Lamb-shift and electric field measurements in plasmas

Fabrice Doveil (1) , Laurence Chérigier-Kovacic (1) , Peter Ström (2)

1 PIIM - Physique des interactions ioniques et moléculaires
2 KTH - KTH Royal Institute of Technology [Stockholm]

The electric field is a quantity of particular relevance in plasma physics. Indeed, its fluctuations are responsible for different macroscopic phenomena such as anomalous transport in fusion plasmas. Answering a long-standing challenge, we offer a new method to locally and non-intrusively measure weak electric fields and their fluctuations in plasmas, by means of a beam of hydrogen ions or atoms. We present measurements of the electric field in vacuum and in a plasma where Debye shielding is measured. For the first time, we have used the Lamb-shift resonance to measure oscillating electric fields around 1 GHz and observed the strong enhancement of the Lyman-α signal. The measurement is both direct and non-intrusive. This method provides sensitivity (mV cm−1) and temporal resolution (ns) that are three orders higher compared to current diagnostics. It thus allows measuring fluctuations of the electric field at scales not previously reached experimentally.

Domaines: Physique des plasmas [physics.plasm-ph]

Fabrice Doveil, Laurence Chérigier-Kovacic, Peter Ström. Lamb-shift and electric field measurements in plasmas. Plasma Physics and Controlled Fusion, 2016, Special issue featuring the invited talks from the 43rd EPS Conference on Plasma Physics, Leuven, 4-8 July 2016, 59 (1), ⟨10.1088/0741-3335/59/1/014020⟩. ⟨hal-01466155⟩