Can this be done?

Getting crabby in our old age are we ?:-)

Phil is probably cursed with Outhouse Excuse.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

Dear All:

I have a possibly very interesting instrument application that requires the application of a very large ac voltage, about 3 kV p-p anywhere between 20 and 50 GHz--it doesn't much matter where.

The actual power dissipated in the instrument is quite small, so I don't want to use a radar transmitter to drive it. Pulsed operation is fine--duty cycles of at least 1% are needed, though.

Waveguides and striplines for these frequencies are quite small, which leads me to worry about corona, rf arcs, and so on.

I don't mind using vacuum if necessary.

Any ideas for less than about $20k in parts?

Thanks,

Phil Hobbs

Dear All:

I have a possibly very interesting instrument application that requires the application of a very large ac voltage, about 3 kV p-p anywhere between 20 and 50 GHz--it doesn't much matter where.

The actual power dissipated in the instrument is quite small, so I don't want to use a radar transmitter to drive it. Pulsed operation is fine--duty cycles of at least 1% are needed, though.

Waveguides and striplines for these frequencies are quite small, which leads me to worry about corona, rf arcs, and so on.

I don't mind using vacuum if necessary.

Any ideas for less than about $20k in parts?

Thanks,

Phil Hobbs

Dear All:

I have a possibly very interesting instrument application that requires the application of a very large ac voltage, about 3 kV p-p anywhere between 20 and 50 GHz--it doesn't much matter where.

The actual power dissipated in the instrument is quite small, so I don't want to use a radar transmitter to drive it. Pulsed operation is fine--duty cycles of at least 1% are needed, though.

Waveguides and striplines for these frequencies are quite small, which leads me to worry about corona, rf arcs, and so on.

I don't mind using vacuum if necessary.

Any ideas for less than about $20k in parts?

Thanks,

Phil Hobbs

On Fri, 01 Apr 2005 19:36:47 -0500, Phil Hobbs wroth:

I *was* going to tell you *exactly* how to do it for about 100 dollars but I changed my mind when you posted *exactly* the same message *three* times.

Jim

the

20

want

leads

times.

I'll give ya about 200 dollars if you'll tell me, and, I'll only ask once.

Bob

Nah, no such excuse, I use Mozilla--it turned out to be a SMTP relay problem. I was sending a bcc: to my email account, which the relay complained about, but silently sent the NG posting along each time.

I deeply apologize that I have inexcusably reduced the wisdom-to-noise ratio of this august NG so much--we almost never get repetitive messages here. ;)

Doing this deep in the guts of a magnetron is a good idea, though it might be hard to get the resulting soft X-rays out of the cavity. (The X-rays are what I'm interested in--details must be left vague at present.) How big a voltage swing do you think I can get in, e.g., an evacuated waveguide resonator before it turns to lava?

Cheers,

Phil Hobbs

Nah, he's not even running WinBlows (OS/2). From his headers:

User-Agent: Mozilla/5.0 (OS/2; U; Warp 4.5; en-US; rv:1.7) Gecko/20040617

--
  Keith

times.

That's possible but I've had to uneccesarily resend messages ( not using OE ) when the news server doesn't acknowledge the message sent. Probably happens when the news server's a bit too busy.

Graham

requires the

between 20

I don't want

fine--duty

which leads

dollars

*three* times.

relay problem.

complained about,

wisdom-to-noise ratio

here. ;)

it might be

X-rays are

How soft is soft? Would a beryllium, boron or diamond window be transparent enough?

waveguide

X-rays

post?

beyond

there is

magnetrons.

The 30GHz radiation is probably exciting a plasma, and the X-rays could come from free electrons encountering positive ions, and dropping into an orbit close to the nucleus, though they could also arise from energetic electrons hitting the walls of the chamber.

The volume may be "evacuated" but it isn't empty, and the residual gas molecules are the source of the plasma. Try searching on "electron cyclotron resonance" for a bit more detail on what might be going on.

----------- Bill Sloman, Nijmegen

want

times.

What is a soft X-ray? What is the relationship between these soft X-rays and the 30 GHz (or whatever) radiation you mentioned in the original post?

I always thought that X-rays were gamma rays with frequencies far beyond the optical. 30 GHz is far below the optical, obviously. No doubt there is something I'm missing, possibly due to my ignorance concerning magnetrons.

-- Mac

wow,

I think I would start with a "conventional" high power Tx then think about a cavity or waveguide based impedance transformer (like a 1/4 wave line) that steps up the voltage (and down the current).

Mark

I'd love to be more specific, but it's a partly-baked idea at present--it doesn't work, I'll post it so we can all have a good laugh, and if it does work, you can read about it in Nature. Odds are probably

60% laugh, 20% inconclusive, 20% important. It's a way to make a bright soft X-ray source fit on a tabletop, instead of requiring a synchrotron. Early simulations are encouraging, but they rather require this big E field at high frequency....

So how big a signal can a 30-GHz waveguide (say) take before it starts arcing in vacuum? Probably it'll be the wall dividing the resonator from the feeder that will melt first, being thinner. My machine shop will love being asked for a platinum-plated tungsten waveguide...

Cheers,

Phil Hobbs

OK, Pozar page 201. At 10 GHz, a typical air-filled waveguide can handle about 2.5 MW, e-field peaking around 3e6 v/m. Power capacity is inverse with frequency, but max e-field stays the same (it's just the air breakdown limit.) He recommends a 2:1 safety factor from that. One can improve things by pressurizing with dry gas, or filling with SF6 at atmospheric pressure. The medical xray people who make microwave-pumped linacs like SF6 so they can make their exit windows very thin.

Vacuum is interesting; look up the Farnsworth Multipactor effect. It's caused some serious problems in satellites.

You will do more than publish a paper if this works; the lithography guys will be all over you. I can introduce you to some folks at Cymer.

John

Seen this? Not the same, of course, but weird and interesting.

"The use of the COOL-X in practical applications will challenge the user's imagination!"

That's funny!

John

Brilliant, thanks.

The litho application had crossed our minds. I'm not sure we can go quite that long in wavelength (litho wants ~100 eV, I think, whereas we'll probably start out at around 1 keV), but we're certainly going to try, once we get it working at all.

I'll go calculate some waveguide septa. Tally-ho.

Cheers,

Phil Hobbs

Calculate the current needed to drive ANY amount of capacitance at all at 50 GHz, and you will find that the power needed is insanely enormous.

UNLESS you can use some sort of precise tuning or matching.

The problem sounds extremely ugly.

--
Many thanks,

Don Lancaster
Synergetics   3860 West First Street  Box 809  Thatcher, AZ 85552
voice: (928)428-4073 email: don@tinaja.com

Please visit my GURU's LAIR web site at http://www.tinaja.com

That's not a huge field inside a waveguide or a resonant cavity.

John