Spatial Profile of Ion Velocity Distribution Function in Helicon High-Density Plasma by Laser Induced Fluorescence Method

Abstract

Helicon plasma sources have been studied in many fields across science and technology because they can supply high-density plasmas with a broad range of external operating parameters. In our laboratory, we aim to develop a completely electrodeless electric thruster, which is expected to have a high efficiency and a long lifetime, leading to be useful on a deep space exploration. In order to demonstrate and optimize this thruster system, it is important to have detailed distributions of plasma flow. Laser induced fluorescence (LIF) diagnostics, which can measure velocity distribution functions of particles, has advantages from a view point of, e.g., high resolution in time and space, and it can determine an absolute particle velocity and its temperature in addition to its relative density. Here, we have been developing a LIF measurement system using a Multi-Pixel Photon Counter (MPPC) for a multi-channel system. Argon ion velocity depending on the magnetic field gradient in a downstream region is measured by this LIF system.

Study on electromagnetic plasma propulsion using rotating magnetic field acceleration scheme

“…(2), may be easier, concerning a signal, instead of a DC component) or an axial magnetic fieldB z by using a magnetic probe, using a Maxwell equation to derive j h , to clarify the penetration of B RMF to induce j h for a future study, in addition to the measurement of spatial profiles of B RMF , as was mentioned. In order to crosscheck the effect of RMF acceleration, it is also planned to introduce other measurements, e.g., measuring thrust by using a thrust stand, which has a cylindrical shape, considering the particle collision with the stand to make the momentum thruster, 16,17 and Laser Induced Fluorescence (LIF) methods, 18 which enable us to measure the plasma parameter in a non-contact condition. Needless to say, in order to see the acceleration effect more, it is necessary to increase both I RMF and a number of turns of RMF coils, e.g., total ampere-turns, which leads to an increase in B RMF , considering the optimized RMF frequency and also the inductances of RMF coils to have a proper impedance matching from an experimental viewpoint, leading to a better thrust efficiency.…”

Spatial measurement in rotating magnetic field plasma acceleration method by using two-dimensional scanning instrument and thrust stand

“…As in situ plasma diagnostics, some measurement techniques have been adopted: Langmuir probe, 3 Mach probe, 4,5 and double probe 6 are major methods due to an easy introduction of local values, although these tools may disturb plasma flow and affect the plasma characteristics. On the contrary, electromagnetic and spectroscopy methods, e.g., microwave interferometer, 7 Laser Induced Fluorescence (LIF) method, [8][9][10] and Laser Thomson Scattering (LTS), 11 are effective ways in terms of non-direct contact measurements with a plasma with good measurement accuracy. In the field of nuclear fusion plasma research, these measurement a) Electronic mail: s172832r@st.go.tuat.ac.jp methods are also utilized widely, reducing contaminations by impurities under the extremely high temperature conditions.…”

Electrodeless plasma acceleration system using rotating magnetic field method

“…Plasma diagnostics in addition to our present probe method, e.g., as non-contact measurements, Laser Induced Fluorescence (LIF) method, 18,22 which can measure an ion velocity and temperature without disturbing plasma, and other spectroscopies, are effective to crosscheck our previous measurement. In addition, using a thrust measurement method, e.g., a target stand type, which has a cylindrical shape, considering the collision between the target and particle 19,25 is an effective method to estimate this RMF acceleration effect.…”

“…In our previous experiment, the magnetic nozzle effect was investigated by the use of Laser Induced Fluorescence (LIF) method and thrust measurement by means of a target type thrust stand w/o RMF method. 18,19 An excitation rf frequency for plasma production is 7 MHz for a 75 ms pulsed discharge (5 % duty) at intervals of 1.5 s, which is controlled by a function generator. With respect to the rf discharge, a high power source (Thamway, T162-6746A), whose maximum power is ∼ 5 kW for the frequency with a range of 3 -15 MHz, and used with an impedance matching box (Thamway, T020-6326AK), which can change values of parallel/series capacitances, are utilized.…”