Design on Target and Moderator of Xband Compact
Design on Target and Moderator of X-band Compact Electron Linac Neutron Source for Short Pulsed Neutrons Kazuhiro Tagi
Self Introduction Ø Name: Kazuhiro Tagi Ø Ø Born near Kyoto 2008 -2012 Graduate School of Engineering in UT Ø Environmental & Energy Problem Ø Ø Global warming, Energy Resource (including nuclear energy) Graduation Thesis: X-ray gas detector for radiation therapy 2012 -2014 Master Course in UT 2014 Ph D student in UT Ø October 16 th, 2013 Nuclear Engineering
Uesaka Lab in the Univ of Tokyo Ø Development of X-band Linac Facility for Medical and Industrial Application October 16 th, 2013
Pinpoint X-ray Therapy with 6 Me. V X-band Linac Accelerator Robot X-ray detector (Developed in this research) X-ray Source CCD camera October 16 th, 2013 Treatment table robot Flat-panel detector
Uesaka Lab in the Univ of Tokyo Ø System development for radiation therapy Ø Laser driven dielectric accelerator for radiation biology Ø Radiation biology October 16 th, 2013
Compact Neutron Source by X-band Linac Ø Ø Ø Facility where nuclear fuels can be measured is limited. Univ. of Tokyo has a reactor ‘Yayoi, ’ which is now under decommissioning, and by installing accelerator in it, it becomes possible to measure nuclear fuel materials. Space in the reactor is limited, so accelerator should be smaller X-band Linac Neutron Source Ø Ø Ø October 16 th, 2013 Accelerator tube of X-band is 1/4 smaller than that if S-band, Beam current is also less than 1/2 If TOF beam line is long, measurement time is also long, so short pulse is necessary for short TOF beam line length.
Demand for Accuracy of Nuclear Cross Section Ø Analysis of debris in Fukushima 1 st nuclear power plant Debris measurement with NRD Ø [1] Spectra of fuel samples Waste treatment with ADS [1] H. Tsuchiya, et. al. , Nucl. Inst. and Meth. A 729 (2013) 338 [2] Behrens et al. , Nucl. Techn. 67 (1984) 162 [2]
Purpose To develop neutron cross section measurement system with Xband linac neutron source in order to analyze debris in Fukushima 1 st nuclear plant and nuclear waste treatment with ADS Ø Now I’m designing Ø Ø Electron incident system Target & Moderator Short pulsed neutron is required. Ø Ø X-band has small beam current Short TOF length (Our plan is 5 m) is required for making measuring time shorter. October 16 th, 2013
Compton Scattering X-ray Source The Linac was originally designed for Compton scattering monochromatic X-ray source. RF source (50 MW) Beam dump Electron Source multi bunch Electron Beam Generation (3 Me. V) Laser Long Pulse(10 nsec) October 16 th, 2013 Accelerator tube (About 30 Me. V) Transportation system Focus magnet +Measurement, Control, vacuum, cooling system
Component of X-band Linac Neutron Source Ø Pulse width of electron beam 10 ns – 1 us is possible in our system Ø Moderator Ø Detector Ce: Li. Ca. F Detector is being developed October 16 th, 2013
Design of Incident System Ø 20 ke. V Thermal Gun + 5 Me. V Buncher Ø Ø Ø Electron beam will be bunched in buncher Efficiency of 25% can be expected. 100 ke. V Thermal gun directly connected to the accelerator Ø Ø Ø October 16 th, 2013 In 100 ke. V, Efficiency of 25% can be expected Easy to make and cheaper Broad Energy spectrum
Optimization of Moderator for 100 ke. V Neutron Ø Motivation Ø Ø Ø In Japan, there is no facility which measures -100 ke. V cross sections of nuclear fuel materials. Accuracy of capture cross section in ke. V region should be improved. Calculation Condition Ø Ø Ø October 16 th, 2013 Neutron Target Ø Photo nuclear reaction, Material is tungsten Moderator material is Polyethylene. Angle between electron beam and neutron beam is 90° Relative intensity and Pulse width was calculated with many moderator geometry. PHITS, one of Monte Carlo simulation code, was used for simulation.
Results of optimization of Polyethylene Moderator Electron Energy Power Pulse Width (10 – 100 ke. V) 30 Me. V 0. 4 k. W 5. 8 ns Neutron Intensity Neutron Flux At 5 m TOF line 1. 3× 1011 n/s 1. 7× 103 n/cm 2/s October 16 th, 2013 Energy Spectrum of Neutrons
Moderator Made of Hydrogen Storage Material Moderator (? ? ) 5 cm × 5 cm Neutron beam 5 cm Tungsten Target Φ= 1 cm October 16 th, 2014 Polyethylene Be. H 2 Ti. H 2 Mg(BH 4)2 Density of Hydrogen 0. 136 g/cm 3 0. 118 g/cm 3 0. 151 g/cm 3 0. 219 g/cm 3 10 -100 ke. V Pulse Width 5. 6 ns 5. 8 ns 4. 4 ns 10 -100 ke. V Flux 4. 2 4. 1 3. 7 4. 3 Thermal Pulse Width 47 us 41 us 14 us 0. 146 us Thermal Flux 5. 5 4. 0 3. 1 0. 01 • If density of hydrogen is bigger, pulse width is shorter • Boron absorbs thermal neutrons in Mg(BH 4)2, so hard spectrum can be gained
Conclusion Ø Ø Ø In the University of Tokyo, compact electron linac driven neutron source is being developed. Focusing on high energy (〜 100 ke. V) neutrons, neutron target and moderator were simulated in order to optimize for short pulse neutron From the simulation result, pulse width of 10 – 100 ke. V neutrons were broadened to 5. 8 ns. Novel materials, such as hydrogen absorbing alloy, has been simulated, and showed excellent properties for short pulse moderator. Neutron detector is also being developed[4], and neutron beam will be measured. October 16 th, 2013
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