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Yosuke Iwamoto , 1,* M. Hagiwara, 2 D. Satoh, 1 H. Iwase, 2 H. Yashima, 3 T. Itoga, 4

SATIF-10@CERN, 2010/6/2-4. Characterization of quasi-monoenergetic neutron energy spectra using the 7 Li(p,n) reactions in the 246 and 389 MeV. Yosuke Iwamoto , 1,* M. Hagiwara, 2 D. Satoh, 1 H. Iwase, 2 H. Yashima, 3 T. Itoga, 4

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Yosuke Iwamoto , 1,* M. Hagiwara, 2 D. Satoh, 1 H. Iwase, 2 H. Yashima, 3 T. Itoga, 4

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  1. SATIF-10@CERN, 2010/6/2-4 Characterization of quasi-monoenergetic neutron energy spectra using the 7Li(p,n) reactions in the 246 and 389 MeV 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

  2. Table of contents • Introduction • Measurements • Analysis • Results • Summary

  3. Introduction Quasi-monoenergetic reference beams using 7Li(p,n)7Be (g.s. + 0.429 MeV) are special important for the calibration of integration detectors. • Neutron energy spectrum R. Nolte et al., NIMA476 (2002) 369. 100MeV 7Li(p,n) • The spectra at large angles are necessaryfor the calibration of integration detectors to reduce the contribution of low-energy part. • Quasi-monoenergetic neutron reference fields above 200 MeV • RCNP facility has the calibration field beyond 210 MeV, • but the neuron field has not been established enough.

  4. Introduction Purpose • Measurements of neutron energy spectra at 7 angles within 0~30o for the 246 and 389 MeV 7Li(p,n) reactionsat RCNP. • Characterization of peak and low-energy continuum parts of neutron energy spectrum. *Neutron energy spectra behind shielding will be presented by Iwase-san at this meeting.

  5. Table of contents • Introduction • Measurements • Analysis • Results • Summary

  6. RCNP cyclotron facility, Osaka University, Japan (Research Center for Nuclear Physics) Neutron experimental hall Ring Cyclotron (Up to 400 MeV and 1mA for proton) AVF Cyclotron (Up to 65 MeV for proton) 100m tunnel Beam dump

  7. Experimental layout • Target: 1cm thick natural Li ( 6Li 7.6% and 7Li 92.4%) • Energy: Time-of-Flight (TOF) method: beam pulse – detector signal Clearing magnet in12cmx10cm collimator • Detector: Liquid organic scintillator NE213 Current measurements with current integrator 246 and 389 MeV

  8. Experimental layout Neutron experimental hall 100 m tunnel collimator Beam swinger collimator dump neutron neutron proton NE213 neutron detector

  9. Table of contents • Introduction • Measurements • Analysis • Results • Summary

  10. Anode signal from NE213 electron proton alpha slow component total component (~300ns) Data Analysis • Neutron-gamma-rays discrimination 25.4 cm diam. and thick NE213 neutrons g-rays Good n-g disc. 7Li(p,n)7Be (g.s.+0.429 MeV) • TOF spectrum • Neutron energy: time(prompt g-rays)-time(neutron) prompt g-rays • Energy resolution: 2.94 MeV for 389 MeV neutron at 95.5m.

  11. SCINFUL-QMD calculation for the detection efficiency 25.4cm NE213 25.4cm NE213 • 12.7 cm x 12.7 cm NE213 • Detection efficiency using SCINFUL-QMD • gives good agreement with data. • 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. 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. Table of contents • Introduction • Measurements • Analysis • Results • Summary

  13. Neutron energy spectra for the Li(p,xn) reaction at 0o 7Be g.s.+0.429MeV 6Be g.s. Quasi free scattering? 7Be Ex= 9.6 MeV? Break up and spallation Evaporation • Our peak neutron at 0o are on the line of 35~40 mb of other experimental data . • fpeak/ftotal are 0.4 ~ 0.5.

  14. Angular distribution of neutron energy spectra 389MeV 246MeV • All neutron fluxes below 50 MeV are almost same. • The shape of the continuum above 100 MeV changes with angles considerably.

  15. Synthetic difference spectrum for integration detectors • To reduce fcontinuum(0o), we have made synthetic difference spectrum using f(10o) and f(30o). • Synthetic spectrum reduces fcontinuum / ftotal by the factor of two in comparison with f(0o). • This procedure will reduce the uncertainty of the response.

  16. Table of contents • Introduction • Measurements • Analysis • Results • Summary

  17. Summary and future plan • 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. • Future plan • TOF method will be compared with activation method for the peak neutron.

  18. Back-up slides

  19. Incident proton energy • Position of peak neutron En • from TOF method: • 243.5±1.3 MeV • 386.6±1.4 MeV • Q value of 7Li(p,n)7Be = -1.644 MeV Ethreshold = -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 p • 0.67 MeV with 389 MeV p • Proton energy = En+ Ethreshold+ Eloss: • 243.5+1.88+0.87 = 246.3±1.3 MeV = 246±1 MeV • 386.6+1.88+0.67 = 389.2±1.4 MeV = 389±1 MeV

  20. 7Li(p,n) reactions 7Be levels Breakup reactions 7Li(p,n3He)a, Q= -3.231 MeV 7Li(p,np)6Li, Q= -7.52 MeV

  21. Data Analysis • 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. Energy resolution: 2.94 MeV for 389 MeV neutron at 95.5m. Dominant error: 15 % of SCINFUL-QMD calculation.

  22. Set high-bias for pulse height 1. Obtain the response with incident neutron energy obtained from TOF method. 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.

  23. Energy resolution and error estimation Dx = 12.7 cm + 0.5 cm The half value of the NE213 and target thickness. Dt = 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. The error of detection efficiency is dominant.

  24. Connection 12.7cm NE213 with 25.4cm NE213 246MeV 389MeV

  25. Peak cross section of 7Li(p,n) at 0o • Conversion factor from s(natLi) to s(7Li) • Composition of natural Li: • 6Li 7.6% and 7Li 92.4% • 160 MeV 6Li and 7Li(p,n) cross sections at 0o s(6Li) lab. = 19.5 mb s(7Li) lab. = 36.8 mb T.N. Taddeucci et al., Nuclear Physics A469 (1987) 125-172. If same cross section above 160 MeV s(7Li)/s(natLi) = 36.8 / (36.8x0.924+19.5x0.076) =1.04 • The average value of our s(7Li) is 35.7 mb. • Our results are on the fitting line of all experimental data. • Activation analysis will be compared with TOF methods.

  26. Comparison this work with Taniguchi data for 246 and 389 MeV 246 MeV 389 MeV Difference of analysis between this work and taniguchi: Detection efficiency and detector size.

  27. Angular distribution of peak cross section of 7Li(p,n) • 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.

  28. Comparison data with PHITS results • 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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