Development of Current Mode Time-of-Flight Technique for Measurement of Thermal Neutron Spectrum

Abstract

A current mode time-of-flight (CTOF) technique was developed as a new technique to measure the high intensity spectra of the thermal neutron produced by the spallation neutron source driven by a few shots. The CTOF technique was developed and tested at KENS by measuring thermal neutrons produced in the water moderator. As a neutron detector, enriched 6Li and 7Li glass scintillators were employed, which were coupled with some different type of photomultiplier tubes. The peak of Maxwell distribution due to the thermal neutron was observed in the TOF spectrum. It is recognized that the time resolution of this technique was well enough to measure the thermal neutrons. For the validation of the CTOF technique, the spectrum was compared with that by a conventional pulse counting TOF technique using boron loaded plastic scintillator. As a result, it is found that the result obtained by current mode technique shows in good agreement with that obtained by the pulse counting technique. It is concluded that the current mode TOF can be applied to the measurement of the neutron spectrum.