Fully Digital Data Acquisition System for the Neutron Time-of-Flight Spectrometer TOFOR at JET

TOFOR is a neutron Time-Of-Flight (TOF) spectrometer installed at JET [1], based on plastic scintillators. In TOF neutron spectrometry for fusion plasmas, the flight-time-scale is on the order of tens of nanoseconds and in order to resolve important spectral features sub-nanosecond timing is required and the system should cope with signal count rates of hundreds of kHz. Until now, while the time information has been stored digitally, the signal processing of TOFOR has been handled by analogue electronics. No information on pulse height is available and therefore it is impossible to correlate energy deposition information with time-of-flight. Replacing the Data AcQuisition (DAQ) electronics of TOFOR with high-resolution, nanosecond-precision digitizers enables pulse height information storage and consequently geometry-based discrimination of the rate-dependent accidental coincidence background. Tests with such a digital DAQ system are currently under way. This paper presents simulations of geometry-based background discrimination applied to TOFOR spectra, comparing them with early experimental results.
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