From: Marco.Denicolai@tellabs.com
Date: Tue, 5 Nov 2002 08:56:44 +0200
Subject: RE: [TSSP] Top Voltage
Paul and Bert, The ionisation and attachment coefficients (alpha and eta) are general quantities that, for instance, are mentioned also in http://elect.mrt.ac.lk/HV_Chap1.pdf It is possible that their calculation is not relevant to the Gallimberti paper and, therefore, is not described there. More, Gallimberti seems to have spent years developing "simplified" models. Shouldn't we start from one of his _latest_ models? Anyway...I'll try to locate the 1972 paper. Hopefully the Nstat will get clear. Best Regards > -----Original Message----- > From: bert.hickman@aquila.net [mailto:bert.hickman@aquila.net] > Sent: 5. marraskuuta 2002 07:36 > To: tssp@abelian.demon.co.uk > Subject: Re: [TSSP] Top Voltage > > > Hi Paul, > > Unfortunately, after much searching, I've determined that the earlier > papers are not available since they either go too far back or are in > journals not included in the corporate IEEE and Journals of Physics > databases I have access to. Perhaps Marco may have better luck at the > university. > > I've located a number of other pertinent appearing papers - > starting to > go through them now. There's really quite a lot of material > out there... > :^) > > Best regards, > > -- Bert -- > -- > Bert Hickman > Stoneridge Engineering > "Electromagically" (TM) Shrunken Coins! > http://www.teslamania.com > > Paul wrote: > > Hi All, > > > > During a busy week I've had just a little time to look at > > the paper > > > > > >>AUTHOR: Bondiou, A.; Gallimberti, I. > >>TITLE: Theoretical modelling of the development of the positive > >> spark in long gaps > >>SOURCE: Journal of Physics D (Applied Physics), vol.27, no.6, > > > > p. 1252-66 > > > > which Bert kindly provided for me. > > > > At first glance, this paper provides a good starting point for > > constructing a model of breakout. It provides a flow chart of > > the modelling, along with the relevant equations for each step. > > > > I thought I might have a bash at computing the first 'step' > > of the model, which is to determine the streamer inception > > voltage. > > > > For streamer inception, the charge within the streamer head > > must exceed a minimum stability charge. Below this minimum > > charge, there is insufficient field around the head to cause > > the head to extend by drawing further avalanches to it. > > > > Above the minimum charge, streamer development progresses. > > > > The first step is to compute this streamer stability charge > > and the terminal voltage at which the streamer head exceeds > > this minimum. > > > > The formula given for the streamer head charge is an integral > > over the active region which involves ionisation and attachment > > coefficients (alpha and eta), or alternatively, by a simplified > > model, coefficients (beta and mu) for energy loss and gain. > > > > The paper refers to earlier work for the values of these > > coefficients, as well as the stability charge Nstab (which is > > a function of the background (geometric) field). > > > > Bert, are any of these earlier papers available? If we > > could calculate this, it would move us beyond the use of > > a fixed field (eg 30kV/cm) as a threshold. > > > > We need the ionisation and attachment coefficients, and > > the streamer stability charge, all as functions of the field > > strength. It isn't quite clear to me which of the earlier papers > > actually provide these functions. > > > > The paper gives an example of streamer onset using long rod-plane > > gap, of 800kV. If I compute this using north/tssp 30kV/cm surface > > field, the value is nearer 300kV. Hence a proper computation > > of streamer onset may move us nearer to measured values. > > -- > > Paul Nicholson, > > -- > > > > > > > > ============================================================ The information contained in this message may be privileged and confidential and protected from disclosure. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient, you are hereby notified that any reproduction, dissemination or distribution of this communication is strictly prohibited. If you have received this communication in error, please notify us immediately by replying to the message and deleting it from your computer. Thank you. Tellabs ============================================================
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.