43,260 will get from this data you will get that how the particle position is changing with 163 00:14:43,260 --> 00:14:48,160 the time i have taken a very small time period so that we can see the trajectory if you take 164 00:14:48,160 --> 00:14:52,460 for the complete experiment say for eight hours ten hours or twenty hours depending 165 00:14:52,460 --> 00:14:57,700 upon the diameter of the column or volume of the column you will see all where the this 166 00:14:57,700 --> 00:15:01,089 kind of a trajectories so what we will get we will get the lagrangian 167 00:15:01,089 --> 00:15:07,060 position time series history for the tracer particle from there as i said by using delta 168 00:15:07,060 --> 00:15:12,470 x by delta t i can calculate the velocity and that velocity will be nothing but the 169 00:15:12,470 --> 00:15:18,980 lagrangian time series velocity of the tracer particle or lagrangian velocity of the tracer 170 00:15:18,980 --> 00:15:24,220 particle so we will get how the tracer particle velocity is changing it shows that how the 171 00:15:24,220 --> 00:15:28,420 sometimes the velocity is higher sometimes velocity is lower sometime velocity is positive 172 00:15:28,420 --> 00:15:33,050 sometime velocity is negative has this curve shows that this is positive this is negative 173 00:15:33,050 --> 00:15:38,540 velocity why it is like that because you are going to see again i said that the solid is 174 00:15:38,540 --> 00:15:43,750 in batch so what will happen it will always remain inside the liquid is passing through 175 00:15:43,750 --> 00:15:49,029 the bottom so it will move with the solid liquid up at the center say and then it will 176 00:15:49,029 --> 00:15:52,920 come down so what will happen once it will be going 177 00:15:52,920 --> 00:15:57,170 up velocity will be positive once it will be coming down the velocity will be negative 178 00:15:57,170 --> 00:16:02,019 so you will get a lagrangian velocity time series that how with the time lagrangian velocity 179 00:16:02,019 --> 00:16:08,330 of the particle exchanging and then come to the eulerian velocity or mean velocity or 180 00:16:08,330 --> 00:16:13,500 ensembled average mean velocity so what we do like c f d we discretize the whole column 181 00:16:13,500 --> 00:16:19,420 in a small parts small cells like i did here so suppose this is my column ok and suppose 182 00:16:19,420 --> 00:16:25,120 this is the diameter of the column so whole diameter a whole column we divide in a small 183 00:16:25,120 --> 00:16:31,160 grid say this way and we see that during the course of the experiment how many times the 184 00:16:31,160 --> 00:16:36,570 particle comes in each grid as i said that as we perform the experiment for sufficiently 185 00:16:36,570 --> 00:16:42,279 long time so that i have a sufficient statistics we weighed that for each cell the particle 186 00:16:42,279 --> 00:16:46,760 comes several time in each cell now if suppose in each cell say this cell 187 00:16:46,760 --> 00:16:52,019 if the particle has come say around hundred times i can calculate the mean velocity of 188 00:16:52,019 --> 00:16:58,410 this cell by doing the ensembled average it means i will do that one upon hundred summation 189 00:16:58,410 --> 00:17:05,630 i equal to one to hundred its v i so i will get that ensembled average velocity of the 190 00:17:05,630 --> 00:17:10,520 tracer particle for each location so what i will get i can get if i plot that i will 191 00:17:10,520 --> 00:17:15,459 get that the mean velocity and it shows that the tracer particle is moving up near the 192 00:17:15,459 --> 00:17:21,179 wall and coming down at the center of the column so in this way we can calculate the 193 00:17:21,179 --> 00:17:26,880 mean velocity once i have a mean velocity i have the instantaneous velocity i can calculate 194 00:17:26,880 --> 00:17:31,950 the whole fluctuation quantities by calculating the fluctuation velocity so we can calculate 195 00:17:31,950 --> 00:17:36,340 the reynolds stress we can calculate the r m s we can calculate the kinetic energy of 196 00:17:36,340 --> 00:17:40,860 the turbulence in case of the solid phase we can also calculate the granular temperature 197 00:17:40,860 --> 00:17:45,059 and so on so all the turbulent quantities you can calculate ok 198 00:17:45,059 --> 00:17:49,850 so this was the flow chart though again as i said that the system looks very easy or 199 00:17:49,850 --> 00:17:55,570 the technique looks very easy it is not that simple because r p t is a multi step process 200 00:17:55,570 --> 00:18:01,500 its not a simple physical stage process so what is the stages involved in the r p t the 201 00:18:01,500 --> 00:18:06,260 first stage is the experimental stage i will not say its a first stage the one stage is 202 00:18:06,260 --> 00:18:12,850 the experimental stage where we keep the particle free inside the bed of interest and see that 203 00:18:12,850 --> 00:18:18,300 how the particle motion is changing with the time or hide the particle position is changing 204 00:18:18,300 --> 00:18:24,710 with the time so what i will get i will get that how with the time the count on each detector 205 00:18:24,710 --> 00:18:29,500 is going to change because with the position the count on each detector will change because 206 00:18:29,500 --> 00:18:34,020 some detector say for particular detector some position can be close to that detector 207 00:18:34,020 --> 00:18:39,350 some position can be far from that detector if it is close your count will be different 208 00:18:39,350 --> 00:18:44,929 ah if you its far your count will be different so what you will get with the time how the 209 00:18:44,929 --> 00:18:49,929 count on each detectors is changing with the time so thats what we get from the experiments 210 00:18:49,929 --> 00:18:54,490 as i shown in the comes of the graph now i have to reconstruct this thing in terms 211 00:18:54,490 --> 00:18:59,350 of the position as i said you by using the suitable reconstruction algorithm now how 212 00:18:59,350 --> 00:19:06,020 to do that to do that what i need i need a calibration i need to know that on the same 213 00:19:06,020 --> 00:19:11,210 location when the tracer particle was there under the controlled motion or no motion how 214 00:19:11,210 --> 00:19:18,520 much tracer particle how much counts was recorded on each detective now this is called calibration 215 00:19:18,520 --> 00:19:22,510 step it means what we are trying to do we are trying to fix the position of the tracer 216 00:19:22,510 --> 00:19:27,640 particle and we are going to measure the counts recorded on each detectors which are placed 217 00:19:27,640 --> 00:19:32,730 around the vessel of interest ok so that is called calibration step the calibration step 218 00:19:32,730 --> 00:19:38,100 can be done in two ways one is by experiments by using the hardware as i said and physically 219 00:19:38,100 --> 00:19:42,790 keeping the particle at several known location the way ah it means what we are going to do 220 00:19:42,790 --> 00:19:47,170 we are going to put the particle at a fixed location you are going to block the location 221 00:19:47,170 --> 00:19:52,900 of the particle and for that particular location we record that how all the detectors are recording 222 00:19:52,900 --> 00:19:58,809 time sorry recording count for all the detectors are for that position and then once that is 223 00:19:58,809 --> 00:20:05,510 completed we actually move to the next position and then again calculate that how the ah photon 224 00:20:05,510 --> 00:20:11,261 count will be recorded on each detector for this next tracer particle position so that 225 00:20:11,261 --> 00:20:16,620 is called experimental way of calibration however if suppose you have a bigger column 226 00:20:16,620 --> 00:20:22,730 diameter or even a smaller column diameter of a little bit bigger size what will happen 227 00:20:22,730 --> 00:20:28,280 you have to do the experimental calibration for very large number of points because you 228 00:20:28,280 --> 00:20:33,220 have the particle is moving continuously you dont have that control that where the particle 229 00:20:33,220 --> 00:20:38,030 should go where the particle should not go so it means what you have to actually do the 230 00:20:38,030 --> 00:20:43,549 calibration for entire range entire column dimensions which is under the investigation 231 00:20:43,549 --> 00:20:49,520 so doing the experimental calibration is going to be very very tedious and time consuming 232 00:20:49,520 --> 00:20:55,110 and therefore a software approach has been developed to do the calibration and that software 233 00:20:55,110 --> 00:20:59,960 approach we will discuss later on but it has been developed to do the calibration and software 234 00:20:59,960 --> 00:21:06,060 also do the same thing it generates the count ah recorded on each director for a fixed position 235 00:21:06,060 --> 00:21:09,720 of the tracer particle so now what we are doing in the calibration 236 00:21:09,720 --> 00:21:16,730 we make a table and just like the real experiment we get the table in which x y z is fixed and 237 00:21:16,730 --> 00:21:21,580 the count on the detector on each director is changing and that is with the time so this 238 00:21:21,580 --> 00:21:29,590 is the time how the tracer particle position and time m is changing ok so that is called 239 00:21:29,590 --> 00:21:34,940 calibration where we change the tracer particle position and we caught the count ok in photon 240 00:21:34,940 --> 00:21:40,350 in the experiments what we do we keep the particle free inside to move and what we get 241 00:21:40,350 --> 00:21:46,480 we get that how with the time photon count on each detector is changing so i have two 242 00:21:46,480 --> 00:21:53,640 tables now one from the experiments one from the calibration calibration and this is are 243 00:21:53,640 --> 00:21:59,110 the experiment now we compare these two tables and once i 244 00:21:59,110 --> 00:22:04,140 compare these two tables i will get what i will get the position of the tracer particle 245 00:22:04,140 --> 00:22:10,330 and that is called reconstruction so once i compare these two tables i will know that 246 00:22:10,330 --> 00:22:14,730 how the tracer particle position is changing with the time and that is called the position 247 00:22:14,730 --> 00:22:19,380 reconstruction of the tracer particle once you reconstructed the position of the tracer 248 00:22:19,380 --> 00:22:24,370 particle as i said we discretize the column we virtually divide the column in a small 249 00:22:24,370 --> 00:22:30,820 grid cells like c f d we see that how many times a particle is visiting each cell and 250 00:22:30,820 --> 00:22:34,370 whatever the time the particle is visiting on each cell we take the ensembled average 251 00:22:34,370 --> 00:22:40,781 of that and that is called the mean velocity of the tracer particle for that cell so that 252 00:22:40,781 --> 00:22:45,940 feeds the way we can calculate the mean velocity and from there we can calculate the fluctuation 253 00:22:45,940 --> 00:22:52,100 and other turbulent quantities so this is the steps in the r p t which is being used 254 00:22:52,100 --> 00:22:58,330 ah to process the data now like other technique p i v l d a or pept 255 00:22:58,330 --> 00:23:03,030 are pretty is not an obsession technique it means you cannot just not a plug and play 256 00:23:03,030 --> 00:23:08,860 device and you have to fabricate it or you are installing from the basic nuclear spectroscopy 257 00:23:08,860 --> 00:23:13,980 hardware so we will get the individual hardware but you will not get a unit name as a radioactive 258 00:23:13,980 --> 00:23:19,010 particle tracking technique that is one of the major problem with the technique that 259 00:23:19,010 --> 00:23:23,770 there is no readymade packages available and one who wants to work with this technique 260 00:23:23,770 --> 00:23:28,809 have to understand the basic sciences he has to understand how to assemble the nuclear 261 00:23:28,809 --> 00:23:34,540 spectroscopy hardware and how to use that hardware for the reconstruction data reconstruction 262 00:23:34,540 --> 00:23:40,179 so some of that hardware we are going to discuss so basically ah this is the flow chart of 263 00:23:40,179 --> 00:23:44,790 the r p t as i have already discussed before going to the hardware that how we do that 264 00:23:44,790 --> 00:23:50,080 how what we do we first do the detector calibration we do the experiment we compare these two 265 00:23:50,080 --> 00:23:55,730 we get the instantaneous position of the tracer particle we discretize the whole column virtually 266 00:23:55,730 --> 00:24:01,330 in like a grid in a small eulerian cells we note down that in each eulerian cell how many 267 00:24:01,330 --> 00:24:07,420 this time the particle comes during all the experiments so we get that how many the particle 268 00:24:07,420 --> 00:24:13,580 position is of this the number of particle times the particle where which kind of visited 269 00:24:13,580 --> 00:24:17,130 the cell then we do the ensembled average suppose it is visited n number time i will 270 00:24:17,130 --> 00:24:22,010 just add those n number times the particle velocity divided by the total number of times 271 00:24:22,010 --> 00:24:27,000 the particle comes in that unit cell so i will get that what is the ensembled average 272 00:24:27,000 --> 00:24:31,220 velocity of the particle once we know that ensembled average velocity of the particle 273 00:24:31,220 --> 00:24:36,540 what we can do we can subtract the mean minus instantaneous i will get the fluctuation velocity 274 00:24:36,540 --> 00:24:41,059 then the beauty of this technique as i said and if you try to understand is that suppose 275 00:24:41,059 --> 00:24:47,500 if i any grid cell if i am taking about talking about and i said that the particle actually 276 00:24:47,500 --> 00:24:52,610 visit the cell several times say n times the weight has been shown so what will mean what 277 00:24:52,610 --> 00:24:58,789 does it mean that you you are going to have not only a single mean velocity for each cell 278 00:24:58,789 --> 00:25:05,180 you are going to have not only the v z mean you are going to have v z fluctuation and 279 00:25:05,180 --> 00:25:11,360 you are also going to have the value that this v z fluctuation we are going to have 280 00:25:11,360 --> 00:25:18,580 v z mean value but you are also going to have the p d f of the instantaneous velocity is 281 00:25:18,580 --> 00:25:40,020 a p d f of instantaneous velocity and p d f of fluctuation fluctuation velocity 282 00:25:40,020 --> 00:25:45,290 and these two are the major advantage of this technique so what i am saying that i am not 283 00:25:45,290 --> 00:25:49,590 going to just tell you that what is the velocity or mean velocity at a particular location 284 00:25:49,590 --> 00:25:55,480 inside the column of interest i am also going to tell that what is the velocity distribution 285 00:25:55,480 --> 00:26:01,770 for whole experiments for whole time for eight to ten hours twenty hours how much velocity 286 00:26:01,770 --> 00:26:10,190 distribution you got for each location you can fight each location and then you can similarly 287 00:26:10,190 --> 00:26:15,429 use that velocity distribution local velocity distribution if you subtract it from the mean 288 00:26:15,429 --> 00:26:22,980 velocity what you are going to get you are going to get that the flow p d f of the fluctuation 289 00:26:22,980 --> 00:26:25,100 velocities so what i am going to get i am going to get 290 00:26:25,100 --> 00:26:30,700 the p d f of instantaneous p d f of the fluctuation velocity it means you will not only get the 291 00:26:30,700 --> 00:26:35,150 mean you will get that what is the distribution of the velocity at a particular location what 292 00:26:35,150 --> 00:26:40,320 is the distribution of the fluctuation at a particular location and now if you are designing 293 00:26:40,320 --> 00:26:45,200 the system you can design your system not based on the mean velocity only which is the 294 00:26:45,200 --> 00:26:51,210 traditional way of doing the designing we can also consider the distribution in the 295 00:26:51,210 --> 00:26:56,770 velocity for each location and that distribution in the each velocity which gives lot of flexibility 296 00:26:56,770 --> 00:27:01,770 to even do the post process the data for a higher order moments which we will discuss 297 00:27:01,770 --> 00:27:06,799 so that is the flow chart of the r p t this is the formula which is being used to calculate 298 00:27:06,799 --> 00:27:12,510 the velocities like if i say the instantaneous velocity it is v z is nothing but delta z 299 00:27:12,510 --> 00:27:18,590 upon delta t similarly we can calculate the v r and v theta but you need to do certain 300 00:27:18,590 --> 00:27:22,580 trigonometry we will discuss some of that i will at least i will show you the formula 301 00:27:22,580 --> 00:27:27,150 that how to calculate the v r theta if you are solving in a polar coordinate if you are 302 00:27:27,150 --> 00:27:33,030 solving in a rectangular coordinate then v x v y v z all will be defined by delta z by 303 00:27:33,030 --> 00:27:37,539 delta t you can calculate the ensembled average velocity as i already said that in each cell 304 00:27:37,539 --> 00:27:41,990 suppose the particle comes for hundred times you add all those hundred velocities divided 305 00:27:41,990 --> 00:27:45,960 by the number of times particle comes it means hundred you will get the ensembled average 306 00:27:45,960 --> 00:27:51,150 velocity we can calculate the fluctuation velocity mean minus instantaneous within that 307 00:27:51,150 --> 00:27:57,390 cell for all the time the particle comes in that cell you will get that what is the fluctuation 308 00:27:57,390 --> 00:28:02,430 velocity each time or you can say that you will get that the p d f of the fluctuation 309 00:28:02,430 --> 00:28:09,220 velocity in that cell then you can calculate the r m s velocity of that cell root mean 310 00:28:09,220 --> 00:28:14,549 square velocity by using the just formula which is nothing but v prime is square so 311 00:28:14,549 --> 00:28:19,150 if suppose i want that v prime square for this so i will get say if i want the z direction 312 00:28:19,150 --> 00:28:24,331 of r m s velocity for each cell whenever the particle comes there is a fluctuation velocity 313 00:28:24,331 --> 00:28:30,600 i will square them and i will add them i will get that what is r m s velocity of the particle 314 00:28:30,600 --> 00:28:34,140 at in that cell similarly i can calculate the reynolds stress 315 00:28:34,140 --> 00:28:40,190 reynolds stress is nothing but rho v v prime reynolds stress is rho v v prime so i can 316 00:28:40,190 --> 00:28:46,460 calculate all the nine component of the reynolds stress suppose if i am talking about or if 317 00:28:46,460 --> 00:28:56,140 this polar coordinate i can calculate v r v z rho v r v r rho v r v z prime v z prime 318 00:28:56,140 --> 00:29:03,540 rho theta prime theta prime and so on i can calculate all the nine components of the reynold 319 00:29:03,540 --> 00:29:10,520 stress and we can also calculate the kinetic energy of fluctuations per unit volume ok 320 00:29:10,520 --> 00:29:15,830 of fluctuating kinetic energy of this per unit volume and fluctuating kinetic energy 321 00:29:15,830 --> 00:29:20,559 has been defined for each cell suppose if the particle is coming hundred times in each 322 00:29:20,559 --> 00:29:25,630 cell ok what will happen you will see the hundred instantaneous velocity you will get 323 00:29:25,630 --> 00:29:30,730 the mean velocity you subtract it you will get the p d f of the insta this fluctuation 324 00:29:30,730 --> 00:29:37,190 velocities now each velocity say v r v theta v z you will get the p d f for v z prime you 325 00:29:37,190 --> 00:29:41,490 will get the p d f for v r prime you will get the p d f for v theta prime 326 00:29:41,490 --> 00:29:47,230 so you will get the p d f of fluctuation velocity for all the three ah velocity components and 327 00:29:47,230 --> 00:29:53,420 then we can do that averaging and half rho v x prime square plus v theta prime square 328 00:29:53,420 --> 00:29:58,750 plus v z prime square or you can right say v x of v r it will be the nothing but the 329 00:29:58,750 --> 00:30:03,549 turbulent kinetic energy per unit volume of the tracer particle why per unit volume because 330 00:30:03,549 --> 00:30:08,710 instead of mass i am taking rho because in case of the fluid we know the rho but knowing 331 00:30:08,710 --> 00:30:13,470 the masses many times is very difficult so that is the fluctuating kinetic energy per 332 00:30:13,470 --> 00:30:18,630 unit volume we use this formula to calculate the quantities we can also calculate diffusivity 333 00:30:18,630 --> 00:30:24,440 we can also calculate autocorrelation and all other data we will discuss that later 334 00:30:24,440 --> 00:30:30,480 now as i said r p t is not an obsession technique and you have to assemble it from the basic 335 00:30:30,480 --> 00:30:35,350 nuclear spectroscopy hardware so lets discuss that what are the hardware which is required 336 00:30:35,350 --> 00:30:41,070 for the r p t experiments now as i said that the most typical part of the r p t experiment 337 00:30:41,070 --> 00:30:47,740 is the tracer particle ok which we are using as a marker of the phase so the first hardware 338 00:30:47,740 --> 00:30:52,890 i will say is nothing but the radioactive particle which should be the gamma ray source 339 00:30:52,890 --> 00:30:57,210 ok and the particle size if you are tracking again i am repeating if you are tracking the 340 00:30:57,210 --> 00:31:03,240 solid phase size shape and density of the tracer particle should be exactly identical 341 00:31:03,240 --> 00:31:08,059 to the size shape and density of the other particles which are presented the flow in 342 00:31:08,059 --> 00:31:13,470 case of liquid tracking the particle size should be smaller and the density should be 343 00:31:13,470 --> 00:31:19,289 equal to the density of the liquid in case of the gas tracking i am sorry that is the 344 00:31:19,289 --> 00:31:25,220 major disadvantage of this technique you can track the gas by using the r p t technique 345 00:31:25,220 --> 00:31:31,059 why because it is very difficult to find a tracer particle solid tracer particle which 346 00:31:31,059 --> 00:31:37,400 can match the density of any gas and therefore the gas tracking cannot be done it can do 347 00:31:37,400 --> 00:31:44,500 either the liquid tracking or the solid tracking so this the first hardware is your radioactive 348 00:31:44,500 --> 00:31:49,230 source this is some typical photograph of the radioactive source and you can see that 349 00:31:49,230 --> 00:31:54,929 depending upon the application the size shape and density of the source is keep on changing 350 00:31:54,929 --> 00:31:59,540 ok so these are the typical sources which we use in our laboratory and thats what i 351 00:31:59,540 --> 00:32:04,810 have shown that it can be from very small to very big and the tribes shape and density 352 00:32:04,810 --> 00:32:10,960 of this particles are kept exactly same to the solid present in the flow ok the second 353 00:32:10,960 --> 00:32:17,159 hardware and his scintillation detectors the job is to actually record the photon counts 354 00:32:17,159 --> 00:32:22,440 which is emitted by the tracer particle the third is to multi input data acquisition 355 00:32:22,440 --> 00:32:29,740 system which also called it midas ah if his job is to use the a kind of acquire the data 356 00:32:29,740 --> 00:32:35,679 recorded or transferred from the detector so detector will adsorb the count it will 357 00:32:35,679 --> 00:32:40,610 transfer that adsorb counts to the midas or to the electronics and electronics job is 358 00:32:40,610 --> 00:32:47,210 to count that number of incidents of the gamma ray which has been detected by the scintillation 359 00:32:47,210 --> 00:32:54,679 detectors so that is the job of the midas and then finally you require a p c for the 360 00:32:54,679 --> 00:32:59,790 data acquisition as well as data processing so these are the typical hardware actually 361 00:32:59,790 --> 00:33:05,029 this is the three main hardware which you require for the r p t experiments ok this 362 00:33:05,029 --> 00:33:08,570 is a typical diagram of the scintillation detectors and we will discuss this diagram 363 00:33:08,570 --> 00:33:15,230 in later in more detail so this is a typical diagram of a scintillation detectors which 364 00:33:15,230 --> 00:33:20,360 we use it and if you see that this scintillation detector is divided in two parts the first 365 00:33:20,360 --> 00:33:30,049 part is called crystal and this part is called photomultiplier tube so this part is called 366 00:33:30,049 --> 00:33:43,870 photo multiplier tube ok so the detector has been actually made of two parts first part 367 00:33:43,870 --> 00:33:48,929 is the crystal which actually do the adsorption shop another part is the photomultiplier tube 368 00:33:48,929 --> 00:33:56,419 which is used generally for this for the supplying the this particle this voltage as well as 369 00:33:56,419 --> 00:34:01,250 to count the signal which is being generated during the adsorption of the photon counts 370 00:34:01,250 --> 00:34:07,040 so how the scintillation detectors work to see that lets assume this is my scintillation 371 00:34:07,040 --> 00:34:11,869 detectors these are my photomultiplier tube and it is connected with a counter now lets 372 00:34:11,869 --> 00:34:16,190 forget that what kind of counter it is but lets assume that it is a counter which counts 373 00:34:16,190 --> 00:34:22,010 the signal so what will happen once this gamma ray is actually emitted on the crystal what 374 00:34:22,010 --> 00:34:27,700 will happen the crystal will actually adsorb that gamma ray ok now once the crystal will 375 00:34:27,700 --> 00:34:34,470 adsorb that gamma ray ok so suppose this is the time when the particle has incidented 376 00:34:34,470 --> 00:34:40,339 of the detectors it will emits a photo electrons so what will happen we know that that once 377 00:34:40,339 --> 00:34:46,770 the gamma ray is adsorbed in any material or any crystal what happen that the crystal 378 00:34:46,770 --> 00:34:51,480 electrons goes to excited states because they got certain energy once they will come back 379 00:34:51,480 --> 00:34:58,150 from that excited state energy they actually emits a photon a photo electron or so that 380 00:34:58,150 --> 00:35:03,750 photo electron actually is covered to the photo cathode to generate a electron and that 381 00:35:03,750 --> 00:35:08,680 electron passed through this multi photomultiplier tube which has actually several diodes placed 382 00:35:08,680 --> 00:35:14,200 to enhance the signal it actually passed through that and once it passed through that it reached 383 00:35:14,200 --> 00:35:19,520 to the anode once it reached to the anode like this way it passes is generate a pulse 384 00:35:19,520 --> 00:35:25,070 a current signal and that pulse or current signal is being actually counted by a counter 385 00:35:25,070 --> 00:35:30,720 which is being placed after the detectors so each photon counts or each photon which 386 00:35:30,720 --> 00:35:37,140 is incidented on the detector adsorb by the detectors because only once the photon adsorb 387 00:35:37,140 --> 00:35:41,910 it will emit a photo electron it will go to high energy state and then it will emit to 388 00:35:41,910 --> 00:35:49,790 follow to an electron so ah so for each gamma ray which has been adsorb by the detector 389 00:35:49,790 --> 00:35:55,390 each current pulse has been generated so it means if you just count the number of times 390 00:35:55,390 --> 00:36:00,360 the current pulse has been generated between the data acquisition system so say if i am 391 00:36:00,360 --> 00:36:04,510 acquiring with one second data acquisition frequency after every one second i am acquiring 392 00:36:04,510 --> 00:36:10,020 the data so i will see that how many times this current pulse have been generated within 393 00:36:10,020 --> 00:36:16,609 that one second and that is been called of that it will be shown as the photon counts 394 00:36:16,609 --> 00:36:23,140 on that detector for that time period for that delta t ok and you will get this kind 395 00:36:23,140 --> 00:36:29,670 of whatever we were discussing you will get this kind of a map for each detector that 396 00:36:29,670 --> 00:36:35,470 how the photon count is changing on each detector with the time clear 397 00:36:35,470 --> 00:36:40,910 so now if the detector is closed definitely number of intensity will be higher more number 398 00:36:40,910 --> 00:36:46,589 of photons counts will be incidented is detector is very far the cone angle the view angle 399 00:36:46,589 --> 00:36:52,230 the factor the attenuation will be higher so the number of photon counts emitted or 400 00:36:52,230 --> 00:36:56,240 incidented on the detector will be low and thats why the counts on that detector will 401 00:36:56,240 --> 00:37:01,740 be low so that is the basic principle we use and we get the photon count time series history 402 00:37:01,740 --> 00:37:04,740 ok so this is the way the scintillation detectors 403 00:37:04,740 --> 00:37:09,030 work and there is a crystal inside most of the time there are different type of crystal 404 00:37:09,030 --> 00:37:13,900 available in the market for different type of detectors but most of the time we use n 405 00:37:13,900 --> 00:37:30,130 a i t l which means sodium iodide dopped with thallium is used as a scintillation detectors 406 00:37:30,130 --> 00:37:34,839 so these are sodium iodide detectors why it is being used because its very cheap compared 407 00:37:34,839 --> 00:37:40,960 to the other detectors like b g o or any other detectors this this is very cheap and thats 408 00:37:40,960 --> 00:37:46,790 why for r p t application generally we use sodium iodide detector scintillation detectors 409 00:37:46,790 --> 00:37:52,849 which is dopped with the thallium ok now the second hardware which is important 410 00:37:52,849 --> 00:37:58,140 is whatever is being put which i keep on telling till now is a counter which is being placed 411 00:37:58,140 --> 00:38:05,050 after the detectors so there several advancement is there in the r p t hardware ok so earlier 412 00:38:05,050 --> 00:38:10,480 this system used to be very huge but with the modern development of the electronics 413 00:38:10,480 --> 00:38:15,910 or develop a modern electronics now the system size has been reduced so what we need actually 414 00:38:15,910 --> 00:38:21,130 this detectors as i said have a photo diodes and those also need a energy so what you require 415 00:38:21,130 --> 00:38:27,500 you require certain high voltage to maintain the particular potential within the that detectors 416 00:38:27,500 --> 00:38:32,940 ok so you need a high voltage supply then the current pulse which is being generated 417 00:38:32,940 --> 00:38:40,630 by incidenting one a photon one gamma rays or photon count photon on the detector the 418 00:38:40,630 --> 00:38:45,630 intensity of that signal is very very weak if density of that current pulse is very very 419 00:38:45,630 --> 00:38:50,810 weak so what we do we need amplifier or series of amplifier depending upon the intensity 420 00:38:50,810 --> 00:38:56,770 we can have a pre amplifier we can have amplifier which will actually amplify the signal so 421 00:38:56,770 --> 00:39:01,890 that i can see the signal and i can discriminate the signal from the noise ok 422 00:39:01,890 --> 00:39:07,750 so i will get that amplifier then we use a single channel analyzer or multi channel analyzer 423 00:39:07,750 --> 00:39:12,380 now what that the job is as i said that single channel it means it has a single channel which 424 00:39:12,380 --> 00:39:18,940 records or which counts the number of photons incidented on each detectors ok so this is 425 00:39:18,940 --> 00:39:23,660 nothing but a counter but its also a single channel analyzer so its also analyze that 426 00:39:23,660 --> 00:39:29,480 that the photon which has been incidented was of what energy because if the energy of 427 00:39:29,480 --> 00:39:35,480 the photons was very high then the probability of absorption of those photons on the scintillation 428 00:39:35,480 --> 00:39:40,490 detector crystal is low and so the intensity will also be different 429 00:39:40,490 --> 00:39:45,630 so we calculate that energy of the system or roughly energy of the system and we get 430 00:39:45,630 --> 00:39:52,850 that this kind of a photo peak curve so if you see that for each detector each time you 431 00:39:52,850 --> 00:39:59,401 will get this kind of a curve for each detectors ok now this is called photo peak we will discuss 432 00:39:59,401 --> 00:40:05,000 about the photo peak once we will do the tomography things but what we get is actually you get 433 00:40:05,000 --> 00:40:12,240 that how the count energy is changing ok number of photon counts versus number of this count 434 00:40:12,240 --> 00:40:17,800 photon count energy so you see that this kind of a curve and then in this channel we put 435 00:40:17,800 --> 00:40:23,550 some discriminator of filters to record the count only which is coming directly from the 436 00:40:23,550 --> 00:40:27,780 source and those counts or those area is called photo peak ok 437 00:40:27,780 --> 00:40:31,580 so what will happen now there is a question there is lo lot of things to discuss i am 438 00:40:31,580 --> 00:40:35,850 trying to cover in a little bit brief if you have any problem please discuss me over the 439 00:40:35,850 --> 00:40:40,180 assignment we can drop me the questions i can i would love to answer those things so 440 00:40:40,180 --> 00:40:47,040 what we do actually that even our tube lights ok is also emitting photons now hardware is 441 00:40:47,040 --> 00:40:51,000 not able to detect the difference between that photon and the photon which is coming 442 00:40:51,000 --> 00:40:55,170 from the gamma rays other than the energy that the energy of this tube light photons 443 00:40:55,170 --> 00:41:00,690 will be much lower compared to the photons which is coming from the gamma rays so and 444 00:41:00,690 --> 00:41:04,119 there will be some noise also as you know that we will all the electronics generate 445 00:41:04,119 --> 00:41:10,630 some noise and thats why we put the preamplifier and amplifier so that i can increase the signal 446 00:41:10,630 --> 00:41:15,380 to noise ratio i can imply by signal so that i can reduce the noise 447 00:41:15,380 --> 00:41:19,690 now this is the ways so all these things are incidenting they are actually contributing 448 00:41:19,690 --> 00:41:25,250 towards the count so to detect that which of the count which is coming from my source 449 00:41:25,250 --> 00:41:29,970 which is relevant to me what are the count which are not coming from my source or which 450 00:41:29,970 --> 00:41:34,359 is coming from the source but has been got attenuated because of the several collision 451 00:41:34,359 --> 00:41:38,180 it means which is not directly coming or straight coming from the source we have to neglect 452 00:41:38,180 --> 00:41:43,410 those counts ok so we draw a pho number of photon on y axis 453 00:41:43,410 --> 00:41:48,850 and energy on the x axis and you will get this kind of a curve in that curve you will 454 00:41:48,850 --> 00:41:54,520 get a prominent peak and that peak will actually represent the energy of this source so like 455 00:41:54,520 --> 00:41:59,619 in this case we are using cesium one thirty seven as a source which energy is six sixty 456 00:41:59,619 --> 00:42:06,480 two k e v and thats why we are getting a peak at six sixty two k e v and this is the sample 457 00:42:06,480 --> 00:42:11,790 where the red bracket you are seeing is called the photo peak it means that is the peak or 458 00:42:11,790 --> 00:42:15,240 that is the peak which is directly coming from the source we are very sure about it 459 00:42:15,240 --> 00:42:20,330 so we put a discriminator of filter which actually reduce the remove the counts which 460 00:42:20,330 --> 00:42:24,790 are below than this photo peak or below the energy which will below in this photo peak 461 00:42:24,790 --> 00:42:29,770 it means any energy which is less than this it will be discriminated it will not be kind 462 00:42:29,770 --> 00:42:34,750 of recorded any energy which is higher than this which also not be recorded so we record 463 00:42:34,750 --> 00:42:40,070 only the photo peak counts and thats what we call it as a photon count time series history 464 00:42:40,070 --> 00:42:44,660 and that is being done by the single channel analyzer or multi channel analyzer where we 465 00:42:44,660 --> 00:42:48,339 can have multiple channels or energy channels ok 466 00:42:48,339 --> 00:42:54,160 so this is the electronics part of it how the data has been recorded so the photon count 467 00:42:54,160 --> 00:42:59,140 which we record actually the time series history the graph which i have shown you is only for 468 00:42:59,140 --> 00:43:04,160 the photo peak its not for these grounds which are actually noise ok so we record the photo 469 00:43:04,160 --> 00:43:10,589 peak counts now in with the development of the electronics earlier we used to use this 470 00:43:10,589 --> 00:43:14,880 all these electronics separately and thats why the system used to be look very bulky 471 00:43:14,880 --> 00:43:19,200 but now with the development in the electronics and coming with the modern electronics now 472 00:43:19,200 --> 00:43:26,040 a days we actually can accommodate all this devices in a single device and that is called 473 00:43:26,040 --> 00:43:31,790 multi input data acquisition system or midas and this is the the multiple data acquisition 474 00:43:31,790 --> 00:43:36,920 system and this one unit if you will see this one unit is called single channel analyzer 475 00:43:36,920 --> 00:43:46,380 analyzer now these knobs you are seeing that knobs 476 00:43:46,380 --> 00:43:53,480 are actually to set the setting of the detectors the so one knob is for high voltage supply 477 00:43:53,480 --> 00:43:57,940 that how much voltage you want to supply one knob is for the discrimination putting the 478 00:43:57,940 --> 00:44:04,120 limits on this energy spectra so that you can acquire the count only those counts which 479 00:44:04,120 --> 00:44:09,859 are directly coming from the source so this is another device we need to do the recording 480 00:44:09,859 --> 00:44:15,860 now there are several steps as i said in the r p t in the r p t there are several steps 481 00:44:15,860 --> 00:44:20,922 as i said that first step is the photon counts second step is calibration and third step 482 00:44:20,922 --> 00:44:26,130 is reconstruction so what we were discussing about the photon count till now and the hardware 483 00:44:26,130 --> 00:44:31,410 which is needed for the photon count experiments now as i said that for the reconstruction 484 00:44:31,410 --> 00:44:37,300 what you need you need to put the tracer particle at a various known location before performing 485 00:44:37,300 --> 00:44:42,589 the experiments and the challenge is to do that at in situ condition in situ condition 486 00:44:42,589 --> 00:44:47,420 means suppose i want to perform the experiments for a particular solid circulation rate or 487 00:44:47,420 --> 00:44:52,839 particular amount of the solids say in the gas solar system particular gas velocity i 488 00:44:52,839 --> 00:44:57,760 have to do the experiments you calibration for exactly same condition it means for that 489 00:44:57,760 --> 00:45:03,369 much amount of the solid and for that solid velocity for that gas velocity 490 00:45:03,369 --> 00:45:08,390 so you have to do that the calibration at in situ and during that in situ calibration 491 00:45:08,390 --> 00:45:13,660 now we put the tracer particle at several known location and you got the count on the 492 00:45:13,660 --> 00:45:18,570 detectors now how we can put the tracer particle there are several ways to put the tracer particle 493 00:45:18,570 --> 00:45:22,460 and if you go and see the literature on the radioactive particle tracking you will see 494 00:45:22,460 --> 00:45:28,440 that every one device ah derive of quantity or design or calibration device based on their 495 00:45:28,440 --> 00:45:34,080 column operating condition column geometry and column size so what we are going to discuss 496 00:45:34,080 --> 00:45:38,980 is one of the method which is very simple and we always use that in our laboratories 497 00:45:38,980 --> 00:45:46,750 so now the first question is you can ask that why in situ calibration because i said that 498 00:45:46,750 --> 00:45:52,589 we are if you are using i equal to i naught e raise to power minus mu l what i need i 499 00:45:52,589 --> 00:45:57,950 need this attenuation coefficient for that location of the tracer particle and this attenuation 500 00:45:57,950 --> 00:46:03,940 coefficient will be differ based on the operating condition so suppose if i am operating a gas 501 00:46:03,940 --> 00:46:09,770 solid fluidized bed say this is my solid and this is the pad bed condition suppose and 502 00:46:09,770 --> 00:46:14,630 we know that if i pass the gas a velocity will come when the particle will start moving 503 00:46:14,630 --> 00:46:18,990 so in the pad bed condition if suppose my trac this is my tracer particle the red color 504 00:46:18,990 --> 00:46:24,130 and these are the detector placed what will happen the attenuation will be more because 505 00:46:24,130 --> 00:46:28,300 all the solids are perfectly packed so attenuation it will see lot of solids 506 00:46:28,300 --> 00:46:33,050 now definitely depending on the density say gas have a very low attenuation the materials 507 00:46:33,050 --> 00:46:36,710 which have a higher density is going to have a very high attenuation so you are going to 508 00:46:36,710 --> 00:46:40,230 see lot of solids your attenuation will be different so what will happen you will see 509 00:46:40,230 --> 00:46:46,119 the different count on all these detectors now if i fluidize suppose what will happen 510 00:46:46,119 --> 00:46:51,890 the similarly these are the detectors which will be placed say and now the particles has 511 00:46:51,890 --> 00:46:55,369 been fluidize so what will happen if they fluidize the particles will move far from 512 00:46:55,369 --> 00:47:01,510 each other and now if suppose this is my tracer particle now the counts recorded on these 513 00:47:01,510 --> 00:47:05,730 detectors will be different because now it is seeing less number of the solids so if 514 00:47:05,730 --> 00:47:10,490 because it is seeing less number of the solids it is going to have less recognition so now 515 00:47:10,490 --> 00:47:15,020 the count will improve so thats the region that you need to have 516 00:47:15,020 --> 00:47:20,750 you have to take care of this mu distribution which is clearly the function of the operating 517 00:47:20,750 --> 00:47:25,490 condition and thats why we need to do the calibration at in situ condition so what we 518 00:47:25,490 --> 00:47:30,290 need to do at in situ condition at the same operating condition we need to put the tracer 519 00:47:30,290 --> 00:47:35,119 particle at several known location now there are several days as i said in literature everyone 520 00:47:35,119 --> 00:47:40,990 use a different method depending upon the operating conditions say what is my operating 521 00:47:40,990 --> 00:47:44,599 condition that i am operating at a very high pressure of very high temperature whether 522 00:47:44,599 --> 00:47:49,870 its a gas solid flow whether its liquid solid flow so depending upon the type of the reactor 523 00:47:49,870 --> 00:47:55,450 depending upon the size of the reactor different calibration strategies has been developed 524 00:47:55,450 --> 00:48:00,220 by the different researcher but idea is to place the particle at a known location 525 00:48:00,220 --> 00:48:05,540 so generally what we do in our lab we put the pores several pores near at the wall so 526 00:48:05,540 --> 00:48:10,550 these are the pores ok and i know the pores because we are designing the column i put 527 00:48:10,550 --> 00:48:17,900 the pores i know the r theta and z position of this pores ok so i can say that instead 528 00:48:17,900 --> 00:48:22,920 of r theta and z say if its a rectangular i will say x y z position of the tracer particle 529 00:48:22,920 --> 00:48:29,280 so i will no sorry of this pores so i know this pores now we take a rod and we put a 530 00:48:29,280 --> 00:48:32,970 tracer particle on the top i dont know how much it is visible but i will show the next 531 00:48:32,970 --> 00:48:37,051 figure where you can see clearly that there is a tracer particle which is on the top so 532 00:48:37,051 --> 00:48:43,000 you can see that there is a small tracer particle here which is on the top ok so this is the 533 00:48:43,000 --> 00:48:49,630 tracer particle and we put your instead of the threaded rod and so that you can move 534 00:48:49,630 --> 00:48:55,819 the thread and you can change the location of the r value so the z of the port is fixed 535 00:48:55,819 --> 00:49:00,740 ok the theta of this port is fixed and you are now changing the r value so you will prove 536 00:49:00,740 --> 00:49:05,690 the you will change the r theta and z position of the tracer particle and you will record 537 00:49:05,690 --> 00:49:09,020 the cups ok so that is the one way of doing the calibration 538 00:49:09,020 --> 00:49:13,060 but that should be at in situ condition i have drawn taking the photograph at empty 539 00:49:13,060 --> 00:49:18,440 column so that we can explain the facts so what we do suppose this is a the the opaque 540 00:49:18,440 --> 00:49:23,300 column so we take this kind of a threaded rod if you see this figure we put the tracer 541 00:49:23,300 --> 00:49:28,339 particle on the top this is my transfer particle and at the in situ condition we place the 542 00:49:28,339 --> 00:49:32,970 transfer particle through these pores ok and they are detected placed which actually record 543 00:49:32,970 --> 00:49:37,589 the counts now definitely these detectors are going to record very high counts compared 544 00:49:37,589 --> 00:49:42,280 to the other detectors which are placed here so i will get for the calibration if i put 545 00:49:42,280 --> 00:49:47,790 it here i will get that what is the count recorded on each detector for dislocation 546 00:49:47,790 --> 00:49:56,579 of the tracer particle it means i will have say r theta z and i will have c one c two 547 00:49:56,579 --> 00:50:02,160 c three and so on on all detector how the counts is changing for r theta and z ok 548 00:50:02,160 --> 00:50:08,160 then what i will get do i will just move this thread further so the particle will move further 549 00:50:08,160 --> 00:50:13,150 inside so i will change the it means what i did i change the position of the r again 550 00:50:13,150 --> 00:50:19,440 i will record the count on each detector so what will happen i will have a lookup table 551 00:50:19,440 --> 00:50:27,380 we call it lookup table which says that how the particle ah trace posit however the detector 552 00:50:27,380 --> 00:50:33,410 counts are changing with the particle position ok so this is called calibration then we perform 553 00:50:33,410 --> 00:50:38,630 the experiments we get the time versus count we compare both two and we calculate that 554 00:50:38,630 --> 00:50:41,180 what is the position of the tracer particle ok 555 00:50:41,180 --> 00:50:46,069 so what you will get actually if you do the calibration experimentally you will get it 556 00:50:46,069 --> 00:50:51,339 that how the count is changing with the distance from the tracer particle so i know the position 557 00:50:51,339 --> 00:50:56,420 of the detector ok i know the position of the detector it means i know the x y z coordinate 558 00:50:56,420 --> 00:51:04,560 of the detector i know the x a i will write it as a detector i know x y z are power position 559 00:51:04,560 --> 00:51:11,880 of the particle i know this coordinates i can calculate the distance ok that will be 560 00:51:11,880 --> 00:51:19,650 nothing but under root x one minus x two square plus y one minus y two square plus z one minus 561 00:51:19,650 --> 00:51:25,109 z two square so i will add one to this say two to this i will get that distance 562 00:51:25,109 --> 00:51:30,810 so what i will get how with the distance tracer particle position ah you can say or you can 563 00:51:30,810 --> 00:51:35,630 say distance from the detector a particular detector the counts on that detector is changing 564 00:51:35,630 --> 00:51:40,069 and as we know it is going to follow i equal to i naught is from minus mu l you can do 565 00:51:40,069 --> 00:51:44,560 the calibration you can validate it whether it is following or not and you can see that 566 00:51:44,560 --> 00:51:49,310 it is following that curve a bell kind of a curve or a gaussian curve which is showing 567 00:51:49,310 --> 00:51:54,690 that it is following the beer lamberts law ok 568 00:51:54,690 --> 00:52:00,520 so it is the exponentially the counts recorded on the detector is changing with the distance 569 00:52:00,520 --> 00:52:06,520 ok so similar graph you can prepare for all the detectors so you will know that at what 570 00:52:06,520 --> 00:52:13,780 distance what count you are expecting on that detector ok now why we need several detectors 571 00:52:13,780 --> 00:52:19,619 because there can be a position when suppose what can get confusion one can ask the question 572 00:52:19,619 --> 00:52:25,750 suppose this is my column i am using this two detector if suppose the particle is moving 573 00:52:25,750 --> 00:52:31,490 vertically downward then the count on this location distance of this location in this 574 00:52:31,490 --> 00:52:36,250 location will be the same so what will happen in that case in that case i will not have 575 00:52:36,250 --> 00:52:40,490 a unique picture i will have i can either reconstruct this position of the particle 576 00:52:40,490 --> 00:52:44,580 or this position of the particle because if i will go to this lookup table they will give 577 00:52:44,580 --> 00:52:49,430 me the same counts this count if i mean distance of say five hundred this is going to give 578 00:52:49,430 --> 00:52:54,210 me the same count and that is the reason why we place the several detectors to cover the 579 00:52:54,210 --> 00:52:58,560 entire area so yes its true that this you will calculate with one detector we will not 580 00:52:58,560 --> 00:53:02,819 get the unique solution so if i take the counts and that is the region 581 00:53:02,819 --> 00:53:07,740 that why while reconstructing we take the counts from all the detectors now if suppose 582 00:53:07,740 --> 00:53:13,599 i have a two detectors here two detectors heres what will happen for this location for 583 00:53:13,599 --> 00:53:18,270 this location now these distances are low these detector distances are low so they are 584 00:53:18,270 --> 00:53:23,700 going to get high counts they are going for this location they are going to get low counts 585 00:53:23,700 --> 00:53:28,380 and the vice versa will be true for this location these two detectors will get higher count 586 00:53:28,380 --> 00:53:33,000 and these two detectors will get lower count so if i do the combine if i take the effect 587 00:53:33,000 --> 00:53:37,980 of all the counts all the detector counts to reconstruct the position of the particle 588 00:53:37,980 --> 00:53:46,609 i will always get a unique solution and that is the major plus point of the r p t technique 589 00:53:46,609 --> 00:53:51,610 that you always get a unique solution because you have only one particle where the counts 590 00:53:51,610 --> 00:53:56,380 are coming compared to the other technique where the unique solution is also sometimes 591 00:53:56,380 --> 00:54:01,010 are difficult ok and that is the major added advantage of this technique 592 00:54:01,010 --> 00:54:05,820 so what we do we generate the photon count time series history that how photon count 593 00:54:05,820 --> 00:54:11,910 time series is changing with the tracer particle location ok so distance and location is same 594 00:54:11,910 --> 00:54:17,520 you are moving far distance is increasing we are coming close distance is reducing but 595 00:54:17,520 --> 00:54:25,260 as i said it is impossible to do the calibration experimental calibration for all the location 596 00:54:25,260 --> 00:54:30,340 inside the tracer partie inside the reactor or inside the column of interest why because 597 00:54:30,340 --> 00:54:35,839 of the two position it is very difficult to put a pores at all the physical location because 598 00:54:35,839 --> 00:54:40,260 the pores require some physical area so you cannot put the tracer particle at all the 599 00:54:40,260 --> 00:54:45,990 location second it will be very time consuming for each firing what you need to do it in 600 00:54:45,990 --> 00:54:50,589 situ condition you have to put the particle at several location pull the particle out 601 00:54:50,589 --> 00:54:54,660 now if you are pulling the particle out suppose its a gas solid or liquid solid what you need 602 00:54:54,660 --> 00:54:59,349 to do you have to first set down the system neither the solids will start leaking from 603 00:54:59,349 --> 00:55:02,020 this pores or liquid will start leaking from this pores 604 00:55:02,020 --> 00:55:06,200 so what you need to do you have to shut down the system then you have to remove it then 605 00:55:06,200 --> 00:55:09,580 again you have to put it into the other pore you have to close this pore you have to put 606 00:55:09,580 --> 00:55:14,290 it in the other pores you have to again operate the system you have to wait for a study state 607 00:55:14,290 --> 00:55:19,329 to achieve and then you have to do the same exercise that you change the location so these 608 00:55:19,329 --> 00:55:25,140 two major disadvantage of the experimental calibration the first is it is almost impossible 609 00:55:25,140 --> 00:55:30,192 to do the calibration at all the location in sight and remember that the tracer particle 610 00:55:30,192 --> 00:55:35,800 is free to move anywhere inside so what you have to do you have to actually need the calibration 611 00:55:35,800 --> 00:55:40,079 at all the known location or you need to depend on the interpolation 612 00:55:40,079 --> 00:55:44,700 now we know that the interpolation had certain accuracy we dont want to get involved in that 613 00:55:44,700 --> 00:55:49,780 so for the better accuracy we want that my i should have a calibration count for all 614 00:55:49,780 --> 00:55:56,680 the possible position inside the vessel of interest ok so for that purpose as i said 615 00:55:56,680 --> 00:56:01,760 earlier that the calibration we cannot do only we cannot depends only on the experimental 616 00:56:01,760 --> 00:56:07,050 we have to also do a software calibration which is actually based on the monte carlo 617 00:56:07,050 --> 00:56:23,849 algorithm now how to do that the software calibration we will discuss it later 618 00:56:23,849 --> 00:56:35,420 thank you