From: Paul
Date: Fri, 24 May 2002 08:14:13 +0100
Subject: Re: [TSSP] Topload breakout potentials
Malcolm Watts wrote: > We are talking about direct connection without disturbing the > external fields aren't we? Oh yes. > Somehow, we have to construct a probe which can go up the centre of > the coil Yes, then the coil will shield the external field from the divider, and we just have to shield the divider from the coil! > (we can quantify any > disturbance it might cause through low power measured comparisons) Up to a point. For example a central divider column will register a mixture of the topvolts and the coil's voltage distribution. The 'mix' will be fixed by the geometry below breakout and thus the topvolts can be calibrated. But above breakout, all is lost unless the divider can be shielded. The performance metric is the ratio between the divider output due to conduction current entering from the topload, verses the divider output due to displacement currents induced by the E-field. For any given divider design we can measure this metric at small signal, and thus assign an error estimate to subsequent topvolts readings. But we can certainly allow for the fixed C of the divider loading the top, so that's not a problem unless the loading is so much that it upsets the breakout behaviour. Anyway, despite the apparent difficulties I don't think we should be too intimidated by this. After all, even a fairly rough and ready divider will give us some sort of result. As we study the data from it we'll begin to notice limitations, but it represents a starting point and it gets things moving. -- Paul Nicholson, --
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.