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Re: Couple of questions

Posted: Wed Jun 27, 2018 9:01 pm
by Richard Hull
30 volts will not create a plasma in the fusor based pressure. In the 866 mercury vapor rectifiers and mercury thyratrons, you developed a true arc in a rarefied metal vapor with a heated filament blasting out tons of electrons. These arcs could not be cut off, once started, unless the voltage across them went to zero.

I studied these high current mercury vacuum tubes in college industrial electronics as these were the only thing that could handle high currents at moderately high voltages in high noise environment where a lot of inductive kick back was found, (motor controllers, inverters, etc.). Silly-con, while making in-roads in the early 60's, was not in many older installed industrial high current apps. There were still a few "tilt" or "swing" start mercury vapor rectifiers in old backwater apps in the 60's.

Silly-con by 1963 had gained almost 100% penetration into milliamp, low voltage circuitry. (Computers, portable telecommunication, and light duty portable consumer stuff). TV's and table radios, however, were still 98% vacuum tube based. Installed industrial was still 80%++ vacuum tube. TV's would still be over 70% vacuum tube based into the 1970's. By the 80's vacuum tubes had pretty much left the consumer market.

Richard Hull

Re: Couple of questions

Posted: Wed Jun 27, 2018 9:31 pm
by Dennis P Brown
Since the average person does not use mercury vapor filled vacuum tubes I would hesitate to tell novices that would be a useful way to create a plasma using 30 volts; mercury has a very high vapor pressure even at atmospheric pressures (hence its extreme danger.) Trying to use air at a torr or less with 30 volts, as I suspect the person here was considering, is useless. I can create thermonuclear fusion at room temperature and atmospheric pressure via random collisions in pure heavy water mixed with palladium metal (one can get a few clicks from a gamma ray detector every minute or so) but that isn't exactly useful. Best not to use extreme's when novices are asking questions since they do not have the knowledge nor experience to realize the issues evolved which could lead them to false conclusions. Fun to see an example but one must be careful to explain the details so people with less experience are not mislead.

Re: Couple of questions

Posted: Wed Jun 27, 2018 11:10 pm
by Rich Feldman
I bet the OP really meant to say 30 kV and 10 mA.

Be sure to question the efficacy of a shadow cone shield, as mentioned earlier in this thread. There are cases where simple geometric shadowing works fine, as in the Parker Solar Probe soon to be launched at the sun. But fusors aren't point sources of neutrons, or the much more hazardous x-rays. Neutrons are scattered as well as absorbed by low-Z materials. X-rays are generally absorbed by high-Z materials, but they are also scattered by air and anything else they penetrate.

Radiographers have had to deal with that practical challenge for more than a century. For example, structures behind the film/detector can appear as artifacts in the image because of backscattering. With thick subjects, loss of contrast due to beam scattering can be mitigated with a lead grid (like miniature Venetian blind) between patient and detector.

Dennis, please keep raising flags when someone appears to be cavalier about safety. Never my intent, but writers might not recognize a possible misinterpretation. When I once showed wire-balling arcs and a xenon short-arc lamp carrying 10 mA, and guessed that normal lamp current was around 1 amp, someone might have thought 1 amp was in the picture. Indeed, that would be foolish to look at without a dense optical filter (and blast protection).

>> heated filament blasting out tons of electrons.

Not literally, of course! :-) Looks like at 1 amp, it would take 49 billion hours to emit a metric ton of electrons.
If an 866A served for 40,000 hours at one DC ampere (that's really pushing it), total emission would have been about 1 gram of electrons.
(1.44e8 coulombs = 1500 moles of electrons. 750 moles = 150 kg of Hg++ transported the other way? Yes, I am a hydragyruphile and proud to say it.)

Re: Couple of questions

Posted: Thu Jun 28, 2018 3:33 am
by Richard Hull
The shadow cone shield is fully effective for x-rays and fast neutron in the fusor environment. Yes, x-rays and even neutrons scatter, but the real danger is the head on rather straight line emission as you face the working fusor at close range. Compared to the head-on that is 99.999% absorbed by a shadow cone shield, the scattering is a microscopic fraction at that range.

I have shown that a direct full-on, unshielded, exposure from a functioning fusor operating at 45kv and 15ma at a range of 8 feet is under 1mr/h in x-rays and immeasurable in neutrons.

An 18" by 18" shadow cone shield at a range of 9-inches from the fusor, composed of 1/8" thick lead, backed by a 2" thick box of borated parafin would produce no measurable radiation of any sort at all 6 feet away within its shadow cone. No fusor yet operated, by anyone here, has produced so much radiation that a shadow cone shield would not completely protect an operator within its shadow cone to the point of not being able to be measured.

Let us not nit-pick about scattering of x-rays from a fusor when compared to a nasty, specially constructed, high emission x-ray tube. The fusor is a terrible x-ray emiting device. X-ray scattering from a fusor is a nervous-nelly's worry.

The time to worry will come when someone reports they are successfully operating a fusor at well over 100,000 volts!

Most nit-pickers related to radiation in these forums have never operated a fusor or a genuine factory produced x-ray tube, nor have they any idea related to the vast difference between the two, based on their own measurements while they operated them. Virtually none of them have the quantity or type of radiation measurement instrumentation to make any sort of realistic claims based upon hands on experience. Most have done a lot of reading and have the theoretical machinations at hand and are of the ALARA mentality.

I can handle a 1,2 or 3mr/hr whole body rate. It's a dawdle. I will never be exposed for more than a few minutes at a time in an acute manner within a days fusor work. I would walk away from the fusor that day with maybe 1millirem total dose, whole body. Remember, this is from my totally unshielded fusor. By the way, the average bat wing dental x-ray blasts your skull with a bit more than 1 millirem total absorbed dose.

I rarely operate my fusor for more than 4 to 6 days per year now.

Richard Hull

Re: Couple of questions

Posted: Thu Jun 28, 2018 6:33 am
by Rich Feldman
OK, Richard, I was being a nervous Nelly about shadow cones. On top of maybe being pedantic and a show-off (enthusiastic presenter of cool stuff for nerds?)

I have indeed dabbled with, and measured doses from, Coolidge tubes. Ionizing photon output from even a little one dwarfs that from the hottest natural radioactive mineral, as you know. Geiger counters anywhere in the room immediately report that the x-rays are on.

But yes, to paraphrase & extend something you said years ago about fusor risks. I bet:

Injury or latent cancer from radiation is a very low probability hazard. Down there with deuterium fires.
Then maybe things bursting or imploding from pressure or vacuum.
Then electrocution, a risk that deserves respect & attention from experts as well as novices.
Then nothing for a few orders of magnitude, probability-wise.
Finally there are amateur science injuries that will get everyone, one way or another. Cuts, scrapes, bruises, or blood blisters from metalworking. Tripping over a cable or hose. Bumping head while attending to something on bottom shelf of cart or rack. Soldering iron burns, etc. Permanent damage to clothing that could have been worn to work, or in public.

Re: Couple of questions

Posted: Thu Jun 28, 2018 10:08 am
by Dennis P Brown
Educating people on safety is always a good idea since it helps people develop lifelong respect for such dangers - as all would agree, an ounce of prevention is worth a pound of cure. I certainly have seen many an educated scientist or experienced technician take extreme risk and have known of tragic results due to an indifference to even simple safety measures. On the opposite side, I've often found some 'required safety procedures' over-the-top too restrictive. Knowing the difference between these extreme's requires both knowledge and experience and those, I feel, are given there in abundance making this one of the best high energy related forums I've ever had the pleasure to read.

Re: Couple of questions

Posted: Thu Jun 28, 2018 5:24 pm
by Richard Hull
Right after electrocution, and perhaps implosion of newbie glass systems, the demo fusor operated over 15kv or the running fusor, itself represent an x-ray hazard I have mentioned before. X-rays blast out of view ports and ceramic insulators on running fusors. look at my fusor and you will see the ideal placement to avoid X-ray beaming into your body. The HV insulator points to the heavens, view port to the floor. In any other arrangement you have to be careful at some range of walking into a high energy X-ray beam. In glass fusors operating above, 12kv, ( a bad situation regardless), you can get really bad burns from low energy x-rays that will rival the worst sunburn you have ever had. That is why you should not work a glass demo system over a few kilovolts.

Running fusors take advantage of a nice .060 thick metal shell to avoid the worst of the x-rays, but due to typical construction, they have at least two possible dangerous X-ray beaming points. This is easily taken care of by proper planning in making the fusor and later in its mounting orientation.

Nice big 4 and 6 inch windowed ports are nice big bore x-ray canons. Use the smallest viewport you can work with.

Richard Hull

Re: Couple of questions

Posted: Thu Jul 05, 2018 9:03 pm
by steventw
So attached pics of what have so far and a basic outline for idea

From vids I seen on YouTube plasma spins around outside of magnet along field lines
So idea is to have a row of magnets with like poles facing each other in center to point there repelling a bit
And then creating plasma at base of magnet and let it
Spin up and hopefully get a sling shot effect like a satalight around a planet
If lucky will increase speed of plasma to where it meets in center where plasma coming from other way will be spinning opposite direction and hopefully overlap and we’ll just have to see what happens

For proof of concept just 2 rows
If looks like working as theorised
Then build prototype with magnets on all 6 sides

From Steven whittam

Re: Couple of questions

Posted: Fri Jul 06, 2018 9:37 am
by Richard Hull
I think it is great you are trying out ideas. I think there are major issues here, but I feel the "live and learn" is worth it.

Richard Hull

Re: Couple of questions

Posted: Tue Jul 10, 2018 8:35 am
by steventw
Judging by this guy
Roughly 4 -5v if lucky
And roughly 1amp
Don’t know but if is
Should be all I need to create a little plasma to build up a steady stream from base of mangnets with 2 seperate copper rings to send to middle to meet plasma concoming spinning opposite direction
One possible out come is creates plasma that’s going to head back to your copper wires
Or to middle