A chopper system for shortening the duration of pulsed supersonic beams seeded with NO or Br-2 down to 13 mu s

作者：Lam Jessica^*; Rennick Christopher J; Softley Timothy P

来源：Review of Scientific Instruments, 2015, 86(5): 053108.

DOI：10.1063/1.4921398

A chopper wheel construct is used to shorten the duration of a molecular beam to 13 mu s. Molecular beams seeded with NO or with Br-2 and an initial pulse width of >= 200 mu s 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 mu s to 13 mu s and was the same for both NO and Br2. 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.

• 出版日期2015-5