Penning plasma based simultaneous light emission source of visible and VUV lights
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OW-TEMPERATURE PLASMA
Penning Plasma Based Simultaneous Light Emission Source of Visible and VUV Lights1 G. L. Vyasa, c, R. Prakashb, U. N. Palb, R. Manchandac, and N. Haldera a Manipal
b Microwave
University Jaipur, Jaipur, 303007 India Tubes Division, CSIR-Central Electronics and Engineering Research Institute, Pilani, 333031 India c Institute for Plasma Research, Bhat, Gandhinagar, 382428 India e-mail: [email protected] Received June 15, 2015
Abstract—In this paper, a laboratory-based penning plasma discharge source is reported which has been developed in two anode configurations and is able to produce visible and VUV lights simultaneously. The developed source has simultaneous diagnostics facility using Langmuir probe and optical emission spectroscopy. The two anode configurations, namely, double ring and rectangular configurations, have been studied and compared for optimum use of the geometry for efficient light emissions and recording. The plasma is produced using helium gas and admixture of three noble gases including helium, neon, and argon. The source is capable to produce eight spectral lines for pure helium in the VUV range from 20 to 60 nm and total 24 spectral lines covering the wavelength range 20–106 nm for the admixture of gases. The large range of VUV lines is generated from gaseous admixture rather from the sputtered materials. The recorded spectrum shows that the plasma light radiations in both visible and VUV range are larger in double ring configuration than that of the rectangular configurations at the same discharge operating conditions. To clearly understand the difference, the imaging of the discharge using ICCD camera and particle-in-cell simulation using VORPAL have also been carried out. The effect of ion diffusion, metastable collision with the anode wall and the nonlinear effects are correlated to explain the results. DOI: 10.1134/S1063780X1606009X
1. INTRODUCTION The penning plasma discharge (PPD) was developed long ago by F.M. Penning with the main application as cold cathode pressure measuring devices [1]. Later on, it has been used for other applications, such as particle trapping [2–4], fusion machines [5, 6], ion sources [7, 8], excitation sources [9], vacuum pumps [10], standard light radiation sources [11–14], etc. For the standard light radiation sources, the high-current hollow cathode discharge (HCD) sources have also been used [15, 16]. The HCD requires three to four orders of magnitude higher working pressure than the PPD source and cannot eliminate the need for differential pumping system altogether. The HCD is also not suitable at shorter wavelength lines, whereas PPD sources can include them in the spectra [13]. Furthermore, in the penning discharge there is less chance of grating contamination than the hollow cathode, because the cathode is not in the direct line-of-sight. Though some initial investigations on PPD as light source for EUV spectroscopy (5−30 nm) have been done [10, 11], but it has not been used in practice as a standard light source due to cathode e
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