Shin Satori

Development and Demonstration of a Cathodeless Electron Cyclotron Resonance Ion Thruster

The electron-cyclotron-resonance microwave-discharge ion thruster system utilizes no cathodes to emit thermionic electrons for plasma generation in both the ion source and the neutralizer. The ion source can generate xenon ions at an ion-production cost of 300 eV and a propellant utilization efficiency of 88 %, with a double-charged-ion population of 8 %. The neutralizer can output 100 m A of electron current with 10 W of microwave power and 0.5 seem of xenon flow. The thruster system combining the ion source and the neutralizer operated for 300 h without detectable erosion of the screen grid and ion source. Except for the primary frequency of 4.2 GHz used to generate plasmas, the system proved experimentally compatible with spacecraft electromagnetic interference requirements in the microwave frequency range.

LOW-POWER MICROWAVE ELECTRON SOURCE FOR ION ENGINE NEUTRALIZER

Operation of an ion engine in space requires an electron source to maintain the spacecrafts electrical neutrality. To neutralize exhausted ions, a low-power, compact microwave electron source was developed. An 18-mm-diameter noncavity-type discharge chamber consisting of an L-shaped antenna and a magnetic circuit was developed, and electron emission current of 100 mA was obtained at the power level of 10 W, maintaining the mass flow rate of xenon at 0.5 sccm.

Plasma coupling of microwave neutralizer

A microwave neutralizer was developed in Institute of Space and Astronautical Science. Three types of the microwave neutralizer were febricated and their operational characteristics were measured. A prototype neutralizer exhibited stalbe operation at low microwave power of 2W. A higher power operation was investigated using a short type neutralizer and showed a high electron current of over 500 mA. Plasma properties in the discharge chamber of the neutralizer were measured using Langmuir probe and a microwave connector called bias-T. Dense plasma over the cutoff density of 2.2xlO cm was observed at the electron extraction orifice.

Electron Cyclotron Resonance Ion Source for Ion Thruster

An electron cyclotron resonance (ECR) ion source was designed and its performance was studied in comparison with a DC ion source. Ion production cost of 340 V/ion for ECR ion source and 189 V/ion for DC ion source were obtained at the pressure of 0.5 mTorr and the discharge power of 50 W. A luminosity distribution of the Ar-II line was imaged through an interferometer filter and a luminous arch hill was observed near the ECR region, where the plasma was resonantly generated. Ion wall loss measurement showed that the ion production cost became worse due to the excessive ion wall loss near the cusped magnets, where the plasma confinement was inferior to that of the DC ion source.

LASER COOLING OF NEUTRAL ARGON FOR SIMULATING THE STORAGE OF ANTIMATTER

The storage of antimatter in an electrically neutral state is one of the breakthroughs required to realize antimatter applications. In this work, use of laser cooling to manipulate the motion of neutral atoms by radiative pressure was demonstrated using a commercial laser diode and metastable argon as antimatter simulant. The concept of critical velocity was introduced as a criterion for the laser cooling and its importance was experimentally demonstrated.

Current Imbalanced Phenomena and Operational Controllability of Clustered Microwave Neutralizers.

An emission current imbalance phenomena involved in the clusterization problem were experimentally investigated using a microwave neutralizer. The fundamental properties of current voltage characteristics was measured. The current imbalanced operation was experimentally demonstrated dependent on a current inflow from other electron source and the imbalanced modes of the microwave neutralizer were categorized. An advisable method to suppress the imbalance was proposed and performed experimentally.

Velocity Measurement of Metastable Argon Flow Using Laser Diode.

The velocity of a metastable argon flow was measured by means of laser induced fluorescence (LIF). A commercial laser diode was employed as the diagnostic instrument. The transition between 1 s5 and 2 p6 was available for LIF and the resultant fluorescence in a vacuum ultraviolet range was detected by an electron multiplier. The velocity of the argon flow estimated at 750m/s and its number density ranged around 103 particles per cm3.