Brief Description of NDP Instrumentation
Shown below is a schematic depicting one simplified configuration for an NDP chamber. Other NDP configurations may include: sample stage motion, neutron focusing lenses, multiple detectors or detectors in a coincident configuration, sample changers, etc. The neutron monitor is placed in the vacuum chamber but may be placed at the entrance window of the chamber. In addition, vacuum pumps and vacuum gauges are required as well as electrical feed thorough connections into the vacuum to supply power or collect signals. These could include detectors, motion controllers, pre-amplifiers, samples, and other equipment.
The photograph below shows a earlier configuration of the NDP Chamber at the NIST Center for Neutron Research. A cold neutron beam (<5 meV, ~1 cm diameter) flows from the neutron source through the blue shielding and passes through the stainless steel vacuum chamber. The neutron beam at the sample position is described in some detail here. Non-reacted (absorbed or scattered) neutrons continue through the chamber to be captured in the beam stop enclosed in additional radiation shielding. During NDP measurements the chamber typically is held at a pressure of <2E-03 Pascal (<1E-05 Torr).