RF power question

:

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ave no idea if that's a thing, but it make some sense.

ngly reactive - apparently charcoal soaked with liquid oxygen was once used as low-brisance commercial explosive, and one of the Open Day tricks was s oaking cotton wool with liquid oxygen and setting it on fire. It produced a brilliant flare.

I once attended an explosives lecture by Colonel B D Shaw where he demonstrated the effect of igniting cotton wool soaked in liquid oxygen. It was spectacular, but not as much so as some of the other mixtures. (Especially noisy were white phosphorus soaked in carbon disulfide and a small but powerful steam explosion.) The liquid oxygen was prepared on site to avoid the difficulties of safe transportation. He passed oxygen gas through a U-tube immersed in liquid nitrogen to condense out liquid oxygen. My earlier comment about icing over of liquid nitrogen dewars is not speculation - I have seen it happen in a very humid atmosphere.

John

IIRR he has said that he did, and that he didn't like them much.

I got a Ph.D. in Physical Chemistry, and Win Hill had the good sense to bail out of one in Chemical Physics, so it might be a sensitive point.

--
Bill Sloman, Sydney

And you can make a still for LOX powered by the more easily available LN2 (one UK pyrotechnician was famous for doing this). BOC would not sell him LOX once he had retired from the chemistry department.

It isn't the LOX that is the serious threat though. Ozone which looks much bluer than O2 also collects in cold traps that are in the vicinity of HT kit and you have to be careful not to just keep on topping it up.

Eventually you can get enough liquid ozone collecting in the bottom for it to go bang when it warms up. We only had it happen the once.

--
Regards, 
Martin Brown

Bill Sloman wrote in news: snipped-for-privacy@googlegroups.com:

You should have been a chemical engineer then.

What do you think of the use of organics in MEMS RNG science?

Wouldn't a good RNG be something like they did with the standards?

The new kilogram is based on the Planck Constant.

Maybe a good RNG generator could look at some atomic or molecular level event each cycle and thereby never have a repeating sequence.

Martin Brown wrote in news:qrg90k$ee6$ snipped-for-privacy@gioia.aioe.org:

Explain.

Ozone gets a bad rap, and at room temps, 'liquid ozone' is a completely different animal.

At cryo temps though... it reacts with other presences.

Only if you warm it past its boiling point temp too fast.

It condenses so quickly as to be strange. If in bringing it back up in temp too fast, it gasses voilently and suddenly.

Kind of like heating water in a microwave to past the boiling point, then, while it is at rest, dumping some powdered substance into it. All those nucleation points and some still stored molecular energy all boils it up again in an instant.

I have also seen a tray of water cooled to below freezing uet still be liquid, and reach in and tap the tray with a fingernail and watch the ice suddenly crystalize across the entire tray.

Taken a cold Miller out of the freeszer too. Still liquid. Set the bottle down on the table with just a tiny bit of firmness, and watch as ice works its way up the entire bottle from bottom to top, creeping along. Same if you just crack the cap open. That one requires below freezing temp, becasue of the alcohol. Apparently Miller HL has less than they claim. :-)

Why? My wife says that all good chemists are ex-chemists, and has a few examples.

I was pretty good chemist, but had to do my own electronics to get the Ph.D. project to work, and got good at that too.

I don't.

can be cute, but I've not come across anybody using organic chemicals to make them up (give or take the photo- or electron-sensitive resists used in the lithography).

Probably not.

I know about the Kibble balance, and I've got Kibble and Rayner on Coaxial AC Bridge on my bookshelf. It's the same Kibble.

Prove it. Brownian motion is famously random, but turning it into a signal would be tricky.

--
Bill Sloman, Sydney

e s

es,

Klystrons and later, Klystrodes were used in high power UHF transmitters. T he largest Tetrode I've seen was a water cooled 25 KW. They were used in '5

0s and '60s designs, by RCA, GE and a few others. RCA built 12.5 and 25 KW versions of that tube. It was developed to convert their TTU-1, 1KW transmi tter to 25 KW. That tube had a pair of heaters. 1.5VAC at 1000A, each.

The newest transmitter I worked on was a Comark, with three 65KW EEV Klystr ons. It was delivered just before Comark switched to Klystrodes. This was i n the late '80s. It cost us $45,000 for the electricity each month to opera te the transmitter site. The EIRP was 5MW on ch 55, with the antenna at 172

2' AAT.

To put it mildly. Ozone - triatomic where regular oxygen is diatomic - can revert to regular oxygen, and releases a lot of heat in the process. The pr ocess goes faster when it is hot, and a shock wave can heat up initially li quid ozone very rapidly, so it can detonate.

There's a lot more energy stored in a molecule of ozone.

--
Bill Sloman, Sydney

mandag den 25. november 2019 kl. 14.21.00 UTC+1 skrev Bill Sloman:

n revert to regular oxygen, and releases a lot of heat in the process. The process goes faster when it is hot, and a shock wave can heat up initially liquid ozone very rapidly, so it can detonate.

It's known hazard.

Sloman has the habit of agreeing with what people say but still calling them stupid for saying it. Why would any sane person elect to be universally disagreeable?

Well, some people here are worse.

When I was a kid, I couldn't get any LN2 so I used home-made liquid propane to make things cold. And I'm still alive! Actually, the nitrobenzine Kerr cell was more likely to be lethal.

Crushed dry ice mixed with acetone gets pretty cold too, -78C. Ice cream trucks would sometimes give away a bit of dry ice.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

A year in high school, two semisters at Tulane. It was mandatory and boring, "Betty Crocker Chemistry." Physics and Beginners Tumbling and EDA were much better freshman courses. And the girls, of course.

UNO used freshman chemistry as a deliberate washout course. It was a free college, and they were brutal about culling.

Were did you go to college? Did you enjoy chemistry?

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

Zener or Johnson noise is random; any small nonrandom effects are easily scrambled out. I don't know why people look for more exotic stuff.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

Not to change the subject, not me, but Northstar sometimes spends $70K a night for electricity to make snow. That prevents cancellations at the Ritz Carlton.

Cable TV makes sense, energetically. How much radiated TV power gets received? Probably not one PPB.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

According to my Philips crib card, N2 boils at 77.3K whereas O2 boils at

90.2K (I'm not going to convert to Fahrenheit for non-scientists). So the N2 is easily cold enough to condense O2 from air if the latter is allowed to circulate. But I don't remember having to take any precautions against that. However we were using N2 to reduce losses of He, so only in modest amounts. During my research studentship, in the late 1960s, it was found worthwhile for the department to buy and install our own N2 plant and stop buying the liquid. It was put in the basement, so I hope they had done their risk analysis...

Mike.

ine

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ter

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rane

t is

tubes,

. The largest Tetrode I've seen was a water cooled 25 KW. They were used in '50s and '60s designs, by RCA, GE and a few others. RCA built 12.5 and 25 KW versions of that tube. It was developed to convert their TTU-1, 1KW tran smitter to 25 KW. That tube had a pair of heaters. 1.5VAC at 1000A, each.

strons. It was delivered just before Comark switched to Klystrodes. This wa s in the late '80s. It cost us $45,000 for the electricity each month to op erate the transmitter site. The EIRP was 5MW on ch 55, with the antenna at

1722' AAT.

Leakage is a major problem, in some markets. CATV systems use the frequenci es allocated to Two way radio, Amateur radio and the Aircraft band. One loo se connection, or illegal connection can shut down an airport, wipe out the fire and police department radios, along wit two meter and the 432MHz Amat eur radio band. We had a monitoring system in our trucks that would trip at a very low level. Some of those radio systems had a sensitivity in the low microvolt range. Any detected leakage had priority over any other problems , since we were close to the Cincinnati Airport.

Oxygen enrichment causing explosion risk

LN2 is cold enough to condense the surrounding air into a liquid form. The concentration of O2 in this condensed air is enhanced.

surfaces of uninsulated/nonvacuum-jacketed lines carrying LN2. This

amplify any combustion/flammable hazards in the surrounding areas.

Open dewars of LN2 can condense O2 from the air and cause an O2 enrichment that can reach levels as high as 80% O2.

Air should be prevented from condensing into LN2 with loose- fitting stoppers or covers that allow for the venting of LN2 boil-off gas.

Large quantities of LN2 spilled onto oily surfaces (such as asphalt) could condense enough O2 to present a combustion hazard.

liquid-handling.pdf

--------------------------------------------------------------------------

Cryogenic Liquids - Hazards

Liquid Dewar Flasks

Liquid dewar flasks are non-pressurized, vacuum-jacketed vessels, somewhat like a "Thermos bottle". They should have a loose fitting cap or plug that prevents air and moisture from entering, yet allows excess pressure to vent.

Oxygen-Enriched Air

Liquid hydrogen and liquid helium are both so cold that they can liquefy the air they contact. For example, liquid air can condense on a surface cooled by liquid hydrogen or helium. Nitrogen evaporates more rapidly than oxygen from the liquid air. This action leaves behind a liquid air mixture which, when evaporated, gives a high concentration of oxygen. This oxygen- enriched air now presents all of the same hazards as oxygen.

Repost to remove unreadable small font:

Oxygen enrichment causing explosion risk

LN2 is cold enough to condense the surrounding air into a liquid form. The concentration of O2 in this condensed air is enhanced.

This condensed liquid air can be observed dripping from the outer surfaces

will be composed of approximately 50% O2 and will amplify any combustion/flammable hazards in the surrounding areas.

Open dewars of LN2 can condense O2 from the air and cause an O2 enrichment that can reach levels as high as 80% O2.

Air should be prevented from condensing into LN2 with loose-fitting stoppers or covers that allow for the venting of LN2 boil-off gas.

Large quantities of LN2 spilled onto oily surfaces (such as asphalt) could condense enough O2 to present a combustion hazard.

liquid-handling.pdf

--------------------------------------------------------------------------

Cryogenic Liquids - Hazards

Liquid Dewar Flasks

Liquid dewar flasks are non-pressurized, vacuum-jacketed vessels, somewhat like a "Thermos bottle". They should have a loose fitting cap or plug that prevents air and moisture from entering, yet allows excess pressure to vent.

Oxygen-Enriched Air

Liquid hydrogen and liquid helium are both so cold that they can liquefy the air they contact. For example, liquid air can condense on a surface cooled by liquid hydrogen or helium. Nitrogen evaporates more rapidly than oxygen from the liquid air. This action leaves behind a liquid air mixture which, when evaporated, gives a high concentration of oxygen. This oxygen- enriched air now presents all of the same hazards as oxygen.

I was told that LN2 gradually turns blue as it absorbs oxygen. I didn't see that myself.

We have an enormous room-temp nitrogen tank in our basement, for the pick-and-place reflow oven. A machine squeezes the nitrogen out of compressed air somehow. I did the math, about danger, and dumping the whole tank would only reduce the oxygen content of the basement by about 1%.

I have seen people evacuate when a superconductive magnet quenched in a small room, or an accelerator tunnel.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics