From: Paul
Date: Fri, 01 Mar 2002 17:55:58 +0000
Subject: Re: [TSSP] Ion Cloud Loading
Hi Terry, That sounds like a pretty sensitive test then. And not a hint of frequency shift, even when the nearby 50kV terminal began to give off corona. But its hard to draw any firm conclusion because we don't know in advance whether ionised gas molecules from the DC electrode would be expected to drift over to the vicinity of the RF terminal. >From Bert's comments, it looks like we ought to forget ionisation and focus on streamer loading. I always used to assume that streamers contained a negligible amount of charge, but following last years discussions on the subject, I've had to revise that understanding. The fact that coilers report more effective streamering from larger toploads (at the expense of top- volts) suggests that a large charge reservoir is required, implying in turn that a large amount of charge is going out into the streamers. Scope traces from Electrum show clear indications of this happening. So now I'm quite happy with the idea, qualitatively at least. Quantitatively, we've a long way to go before we can say how long the streamers will be from a given system, I think? Our previous discussions on this reached a point where it would be nice to measure the topload field gradient at the point of breakout, because we decided that this would occur at a certain V/cm. If we could show that breakout was predictable, we could then say with confidence at what variac setting a particular coil would break out. Considering that we can calculate the top volts quite accurately, given a scope trace of the base current, and that E-Tesla can report the max gradient around the topload for a given Vtop, this is something that we ought to be able to do, I think. > Snow Day!! :-)))) I'll have some of that! Hope you're set for a day of interesting experiments. Got any short h/d coils? We could do with some measurements of Les, because it sounds like there are some folk who still need convincing about effective inductance. Measuring the base current and top voltage on a short solenoid (h/d < 1) or flat spiral would demonstrate the point nicely, by giving an inductance noticeably larger than Ldc. Wonder...what's the Fres of that little helical primary you have in the picture? h/d about 0.8 is it? -- Paul Nicholson, --
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.