[Objectives]
In the deuterium plasma, 2.5 MeV neutrons are generated by d(d, n)He-3 reactions. The neutron emmision rate is the most important parameter to indicate the fusion performance. The neutron monitor measure the absolute neutron emission rate with high temporal resolution.
[Detectors]
U235 fission chamber with 5 cm-thick polyetheylene modelator
U238 fission chamber with 5 cm-thick lead gamma-ray shield
Specifications
| ・Time resolution | : | 1 ms |
| ・Dianamic range | : | 0 ~ 105 counts/s (pulse counting mode) 104 ~109 counts/s (Campbelling mode) |
| ・Energy range | : | 0.55 eV~ 15 MeV (U235) > 1 MeV (U238) |
| ・Position | : | In front of the horizontal port in P-3, P-7and P-13 sections. |
| ・Detector | : | A set of U235 and U238 fission chambers |
Calibration
The relation between the toral neutron emission rate and the detector output was calibrated by scaning the Cf-252 neutron source on the plasma axis inside the vacuum vessl.
Reference
(1) T. Nishitani, et al., "Absolute Calibration of the JT-60 Neutron Monitors Using a 252Cf Neutron Source", Rev. Sci. Instrum., Vol. 63 (1992) 5270.