Adaptation of the testing facilities and diagnostic capabilities improvement
Adaptation of the testing facilities and diagnostic capabilities improvement
The final assembly will be tested to prove its functionality and performance at USTUTT, using the diagnostic tools developed at CNRS. The present USTUTT facility “Tank 12” will be adjusted to allow the operation of iodine: the sealings will be replaced, the vacuum pumps upgraded, instruments will be reviewed, and materials changed in case corrosion is to be expected. The intrusive diagnostics available in the facility to be improved for iodine-plasma characterization include Langmuir probes (LP), Faraday probes (FP), and back-vacuum retarding potential analyzer (RPA). Furthermore, the existing Laser Absorption Spectroscopy (LAS) setup will be updated in the wavelength required for iodine measurements. In addition to these measurement capabilities, CNRS diagnostic tools will enable the evaluation of the iodine singly-charged ion I+ velocity distribution function by means of Laser-Induced Fluorescence (LIF) spectroscopy. This will be obtained updating a state-of-the-art compact LIF optical setup developed at ICARE to allow detection of I+ ions in the red domain. A compact Optical Emission Spectroscopy (OES) setup will be developed to observe atomic ionic and molecular emission lines in RF discharges. With iodine, the setup will allow the observation of I, I+, I2, I2+ excited states, which provide relevant information about the plasma properties and device performances. Testing and qualification of the diagnostic tools will be performed using a 13.56 MHz radio-frequency reactor with an input power up to 1 kW, currently supplied with various atomic and molecular gases, that will be equipped with a new injection system specifically designed for iodine.
The facility at USTUTT is completed by a variety of thrust measuring instruments available to characterize the performance in the range of µN-N. This includes an inverted pendulum thrust stand and a baffle plate design. The latter is further capable of mapping the cross-sectional thrust density distribution. The reliability of the reviewed instrumentation will be assessed at USTUTT via a comparison against preliminary measures accomplished on each of the building blocks by the partners charged with their realization. In addition, measurement techniques such as OES, different types of electrostatic probes as well as advanced optical diagnostics, e.g. Mach-Zehnder Interferometer (MZI), are in use for the facility.
As a result, a very complete set of diagnostics will be available to deeply characterize iodine-based electric thrusters from very low up to medium power levels (i.e., <5 kW). These instruments are mandatory to prove the achievements of the BOOST project. Moreover, an iodine-compatible vacuum facility, equipped with advanced and reliable instrumentation, will be available in a public institution for the development of the future next generation industrial applications and/or products. Finally, a number of good practices and/or standards to test iodine-propelled electric thrusters will be identified and shared with the scientific community in order to further boost the widespread diffusion of this technology.