A two-dimensional detector array has been fabricated from a single 10-mm-diam by 100-μm-thick chemical vapor deposition diamond disk by applying a 1×1 mm2 metallization grid of 4×4 pixels with centered bias connections. This diamond has been exposed to high power pulsed laser radiation. It has been shown that this kind of diamond array operates as a radiation hard, ultrafast laser beam profiler and can obtain spatial profiles with 500 ps temporal resolution. Ten spatial profiles were obtained within a single 5 ns duration laser pulse, revealing in detail the temporal and spatial development of the laser beam intensity. No attenuation is necessary for this profiler when making single-shot measurements at intensities up to ∼100 MW/cm2.

A new type of vacuum arc thruster in combination with an innovative power processing unit (PPU) has been developed that promises to be a high efficiency (∼15%), low mass (∼100 g) propulsion system for micro- and nanosatellites. This thruster accelerates a plasma that consists almost exclusively of ions of the cathode material and has been operated with a wide variety of cathodes. The streaming velocity of the plasma exhaust varies with cathode material, from a low of 11 km/s for Ti up to 30 km/s for Al, with a corresponding range of specific impulse from 1100 s for Ta to 3000 s for Al. Initiation of the arc requires only a few hundred volts due to an innovative “triggerless” approach in which a conductive layer between the cathode and the anode produces the initial charge carriers needed for plasma production. The initial starting voltage spike as well as the energy to operate the vacuum arc are generated by a low mass (<300 g) inductive energy storage PPU which is controlled using +5 V level signals. The thrust-to-power ratio has been estimated to reach up to ≈20 μN/W. The vacuum arc thruster was tested at the Jet Propulsion Laboratory using W as cathode material. Experimental results are within 65% of the estimated values.

Summary form only given, as follows. Unlike present electric thrusters that are difficult to scale down in size, thrust and power, a vacuum arc thruster (VAT) is a good candidate for micro-spacecraft propulsion. In the VAT, highly ionized plasma is produced by an arc discharge from a cathode and propagates downstream generating thrust. The VAT is operated in a pulsed mode with an average power of /spl sim/1-100 watts and an overall efficiency of 16-20%. We have developed a compact inductive energy store driver that allows the VAT to be scaled down even further. The arc source of the VAT was characterized using a conventional multi-stage pulse-forming network as a driver. Several cathode elements have been evaluated. The measured arc plasma resistance is /spl sim/40 mohm, and the cathode voltage is 18 V. The arc plasma streaming velocity is in the range of 1-3e4 m/s, depending on the arc material. The ion current of the arc plasma is roughly 8% of the cathode current with an ion mean charge state of 1+ to 3+. From the tungsten arc measurements, the ion streaming velocity, arc voltage (at 50 A), cathode erosion rate and propellant utilization rate are 1.4e4 m/s, 20 V, 60e-9 kg/C and 80%, respectively. Beside the arc plasma studies, we have made a breakthrough of an inductive energy store power processing unit (PPU) that can deliver /spl sim/10-100 A pulses to the thruster at firing rates up to 600 Hz, from a package that has <100 g mass. The efficiency of this PPU is >=90% as measured. Using this PPU the overall efficiency is estimated to be /spl sim/20%. These results imply that the VAT is a promising new candidate for small spacecraft propulsion applications.

Burning voltages of vacuum arcs were measured for 54 cathode materials and compared with literature data. As anticipated, a correlation between the arc burning voltage and the plasma temperature was found. However, more importantly, a correlation between the cohesive energy of the cathode material and the arc burning voltage could be demonstrated. This link between a cathode material property, the cohesive energy, and a discharge property, the arc burning voltage, is essential for the operation of the vacuum arc discharge because is determines the plasma temperature. Energy balance considerations show that this “cohesive energy rule” is responsible for several other secondary relationships, such as the correlation between the mean ion charge state and the boiling temperature of the cathode.

A vacuum arc thruster (VAT) in combination with an innovative inductive energy storage power processing unit (PPU) has been developed for microspacecraft propulsion. The VAT can be operated with a variety of materials, each of which provides ions with a different specific impulse ranging from 1100s for Ta to close to 3000s for Al. Initiation of the arc requires only a few hundred volts due to the innovative 'triggerless' approach in which a conductive layer between the cathode and the anode produces the initial charge carriers needed for plasma production. The initial starting voltage as well as the energy to operate the vacuum arc is generated by a low mass (<300 g) inductive energy storage PPU, which can be controlled with TTL level signals. Calculations have shown that the expected thrust efficiency can reach up to 18µN/W for tungsten. The VAT has been tested at JPL to verify the predicted performance using Ti as cathode material. Thrust measurements with a resolution down to 1µN-s showed thrust/power values of 2.2µN/W, versus a predicted value of 6.7µN/W The large discrepancy is explained by the very non-ideal electrode geometry that was used. With optimized geometry, it is expected that the VAT can achieve ≈12 to 13% overall efficiencies with Ti and W cathodes.

Summary form only given. We report the development of a new type of intense electron source based on vacuum arc technology. The primary application of this source is to pre-ionize gas jets used as z-pinch loads. We have designed and fabricated a 1 kA, 10 kV, 6 cm diameter electron source. The source will be used to ionize a gas puff. Using our 2-color, 8-channel fiber optic interferometer, the gas and the electron density profiles are measured and the ratios of the neutral to the electron densities are determined. Details of the electron source will be reported.