The Neutron Spectrometer
Requirements for the TOF spectrometer (conclusions of the Madrid meeting pointed out by N. Orr - LPC Caen):
for reducing backgrounds, enable b-2n,3n
Liquid scintillators (or "new" solid scintillators) NE213 + EJ309 (only for short detectors), EJ325 (?, inexpensive).
Longer bars, higher threshold!
Plastics/crystals like Stylbene.
The best n/g discrimination comes from a granular array. Test NE213 with various PMT, EJ309 and EJ325 pushing the thresholds down as much as possible.
Improve DEn/En and eliminate "tails" in TOF spectra visible in TONERRE (BC400 plastics)
Thin, small volume detectors with increased dflight~3,4 m (space for both n and g setups)
Neutron energy range
0 < En < 10 - 15 MeV with a reasonable efficiency.
To have the lowest possible threshold in En requires thin, small volume detectors (no bars) + digital electronics (30 keV En)
cross-talk rejection will enable b-2n,
A modular, highly granular array (>100 detectors) and with variable geometry (cm alignment precision) will be necessary. 2 options: DEMON-like or TONERRE-like (curved or straight bars). The cross talk rejection will be performed by time and energy deposited in the detectors.
Neutron detection efficiency
The detection efficiency should be as high as possible over the entire energy range.
Solid angle to be covered should be as high as possible: 1p≤ DWn ≤ 2p depending on the type of experiment.
g-ray detection efficiency
Should be also as high as possible for the identification of neutron decay to excited states
Large volume high efficiency Ge detectors will be necessary, which is in conflict with the need for high DWn.
Will be used for a better control of systematic uncertainties. Flash ADCs with 1 GSample/s and resolution larger or equal than 10 bits are requested. Pulse shape analysis algorithms will be programmed on a PC farm or FPGAs.
minimise the amount of dead material in and around the implantation setup: no B, no Li, no Br, avoid plastics (or materials rich in hydrogen). Al is a \93tentatively good material\94 (low cross sections).
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