Yosuke Iwamoto,1,* M. Hagiwara,2 D. Satoh,1 H. Iwase,2 H. Yashima,3 T. Itoga,4 T. Matsumoto6, A. Masuda6, J. Nishiyama6, T. Sato1, Y. Nakane,1 H. Nakashima,1 Y. Sakamoto,1 A. Tamii5, C. Theis7, E. Feldbaumer7, L. Jaegerhofer7, C. Pioch8, V. Mares8, T. Nakamura9

1 JAEA, 2KEK, 3Kyoto University, 4RIKEN, 5RCNP,Osaka University, 6AIST, 7CERN, 8 German Research Center for Environmental Health, 9Tohoku University

SATIF-10@CERN, 2010/6/2-4

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2

Introduction

Measurements

Analysis

Results

Summary

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The spectra at large angles are necessary for the calibration of integration detectors to reduce the contribution of low-energy part.

Neutron energy spectrum

100MeV 7Li(p,n)R. Nolte et al., NIMA476 (2002) 369.

Quasi-monoenergetic reference beams using 7Li(p,n)7Be (g.s. + 0.429 MeV) are special important for the calibration of integration detectors.

Cyclotron Facility Maximum proton energy (MeV)

TRIUMF, Canada 200

PTB, Germany 200

NAC, South Africa 200

RIKEN, Japan 210

RCNP, Osaka University, Japan 390

RCNP facility has the calibration field beyond 210 MeV, but the neuron field has not been established enough.

Quasi-monoenergetic neutron reference fields above 200 MeV

Measurements of neutron energy spectra at 7 angles within 0~30o for the 246 and 389 MeV 7Li(p,n) reactions at RCNP.

Characterization of peak and low-energy continuum parts of neutron energy spectrum.

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Purpose

*Neutron energy spectra behind shielding will be presented by Iwase-san at this meeting.

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Introduction

Measurements

Analysis

Results

Summary

AVF Cyclotron(Up to 65 MeV for proton)

Beam dump

Ring Cyclotron(Up to 400 MeV and 1A for proton)

Neutron experimental hall

RCNP cyclotron facility, Osaka University, Japan

(Research Center for Nuclear Physics)

100m tunnel

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Detector thickness and diameter (cm)

Flight path (m)Neutron energy

range (MeV)Emitted angle (degree)

5.08 6.4 2 - 10 0,(30)12.7 15.5 (246 MeV), 17.3 (389 MeV) 10 - 100 0, 2.5, 5, 7.5, 10, 15, 20, 3025.4 60 (246 MeV), 95.5 (389 MeV) 100 - 0, 2.5, 5, 7.5, 10, 15, 20, 30

Detector: Liquid organic scintillator NE213 Clearing magnet in12cmx10cm collimator

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Target: 1cm thick natural Li ( 6Li 7.6% and 7Li 92.4%)Energy: Time-of-Flight (TOF) method: beam pulse – detector signal

246 and 389 MeV

Current measurementswith current integrator

Experimental layout

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Beam Beam swingerswinger

neutroneutronn

protonproton

dumdumpp

collimatorcollimator

collimatorcollimator

neutroneutronn

NE213 neutron NE213 neutron detectordetector

100 m tunnel

Neutron experimental hall

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Introduction

Measurements

Analysis

Results

Summary

Data Analysis

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Good n- disc.

Neutron-gamma-rays discrimination

total component (~300ns)

slow component

electron proton

alpha

Anode signal from NE213

neutrons

-rays

25.4 cm diam. and thick NE213

prompt-rays

7Li(p,n)7Be (g.s.+0.429 MeV)

TOF spectrum

Neutron energy: time(prompt -rays)-time(neutron)

Energy resolution:

2.94 MeV for 389 MeV neutron at 95.5m.

25.4 cm x 25.4 cm NE213 above 43.3 MeVee, SCINFUL-QMD successfully represents the experimental data of response

functions.

Detection efficiency using SCINFUL-QMD and flux normalized by this result are reliable. 11

D. Satoh, T. Sato, N. Shigyo, and K. Ishibashi, SCINFUL-QMD: Monte Carlo Based Computer Code to Calculate Response Function and Detection Efficiency of a Liquid Organic Scintillator for Neutron Energies up to 3 GeV, JAEA-Data/Code 2006-023, (2006).

12.7 cm x 12.7 cm NE213Detection efficiency using SCINFUL-QMD gives good agreement with data.

25.4cm NE213

25.4cm NE213

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Introduction

Measurements

Analysis

Results

Summary

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　 Hagiwara This work Taniguchi This workProton energy [MeV] 140 246 352 389

Peak neutron energy [MeV] 137 244 350 387

Peak intensity (cross section) of 7Li(p,n) [n/sr/µC]

1.04×1010

(35.8 mb)(1.11 ± 0.17) ×1010

(38.2± 5.9 mb)1.07×1010

(36.9 mb)

(0.96 ± 0.15) ×1010

(33.2±5.1 mb)peak/total (10MeV<En) 0.38 0.50 0.44 0.40

peak/total are 0.4 ~ 0.5.

7Be g.s.+0.429MeV

7Be Ex= 9.6 MeV?

6Be g.s.

Evaporation

Break up and spallation

Our peak neutron at 0o are on the line of 35~40 mb of other experimental data .

Quasi free scattering?

All neutron fluxes below 50 MeV are almost same.The shape of the continuum above 100 MeV changes with angles considerably.

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246MeV 389MeV

Synthetic spectrum reduces continuum / total by the factor of two in comparison with 0o.This procedure will reduce the uncertainty of the response. 15

　 Integrated Continuum flux (En>10MeV)

　 　 n/sr/MeV/uC continuum / total

246MeV natLi(p,n)0o) 1.09E+10 0.51 0o)-0.4x0o)-0.3x0o) 2.70E+09 0.21

389MeV natLi(p,n)0o) 1.36E+10 0.67 0o)-0.3x0o)-0.3x0o) 4.44E+09 0.33

To reduce continuum(0o), we have made synthetic difference spectrum using (10o) and (30o).

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Introduction

Measurements

Analysis

Results

Summary

Summary

We have measured neutron energy spectra using 7Li(p,n) reaction with 246 MeV and 389 MeV at 7 angles (0o, 2.5o, 5o, 10o, 15o, 20o and 30o).

Our peak neutron at 0o are on the line of 35~40 mb of other experimental data .

The shape of spectrum above 100 MeV change with angles considerably.

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Future plan

TOF method will be compared with activation method for the peak neutron.

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Q value of 7Li(p,n)7Be = -1.644 MeVEthreshold = -Q (Mp+M7Li)/M7Li = -(-1.644)x(938.256+6558)/6558 = 1.88 MeV

Energy loss in 5 mm thick (a half of 1 cm) Li using TRIM code Eloss:0.87 MeV with 246 MeV p0.67 MeV with 389 MeV p

Position of peak neutron En from TOF method:243.5±1.3 MeV386.6±1.4 MeV

Proton energy = En+ Ethreshold+ Eloss:243.5+1.88+0.87 = 246.3±1.3 MeV = 246±1 MeV386.6+1.88+0.67 = 389.2±1.4 MeV = 389±1 MeV

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Elevel (keV)

0.0429.20 4.61×103 6.51×103

7.21×103 9.6×103  10.79×103

 11.3×103? 12.3×103?  13.24×103?  14.39×103?  15.3×103?  16.3×103?  18.3×103?  19.7×103?  20.5×103?

7Li(p,n) reactions

7Be levels

Breakup reactions7Li(p,n3He), Q= -3.231 MeV

7Li(p,np)6Li, Q= -7.52 MeV

Procedure of TOF analysis 1. Separate neutron events from gamma-ray events by PSD. 2. Set bias for pulse height (> 0.473MeVee[calib. with 241Am-Be,

60Co, 137Cs]). 3. TOF conversion into energy spectra by the following equation:

m0 : Rest mass of a neutron i : Channel number of the events

L : Flight path c : Light velocity.

4. Normalize energy spectra by dividing by detector efficiency

calculated by SCINFUL-QMD code, solid angle, and the beam current.

Beam current was measured with the current integrator(C.I.) from

the dump. We will compare the C.I. data with the results of activation

method.

5.

Data Analysis

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)(

)(1

1

1)(

2

20

20

2

iTc

L

c

xvcmcmmciE

n

nn

Energy resolution:2.94 MeV for 389 MeV neutron at 95.5m.

Dominant error: 15 % of SCINFUL-QMD calculation.

1. Obtain the response with incident neutron energy obtained from TOF method.

)29.0exp(143.281.0 EEL 2. Set the light output using equation:For example, 65 MeV = 50.2 MeVee.

3. Set the ADC channel corresponding to the peak deposit energy in NE213. For example, 934 channel for En = 65 MeV = 50.2 MeVee in NE213.

4. Obtain relation between light output and ADC channel.

Maximum bias in this experiment was 43.3 MeVee.

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Energy resolution and error estimation

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x = 12.7 cm + 0.5 cmThe half value of the NE213 and target thickness.

= 0.7 ns FWHM of the prompt-gamma rays after time walk correction.

Energy resolution: 2.33 MeV for 246 MeV neutron at 60 m.2.94 MeV for 389 MeV neutron at 95.5m.

Error composition Peak othersCounting statistics < 0.16% 1 - 3 %Detection efficiency 15%Beam current integrator(10-50nA)

2%

Bias set 3%Total 15.4% 16.2 %

The error of detection efficiency is dominant.

246MeV389MeV

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(6Li) lab. = 19.5 mb(7Li) lab. = 36.8 mb

The average value of our (7Li) is 35.7 mb.Our results are on the fitting line of all experimental data.Activation analysis will be compared with TOF methods.

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Conversion factor from (natLi) to (7Li) Composition of natural Li:

6Li 7.6% and 7Li 92.4%

(7Li)/(natLi) = 36.8 / (36.8x0.924+19.5x0.076)=1.04

160 MeV 6Li and 7Li(p,n) cross sections at 0o

If same cross section above 160 MeV

T.N. Taddeucci et al., Nuclear Physics A469 (1987) 125-172.

Difference of analysis between this work and taniguchi: Detection efficiency and detector size.

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389 MeV246 MeV

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Bessel function formula with nine terms for the p-7Li angular distribution.T.N. Taddeucci et al. PRC 41 6 (1990) 2548.

Taddeucci formula gives good agreements with our data.

N

jjj qqzJaq

1lim000 )/*(*)(

Large difference @ 0o.

No reaction of 7Li(p,n)7Be (g.s. + 0.429 MeV) in models.

Small difference at 30o.

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