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video of magnetron operation

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Ash Small

Wed Apr 06 2011, 04:26PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

This is a quote from Doug Coulter's article on microwave ion sources:

"Pyrex has a heck of a lot of loss at 2.45 GHz"

I know he tried pyrex first and didn't get very good results. His results with quartz were much better.

Other articles I've read say pretty much the same thing.

Marko

Wed Apr 06 2011, 04:51PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Steve McConner wrote ...

You can really see the inverse square law at work, as the fluorescent tube doesn't light until it gets very close. But hopefully there's enough power left to accidentally microwave his testes and earn him a Darwin.

I highly doubt that is possible unless one holds a magnetron at 10cm from their groin for several minutes, which would also likely cause enormous pain in process.
Even if they were standing in front of the apparatus at the same distance as in the video, I suspect the received intensity would be much smaller than one receives by sunbathing in the noon. For some reason still people think that 1kW/m^2 is much scarier in microwave spectrum than in visible.

Touching a MOT powered apparatus with fluorescent tube in bare hand seems like a significant risk of death in my opinion though.

Marko

Ash Small

Wed Apr 06 2011, 05:12PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

I'll re-post this link on microwave burns here. Exposure for even a few seconds can result in permanent nerve damage, etc.:

klugesmith

Wed Apr 06 2011, 08:08PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

As with x-rays, there are reasonably safe and unsafe exposure levels.
Caution is advised for people who don't know what they are doing.
As Marko warns, don't overlook the possibility of unexpected electrical conduction in sealed vessels of low-pressure gas. Touching the MOT secondary or magnetron cathode connection with a metal terminal of fluorescent tube, while your hand touches the other, could end very very badly.

In the USA, per FDA title 21, the maximum allowable leakage from a consumer microwave oven is 5 mW/cm^2, measured 5 cm from the oven. That intensity is deemed not to create a hazard from heating of tissue - even if you put your eye there. It's 50 watts/m^2; about 5% of the intensity of sunlight that Marko pointed out. If 1200 watts of microwave power were radiated isotropically into a half-sphere solid angle, the power density would fall to the regulatory 5 mW/cm^2 at a distance of 2 meters. Don't overlook the possibility of exposed magentron antennas creating a beam pattern with an intense lobe in the direction of your eyes or your gonads -- unless you understand microwave antennas!

I think this guy (Neon John) is not being stupid in the upper-left picture at

with disclaimer in lower left corner. He knows, quantitatively, what he's willing to expose his hand to. It's probably stupid to just say "this is safe", because uninformed kids may attempt to duplicate it, and not understand when their procedural changes make it unsafe.

Microwave heaters intended for living human tissue are called diathermy machines.
"The present informal position of the Food and Drug Administration is that a diathermy device should be capable of producing heat in tissue from a minimum of 104 F to a maximum of 114 F at a depth of two inches in not more than 20 minutes. When diathermy equipment is utilized, the power output is maintained below the pain threshhold of the patient."

Steve Conner

Thu Apr 07 2011, 09:21AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Ash Small wrote ...

I'll re-post this link on microwave burns here. Exposure for even a few seconds can result in permanent nerve damage, etc.:

The "H.F." case sounds like a bunch of ambulance chasing pish. As was pointed out, diathermy machines expose the patient to much higher power densities.

The little antenna on top of a magnetron is basically a quarter wave whip, as such it has a maximum directional gain of (IIRC) 6dB over an isotropic radiator. So maybe you have to stand 6dB further away, or 3dB or whatever.

quicksilver

Sat Apr 09 2011, 07:55PM

Registered Member #1408 Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679

Klugesmith wrote ...

I think this guy (Neon John) is not being stupid in the upper-left picture at

In a "less-lethal weapon" symposium, several years back at a local university the use of a "microwave gun" was discussed and several examples examined for use by both the military and police for crowd control, etc. The concept was well known and a few proto-types were funded and examined. However, after several trials and the inclusion of a medical team (I think for John Hopkin's) in evaluation, the idea was shelved because there simply was no conclusive evidence that microwave radiation could be controlled in a manner sufficiently well enough to guarantee safety of exposure. This was with high-end equipment.

I was always hesitant regarding experimentation with magnetron savaged from container microwave units as the focus of the output is extremely crude and the complexities of restraining that source, not well known..... Personally, sweeping statements such as "this is harmless" are too generalized in that setting for me to feel comfortable with it.

Ash Small

Sat Apr 09 2011, 08:56PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

"Western scientists believed that serious injuries could result only at levels of 100 Milliwatts per square Centimeter (mw/ cm2) or higher. It was theorized that a built in safety factor of 10 times would be a safe margin. So, in the mid-1950â€™s a voluntary industry standard of 10 mw/cm2 (or, one-tenth of 100 mw/cm2) was adopted."

â€˜"Soviet scientists were focusing their efforts on the lesser-known effects of prolonged or repeated exposure to low levels of microwaves. Their research, which began quite some time before that of their Western counterparts, has yielded some rather unsettling reports. Soviet studies show that long-term exposure to low levels of microwave energy could result in unpleasant effects that are not attributable to over-heating (or thermal effect) alone. These effects could be seen at exposure levels at and below 10mw/cm2, which is the occupational safety standard in the U.S.

The USSR, and other European countries, has thus set their own strict guidelines for microwave safety, concluding that Western safety standards are simply not safe. For example, Russian workers are required to wear protective goggles any time they are temporarily exposed to a microwave radiation level of 1mw/cm2, a level routinely allowed to leak (although in recent years, rarely does) from U.S. microwave ovens.

These reports have provoked a reexamination of Western safety standards and heightened experimentation. Several American laboratories have since found low-level exposure to microwaves to cause cumulative harmful effects on the eye, such as cataracts. (Cumulative means that one low-level dose in itself would not be enough to affect you, but if you add another and another, and so on, then eventually the effects would be seen.) Research also reports a reduction in personnel efficiency, and in the ability to perform certain tasks, and even a possible link to cancer. Thus, while not all the research is complete, there has been enough evidence in support of Soviet findings to likely cause an eventual toughening of U.S. standards."

Marko

Sat Apr 09 2011, 09:54PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Steve McConner wrote ...

Ash Small wrote ...

I'll re-post this link on microwave burns here. Exposure for even a few seconds can result in permanent nerve damage, etc.:

Hi guys,

Yeah, that one does not sound credible to me either. If one models human arms with say 250g of water, and gratuitously assumes there is no cooling from blood circulation and the tissue is absorbing all 600W of power (impossible from an open oven), 5 second exposure would only raise it's temperature by about 3 degrees C. In reality it would be several times smaller and even unlikely to be felt over just 5 seconds.

I used to do some stunts with a SSTC such as lighting incandescent bulbs, that caused large amounts of dissipated power in my body, in range of hundreds of watts, mostly without ill effects. Once I held my bare hand so close to a breakout-suppressed SSTC that I could feel my skin on it getting hot, before I decided it would be wise to back off.

I used to light bulbs by just holding them with just my index finger and thumb, with like half an ampere going there which was rather unwise I believe. I once developed a weird joint pain in base of my thumb that lasted like a day or two, around the time I lit bulbs this way. I'm not sure if it is related at all, but now I do it by holding a copper pipe firmly with both hands.

I guess a horrible microwave injury is more possible on isolated body parts, such as fingers, if they wander into extremely high power density area. But I think one would still feel a lot of pain before irreversible damage was actually done.

I've heard countless stories about possible unknown, non-thermal effects of microwaves, both for and against them, but never a single piece of credible, objective research. Not even breeding a population of mice under low level microwave radiation and comparing statistics to 'unirradiated' ones, or something like that.
And those people who claim to have "electromagnetic hypersensitivity" syndrome or whatever it's called, which sounds so paranormal to me. Could be very useful for secret spy communications if it was real.
I'm not into mainstream for like last 2 years though, so please inform me if there are any new, serious developments on this matter.

Marko

Ash Small

Sat Apr 09 2011, 10:49PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Marko wrote ...

.
I've heard countless stories about possible unknown, non-thermal effects of microwaves, both for and against them, but never a single piece of credible, objective research........Marko

I think it would be difficult to 'conclusively prove' that, for example, prolonged or intermittent exposure lead to an increase in cataracts......especially if the manufacturers have a 'competant' legal team.

(apparently the threshold for permanent damage 17mm below the skin (apparently where most 2.45 Gh radiation ends up) is 42 degrees, while the pain threshold is 45 degrees, due to fewer nerves, so it is possible to suffer deep burns without being aware of it.....according to the link I posted above)

I'm still researching, as I wish to experiment with microwave ion sources, but I also want to be aware of/minimize the risks involved.

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