Ranjan A, Patel A, Wang X, Shashurin A. Thomson microwave scattering for diagnostics of small plasma objects enclosed within glass tubes.
THE REVIEW OF SCIENTIFIC INSTRUMENTS 2022;
93:113541. [PMID:
36461545 DOI:
10.1063/5.0111685]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Accepted: 10/31/2022] [Indexed: 06/17/2023]
Abstract
In this work, coherent microwave scattering in the Thomson regime was demonstrated for small-scale plasmas enclosed within a glass tube and validated using a well-known hairpin resonator probe technique. The experiments were conducted in a DC discharge tube with a diameter of 1.5 cm and a length of 7 cm. Thomson microwave scattering (TMS) diagnostics yielded electron number densities of about 5.9 × 1010 cm-3, 2.8 × 1010 cm-3, and 1.8 × 1010 cm-3 for air pressures in the discharge tube of 0.2, 0.5, and 2.5 Torr, respectively. Measurements using the TMS technique were consistent across the tested microwave frequencies of 3-3.9 GHz within the margin of error associated with non-idealities of the IQ mixer utilized in the circuit. The corresponding densities measured with the hairpin resonator probe were 4.8 × 1010, 3.8 × 1010, and 2.6 × 1010 cm-3. Discrepancies between the two techniques were within 30% and can be attributed to inaccuracies in the sheath thickness estimation required for correct interpretation of the hairpin resonator probe results.
Collapse