1. Design on Target and Moderator of X- band Compact Electron Linac Neutron Source for Short Pulsed Neutrons Kazuhiro Tagi

2. Self Introduction  Name: Kazuhiro Tagi  Born near Kyoto  2008-2012 Graduate School of Engineering in UT  Environmental & Energy Problem  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  Nuclear Engineering October 16th, 20132

3. Uesaka Lab in the Univ of Tokyo  Development of X-band Linac Facility for Medical and Industrial Application October 16th, 20133

4. Pinpoint X-ray Therapy with 6 MeV X-band Linac October 16th, 20134 Robot Flat-panel detector X-ray Source Treatment table robot Accelerator X-ray detector (Developed in this research) CCD camera

5. Uesaka Lab in the Univ of Tokyo  System development for radiation therapy  Laser driven dielectric accelerator for radiation biology  Radiation biology October 16th, 20135

6. Compact Neutron Source by X-band Linac  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  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. October 16th, 2013 X-band Linac Neutron Source 6

7. Demand for Accuracy of Nuclear Cross Section  Analysis of debris in Fukushima 1st nuclear power plant  Waste treatment with ADS Debris measurement with NRD [1] Spectra of fuel samples [2] [1] H. Tsuchiya, et. al., Nucl. Inst. and Meth. A 729 (2013) 338 [2] Behrens et al., Nucl. Techn. 67 (1984) 162 7

8. Purpose  Now I’m designing  Electron incident system  Target & Moderator To develop neutron cross section measurement system with X- band linac neutron source in order to analyze debris in Fukushima 1st nuclear plant and nuclear waste treatment with ADS October 16th, 2013 Short pulsed neutron is required.  X-band has small beam current  Short TOF length (Our plan is 5 m) is required for making measuring time shorter. 8

9. Compton Scattering X-ray Source October 16th, 20139 RF source （ 50 MW ） Electron Source multi bunch Electron Beam Generation （ 3 MeV ） Accelerator tube (About 30 MeV) Beam dump Laser Long Pulse （ 10 nsec ） Transportation system Focus magnet ＋ Measurement, Control, vacuum, cooling system The Linac was originally designed for Compton scattering monochromatic X-ray source.

10. Component of X-band Linac Neutron Source October 16th, 2013  Pulse width of electron beam 10 ns – 1 us is possible in our system  Moderator  Detector Ce:LiCaF Detector is being developed 10

11. Design of Incident System  20 keV Thermal Gun + 5 MeV Buncher  Electron beam will be bunched in buncher  Efficiency of 25% can be expected.  100 keV Thermal gun directly connected to the accelerator  In 100 keV, Efficiency of 25% can be expected  Easy to make and cheaper  Broad Energy spectrum October 16th, 201311

12. Optimization of Moderator for 100 keV Neutron  Motivation  In Japan, there is no facility which measures -100 keV cross sections of nuclear fuel materials.  Accuracy of capture cross section in keV region should be improved.  Calculation Condition  Neutron Target  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. October 16th, 201312

13. Results of optimization of Polyethylene Moderator October 16th, 2013 Electron EnergyPowerPulse Width (10 – 100 keV) 30 MeV 0.4 kW 5.8 ns Energy Spectrum of Neutrons Neutron Intensity Neutron Flux At 5 m TOF line 1.3×10 11 n/s1.7×10 3 n/cm 2 /s 13

14. Moderator Made of Hydrogen Storage Material October 16th, 2014 Moderator (??) 5 cm × 5 cm Neutron beam Tungsten Target Φ= 1 cm 5 cm PolyethyleneBeH2TiH2Mg(BH4)2 Density of Hydrogen 0.136 g/cm30.118 g/cm3 0.151 g/cm3 0.219 g/cm3 10-100 keV Pulse Width 5.6 ns5.8 ns4.8 ns4.4 ns 10-100 keV Flux4.24.13.74.3 Thermal Pulse Width 47 us41 us14 us0.146 us Thermal Flux5.54.03.10.01 If density of hydrogen is bigger, pulse width is shorter Boron absorbs thermal neutrons in Mg(BH4)2, so hard spectrum can be gained 14

15. Conclusion  In the University of Tokyo, compact electron linac driven neutron source is being developed.  Focusing on high energy ( 〜 100 keV) neutrons, neutron target and moderator were simulated in order to optimize for short pulse neutron  From the simulation result, pulse width of 10 – 100 keV 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 16th, 201315