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

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

Kazuhiro Tagi

2

Self IntroductionSelf 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 EngineeringOctober 16th, 2013

3

Uesaka Lab in the Univ of TokyoUesaka Lab in the Univ of Tokyo Development of X-band Linac Facility for

Medical and Industrial Application

October 16th, 2013

4

Pinpoint X-ray Therapy with 6 MeV X-band LinacPinpoint X-ray Therapy with 6 MeV X-band Linac

October 16th, 2013

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 TokyoUesaka Lab in the Univ of Tokyo

System development for radiation therapy

Laser driven dielectric accelerator for radiation biology

Radiation biology

October 16th, 2013

6

Compact Neutron Source by X-band LinacCompact 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

7

Demand for Accuracy of Nuclear Cross SectionDemand for Accuracy of Nuclear Cross Section

Analysis of debris in Fukushima 1st nuclear power plant

Waste treatment with ADSDebris 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

8

PurposePurpose

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.

　　

9

Compton Scattering X-ray SourceCompton Scattering X-ray Source

October 16th, 2013

RF source 　（ 50 MW ）

Electron Source　 multi bunch　 Electron Beam Generation （ 3 MeV ）

Accelerator tube　 (About 30 MeV)

Beam dump

LaserLong Pulse （ 10 nsec ）

Transportation systemFocus 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 SourceComponent 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

11

Design of Incident SystemDesign 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, 2013

12

Optimization of Moderator for 100 keV NeutronOptimization 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, 2013

13

Results of optimization of Polyethylene ModeratorResults of optimization of Polyethylene Moderator

October 16th, 2013

Electron Energy Power Pulse Width(10 – 100 keV)

30 MeV 0.4 　 kW 5.8 ns

Energy Spectrum of NeutronsNeutronIntensity

Neutron FluxAt 5 m TOF line

1.3×1011n/s 1.7×103 　 n/cm2/s

14

Moderator Made of Hydrogen Storage MaterialModerator Made of Hydrogen Storage Material

October 16th, 2014

Moderator (??)5 cm × 5 cm

Neutron beam

Tungsten TargetΦ= 1 cm

5 cm

Polyethylene

BeH2 TiH2 Mg(BH4)2

Density of Hydrogen

0.136 g/cm3 0.118 g/cm3

0.151 g/cm3

0.219 g/cm3

10-100 keV Pulse Width

5.6 ns 5.8 ns 4.8 ns 4.4 ns

10-100 keV 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(BH4)2, so

hard spectrum can be gained

15

ConclusionConclusion

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, 2013