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OUTLINE Concept Neutron Spectrum in a collimator-optimaization with MCNP

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

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OUTLINE Concept Neutron Spectrum in a collimator-optimaization with MCNP

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  1. TOF spectrometers for measurement of nd/nt ratiosK.Okada, T.Nishitani2, K. Ochiai2, K.Kondo2, M.Sasao, M. Okamoto, K.Shinto, S.KitajimaTohoku Univ. 2JAEA • OUTLINE • Concept • Neutron Spectrum in a collimator-optimaization with MCNP • Time-of-flight (TOF) spectrometer design • High-counting-rate TOF electronics • POP experiment of High-counting-rate TOF electronics • Future work and Summary

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

  3. 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.

  4. (distance from center of plasma : 10 m, collimator radius : 10 cm) Ti=25 keV 2.0 1.5 1.0 0.5 0.5 MeV Neutron flux [/0.1MeV/cm2/source] The energy resolution demanded is below 0.5 MeV grade. Neutron Spectrum in a collimator - optimaization with MCNP(2)

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

  6. 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. High-counting-rate TOF electronics(1)

  7. -2300 V HV Control room 65 ns DL1 DD Linear FAN-in/out d1 PMT Discri Coin Delay MCA Anti stop Target room Gate TAC ADC Discri GDG DL2 start Target room Linear FAN-in/out Linear FAN-in/out PMT d2 Discri d1～DD stop DL5 start HV d1～DT stop Discri Delay TAC -1300 V stop 65 ns DL3 ADC MCA start DT High-counting-rate TOF electronics(2)Experiment circuit

  8. POP experiment of High-counting-rate TOF electronics at FNS, JAEA 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. DD DT cps g-ray Total TOF spectrum Time (ch)

  9. POP experiment of High-counting-rate TOF electronics(2) DD DT Separation by a circuit g-ray DT spectrum Total TAC spectrum conversion DT spectrum is separated from total spectrum by fast Discri. DT time spectrum

  10. POP experiment of High-counting-rate TOF electronics- DD output of TAC (3) DT peak DD DT DD peak Separation by a circuit g-ray g-ray 12C(n,n’g)12C 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. 16.7 ns 44.3 ns

  11. POP experiment of High-counting-rate TOF electronics(3) DD energy spectrum DD peak DD spectrum is separated from total spectrum

  12. 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. Future work and Summary (1)

  13. 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. Future work and Summary (2)

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