Thomson scattering using an atomic notch filter

Abstract

One of the biggest problems in performing Thomson scattering experiments in low-density plasmas is the very high stray light intensity in comparison with the Thomson scattering intensity. This problem is especially present in fluorescent lamps because of the proximity of the glass tube. We propose an atomic notch filter in combination with a dye laser and an amplified spontaneous emission ͑ASE͒ filter as a way of reducing this stray light level. The dye laser produces 589 nm radiation which is guided through the ASE filter that increases the spectral purity. The beam is then guided in the fluorescent lamp, where the Thomson scattering process takes place. The scattered light is collected and guided through a sodium vapor absorption cell, where the stray light is absorbed because it is resonant to the D 2 transition of sodium. The spectral width of the Thomson scattering light is large enough to be transmitted through the absorption cell. In this way we only measure the Thomson scattering light.

Thomson scattering in a low-pressure argon mercury positive column

“…This scattered light is then detected by the ICCD camera, which is mounted on the spectrograph With respect to the setup described in Ref. 4, we made some minor changes. In the detection branch, the two imaging lenses are replaced by lenses with a focal distance of 250 mm.…”

“…In Ref. 4, we give an extended discussion on this cross section and the intensity calibration procedure. The error in the cross section is 8%.…”

“…In a recent article, we report Thomson scattering measurements in a fluorescent lamp. 4 Especially the use of an atomic vapor absorption cell that absorbs the stray light in the setup described in this article makes it possible to measure a Thomson scattering spectrum in a fluorescent lamp.…”

Thomson scattering in a low-pressure neon mercury positive column

“…8 we made some minor changes. In the detection branch, the two imaging lenses are replaced by lenses with a focal distance of 250 mm.…”

“…6 Furthermore, we measured the mercury ground state density profile 5 and the emission and excited state density profiles. 7 With our Thomson scattering setup 8 we investigated the influence of radial cataphoresis on the electron velocity distribution function in an argon-mercury discharge. 9 Since these Thomson measurements are much easier to perform in such a discharge than in a neon-mercury discharge, this was our starting point.…”