High power vacuum ultraviolet source based on gasdynamic ECR plasma

• Published in: Journal of applied physics 2022-03, Vol.131 (9)
• Main Authors: Lapin, R. L., Skalyga, V. A., Golubev, S. V., Izotov, I. V., Razin, S. V., Tarvainen, O.
• Format: Article
• Language: English
• Subjects: Applied physics; Cyclotron resonance devices; Discharge; Electron cyclotron resonance; Emission; Microwaves; Optimization; Plasma; Plasma density; Power
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/5.0074388

We report experimental results of vacuum ultraviolet (VUV) emission from the plasma of an electron cyclotron resonance (ECR) discharge in hydrogen, sustained by millimeter-wavelength radiation of a gyrotron. The considered discharge is characterized with the high plasma density ( 10 13 cm − 3 order of magnitude) and, at the same time, the high electron average energy (10–300 eV), which makes it possible to significantly increase the efficiency of VUV re-emission of the energy deposited into the plasma by the microwave radiation. Experiments were performed with the plasma confined in a simple mirror trap and heated by pulsed gyrotron radiation of 37.5 GHz/100 kW under the ECR condition. The measured volumetric VUV emission power of Lyman-alpha line (122 10 nm) overlapping with the Werner band, Lyman band (160 10 nm), and molecular continuum (180 20 nm) reached 45, 25, and 55 W/cm 3, respectively. The total absolute radiation power in these three ranges integrated over the plasma volume is estimated to be 22 kW, i.e., 22% of the incident microwave power, which matches theoretical predictions. The development of effective technological VUV sources of a kilowatt power level is expected to be the next step following the optimization of the conditions of the ECR hydrogen discharge sustained by powerful gyrotron radiation.