Unipolar arc erosion rates measured using an ion beam activation technique

Read, P.M.; Asher, J.; Conlon, Thomas; Sofield, C.J.

doi:10.1016/0022-3115(81)90192-6

Cited by 6 publications

(4 citation statements)

References 15 publications

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“…The surface layer activation technique was developed by the Nuclear Physics Division at the AERE Harwell Laboratory [17][18][19][20] and has been used in many applications, including measuring component wear in internal combustion engines 18 and turbines, 21 corrosion in chemical plants, 22 unipolar arcing damage in tokomaks, 23 and wear in prosthetic hip joints. 20 It has also been employed to measure the erosion rates of tungsten cathodes, copper anodes, and boron nitride backplates in magnetoplasmadynamic thrusters [24][25][26] and, as noted above, molybdenum keeper electrodes in ion thrusters.…”

Section: The Surface Layer Activation Techniquementioning

confidence: 99%

Use of an accelerated testing method to characterize inner front pole cover erosion in a high power Hall thruster

Polk

Lobbia

Barriault

et al. 2021

Journal of Applied Physics

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Erosion characteristics on the cover of the inner front pole in a 12.5 kW Hall thruster were measured over a wide range of operating conditions in tests of 6–14 h duration using an accelerated test method and a very sensitive, radioactive tracer-based erosion diagnostic. The operating points included the nominal 300–600 V conditions on a constant 20.8 A throttle curve and conditions at other currents spanning the throttling envelope and with varying magnetic field strength, facility pressure, and discharge voltage oscillation amplitude. Surprisingly, the results show that the highest wear rates occur at the lowest voltages and currents. The wear rates were insensitive to discharge voltage ripple but increased monotonically with magnetic field strength, particularly near the inner radius of the pole cover. The inner region was also sensitive to facility pressure, showing lower rates at a higher pressure level. Separate experiments in which the energy distributions of ions generated by the hollow cathode were measured suggest that the cathode plume may be a source of energetic ions responsible for some of the erosion trends, in addition to ions originating in the thruster plume.

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Section: The Surface Layer Activation Techniquementioning

confidence: 99%

Use of an accelerated testing method to characterize inner front pole cover erosion in a high power Hall thruster

Polk

Lobbia

Barriault

et al. 2021

Journal of Applied Physics

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“…These arcs lasted about 7 0 p and a total charge of about 850 pC was transferred; values similar to those recently measured for arcs in DITE. 5 Several batches of three Ti cathodes were studied: one batch activated in air (I), one batch activated in v m u o (2), one batch activated over half its area in air, the other half being masked from the activating proton beam (3), one batch irradiated in air for a proton beam energy below that required to produce the active 48V isotope (4), and a batch of unirradiated specimens (5). Prior to the tests the samples were vapour degreased with trichloroethylene, swilled in distilled water and vacuum baked for two hours at a pressure of 10-6 torr and a temperature of 600°C.…”

Section: Experiments and Observationsmentioning

confidence: 99%

“…Again batches of three samples suitable for cathodes in the laboratory arcing rig were produced as follows: in air (l), in uucuo (2), in air at a proton energy below the threshold for s6C0 production (3), and some blank specimens, i.e. unirradiated (4). In addition, two blank specimens were irradiated with 200 keV N+ ions to a dose of 1015 ions/cm2 The results of the arcing tests on these specimens are shown in Figure 6.…”

Section: Experiments and Observationsmentioning

confidence: 99%

The effect of penetrating radiation on the initiation of unipolar arcs

1983

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The rate of unipolar arcing to a Ti sample which had been activated by 7 MeV protons impinging on part of it after passing through an NZ atmosphere has been observed t o be considerably reduced compared t o the rate of arcing on the unirradiated part of the sample. This observation, first made in the DITE Tokamak, was confirmed by laboratory arcing studies on Ti and stainless steel specimens. It has been shown to be the consequence of irradiation through a gaseous atmosphere and to be avoidable by irradiation in uacuo.The mechansim for this effect has been explored and appears to arise from secondary electrons produced in the gaseous atmosphere by the incident protons which then cause radiation damage in arc-initiating insulating inclusions in the metal samples.The sensitivity of these inclusions to radiation damage and the consequent suppression of their role in arc initiation has obvious implications for arcing in Tokamaks.Other technological areas which involve electrical breakdown phenomena may also be amenable to beneficial treatment by irradiation with penetrating ions.

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“…Selected radioisotopes produced from natural molybdenum having proper half-lives, intense c-lines with proper c-energies are listed in Table 1. Some of these have already been used by other authors for wear measurements with TLA [13][14][15][16]. The goal of this study was to determine the production parameters for these radioisotopes in order to prove their applicability as radioactive wear tracers.…”

Section: Introductionmentioning

confidence: 99%