Neutron TGEM Detector Abdel
Haithem's logbook for developing neutron sensitive TGEM detector
1/23/09
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1.) Search the web for patent which coats GEM detector with neutron sensitive materials. I think it is for Thermal neutrons.
Materials of high neutron capture cross section are studied widely, an example is the following patent
[[1]]
Most of the high neutron capture cross section materials were measured for different neutron energies. A comprehensive work is published in 2000. The project was supported by Korea Atomic Energy Research Institute and Brookhaven National Laboratory [[2]]
U-235 is the one of the best choices since it has a high neutron fission cross section and a long half life compared to other the other isotopes that may come under choice.
A second choice is Th-238 and U-238 which have fission cross section less than that of U-235 but still good for our experiment.[[3]]
A boron coated GEM foil is being made by the company below http://n-cdt.com/
Another method uses BF3.
We are interested in a fissionable material coated onto the copper foils that is thin enough to allow the fission fragments to escape the foil and ionize the gas in the detector.
2.) Search for companies which use either sputtering or coating technology to apply the above material to caopper PCboards with hole int them such that the material does not fill up the hole. Hole diameter = ?
The material sputter onto the copper would have thickness on the order of Angstroms.
The TGEM PCboard would have a surface area of 10 cm x 10 cm.
3.) Current neutron efficiency plots for several detector
Media:NeutronDetectionEfficiency-vs-Energy_Ne-213_BaF.pdf
1/30/09
1.) Investigate if Thorium Oxide will be a good candidate for the fission chamber. You would use electrolysis to coat a TGEM board.
Ways to make thorium fission chamber
2.) Find reference for THGEM9, this was used to determine optimal THGEM design 2 years ago
GEM-copper plate has dimensions of 3X3cm or 10X10cm with thinkness 5 micrometer copper layers.It has holes with diameter 60-80 micrometer.(From Operation of a triple GEM detector with CsI photocathode in pure BF4)
2/6/09
Thin deposition ThO2 molecular plating
2/13/09
Check if the people below can deliver Th coated Al or Cu sheets , coating thickness smaller than 5 micron, the thinner the better. http://www-wnt.gsi.de/tasca/
2/20/09
2.5 x 2.5 cm thorium coated TGEM cards coated by ISU chemistry.
chemistry Department cant not do the sputtering for safety purposes, they like to avoid radiation contamination.
Need a mask for the predrilled TGEM cards to prevent Thorium from entering holes
Radioactive waste procedure if we are allowed to sputter in chemistry.
Write report describing the process we want to do.
Radioactiving of Thorium may be a stumbling blog because of waste generated.
If we go for non-radioactive materials look up fission X-sect for Bismuth and Dysprosium
Fission cross section for Bi starts to be effective when the neutron energy is more than the range of interest.
Dy-isotopes are very good for absorbing neutrons in the range between 0.01- 10 MeV.
Media:Zaidi_RadChem_vol93_2005.pdf
2/27/09
1.) Dysprosium (Dy) makes a lot of gammas and maybe 100 less alphas
2.) Don't give up trying to make thorium coated materials
try to send e-mail to one of these authors
N. Takahashi, Zeitschrift für Physik A Hadrons and Nuclei Volume 353, Number 1 / March, 1995
3.) Fission cross-section n,f for Tb
3/13/09
1.) look for a company that does resistive evaporative coatings
This company sells the machine http://www.lesker.com/newweb/Deposition_Sources/ThermalEvaporationSources_Resistive.cfm
2.)(n,f) X-sect for Dysprosium (Dy) ?
3.) Thorium and thorium oxide thin films (19 to 61 nm thick) were RF-sputtered onto mirrors. RF sputtering onto copper plates?
The neutron fission cross sections of 92235U and 92238U between 0.3 and 12.5 MeV W W Osterhage et al 1978 J. Phys. G: Nucl. Phys. 4 587-595
http://www.inf.uu.se/Reports/publications.html
Neutron-induced fission cross sections of natPb and 197Au in the 45-180 MeV region, V.P. Eismont, A.V. Prokofiev, A.N. Smirnov, S.M. Soloviev, H. Condé, K. Elmgren, N. Olsson and P.-U. Renberg Conference Proc. ADTTA99, 1999, (in press).
Up-to-date status and problems of the experimental nucleon-induced fission cross section data base at intermediate energies, V.P. Eismont, A.V. Prokofiev, A.N. Smirnov, I.V. Ryzhov, G.A. Tutin, H. Cond, K. Elmgren, N. Olsson and P.-U. Renberg, Proc. ADTTA99, 1999, (in press).
Neutron-induced fission cross section ratios of 209Bi and 238U at 75 and 96 MeV, V.P. Eismont, A.V. Kireev, I.V. Ryzhov, S.M. Soloviev, G.A. Tutin, H. Condé, K. Elmgren, N. Olsson and P.-U. Renberg, Proc. ADTTA99, 1999, (in press).
Neutron-induced fission fragment angular distribution of 238U at 96 MeV, V.P. Eismont, A.V. Kireev, I.V. Ryzhov, S.M. Soloviev, G.A. Tutin, H. Condé, K. Elmgren, N. Olsson and P.-U. Renberg Proc. ADTTA99, 1999, (in press).
Measurements of neutron-induced fission cross sections of heavy nuclei in the intermediate energy region, V.P. Eismont, A.V. Prokofyev, A.N. Smirnov, K. Elmgren, J. Blomgren, H. Condé, J. Nilsson, N. Olsson and E. Ramström, Accelerator-Driven Transmutation Technologies and Applications, Kalmar, ed. H. Condé (Uppsala: Uppsala University, 1997) p 606-612.
4/2/09
Summury of events through the last two weeks:
1- Looking for a neutron fission cross section for Dyspromium.
2- Looking for other possile elements that can be sued beside our choices for Thorium and Dysprosium.
these elemets should have a high neutron cross for fission (n,f),(n,gamma),(n,p) or (n,alpha).
3- Using Neutrons cross sections (by D. Hughes and R. Schwartz, 2nd edition, 1957) as comphensive reference for our choice.
Comparison between Thorium and Dysprosium
.
Thorium: chacterized by relatively high neutron fission cross for both of its isotopes (Th-232 nad Th-230) compared to the stable elements but it is one of low fission cross sections compared to radioctive actinides. A lot of efforts are spent even in coating or finding the appropriate place or group to do that, since most of people are totally disencouraged to coat radioctive elements.
Dysprosium: radioactively stable,it has 5 isotopes Dy-160, 161, 162, 163 and 164. It is one of the best elements for detecting the neutrons because of high neutron capture cross section in the energy range of interest.
Also dysprosium pulls out alpha paticles (σ(n,α)= 3.6 mb at 14.2 MeV).
Other Possible Elements
. Generally,the highest values for neutron cross sections (σ(n,f), σ(n,p), σ(n,γ) and σ(n,α)) are for radioactive isotopes, which are not desirable for coating. Fortunately, there are non- radioactive elements have a relatively high neutron cross sections, for example:
σ(n,γ) at 0.025 MeV (in mb): Gd-158(710(70)), Sm-152 (670(100)), Br-81 (550(55)), Sm-154 (530(70)), Ce-142 (425(45)),
Hf-180(440(70)), Ru-96(320(60)), Ru-102 (390(40)), W-186 (300(40)), Zr-96 (240(40)), Hg-202(57(13))
σ(n,γ) at 1 MeV (in mb): Re-185(180), (390(40)), Ru-102 (30), Ru-104 (31), Hg-204(100), Br-81 (17)
σ(n,γ) at 14.5 MeV (in mb): Gd-160 (19(5)), Zr-96 (<4),
| Element | X-sect (mb) |
| Re-185 | 180 |
| Ru-102 | 390 |
4/3/09
1.) Derive equations for voltages at each GEM stage and the net current for our voltage network and check them with measured values for the 4kV version of the voltage network.
2.) Reference [J.C. hadler, Radiation Measurements Vol 43 (2008) pf S334-S336] says
- R = 14 \mu m = mean range of fission fragment6s in U_3 O_8
- R= 12 um for UO_3
- 0.1 um thickness U( Th) will reduce mean length of fission tracks by 2%
3.) Plot N -vs- d using Equation 2 of Reference [J.C. hadler, Radiation Measurements Vol 43 (2008) pf S334 The number of particles per unit area is given by the equation:
d : the thickness in (um)
The range of the fragments in the emulsion is 12.07 um
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4/17/09
A call conference with Dr.Wolfe, As result, the following is considered as next step for the project:
1- Check the melting temperature that a PC boeard can hold ( the size of the chamber can hold the 10 X 10 PC board ). The experiment is done, the temperature in average was aroubd 305oC, the PC board can hold that temperature easily,
the PC board was just burned since the medium around is O2, but there is one thing I want ot be sure of, if the PC board has a very light layer of certain material covers its surface and can't hold up that temeperature?
An experiment is done today (4/30/09) to check the PC board behavior at 350oC. A peace of copper sticked by normal used glue.
PC boeard can't hold up the temperature 350oC.
2- Checking from a vender for chunk bulk ThF4 with size min. 30 cc.
3- Checking the thermal properties of ThF4 specially the melting point and if Thorium is adhere to copper in that temperature.
4- A mask should be prepared from stainless steal (Al is not preferable),inaddtion to thinking of drilling process and who
is going to do it.
Laser machining can cut 1" stainless steel sheets
5- Dr. Forest is going to send the email after collecting all the information needed to Dr. Wolfe.
Coaing process is going to be by electron beam, thorium should be heated to 1750 C. (the melting point for pure Th).
Until this point the uniformity of the surface is not an important factor, but I think it would be important whenever we start thinking of the track and the direction for Th fission fragments.
4/23/09
1- Check the melting temperature that a PC board can hold ( the size of the chamber can hold the 10 X 10 PC board ).
Basically FR-4, FR-1, CEM-1 or CEM-3 PCB are made of polytetrafluoroethylene which has (327 °C (620.6 °F))as a melting point.
The experiment is done, the temperature in average was around 305 °C, the PC board can hold that temperature easily,the PC board was just burned since the medium contains O2, but there is one thing I want to be sure of, if the PC board has a very light layer of certain material covers its surface?
2- Checking from a vender for chunk bulk ThF4 with size min. 30 cc.
http://www.element-collection.com/RGB_Elements_OCT04_rev05.pdf
Element-collection sells thorium with 190$/gram !
3- Will Thorium adhere to copper
Thorium flouride is used for optical purposes, according the technical applications they have a number of recommendations related to sputtering by E-beam, and other materials that helps in thorium flouride adhesion.[4]
Looks there is a little change, Dr. Forest is going to check a vendor for U-238, which has a better fission cross section (3 times higher compared to Th-232),in addition to , the high price for Th-232 and risk of having flakes after sputtering, Throium by itself does not adhere with the surfaces unless other materials are used through the sputtering process (as methioned in the case of coating glass with thorium fluoride).
5/1/09
1.) Results from PCboard heating test: Board melts at 350 but not 310 degrees Celcius (Documents suggest 327 as the melting point.)
| Before heating to 350 | After Heating to 350 |
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| Before heating to 298 | After Heating to 298 |
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The experiment is done on the PC-board, it was heated for an hour under 298°C. The result is shown by the second photo, looks that PC-board should be replaced by another material that can hold this temeperature for longer time.
2.) Oak Ridge will give us 1 kg of metal Th-232. We pay for shipping and we need to do rad licenses. Dr. Forest e-mail Dr. Brey and the paper work is beginning.
Contact info
Lloyd J. Jollay Manager Nuclear Technology and Nonproliferation Y-12 National Security Complex P.O. Box 2009 Oak Ridge, TN 37831-8112 Office: 865-241-1872 Fax: 865-574-5169 Pager: 865-873-9146 Mobile: 865-206-9663
3.) Laser cutting can do up to 1" thick stainless steel sheets, we can make a mask! Need to learn CAD to create a drawing of the mask which will be uploaded to the laser cutting machine. make tolerances around 500 micron (1/2 mm).
Insert picture of our GEM PC board with a table of distances.
4.) Meting Point for U-238 =?
Melting Point: 1408 K (1135°C or 2075°F). Boiling Point: 4404 K (4131°C or 7468°F)
5/8/09
1.) It appears the FR-7 melts at 220 celsius so we may not be able to coat copper clad FR4 with U-28 or Th-232. This means we will most likely coat a copper sheet which is attached to a frame for tension and then laminate FR4 after we have coated the copper sheet with U-28 or The-232.
Determine melting point of our current PC boards.
Melting point for the PC board is 260 degrees Celsius,within this degree a change took place in the shape of the board which will make the possibility to use it for sputtering process is very little, the color of the PC-board starts to change at 200 degrees Celsius.
| 200 | 210 | 260 |
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 , 
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2.) The distance between holes in the TGEM appear to be 1mm. A laser can cut through 1" of stainless steel. What accuracy can the laser have when cutting through the thinnest available SS we want to use for a mask.
Find laser resolution (200 microns?)
The following company [5] can reach to a tolerance of 10 micrometer if the thickness of the plate is bigger than 300 micrometer, in our case the thickness of copper foil is 45 micrometer, and the hole is diameter is 1 mm, a tolerance of 200 micrometer is going to be good for the drilling the holes and doing the mask. an email from the company will confirm the expectations.
Determine thinnest SS mask
still waiting for the email.
3.) HV distribution chain calculation. Low voltage version?
Order resistors based on power calculation, work with Tumuna on the order.
4.) Install GEANT4 in your Inca account, Start GEANT4 Fission model (CHIPS or GEISHA).
5/15/09
1.) Insert picture of PCboard at 220 and 260 and denote time spent at that temperature.
2.) The distance between holes in the TGEM appear to be 1mm and are staggered between rows. A laser can cut through 1" of stainless steel. We would like a laser with position accuracy to at least 100 microns (4 mils :1000 mils = 1 in) which can drill a hole whose diameter is accurate to 4 mils. What accuracy can the laser have when cutting through the thinnest available SS we want to use for a mask.
Find laser resolution (10 microns?)
Determine thinnest SS mask
3.) HV distribution chain calculation. Low voltage version?
Look at the following diagram :Media:GEM_HV_circuit.ps
Order resistors based on power calculation, work with Tumuna on the order
4.)GEANT4 is installed in Inca account, ExampleN02 was compiled and runs.
Add GEANT4 Fission model (CHIPS or GEISHA) to ExampleN02 program. Goal is to find a model which reproduces the X-section data for Th-232 above.
5/22/09
1.) heat PC board for 3 hours at 210C
2.) Determine laser resolution for a 45 micron thick copper sheet
3.) HV distribution chain calculation. Do a sample calculation for =?
4.) Going to order 25 resisters of each Ohm setting. Prepare a HV board for stuffing and assemble after resistors arrive.
5.)Add GEANT4 Fission model (CHIPS or GEISHA) to ExampleN02 program. Goal is to find a model which reproduces the X-section data for Th-232 above.
6/9/09
1.) Write a brief description ( 2 paragraphs) of the experimental objectives and methods with justification for the specific radionuclides and quantities.
We propose constructing a fission chamber which contains copper PCboards coated with U-238 and Th-232. Our goal is to construct a fast neutron detector. A safe in the LDS will serve as a repository for the U-238 and Th-232 bulk material. A small fraction of the material (100 g) will be sent to a collaborator at another University who will use Electron Beam-Physical Vapor Deposition to coat a 10 cm x 10 cm PCboard with U-28 or Th-232. The radioactive material will be a 5 micron or less coating attached to the PCboard. The PCboard will reside inside a gaseous detector. The quantities of each bulk material are given in the table below. Oak Ridge national Lab will supply 1kg of Th-232 at no cost. Unfortunately, 1kg is the smallest size available.
| U-238 | Th-232 |
| 200 g | 1000 g |
U-238 has a atomic number 92, and mass number of 238.050785, it is mainly an alpha emitter. Th-232 has a atomic number 90, and mass number of 232.038051 , it is also an alpha emitter.
2) Describe the facility used to store the materials, diagram of room layout. location of safe.
A floorplan of the Laboratory for Detector Science is shown below.
Media:LDS dimension Model(1).pdf
The LDS has 2 safes available for storing radioactive materials. A solid steel safe manufactured by Bunker Hill with the outer dimensions of (25 cm)H X (35 cm) W X (25 cm) D and inner dimensions of 9-1/2” H X 13-1/2” W X 9-5/8” is controlled by a digital lock. The safe itself weighs 15 kg and is mounted to a wall in the LDS. A second iron safe, manufacturer unkown, uses a combination lock and has the outer dimensions of 62 H X57 W X 45 (cm)D.
3.) Describe radiation survey instruments available for monitoring.
We ask that the TSO provide us with all necessary monitoring devices.
4.) Description and estimate of radioactive waste being generated.
We do not expect to generate radioactive was.
6/12/09
1.) heat PC board for 3 hours at 210C
| 210 |
|
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2.) Determine laser resolution for a 45 micron thick copper sheet
50 micron
3.) HV distribution chain calculation. Do a sample calculation for =?
resisters have arrived currently soldering ready to measure HVs (remember, Digital voltmeter has 1 kV max)
4.)Add GEANT4 Fission model (CHIPS or GEISHA) to ExampleN02 program. Goal is to find a model which reproduces the X-section data for Th-232 above.
6/19/09
1.) Th-232 mask due July 1,2009
2.) HV distribution chain calculation. Do a sample calculation for =?
3.)Add GEANT4 Fission model (CHIPS or GEISHA) to ExampleN02 program. Goal is to find a model which reproduces the X-section data for Th-232 above.
Th-232 and U-238 Activity in mCi
General information:
| Physical properties | U-238 | Th-232 |
| Half life in years | 4.468 X 10^9 | 1.405 X 10^10 |
| Decay rate per second | 4.91 X 10^-18 | 1.56 X 10^ -18 |
| Molar Mass g/mol | 238.02891 | 232.0381 |
| Activity of 2 kg in mCi | 0.68 | 0.22 |
Avogadro's number is 6.0221 X 10^23 /mol
1 Ci = 3.7 X 10^10 disintegration/ second
References
Simulations_of_Particle_Interactions_with_Matter
Voss and 3 russian references for Dy(n,x) cross sections
Media:Shalem_MSthesis_march2005.pdf
http://arxiv.org/abs/0903.3819 Dy photon gammas spectrum
http://www.ippe.obninsk.ru/podr/cjd/kobra13.php?SubentID=30974002
http://www.americanelements.com/thoxst.html
http://arxiv.org/pdf/physics/0404119
NIM_A535_2004_93[6]
File:NIM A590 2008 pg134 Eberhardt.pdf Prep Targets
Neutron cross sections for different elements Media:Neutron_cross_sections.pdf
http://www-nds.iaea.org/RIPL-2/
Media:n gamma cross sections at 25 keV.jpg
Media:n alpha cross section at 14.2 MeV.jpg
Media:ne cross section at 14 MeV.jpg
Media:high enegy fission x-section.jpg
Media:N_gamma_x-section_at_400_keV.jpg
Media:x-sections of reactions at 14 MeV.jpg
Media:n p x-section at 14.3MeV.jpg
Media: n gamma x-section at 14.5 MeV.jpg
Media: elastic x-section at 0.5 MeV.jpg
Media: n gamma x-section at 1 MeV.jpg
Media: n 2n x-section at 14.3 MeV.jpg
Donald James Hughes, Neutron cross sections, 2nd edition 1958, u.s.a atomic energy commission.Media:Neutron cross sections.pdf
File:NSAE 151 2005 319-334 Y.D. Lee.pdf
12 Volt power supply system.
http://www.lnf.infn.it/esperimenti/imagem/doc/NIMA_46128.pdf
http://electrontube.com.Media: rp097mono HV divier.pdf
http://www.cerac.com/pubs/proddata/thf4.htm#anchor550078