Characteristics of a piezoelectric pulsed nozzle beam

Abstract

The characteristics of a molecular beam from a piezoelectric pulsed nozzle source are given and, where appropriate, compared to a continuous beam. These include variation during the pulse in the relative intensity and speed ratio for the gases He, Ar, Ne, and N₂. The measurements were made by standard time‐of‐flight and laser‐induced fluorescence techniques. For gas valve pulses of time duration less than 500 μs, there was a single peak during which the gases reached continuum steady flow behavior. Typical speed ratios (parallel temperatures) for the gases He, Ar, Ne, and N₂ were 19, 34, 34, and 20 (2.1, 0.7, 0.7, and 1.9 K), respectively. These values are comparable to those from a continuous source with equivalent values of p₀d, the product of source pressure and nozzle diameter. The dimer concentrations for Ne and Ar were also measured and found to be 0.4% and 0.7%, respectively. A major problem with the valve was its inability to open fully because of the limited motion of the piezoelectric element.