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Logic Level MOSFET

J

Joerg

Jan 1, 1970
0
John said:
I think they expect net fusion energy greater than the laser light
input to the target chamber, but that's far from wall-plug break-even.
As they like to say, they expect about as much fusion energy as there
are calories in a jelly donut.

That's what I heard a chemical engineer say before an experiment.
"Statisticaly there will never really be more than one or two going
off". Then ... KABLAM!

After the smoke had wafted off and the coughing eased up we could see
that everyone was dirty but ok. Even the supposedly unbreakable blast
plate lay there on the floor in shards.
 
L

LVMarc

Jan 1, 1970
0
John said:
NIF has 192 beam lines, each a big pipe full of flashtube pumped
amplifiers. The input to each line is a fiberoptic blip of light at
about 1100 nm; it makes 4 free-space passes through the slabs and
emerges at the and, goes through a tripler, and enters the target
chamber as UV. It all converges on a little gold capsule full of
tritium and stuff.

The beamlines are grouped as 48 quads. In the MOR, the master
oscillator room, there's a master laser that feeds 48 of our modulator
boxes. Each box has a 4 gs/s 16-bit arb and a programmable 1 ps
resolution square-pulse generator, and a bunch of bias stuff. We drive
a 2-stage Mach-Zehnder optical modulator, one stage being a square
pulse gate and the other being an arbitrary waveform. The output of
our boxes gets optically amplified and is then run to the 192 big amps
out on the floor. The idea is to precisely shape the waveforms of the
light that ultimately whacks the target with about 1.5 MJ of UV.

What's a little unusual about the arbs is that they are triggered and
generate their one-shot waveform with a couple picoseconds of jitter.
The whole system - arbs, modulator, downstream amps - is fairly
nonlinear, so they fire the MOR stuff 24/7, at 960 Hz, and sample
downstream optical signals, and close a loop on the desired waveforms.
So everything up the the main flashtubes is run and tweaked
continuously.

The arb is done by sheer brute force. There are 140 gaussian impulse
generators, each a delay circuit, a gaasfet, and a shaping network.
Each is dac programmed for amplitude and time of peak, and all 140 are
fired at 250 ps intervals and summed. If we had to do it again, we'd
probably go with a ring of staggered-triggered medium-fast dacs,
mux'ed somehow.

We also generate some 90 ps wide fiducual pulses, for aligning shot
diagnostics.

The math of summing gaussian impulses is interesting. It has analogies
to making arbitrary shapes from power or Fourier series.

John
John,

Nice project and concise description! Did you get to build the multiple
systems as well conjure the designs of the prototypes? Great project
for high speed triggering, synchoronzation and general electronics fun.

Best regards

Marc Popek
 
J

John Larkin

Jan 1, 1970
0
John,

Nice project and concise description! Did you get to build the multiple
systems as well conjure the designs of the prototypes? Great project
for high speed triggering, synchoronzation and general electronics fun.

We collaborated with the NIF people on the architectural design of the
modulators and the timing system, and we did the detail circuit
design. We built about 55 modulator chassis and about 250 VME timing
modules.

These are the timing modules. Each one receives a master OC-3 fiber
timing signal that's distributed all over the site. We phaselock to it
and decode data packets that tell each channel when to fire.

http://www.highlandtechnology.com/DSS/V880DS.html

Note the crystal oscillator mounted on tiny springs.

The head-end system that generates the master optical data streams was
done by Timing Solutions.

These Big Science projects are interesting and can be profitable,
bacause they buy a lot of stuff. The problem is that they only happen
once in a while and once they're built, that's it... no more business.
It's like crossing a river on the backs of the alligators. The other
problem is that sometimes they get cancelled for political reasons,
like the Supercollider and AVLIS.

John
 
J

JosephKK

Jan 1, 1970
0
Joerg [email protected] posted to
sci.electronics.design:
That's what I heard a chemical engineer say before an experiment.
"Statisticaly there will never really be more than one or two going
off". Then ... KABLAM!

After the smoke had wafted off and the coughing eased up we could
see that everyone was dirty but ok. Even the supposedly unbreakable
blast plate lay there on the floor in shards.

Yep, Nemisis came along on his rounds after Hubris visited.
 
J

Joerg

Jan 1, 1970
0
JosephKK said:
Joerg [email protected] posted to
sci.electronics.design:


Yep, Nemisis came along on his rounds after Hubris visited.

The other one was a chemist just before he got his masters. "We had a
minor mishap" ... "What happened?" ... "Well, remember my lab?" ...
"Yeah." ... "It's a black hole now. Even the door blew out."
 
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