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arXiv · 1505.01720

A chopper system for shortening the duration of pulsed supersonic beams seeded with NO or Br2 down to 13 microseconds

Jessica Lam·Chris Rennick·Tim Softley
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Abstract

A chopper wheel construct is used to shorten the duration of a molecular beam to 13 microseconds. Molecular beams seeded with NO or with Br2 and an initial pulse width of greater or equal to 200 microseconds were passed through a spinning chopper wheel, which was driven by a brushless DC in vacuo motor at a range of speeds, from 3,000 rpm to 80,000 rpm. The resulting duration of the molecular-beam pulses measured at the laser detection volume ranged from 80 microseconds to 13 microseconds, 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.

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Jessica Lam, Chris Rennick, Tim Softley. 2015-05-07. A chopper system for shortening the duration of pulsed supersonic beams seeded with NO or Br2 down to 13 microseconds. https://arxiv.org/abs/1505.01720

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