RKA: basis for a nasty weapon

[Dr Mordrid]

Found this abstract today while digging around for info on high powered microwave weaponry;

This paper addresses the development of the relativistic klystron amplifier (RKA) which is a high power microwave (HPM) source. This source was invented at the Naval Research Laboratory and developed during the last ten years. The present RKA has a 50 db gain and is operated at a frequency of 1.3 GHz with a peak output power > 10 GW and with an efficiency > 35%. However this HPM amplifier is rather large and expensive for many applications. Moreover, extending the frequency of the NRL RKA to frequencies above 3.5 GHz was not fully successful. Recently, it was suggested that incorporation of two modifications to the RKA technology should improve the capabilities of the present NRL HPM source by orders of magnitude and extend the operational frequency to X-band (8.0–12.0 ghz). These improvements enhance the potential for successful and effective military and civilian applications. These modifications are described.

10 GIGA watts now and that could be extended by an orders of magnitude?

That's one helluva microwave oven

Dr. Mordrid

[Marshmallowman]

10GW for how many micro seconds tho, theses are pulse devices no continuous.

They increase the power output by narrowing the pulse, but that is one powerfull pulse.

Your microwave popcorn would go from, unpopped to its atomic components in less than 0.0000000001 of a second

[Jon P. Inghram]

Heh, with a 50 dB gain it needs 100 kilowatts of input power to hit 10 gigawatts...

NEXRAD radars run at 2.7 to 3 GHz and put out around 1.56 kW average, 750 kW peak power.

[Dr Mordrid]

100 kw is no problem. Ever hear of the portable turbine/superconducting power sources the USAF is working on for airborn MW weaponry? Each generator is the size of a beer keg, can produce up to 5 MW continuous power and the only time limitation is how much fuel you can carry.

Dr. Mordrid

[Marshmallowman]

Superconductors are a tricky thing to work with, when I see it I'll believe it.

eg you temperature goes up few degrees or field stength or voltage/current goes out of spec and your superconductor no longer superconducts, those mega amps/volts that were circulating with no resistance now start to "resists" and then you get a loud Boom and a motlen blob

Actually 100kw's is not "that much", well within what a ground vehicle or naval vessle could produce, and proably a few aircraft

[Dr Mordrid]

Worked with superconducting magnets many times in the portable MRI systems that they mount in semi trailers.

These are highly reliable and the cooling tech could be easily ported to the USAF application, especially if the article I read is correct about the generator being the size of a beer keg. MRI magnets are just a tad bigger and deliver ~1.5-7 Tesla;





Dr. Mordrid

[Marshmallowman]

The stuff you worked with would all be using nice consistant and controlled way, and not even trying to push the superconducting envelope...and its a pretty tight envelope.

You make superconducter that runs at higher temperatures and the em field or current it can support drops drasticly. You push it one way and you lose out another way.
I have no doubt they can do it, I just don't want stand next to it

[Dr Mordrid]

You never worked in one of those trailers. The ambient temp. was anything but consistant, but the MRI systems, including the magnets, handled it quite nicely. They not only can do it, but they do it quite well. In fact the MRI's magnets gave us less trouble than the AC unit used to cool the trailer

Example: the medical "clinic" we go to is a satellite of Henry Ford Hospital in Detroit. This place has outpatient surgery, up to 3 day admissions, a 24 hour ER and every kind of clinic you can think of, so it's quite a nice place and well equipped.

They have had an MRI trailer parked ouside their ER for at least 5 years, and they run it 24/7/365. One day I asked the tech about the uptime. He said about 85-90%, and believe me that's good even compared to a CT scanner....and they aren't superconducting.

Much of the downtime for one of these things is a topping off of the Helium tank and checking the systems every few weeks.

Dr. Mordrid

[Marshmallowman]

I may be wrong here, but the superconductors were used in the detector and/or shileding ? eg low current high sensitivity(quite easy to keep within the envelope)

With (compact)power generation you would be trying to maximise the current in the superconducting part (eg power ouput) while that can be done quite well, however it is susceptible (ala boom) to excesive currents/temperature and emf fileds. So they either run on the edge and keep well away from it, ot they build in redundant back for the cooling, and very good shielding as well as very good load control(pretty hard with a pulsed device)

Think about 100amps no resitance....oops went out spec for a micro second, in that micro second it started to warm up becasue it got some resistance, and since it warmed up .1 C the superconuction decrease even more...catostrophic failure.

It can be done it just the backup systems to do safely tend negate the original size reduction possible becasue of superconductors.

Superconductors in general for detectors/shielding and "low power" applications is pretty much well etsablished though.

I don't think they need such a power source for the above device , a lot of cars easily produce more tan 100kw of power.

Though I am interested in the "power keg" , they are obviuosly progressing(i still don't want to stand next to it ) Do you have any links?

[Dr Mordrid]

The superconducting magnet in an MRI is used to "flip" the orientation of every water molecule in a persons body into polar alignment. They are continuous duty devices and at 1.5-7 Tesla their field strength is HUGE (sunspots = 8-12 Tesla).

Separate coils are used for applying an RF pulse and picking up the return signal to produce the image. Shielding is done on a room basis, meaning the walls, floor and ceiling. Theoretically everything in the room has to be non-magnetic or held down, but you know how that goes

I've heard of one pulling the tines off a forklift into an MRI suite from the hallway and seriously injuring a guy doing maintenance on the system. Several people have been seriously injured or killed by objects that became airborn via MRI magnets: ladders, laundry carts, mop buckets, stretchers, chairs, IV poles, medical instruments, clothing clasps (yes, bra snaps) all can become MRIFO's.

The USAF "toy";

http://www.commondreams.org/cgi-bin/print.cgi?file=/headlines04/1005-20.htm

And that weight is likely the turbine + colling hardware + fuel etc. and not just the "can".

Dr. Mordrid

[Marshmallowman]

I should of remembered that stuff about MRI

Ok it certianly seems doable,

He said the proposed system could be expensive to maintain and might require multiple backup systems.

I am stil not going stand next to it

oh, and the generaor is the size of a beer keg...and the turbine is how big

Probably still quite a while away though.

[Dilitante1]

instant popcorn! no more Jiffy pop

[Dr Mordrid]

Just for the helluvit, this is what can happen when you bring metal equipment or furnishings near an MRI suite;



Remember; these things got where they are by air mail

Dr. Mordrid

[Tjalfe]

Heh, with a 50 dB gain it needs 100 kilowatts of input power to hit 10 gigawatts...

so it can produce 100 times the output power than what is supplied to it.. impressive. sounds like our energy problems are solved

[Jon P. Inghram]

Yep, that's how amplifiers work, just stick some RF in one end and it comes out stronger from the other end!