Speaker
Dr
Jean-Paul Booth
(LPP-CNRS)
Description
Electric propulsion technology (plasma thrusters) for satellite positioning and orbit change is a rapidly expanding field. Whereas most existing devices (principally Hall Effect Thrusters) use xenon gas, due to its high mass and low ionisation potential, there is growing interest in the use of Iodine[1], due to its ease of storage (solid state) and low cost, in addition to a mass and ionisation potential comparable to xenon. However, the physical processes occurring in an iodine plasma are more complex, including electron-impact dissociation, negative ion formation by dissociative attachment, and surface-catalysed recombination. Models of iodine plasmas are being developed, but much fundamental data is absent, and there is an urgent need for experimental validation.
We have used infra-red diode laser absorption spectroscopy to detect iodine atoms in a pure I2 inductively-coupled discharge, using the spin-orbit transition occurring at 1315 nm [2]. Since the transition strength is weak, the beam is passed 4 times through the 10 cm-wide reactor, operating at pressures of 10-100 mTorr and with radiofrequency power up to 250 W. From the absorption intensity and Doppler width the absolute I atom density and translational temperature was determined as a function of gas pressure and RF power. In future work we intend to determine the I atom recombination probability at the reactor surface from the I density decay rate in the afterglow in pulsed discharges.
[1] P. Grondein, T. Lafleur, P. Chabert, and A. Aanesland, Physics of Plasmas, 23, (2016)
[2] T.K. Ha, Y. He, J. Pochert, M. Quack, R. Ranz, G. Seyfang, and I. Thanopoulos, Berichte Der Bunsen-Gesellschaft-Physical Chemistry Chemical Physics, 99, (1995) 384
Primary author
Dr
Jean-Paul Booth
(LPP-CNRS)
Co-authors
Dr
Anne Bourdon
(LPP-CNRS)
Dr
Pascal Chabert
(LPP-CNRS)
Mr
Theo Courtois
(LPP-CNRS)
