The Gamma Camera installed at JET consists of a vertical and a horizontal camera made of 9 and 10 collimated lines of sight, respectively. Measurements along this multiple set of channels allow the tomographic reconstruction of the gamma emission source in the plasma. In particular, in Deuterium-Tritium thermonuclear plasmas (DT), the detection of the 4.44 MeV gamma-rays emitted by 9Be(,n )12C reactions plays a key role in the study of the alpha particle confinement. The new detectors will be installed in 2017 enabling gamma-ray spectroscopy in the forthcoming high power plasma campaigns with and without tritium. The upgrade aims to improve the spectroscopic capabilities allowing gammaray measurements at MHz counting rate with enhanced energy resolution in a harsh neutron-gamma mix environment. In order to meet these requirements together with important limitations given by the detector available space, the project team has developed a compact gamma-ray spectrometer based on a Silicon Photo-Multiplier (SiPM) coupled to a LaBr3(Ce) scintillator crystal. Silicon Photo-Multipliers represent a good alternative to standard photomultiplier tubes due to their insensitivity to magnetic fields, high internal gain and extremely compact size. In this work we present the response of the LaBr3(Ce) crystal to 14 MeV neutron irradiation measured at the Frascati Neutron Generator (FNG) including a comparison with the results from MCNP simulations. The neutron resistance of the SiPM has been also assessed after a neutron irradiation up to about 10^10 n/cm2. The SiPM showed a significant increase of dark current and a change in the current-voltage characteristic curve, but without changes in the recorded pulse height spectrum. A partially self-recovering process of the SiPM has also been observed leading to a decrease of dark current and I-V curve after few weeks. Based on these results we can extrapolate that the developed prototype can sustain neutron fluxes corresponding to approximately 100 record DT JET plasma discharges.
Characterization of a compact LaBr3 detector with Silicon photomultipliers at high 14 MeV neutron fluxes
Rigamonti Davide;Nocente Massimo;Tardocchi Marco;Gorini Giuseppe;Murari Andrea;
2017
Abstract
The Gamma Camera installed at JET consists of a vertical and a horizontal camera made of 9 and 10 collimated lines of sight, respectively. Measurements along this multiple set of channels allow the tomographic reconstruction of the gamma emission source in the plasma. In particular, in Deuterium-Tritium thermonuclear plasmas (DT), the detection of the 4.44 MeV gamma-rays emitted by 9Be(,n )12C reactions plays a key role in the study of the alpha particle confinement. The new detectors will be installed in 2017 enabling gamma-ray spectroscopy in the forthcoming high power plasma campaigns with and without tritium. The upgrade aims to improve the spectroscopic capabilities allowing gammaray measurements at MHz counting rate with enhanced energy resolution in a harsh neutron-gamma mix environment. In order to meet these requirements together with important limitations given by the detector available space, the project team has developed a compact gamma-ray spectrometer based on a Silicon Photo-Multiplier (SiPM) coupled to a LaBr3(Ce) scintillator crystal. Silicon Photo-Multipliers represent a good alternative to standard photomultiplier tubes due to their insensitivity to magnetic fields, high internal gain and extremely compact size. In this work we present the response of the LaBr3(Ce) crystal to 14 MeV neutron irradiation measured at the Frascati Neutron Generator (FNG) including a comparison with the results from MCNP simulations. The neutron resistance of the SiPM has been also assessed after a neutron irradiation up to about 10^10 n/cm2. The SiPM showed a significant increase of dark current and a change in the current-voltage characteristic curve, but without changes in the recorded pulse height spectrum. A partially self-recovering process of the SiPM has also been observed leading to a decrease of dark current and I-V curve after few weeks. Based on these results we can extrapolate that the developed prototype can sustain neutron fluxes corresponding to approximately 100 record DT JET plasma discharges.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.