Small‐angle scattering technique with a simplified angle selection

• Published in: Review of scientific instruments 1989-06, Vol.60 (6), p.1075-1079
• Main Author: Küttel, O. M.
• Format: Article
• Language: English
• Subjects: Exact sciences and technology; Physics; Physics of gases, plasmas and electric discharges; Physics of plasmas and electric discharges; Plasma diagnostic techniques and instrumentation
• ISSN: 0034-6748; 1089-7623
• DOI: 10.1063/1.1140320

A simplified homodyne small‐angle scattering technique for plasma fluctuation measurements is described. The local oscillator is produced by a beam splitter which lies just behind the scattering area in the main laser beam. The scattered radiation is reflected from the beam splitter and directed onto the detector. Meanwhile, the transmitted portion of the beam is reflected back to the same beam splitter and superimposed with the scattered light so as to act as a local oscillator. The proposed method has several advantages. No separate local oscillator path is necessary, and the alignment and selection of different scattering angles is easily done by two microprocessor‐controlled step motors. With a variable attenuator the local oscillator power is adjustable to any desired value. Heterodyning is possible by adding an acousto‐optic modulator which shifts the LO frequency. First results of measurements on microturbulences in a plasma are presented.