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Title: A chopper system for shortening the duration of pulsed supersonic beams seeded with NO or Br{sub 2} down to 13 μs

A chopper wheel construct is used to shorten the duration of a molecular beam to 13 μs. Molecular beams seeded with NO or with Br{sub 2} and an initial pulse width of ≥200 μs were passed through a spinning chopper wheel, which was driven by a brushless DC in vacuo motor at a range of speeds, from 3000 rpm to 80 000 rpm. The resulting duration of the molecular-beam pulses measured at the laser detection volume ranged from 80 μs to 13 μs and was the same for both NO and Br{sub 2}. The duration is consistent with a simple analytical model, and the minimum pulse width measured is limited by the spreading of the beam between the chopper and the detection point as a consequence of the longitudinal velocity distribution of the beam. The setup adopted here effectively eliminates buildup of background gas without the use of a differential pumping stage, and a clean narrow pulse is obtained with low rotational temperature.
Authors:
; ;  [1]
  1. Department of Chemistry, University of Oxford, Chemistry Research Laboratory, 12 Mansfield Rd, Oxford OX1 3TA (United Kingdom)
Publication Date:
OSTI Identifier:
22392492
Resource Type:
Journal Article
Resource Relation:
Journal Name: Review of Scientific Instruments; Journal Volume: 86; Journal Issue: 5; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; BROMINE; DETECTION; LASERS; MOLECULAR BEAMS; MOTORS; NITRIC OXIDE; OPTICAL PUMPING; PULSES; VELOCITY