4. Results and discussion

ð16Þ

ð17Þ

ð18Þ

ð19Þ

ð20Þ

b. The calibration devices are settled on the thrust stand with keeping the distance of permanent magnet plates and the relative location between the permanent magnet plates and the conducting wires. And the pendulum is propelled by the Ampere force with duration of t. Therefore, the relationship of PSD signals S and the volts d.c. output X of function gene-

For the sake of simplification and considering that the pendular period of pendulum is generally longer than 5 s in the experiments, the duration of Ampere force t can be set 1 s by the

where, the coefficients A and B in expressions (18) could be obtained in the calibration procedures, as shown in Table 1. Besides, according to expression (15), the impulse bit I<sup>b</sup> can be

The uncertainty analysis is important and conducted herein. There are many sources of error for operating this thrust stand which must be identified, then quantified in order to evaluate the accuracy of the impulse bit measurement. It is shown in the expression (20) that the impulse bit is calculated from the voltage values of PSD signals and the coefficients in calibration procedures, A, A0, B and B0. Therefore, the uncertainties in the system data and results can be categorized into two main types. Firstly, the calibration procedures may generate errors for obtaining the coefficients A, A0, B and B0. Secondly, the impulse bit measurement is another

The mass shots are measured for the six cases by using an electronic balance (Mettler Toledo XS205, minimum mass 10 μg). It is apparent that the mass shots with different charged energy for a laser pulse energy of 600 mJ are approximately the same for the first five cases in Table 1, because of the isolation of laser ablation and discharge processes in the thruster. The typical number of pulse-shots to measure the mass shots is 100 times. The mass consumptions of propellants per shot are tested approximately as 15.7 and 7.8 μg for PTFE and aluminum, respectively. It is remarkable that the ablation of ceramic tube and ceramic insulator is much

function generator hereafter. Hence, the expression (16) can be expressed as:

c. The relationship of impulse bit and PSD signal S can be obtained as:

According to further study, it's indicated that the expression (17) can be simplified as:

rator can be obtained and written as:

198 Plasma Science and Technology - Basic Fundamentals and Modern Applications

expressed as:

source of error.

3.3. Measurement for mass shots

weak and not considered herein.
