design study on neutron source driven by 100-mev proton

K O M A CKorea Multi-purpose Accelerator Complex양 성 자 가 속 기 연 구 센 터

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Design Study on Neutron Source Driven by

100-MeV Proton Accelerator

Jeong-jeung Dang

On behalf of the KOMAC Accelerator team

17 April, 2019

KOMAC, KAERI

The 7th ACFA HPPA Mini-workshop

17-10 April, 2019, Rokkasho Fusion Institute, QST, Rokkasho, Japan


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Outline

KOrea

Multi-purpose

Accelerator

Complex

Fast Neutron Source for Space / Natural Radiation Test Facility

Activities on Neutron Source Driven by 100 MeV linac

Activities on Neutron Source Driven by 1.7 MV Tandem Accelerator

Summary


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Fast Neutron Source for Space / Natural

Radiation Test Facility


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Space / Natural Radiation

Space / Natural Radiation Simulation Facility

• Recent issues :

- Failure of electronics on automotive by radiation on the ground.

- Damage of semiconductor during air transport.

- Quality assurance / control of device for space industry

• Source of Space/Natural radiation : Galactic cosmic ray, Solar proton

• High energy proton/heavy ion are converted to the neutron and other

particles according to the altitude.


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Neutron Facility at KOMAC

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(1)Pulsed fast neutron source based on the 100 MeV proton accelerator

(2)Quasi mono-energetic neutron source based on the 1.7 MV tandem

accelerator

(3)D - Be neutron source based on 1 MeV/n RFQ (under-developed)


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Activities on Neutron SourceDriven by 100 MeV linac

- Present Status -


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Neutron Production at Beam Dump

Proton beam dump assembly

at the end of linac

Neutron Production at Beam Dump Irradiated by 100 MeV Proton beam

• Material : Copper(dump), STS (chamber, coolant guide tube)

• Conical geometry with Hypervapotron type cooling channel

Beamdump

Chamber

Coolantguide


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Neutron Monitoring

• Neutron monitor : plastic scintillator (+ PMT)

• Installed 31 meters away from beam dump

• Measured anode(PMT) current signal was synchronized with beam pulse

Beam pulse

Anode signal of

a 10-mm-thick

plastic scintillation detector

Neutron Monitoring

Beam dumpNeutron

Monitor

31 m Proton


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Monte Carlo Simulation

Simulation Geometry

• Monte Carlo code : Geant4

• Geometry : Beam dump, simplified tunnel

• Beam condition : 100 MeV, 1 μAavg.

• Flux (@ 2.2 m away from dump, 15o)

− Total : 7.1✕106 n/cm2/s

− Fast (En > 10 MeV) : 3.5✕106 n/cm2/s

Monte Carlo Simulation for Characterization

Angular distribution Energy spectrum


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Comparison of Experiment and Simulation

- Energy calibration

parameters were obtained by

using MINUIT on calculated

and measured Δ-E spectrum

- Neutron energy spectrum

was reconstructed from the

detector response function

by using a unfolding

algorithm.

Energy spectrum

Eth ~ 6 MeV

Fluxes calculated

with the injected

proton beam current

and the neutron

detector are found to

agree with each other

within ±10% error

Neutron flux

Δ-E spectrum

Neutronspectrum

Detectorresponsefunction


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Pilot Operation and Activities on Diagnostics

• Neutron beam line is under pilot

operation.

• Neutron has been served for the

space/natural radiation simulation.

• Various detectors and measurement

method have been tested to

characterize fast neutron.

− Plastic scintillator

− Liquid scintillator

− Organic scintillator

− Neutron activation analysis

− Diamond detectorEstimated spectrum

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1. M. S. Gordon, et al., “Measurement of the Flux and Energy Spectrum of Cosmic-Ray

Induced Neutrons on the Ground,” IEEE Trans. Nucl. Sci., 51 (2004), pp. 3427-3434


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Activities on Neutron SourceDriven by 100 MeV linac

- Near Future Plan -


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Fast / Thermal Neutron Source

Neutron Target System

Slow

neutron

Reflector

Fast

neutron

Moderator

Proton

beam

Neutron target

Target – Moderator – Reflector (TMR)


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Numerical Study for Target System

Neutron Target

• Monte Carlo simulation for target design

− Code : GEANT4

− Cylindrical thick target assumption

− 1 kW proton beam (100 MeV x 10 μAavg.)

− Material (atomic number) : Carbon(6), Aluminum(13), Titanium(22),

Copper(29), Molybdenum(42), Tungsten(74)

Neutron yield Neutron energy spectrum

− Material

− Geometry

− Yield

− Spectrum

− Cooling

− Activation


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Effect of Proton Energy on Neutron Source

To increase neutron yield and neutron energy,

higher energy proton beam is required.


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Higher Proton Energy

Superconducting linac has been developed to upgrade proton

energy up to 160 MeV.

SCL will be installed at existing tunnel space (end of 100-MeV

linac).

SCL


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Activities on Neutron SourceDriven by 1.7 Tandem Accelerator

- Present Status -


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1.7 MV Tandem Accelerator Facility

• 1.7 MV Tandem Accelerator

− Pelletron (NEC)

− Emax = 3.4 MeV

− Imax = 10 μA

− Iop. = 1 ~ 2 μA

Tandem Accelerator and Neutron Target Room

Acceleration tubes

and pressure vessel

Ion source

LiF

target

He-3 detector

shadow cone

Target

chamber

Proton

Neutron

target room

Sample station

(movable)


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Neutron production Target

• Neutron production target

− p(7Li, n)7Be reaction (Eth = 1.881 MeV, Q = -1.644 MeV)

− Homemade lithium fluoride (Nat.LiF) target on 1 mm thick aluminum

substrate.

Al substrate

LiF

(layer)

LiF

deposition

chamber

Electronics

for control

and monitoring


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Neutron Measurement

Mono-energetic neutron measurement

0

5

10

15

0 500 1000 1500En

erg

y Spre

ad (%

)

Neutron Energy (keV)

• Detector :

Li-7 enriched Cs2LiYCl6:Ce (CLYC-7)

LiF

target

CLYC-7

γ rays

neutron

Energy (keVee)

Pu

lse

Sh

ap

e D

isc

rim

ina

tio

n (

arb

.)


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Activities on Neutron SourceDriven by 1.7 Tandem Accelerator

- Near Future Plan -


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Standard Neutron Field

• Proton energy loss in LiF target is considered in calculation.

• I = 1 μA

Numerical Study for Standard Neutron Field

𝒀𝒏 = 𝑰𝒃𝒄𝒕න𝑬𝒊

𝑬𝒇 𝝈 𝑬

Τ𝒅𝑬 𝒅𝒙𝒅𝑬

p(7Li, n)7Be

Be

p

n

Li

Ep

mp

mn

En

θ

mBe

𝑬𝒏 =𝑬𝒑𝒎𝒑𝒎𝒏

𝒎𝑩𝒆 +𝒎𝒏𝟐𝒄𝒐𝒔𝝑 + 𝒄𝒐𝒔𝝑 +

𝒎𝑩𝒆 𝒎𝑩𝒆 +𝒎𝒏

𝒎𝒑𝒎𝒏𝟏 −

𝒎𝒑

𝒎𝑩𝒆+𝑸

𝑬𝒑

𝟐

p

LiF target

Ei Ef


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Optimization of LiF Target

Neutron flux vs. LiF thicknessNeutron energy

Neutron energy spread

• Neutron energy depends on the proton

energy and angle.

• Energy spread should be minimized with a

certain flux.

• Target thickness should be optimized.

• Characterization of energy and its spread

is important to establish the standard field.


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Buncher

Ion sourceAcceleration

tube

• Beam buncher

− short pulse beam is required for n-TOF

− preliminary experiment was conducted.


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Summary

KOMAC has developed the neutron source for the

space/natural radiation test.

The measurement and the simulation has been conducted

to characterize the neutrons generated at the beam dump of

100 MeV linac.

To improve the fast neutron source, TMR and SCL have

been researched.

Quasi mono-energetic neutron is generated by 1.7 MV

tandem accelerator with LiF target.

Neutron energy and its spread were measured by CLYC-7.

Quasi mono-energetic neutron source is being improved

for the standard neutron field.


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Thank you

design study on neutron source driven by 100-mev proton

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