A sensitive time-of-flight molecular beam detector

A molecular beam detector based on a charged particle oscillator is described. It is characterized by high sensitivity, good time resolution and marked simplicity of construction. The molecular beam passes through a band of oscillating electrons formed within the detector, and is detected by measurement of the resultant current of ions. The length of beam intercepted can be set within the ranges 0-5 mm and 0.70 mm according to whether the beam passes across or along the band of electrons. At an electron emission current of 10 mu A the probability of ionization is 2.5*10 -6 molecule -1 mm -1 length of intercepted beam for argon at 20 degrees C. A feature of general application to devices based on the charged particle oscillator is the means adopted to minimize the field distortion occurring at the ion exit slot.