Trichel: central claims
The folder holds a single document, a 2010 conference paper by Sattari, Castle and Adamiak (University of Western Ontario), "Numerical Simulation of Trichel Pulses in a Negative Corona Discharge in Air". Its text is fully readable (15 pages, no OCR; equations and figures checked on page images). No source gap, but note that nothing written by G. W. Trichel himself is in the folder, so any statement about his 1938 work rests on this paper's description of it [read: p.2] or on [memory].
- A negative point-to-plane corona in air emits a regular train of short current pulses (Trichel pulses), which exist only in electronegative gases and only in a limited voltage range. (Background claim quoted from earlier literature [read: p.1-2]. The paper supports it only by citation: it says Loeb, Kip and Hudson (Phys. Rev. 60, 714, 1941) 'confirmed' that the pulses exist only in electronegative gases and that nitrogen gives continuous current without pulses [read: p.1-2]; no gases, purities or data are given in the paper, and the 1941 paper itself has not been read.)
- The pulsing arises from space-charge dynamics: an avalanche near the needle tip creates electron and positive-ion clouds, the positive ions are absorbed by the needle within nanoseconds and switch ionization off, and the slowly drifting negative ions (mobility 2e-4 m2/Vs) must clear away before the tip field recovers to threshold, which sets the multi-microsecond period. (Presented as Trichel's 1938 idea, reproduced numerically by the authors. Note that the authors' own description of Trichel's account gives the positive-ion cloud the central role: it shields the field near the point and, drifting into the point, narrows the enhanced-field region until ionization stops [read: p.1-2]. The emphasis on negative-ion clearing as the period-setting step is not attributed to Trichel in the paper.)
- A 2D finite-element plus flux-corrected-transport (FEM-FCT) model with three species (electrons, positive ions, negative ions) reproduces a regular pulse sequence, including a small post-pulse after each main pulse and an unusually large, delayed first pulse formed in charge-free space (25 to 37 mA against about 2 mA steady). The authors claim this is the first successful 2D FEM-FCT simulation of Trichel pulses at several voltages. Prior art as they list it [read: p.2]: Morrow 1985 (1D, first pulse only), Napartovich 1997 (1.5D, pulse trains in dry air, gaps under 1 cm), MacAlpine and Yim 1995 and Soria 2007 (particle-in-cell, pure oxygen), so the priority claim is checkable against that literature.
- Pulse repetition frequency rises with applied negative voltage; the simulated average period falls from 11.33 us at -7 kV to 2.46 us at -11 kV, following the trend of Lama and Gallo's 1974 measurements (21.85 us to 5.07 us).
- The simulated periods are about half the measured ones (ratios 0.52, 0.47, 0.37, 0.49), a discrepancy the authors attribute, without a tested cause, to approximations in the numerical technique.
Caveats recorded by the fact-finder from the deep read (no verdicts): the paper gives no rise time or width for its simulated pulses; the printed ionization formula and two continuity equations appear inconsistent as written; the experimental geometry and external resistance are not stated; several constants come from an unpublished 1997 contractor report for ABB.
QE revision (introduction pp.1-3 re-read): the paper's abstract says pulse frequency 'decreases' with voltage while its results show the period falling; the rise time is quoted as 1.3 ns (p.1) and 1.5 ns (p.2); the Trichel reference (ref. 2) is printed with the word 'positive' in its title. Empirical laws attributed to Trichel [read: p.1]: frequency varies linearly with corona current, inversely with tip radius at fixed current, and not with gap length.