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Re: thyratron
Subject: Re: thyratron
Date: Tue, 17 Jun 1997 01:27:30 -0400 (EDT)
From: richard hull <rhull-at-richmond.infi-dot-net>
To: Tesla List <tesla-at-pupman-dot-com>
At 01:19 AM 6/13/97 -0500, you wrote:
>Subject: Re: RE- Secondary wire & insu
> Date: Thu, 12 Jun 1997 17:40:46 -0700 (PDT)
> From: "Edward V. Phillips" <ed-at-alumni.caltech.edu>
> To: tesla-at-pupman-dot-com
>
>
>"I just mailed it out last night.
>
>RG-214 dual braid coax 6 turns (can be five) about 25uh. 3" tall 12.5"
>diameter. Capacitor is .0068
>
>Richard Hull, TCBOR"
>Richard:
> I saw that one. What I really want to know (and should
>have been more explicit about) is the circuit for the thyratron
>switch, and in particular if you've rigged things so that the
>current through it doesn't want to "go negative". If you
>described that I REALLY missed it!
>Thanks,
>Ed
>
>Ed,
The key is to release the grid drive way before the negative excursion
of
the first current peak's first zero crossing. Thus for a 500KHZ system
that
means a 1 micro second grid pulse. The tube turns off so completely
that
there is just no real reverse current in the tube. Although I am sure a
few
nanoseconds worth might exist as the coil's primary reverses polarity,
but
this slams the tube off. I have seen no detrimental results from the
circuit. I keep a close eye on the tube for sparkles of cathode
material
being ripped away. So far I have seen none and observed no reverse
current
on the wideband pearson C.T.
In the old days they used a vacuum diode to limit reversal problems and
placed it across the thyratron in reverse. I have no such circuit or
nicety.
Richard Hull, TCBOR
Richard