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TOF spectrometers for measurement of n d /n t ratios K.Okada, T.Nishitani 2, K. Ochiai 2, K.Kondo 2, M.Sasao, M. Okamoto, K.Shinto, S.Kitajima Tohoku Univ. 2 JAEA OUTLINE Concept Neutron Spectrum in a collimator-optimaization with MCNP Time-of-flight (TOF) spectrometer design Time-of-flight (TOF) spectrometer design High-counting-rate TOF electronics POP experiment of High-counting-rate TOF electronics Future work and Summary

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2/13 10th ITPA diagnostics meeting, Moscow 10-14/04/06M. Sasao Neutron Spectrum in a collimator - optimaization with MCNP(1) H area Blanket SUS 316LN Vacuum vessele 20 deg. 10 m Collimator radius:10 cm Reflection of all particle First wall Estimation of scattered/energy-degraded neutrons originated DT neutrons The fuel ratio in center of plasma line of sight on center of plasma

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3/13 10th ITPA diagnostics meeting, Moscow 10-14/04/06M. Sasao Neutron Spectrum in a collimator - optimaization with MCNP(2) In a neutronics calculation on the model of ITER, the possibility of separating the DD component from that of the DT reaction was examined. The separation in a neutron spectrum is possible at an appropriate measurement position with a collimator 1–10 cm in diameter.

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4/13 10th ITPA diagnostics meeting, Moscow 10-14/04/06M. Sasao Neutron Spectrum in a collimator - optimaization with MCNP(2) (distance from center of plasma : 10 m, collimator radius : 10 cm) T i =25 keV 0.5 MeV The energy resolution demanded is below 0.5 MeV grade. Neutron flux [/0.1MeV/cm 2 /source] 2.0 1.5 1.0 0.5

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5/13 10th ITPA diagnostics meeting, Moscow 10-14/04/06M. Sasao Time-of-flight (TOF) spectrometer design d2 d1 d L n n’ The second detector R W The optimization is on going using MCNP calculationfor both high detection efficiency for interesting events (2-3 MeV) and the energy resolution. > 35 [deg.] 70~ [cm] 5 ×10×~1 [cm] 30×60×2 [cm] scatter angle q distance L d1 size d2 size Optimal value

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6/13 10th ITPA diagnostics meeting, Moscow 10-14/04/06M. Sasao High-counting-rate TOF electronics(1) Number of interesting events is only ~1/1000 of total events. Fast rejection of DT neutrons and gamma events in the D1 detector is essential. The TOF geometry defines the energy loss (pulse height) of DD neutrons in the D1 detector. We propose fast selection of interesting events by pulse height discrimination.

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7/13 10th ITPA diagnostics meeting, Moscow 10-14/04/06M. Sasao DD 65 ns DL1 d1PMT HV Linear FAN-in/out Linear FAN-in/out Discri Coin GDG TAC Delay ADC MCA DelayTAC ADCMCA d2 HV PMT Linear FAN-in/out Discri -2300 V -1300 V DT Anti 65 ns Gate start stop start stop DL2 DL3 Target room d1 ～ DD stop d1 ～ DT stop start DL5 Control room Experiment circuit High-counting-rate TOF electronics(2) Experiment circuit

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8/13 10th ITPA diagnostics meeting, Moscow 10-14/04/06M. Sasao POP experiment of High-counting-rate TOF electronics at FNS, JAEA DT DD -ray Total TOF spectrum Time (ch) Using contaminated deuterium in the tritium target, the principle has been tested at FNS. D1 - 0.5 cm t NE102A (active divider had a trouble), D2-NE201A, 60 cm apart, 0.35 deg. cps

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9/13 10th ITPA diagnostics meeting, Moscow 10-14/04/06M. Sasao POP experiment of High-counting-rate TOF electronics(2) DT DD -ray Total TAC spectrum DT spectrum Separation by a circuit DT time spectrum conversion DT spectrum is separated from total spectrum by fast Discri.

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10/13 10th ITPA diagnostics meeting, Moscow 10-14/04/06M. Sasao DD peak DT peak g-ray 12 C(n,n’g) 12 C 16.7 ns 44.3 ns DD output of TAC POP experiment of High-counting-rate TOF electronics- DD output of TAC (3) DT DD -ray Total TAC spectrum DD separation is not perfect due to the active devider trouble, but the DT component is reduced more than factor 10, by fast Discri. Separation by a circuit

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11/13 10th ITPA diagnostics meeting, Moscow 10-14/04/06M. Sasao POP experiment of High-counting-rate TOF electronics(3) DD energy spectrum DD peak DD spectrum is separated from total spectrum

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12/13 10th ITPA diagnostics meeting, Moscow 10-14/04/06M. Sasao Future work and Summary (1) In a neutronics calculation on the model of ITER, the possibility of separating the DD component from that of the DT reaction was examined. The separation in a neutron spectrum is possible at an appropriate measurement position with a collimator 1–10 cm in diameter and a spectrometer with energy resolution better than 0.5 MeV. The optimization TOF spectrometer design is on going using MCNP calculationfor both high detection efficiency for interesting events (2- 3 MeV) and the energy resolution. High detection capability with 0.5 MeV energy resolution can be realized with a single D2 detector. We proposed a high counting rate TOF electronics using fast selection of interesting events by fast pulse height discrimination (<10 ns). FNS experiment showed the POP of the high counting rate TOF electronics.

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13/13 10th ITPA diagnostics meeting, Moscow 10-14/04/06M. Sasao Future work and Summary (2) After changing the PMT of D1, the experiment will be repeated. The experiment with a full size D2 detector is scheduled. In order to have larger dynamic range, multi-layer D1 detecors, and multi D2 detectors are necessary. The measurement with present machines is desired.

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