Magnetic pulse Tesla Coil

From:  Scott Stephens [SMTP:stephens-at-enteract-dot-com]
Sent:  Sunday, April 05, 1998 3:33 AM
To:  tesla-at-pupman-dot-com
Subject:  Re: Magnetic pulse Tesla Coil

At 09:46 PM 3/29/98 -0700, you wrote:

>From: Malcolm Watts <MALCOLM-at-directorate.wnp.ac.nz>
>To: Tesla List <tesla-at-pupman-dot-com>
>Subject: Re: Magnetic pulse Tesla Coil needs megawatt directional co
>Hi Scott,
>           I printed this post off the HV List and carefully read it 
>during the weekend. I have a few comments, the first of which that it 
>is a little difficult to tell exactly where your 10mH inductor fits 
>into the finished item (apart from being an energy store).
Fet switch has source - ground, drain - inductor 1, inductor 2 - +200V

>> From:  Scott Stephens [SMTP:stephens-at-enteract-dot-com]
>> Sent:  Thursday, March 26, 1998 7:52 PM
>> To:  tesla-at-pupman-dot-com
>> Subject:  Magnetic pulse Tesla Coil needs megawatt directional coupler

>> A FET switches a 200 volts across an inductor of 10mH for 2.25 milliseconds
>> (ms); 200V for 2.25ms will charge up to (200V=10mH di/dt) or 45A, and store
>> E=.5LI^2=10J. This 10mH inductor will take (if I'm guesstimating correctly)
>> a slug of volume around 2 cubic inches. Far more compact than the cap.
>The slug is quite incapable of storing that amoung of energy. Most of 
>the energy is stored in the air around the slug. The gap is so large 
>that you would be better off with no core (and non-linearities) at 
>all IMHO.

Realy? Ferrite, with mu-eff=1000? I'll find out.

>> But how do you get the energy out in a form that can 1) drive a tesla
>> primary and 2) not destroy a wimpy FET?
>I am not at all clear on the total setup. Could you post a simple 
>ASCII diagram please? Forget jpgs unless they are uuencoded. My 
>mailer can't handle the various arcane formats that come my way. 

          B 10mH
---||<-    ||B   Hard ferrite           B 10ohm Tesla primary
    |--    ||B   magnetic saturating    B
      |    ||B   switch                 |
      |  core|    80 ohms off           |
     GND     |    2  ohms on           GND

>You can do an awful lot better than 1/3. A HV diode is typically used 
>as the steering element in flyback designs.

Where can I find a HV diode that can handle around 2KV at 2KA!

>> 3) (extra credit) Save or conserve any reflected energy from the Tesla Coil,
>> via the reflected port on the directional coupler. Another directional
>> coupler? A circulator?
>Try an energy recovery winding. An additional benefit is that it can 
>be used to clamp Vds to a specific voltage above Vsupply if the 
>seconday ever becomes unloaded. 

Energy recover? Where & how?

>Perhaps I'm misreading what you are trying to do. A diagram would be 

I've been reading about things like transductors and saturating switches.
Because the magnetic diode's core saturates, at high currents it acts as a
low impedance. After 1/3 to 1/2 the energy get absorbed by the coil, the
reflected  energy returning to the magnetic diode won't have enough energy
to saturate it. Kind of like a high ocean wave can wash over a wall, and
then the wave ripples in a holding pool.