John Larkin wrote:
On Mon, 05 May 2008 13:40:11 -0700, Joerg
notthisjoergsch at (no spam) removethispacbell.net> wrote:

Hey guys,

Seems like thyratrons have become quite rare these days and SCRs or GTOs
are just too freaking slow. Is there a readily available alternative
that doesn't cost an arm and a leg, meaning under $100? A kilovolt would
be nice and >50A.

How slow is "too freaking"? The Russians still make some nice hydrogen
thyratrons; Los Alamos used to buy them on the sly, maybe still do.


I need to switch within 100nsec or so. Do you remember the Russian
company? Svetlana or Sovtek? Boutique prices? A thyratron would be cool
but it'll have to be something that can still be bought a few years from
now.

You can get 1KV from one or two mosfets, tens of amps in a few ns. A
string of maybe 3 avalanche transistors, like the Zetex SOT-23's, will
output 30 amps or so at 1KV, for short pulses.


In my case a FET would work, that's what I am trying right now. But it
ain't ideal because it should turn off when a certain resonance has run
its course, not when a gate driver tells it to. In a pinch I can try
some nifty feedback for that, and maybe I have to.

I did one gadget that puts 1200 volt pulses into 50 ohms, 2400 volts
into a small capacitive load, with 3 ns pulse width, at up to 500 KHz.
It uses a drift step-recovery diode (another Russian invention) driven
by a couple of 400 volt mosfets.

http://www.highlandtechnology.com/DSS/T220DS.html

It was fun, but we didn't sell many.


Sure looks high-tech but we'd need a good order of magnitude higher PRF.
Do you think it can be spiffed up some more?

Hey guys,

Seems like thyratrons have become quite rare these days and SCRs or GTOs
are just too freaking slow. Is there a readily available alternative
that doesn't cost an arm and a leg, meaning under $100? A kilovolt would
be nice and >50A.

Hey guys,

Seems like thyratrons have become quite rare these days and SCRs or GTOs
are just too freaking slow. Is there a readily available alternative that
doesn't cost an arm and a leg, meaning under $100? A kilovolt would be
nice and >50A.

Supertex has one that can do this current but the problem would be the
lifetime. I believe they quoted 4e11 avalanches. That's high but not
infinite and I'd blow through a set within days.

"Joerg" <notthisjoergsch at (no spam) removethispacbell.net> wrote in message
news:IRMTj.2332$3O7.1972 at (no spam) newssvr19.news.prodigy.net...
Supertex has one that can do this current but the problem would be the
lifetime. I believe they quoted 4e11 avalanches. That's high but not
infinite and I'd blow through a set within days.

Somehow I don't think you'll manage to run a thyratron at 1.5MHz, Joerg.
Check your numbers...!?

(Conservative estimate, 4e11 / (7 days = 0.6M seconds) = 1.5MHz.)

On Mon, 05 May 2008 16:45:33 -0700, Joerg
notthisjoergsch at (no spam) removethispacbell.net> wrote:

John Larkin wrote:
On Mon, 05 May 2008 13:40:11 -0700, Joerg
notthisjoergsch at (no spam) removethispacbell.net> wrote:

Hey guys,

Seems like thyratrons have become quite rare these days and SCRs or GTOs
are just too freaking slow. Is there a readily available alternative
that doesn't cost an arm and a leg, meaning under $100? A kilovolt would
be nice and >50A.
How slow is "too freaking"? The Russians still make some nice hydrogen
thyratrons; Los Alamos used to buy them on the sly, maybe still do.

I need to switch within 100nsec or so. Do you remember the Russian
company? Svetlana or Sovtek? Boutique prices? A thyratron would be cool
but it'll have to be something that can still be bought a few years from
now.


And a thyratron won't be cheap. 1000 volt fets and transistors are
cheap. At 100 ns, I'd thik that a horizontal output transistor might
work.

You can get 1KV from one or two mosfets, tens of amps in a few ns. A
string of maybe 3 avalanche transistors, like the Zetex SOT-23's, will
output 30 amps or so at 1KV, for short pulses.

In my case a FET would work, that's what I am trying right now. But it
ain't ideal because it should turn off when a certain resonance has run
its course, not when a gate driver tells it to. In a pinch I can try
some nifty feedback for that, and maybe I have to.


The Zetex avalanche things would certainly turn off, a lot like an scr
or a tyratron.

I did one gadget that puts 1200 volt pulses into 50 ohms, 2400 volts
into a small capacitive load, with 3 ns pulse width, at up to 500 KHz.
It uses a drift step-recovery diode (another Russian invention) driven
by a couple of 400 volt mosfets.

http://www.highlandtechnology.com/DSS/T220DS.html

It was fun, but we didn't sell many.

Sure looks high-tech but we'd need a good order of magnitude higher PRF.
Do you think it can be spiffed up some more?

PRF of 5 MHz? That excludes most devices, including thyratrons.

On May 5, 1:40 pm, Joerg <notthisjoerg... at (no spam) removethispacbell.net
wrote:
Hey guys,

Seems like thyratrons have become quite rare these days and SCRs or GTOs
are just too freaking slow. Is there a readily available alternative
that doesn't cost an arm and a leg, meaning under $100? A kilovolt would
be nice and >50A.

How about:

http://www.appliedpulsedpower.com/prod/switches.htm

In article <NgKTj.8556$iK6.2263 at (no spam) nlpi069.nbdc.sbc.com>,
Joerg <notthisjoergsch at (no spam) removethispacbell.net> wrote:

Seems like thyratrons have become quite rare these days and SCRs or GTOs
are just too freaking slow. Is there a readily available alternative
that doesn't cost an arm and a leg, meaning under $100? A kilovolt would
be nice and >50A.

Don't know what the prices run (damned priceless websites), but Perkin
Elmer claims they still make them, and the baby of the bunch (HY-2)
would exceed your ratings. The one source one distributor setup probably
won't sit well with you, and the price may not be low enough either.

http://industrial.rell.com/et_Hthyratrons.asp

I used to use something similar to the HY-3192 on Nitrogen lasers, but I
think it was an EG&G part. Suppose it's possible one bought the other in
the couple of decades I haven't been doing that.

Google spits up two websites from China, not my idea of a good source,
especially if your hush-hush application is in your typical medical
field.

On Mon, 05 May 2008 13:40:11 -0700, Joerg
notthisjoergsch at (no spam) removethispacbell.net> wrote:

Hey guys,

Seems like thyratrons have become quite rare these days and SCRs or GTOs
are just too freaking slow. Is there a readily available alternative
that doesn't cost an arm and a leg, meaning under $100? A kilovolt would
be nice and >50A.

How much forward drop can you tolerate while it's on?

What kind of pulse, magnitude and duration will trigger it on?

"Joerg" <notthisjoergsch at (no spam) removethispacbell.net> skrev i en meddelelse
news:NgKTj.8556$iK6.2263 at (no spam) nlpi069.nbdc.sbc.com...
Hey guys,

Seems like thyratrons have become quite rare these days and SCRs or GTOs
are just too freaking slow. Is there a readily available alternative that
doesn't cost an arm and a leg, meaning under $100? A kilovolt would be
nice and >50A.

How about a Cascode with a high-voltage bipolar transistor "on top" and a
low-voltage MOSFET driving the Emitter of the bipolar?

Just remember that while the Bipolar storage time runs, the full collector
current is diverted to the Base so you have to have somewhere to put the
charge. After storage time the whole contraption blocks in about 10-20 ns
so, again, there will be transients. The MOSFET only need to be able to hold
the maximum B-E voltage so it will be cheap and efficient; the Bipolar does
not have to be particularly fast and since the Emitter is cut at turnoff
it's SOA becomes square, right to the VCEmax limit.

Hope that helps.

John Larkin wrote:
On Mon, 05 May 2008 13:40:11 -0700, Joerg
notthisjoergsch at (no spam) removethispacbell.net> wrote:

Hey guys,

Seems like thyratrons have become quite rare these days and SCRs or GTOs
are just too freaking slow. Is there a readily available alternative
that doesn't cost an arm and a leg, meaning under $100? A kilovolt would
be nice and >50A.

How slow is "too freaking"? The Russians still make some nice hydrogen
thyratrons; Los Alamos used to buy them on the sly, maybe still do.


I need to switch within 100nsec or so. Do you remember the Russian
company? Svetlana or Sovtek? Boutique prices? A thyratron would be cool
but it'll have to be something that can still be bought a few years from
now.


You can get 1KV from one or two mosfets, tens of amps in a few ns. A
string of maybe 3 avalanche transistors, like the Zetex SOT-23's, will
output 30 amps or so at 1KV, for short pulses.


In my case a FET would work, that's what I am trying right now. But it
ain't ideal because it should turn off when a certain resonance has run
its course, not when a gate driver tells it to. In a pinch I can try
some nifty feedback for that, and maybe I have to.

I did one gadget that puts 1200 volt pulses into 50 ohms, 2400 volts
into a small capacitive load, with 3 ns pulse width, at up to 500 KHz.
It uses a drift step-recovery diode (another Russian invention) driven
by a couple of 400 volt mosfets.

http://www.highlandtechnology.com/DSS/T220DS.html

It was fun, but we didn't sell many.


Sure looks high-tech but we'd need a good order of magnitude higher PRF.
Do you think it can be spiffed up some more?