2014-July Pulsotron-2 Plasma Thrusters test report

Javier Luis López Segura,
Jorge Juan López,
Judy Atkins
Pulsotrón SL


Abstract.-
Cuenca.  In the July 2014 test campaign different ion speed measurement sensors installed in the Pulsotron-2 test tower were tested.  Using said sensors plasma jet emerging from 14 new plasma thrusters was measured.

Table of contents
1.    The plasma thrusters tested.-
2.    The measurement system.-
3.    Test results.-
4.    Conclusions.-
5.    Some high speed video captures.-

1.    The plasma thrusters tested.-

The first plasma thruster design consisted of a high magnetic field reactor that is destroyed when discharging a high current pulse through itself.  The high electric discharge generates a strong magnetic field which compresses ions until the internal pressure of the ions surpasses the magnetic field pressure blasting and ejecting the ions at a very high speed.
In the new plasma thruster design the coil is not destroyed as less power is injected but during a longer time. The new design is also more robust and admits various discharges.

2.    The measurement system.-

Basically two speed probes were tested.

The first one based on two Langmuir probes separated about 10mm from each other and connected to a constant voltage of 40 volts through low impedance resistors and where electrically isolated:

Langmuir sensors installed on test tower

The second one consists of two Schottky photodiodes separated by 10mm and then installed after two apertures:
Schottky diodes probe
 3.    Test results.-

14 tests were made; in 12 of them the ion speed using both methods was measured.  In the first test 140 km/s was reached but in the majority of them they were between 30 and 40 km/s:
Test results

 In the following plot the photodiodes are used. The beginning of the plasma wave and its peak can be measured.  Channel 3 is connected to the photodiode nearest the Plasma Thruster, and channel 4 is connected to the next photodiode:
 
The ion speed using the Langmuir probes method was also tested.  The channel 3 is connected to the Langmuir probe pair closest  to the Plasma Thruster nozzle and the channel 4 is connected to the second one that is located about 10mm from the previous one:

4.    Conclusions.-
Both sensors measure accurately the arrival of the plasma cloud and the peak of the same.
Most of the tests were performed using the Langmuir probes because the voltage levels were higher.   We would recommend using a greater aperture in the Schottky photodiodes in order to obtain higher voltage levels.

The Schottky photodiodes measure the temperature waveform of the plasma and the Langmuir proves its ionization levels.  Both sensors are precise and can be used together.

5.    Some high speed video captures.-

 

Test 420: Plasma Thruster TDD-2

 
Test 423: Plasma Thruster TDD-4

 

About jlopez2022

Experimental Physicist
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