From: Marco.Denicolai@tellabs.com
Date: Wed, 5 May 2004 09:30:27 +0300
Subject: [TSSP] Measuring Thor (was: Modeling with ANSOFT)
Hi Bert, > The distributed liquid divider you've described sounds very > interesting! Do you recall which book described this device? After a long search I finally found out were my PDF was from. Check http://www.fieldp.com/cpa/cpa.html Check near the end of Chapter 9. There is a picture (figure 9.54) and a short explanation of this divider. That could be built and hanged from the roof on the top of Thor's toroid, to touch it. My only worry is, will the grid be sensible to the Efield? On the other hand, it would be unusable if it had to be shielded. Any opinion? > Malcolm's suggestion of using a chain of capacitors down the > center of the resonator is excellent, and I seem to recall that Greg > Leyh tried this approach using a chain of ceramic (doorknob?) > capacitors to add bulk C to a small topload. I am afraid, going that way, to get into the same business of building a (traditional) compensated probe. That means PSpice, etc. With the difference that, this time, the voltage to be measured ought to be about 600 kV. One thing to consider is the strong Efield Thor generates. It seems to me that any measuring device placed in that environment has to be shielded (and shield grounded) to perform a meaningful measurement. Expecially if going to measure a tiny charge on the bottom of a capacitor chain. My last month measurements were a family of curves type Number_of_bangs = f(d,V) where: Number_of_bangs = N. of bangs to reach a grounded stick d = distance of the stick V = capacitor charging voltage (bang energy) I collected a nice data set, showing roughly normal distribution (somebody argued I should have looked for Weibull distribution). It is also possible to see how the Efield requirement for the leader to proceed bends over 1 m distance. This means that, after 1 m is reached, the same amount of bangs produces a longer jump. The "stick reached" condition was detected with a Pearson current probe measuring the stick current to ground. The hit condition was set to a current of at least 3 A. Sadly the probe was capturing also a sensible fraction of the Efield. My understanding of the problem is that the stick was capturing also the Efield and creating a current to ground. In my next setup: - only the stick top (a 60 mm sphere) is going to be unshielded - the sphere must be grounded through the central conductor of a shielded cable - the cable must be protected (insulated) by, say, a PVC tube - the shield of the cable is grounded at its bottom - the central conductor is passed through the Pearson probe and grounded at the bottom too - the probe is contained in a shielded and grounded case - the probe shielded cable (to the O-scope) its grounded at both sides - the Thor toroid protuberance is substituted by a 25 mm stainless steel sphere, easier to model and reproduce This way I hope to have only the top ball immersed in the Efield and the rest of the stick (and the probe) shielded from it. What is your opinion? Best Regards ----------------------------------------- ============================================================ 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.