lamp, 0; the trigger pulsewidth, t,; and the normalized trigger pulse overvoltage (V, - V,,)/Vd, ... circuits for xenon flashlamps is the reliability whh which the energy ...
116G
IEEETRANIACTIONS
ON ELECTRONDEVICES,
VOL. ED-23, NO. 10, OCTOBER 1976
Trigger Reliability of Xenon Flashlamps WILLIAM F. H U G AND ROBERT C. LEE
Abstract-The probability that a trigger pulse will successfu::ly allow a driver circuit to discharge its energy through a xenm flashlamp is discussed. Based on a classicaldescription of trigger spark formation and propagation statistics, the misflash probubility, P,, is described in terms of the ionization rate in the flashlamp, 0; the trigger pulsewidth, t,; and the normalizedtrigger pulse overvoltage ( V , - V,,)/Vd,. This model was experimentally va lidated for series and parallel trigger circuits over a broad range of trigger pulse voltages, V,, and pulseforming network voltagos, VB.
sufficiently high to allow discharge of the externaldriving circuit. If t , is the widthof the trigger voltage pulse, p the rate atwhich electrons are produced in the electrode gap, in a region and P the probabilityof an electron appearing of the gap where (given sufficient time) it will lead to a trigger spark, then themisflash probability of the flashlamp systemPm defined as the probability that triggering of the lamp will not occur within the timeperiod t,, is given bY Pm = exp (-t,pP). (1)
INTRODUCTION N IMPORTANT criterion in the design of drivbg The average statistical timelag of the trigger spark is decircuits for xenon flashlamps is the reliability whh fined by 7s = 1IpP. which the energy stored in the driving circuit can he p is comprised of two parts p’ p” where 0’ is the amtriggered to discharge through the flashlamp.A numb’3r bient ionization ratein the lamp due to either internally of earlier papers have described the impedance charaz- or externally generated radiation, and p” is the residual teristics of flashlamp discharges [l], [2] the design (If ionization rate due to decay of a preceding flash discharge. driving circuits’[3], [4]and trigger circuits [5] for the!;e The ambientionization rate p’ is not a strong function of flashlamps, and many of the problems related to the interelectrode spacing or ambient radiationlevel for long triggering of flashlamps [6]. None of these papers, however, arc-gap lamps(-22 cm), andp’ E 1 0 7 s-l. For short arctreats the problem of trigger reliability, although this gap lamps, the influence of both interelectrode spacing and problem is of great importancein the design of flashlamp external radiation level can be significant. For short arcsystems. gap lamps located in dark enclosures, the value of p’ is It is common inflashlamp systems to require a reliabi1:iLy often sufficiently small that unreasonably high voltages better than 106 flashes per misflash. Flashlamp triggerir.g are required to produce reliable triggering. For these cases, is provided whena voltage pulseof short duration(
