| Issue |
EPL
Volume 104, Number 3, November 2013
|
|
|---|---|---|
| Article Number | 35001 | |
| Number of page(s) | 5 | |
| Section | Physics of Gases, Plasmas and Electric Discharges | |
| DOI | https://doi.org/10.1209/0295-5075/104/35001 | |
| Published online | 26 November 2013 | |
Lyman-α radiation of a probe atomic beam to explore the electric field in plasma sheaths
1 UMR 7345 CNRS–Aix-Marseille-Université, campus Saint-Jérôme - case 321, av. esc. Normandie-Niemen, 13397 Marseille cedex 20, France
2 CAMECA SAS - 29 Quai des Grésillons, 92622 Gennevilliers Cedex, France
Received: 21 August 2013
Accepted: 29 October 2013
An innovative way to non-intrusively measure weak electric fields in plasmas is presented. The electric field is produced between two planar plates which can be immersed in a thermionic plasma. An atomic probe beam, obtained from the conversion of 
ions into H(2s) in a resonant charge exchange cesium vapor cell, is sent between the two plates. Emission of the Lyman-α line is induced by the external electric field. It originates in the Stark mixing of the two 
and 
levels that are separated in energy by the so-called Lamb shift. The light is collected in a direction perpendicular to the probe beam. Theory predicts that its intensity is proportional to the square modulus of the electric field below a critical value. With a proper calibration through measurements in vacuum, the amplitude of the electric field is obtained. Creating an electric field within a plasma, Debye shielding is thus clearly observed. Such measurement can also be done in transparent diluted media. The presented method answers to a long-standing challenge in experimental physics.
This paper is dedicated to late Professor R. A. Stern who was the inspirer of this research
PACS: 52.70.Ds – Electric and magnetic measurements / 52.75.Xx – Thermionic and filament-based sources (e.g., Q machines, double- and triple-plasma devices, etc.) / 34.50.Fa – Electronic excitation and ionization of atoms (including beam-foil excitation and ionization)
© EPLA, 2013
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