Fourier Analysis of Fast Vacuum Arc Parameters
Vacuum arcs are known for their noisy character: allparameters show more-or-less rapid fluctuations. This is of particularconcern to those who would like to utilize the exceptional properties ofthe vacuum arc plasma in ion sources and other devices. Among theseproperties are the very high degree of ionization and the presence ofmultiply ionized species. The rapid fluctuations are known to beultimately caused by the explosive nature of the perpetual spot ignitionand plasma production. We present a systematic application of the FastFourier Transform to the fluctuating arc voltage and current. Newpossibilities have arisen with the advent of fast digital oscilloscopesand low cost computation of large amounts of data. We show that thespectral power density (SPD) scales with a power law in log-logpresentation for all frequencies below 50 MHz, supporting a fractaldescription of the cathode spot phenomena below this limit. At higherfrequencies, the result is less clear. The fractal behavior seems to becut off as indicated by material dependent fluctuations which are abovethe level found for the power law at lower frequencies. This might beassociated with approaching the region of individual explosive processes,also known as ectons. However, the nonlinear behavior of the SPD containspeaks that are the same for different materials, indicating thatresonances in the measuring circuit play a role, too. Hence, fractalbehavior may be possible for frequencies faster than 50 MHz.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE. Administrator for the National Nuclear SecurityAdministration. Nonproliferation and National Security Program Direction; Russian Foundation for Basic Research Grant # 05-02-16256a
- DOE Contract Number:
- DE-AC02-05CH11231
- OSTI ID:
- 919817
- Report Number(s):
- LBNL-59135; R&D Project: Z2N196; BnR: NN4101010; TRN: US0806501
- Resource Relation:
- Conference: XXIIth International Symposium on Discharges andElectrical Insulation, Matsue, Japan, Sept 24 - 29,2006
- Country of Publication:
- United States
- Language:
- English
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