JAEA-Conf 2011-002 - 日本原子力研究開発機構

JAEA-Conf 2011-002
39cm and 49cm from one side edge, at which each of the full energy peaks was expected to be observed. There
are several peaks in the spectrum. Each peak was assigned to each position carefully. The 9cm, 16cm, 25cm,
32cm, 39cm peaks were clearly identified. But no full energy peaks for the 4cm and 49cm signals were observed,
and thus they could not be identified. From this result and other additional experiments it was found that we
could obtain the detection position distribution at Z=6cm~44cm.
Fig.6 Position detection by the Cd collimator.
3.3 Measurable neutron energy range
Limit of measureable detection depth can affect the measurable neutron energy range. The measurable energy
range was derived by the experimental results described in the previous section and the response matrix of the
detector. At 6cm in depth, there exists an enough large value in the response matrix for neutrons of over 0.005eV.
And over 1keV, the response difference was too small to discriminate energy. Consequently, this detector can be
expected to measure neutrons of 0.005eV~1keV, which mostly cover the thermal/epithermal region. For the
BNCT facilities these energy neutrons will be used and this spectrometer can obtain the crucial information of
the neutrons.
4. Future works
We have been carrying out basic research & development for the thermal/epithermal neutron spectrometer.
From this series researches, we made it appear that the detection position could be distinguished in the test
measurement. In the next phase, the incident direction of neutrons is changed to be parallel to the detector axis,
as shown in Fig.7, in order to check how well the neutron spectrum could be reproduced from the measured
detection depth distribution. For this purpose, several neutron sources having different neutron spectra are to be
utilized, i.e., mono-energetic thermal neutrons at JRR-3M, JAEA, thermal/epithermal neutrons at OKTAVIAN
facility of Osaka University and 8 keV neutrons at FRS facility of JAEA. We will use them to check one-to-one
correspondence between the direction depth distribution and the incident neutron energy through measuring the
response function. Finally we will confirm whether the neutron energy spectrum will be reproduced by unfolding