Helium-3 Squashed Neutron Detectors

Features

• Excellent accuracy in Time-of-Flight measurements
• Important surface coverage or accurate angular resolution
• CANBERRA Eurisys patented (formerly LMT)
• Active thickness: 2.5 to 15 mm
• Active width: 11 to 35 mm
• Active length: 10 to 40 cm and special lengths upon request (more than 10 pieces)
• Helium-3 pressure: up to 20 bars
• Electrical output on wire or connector

Description

The squashed and rectangular section neutron detectors are very innovative devices; they were developed to meet the requirements of some neutron scattering experiments: Time-of- Flight (accurate localization of neutrons within ultra-thin active thickness), scattering angle measurements (excellent angular resolution associated with a high detection efficiency), covering of large detection areas with a minimized number of detectors.

The active thicknesses available now range from 2.5 mm (unequalled ultra thin thickness, associated with a high Helium-3 pressure, up to 20 bars) to 15 mm, with detection widths ranging from 11 to 31 mm.
Some typical detectors are presented overleaf. For quantities above several ten pieces, the active section and also the active length, the Helium-3 pressure and the gas mix may be adapted to specific spectrometer characteristics.

The specifications of these detectors (FWHM resolution, high voltage plateau, background and reliability) are fully similar to those of circular section detectors. The manufacturing process (LMT patent N° 2427682) permits the use of standard tubes and circular end pieces, thus warrantying low costs and delivery times.

Several thousands of detectors of such detectors operate satisfactorily since 1975, for example the historical TOF IN6 spectrometer of the Laue Langevin Institute at Grenoble-France with a total of 350 squashed detectors. The TOF DCS spectrometer of NIST is equipped with more than one thousand 90NH40REC detectors associated with ACHN92 charge amplifiers optimized for Time-of-Flight measurements.
More recently, the Munich University has equipped the TOF-TOF spectrometer located on the new FRM-II reactor of Garching with 600 off 120NH40RTF detectors. For this application, a very heavy gaz (CF₄) has been added to the Helium-3 to minimize the electronic collection time, thus optimizing the Time-of- Flight measurements.