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Dragon64

Wed Aug 06 2008, 02:39AM

Registered Member #1438 Joined: Sat Apr 12 2008, 12:57AM
Location: Canada
Posts: 218

I was going to post this in the Sale topic but im not buying anything.

I've been longing to produce X-rays. The only problem im having however is that I cant find any vacuum tube.
I cannot purchase vacuum tubes online for several reasons.

Does anyone know if there is a way to find a vacuum tube or another way to achieve x-rays?

I've tried a magnet free magnetron and a CRT without much luck.

I also cant make nice vacuum tubes due to lack of equipment.

Thanks

Hon1nbo

Wed Aug 06 2008, 02:49AM

Registered Member #902 Joined: Sun Jul 15 2007, 08:17PM
Location: North Texas
Posts: 1040

1) look for some old radios with tubes... if it has some of the metal based "getter" on the top, it might be usable with some foil on the end...
2) goto a Guitar Center, they many times stock tubes, as many people (including me) like tube quality better than transistor based).

hope that helps...

teslacoolguy

Wed Aug 06 2008, 02:54AM

Registered Member #1107 Joined: Thu Nov 08 2007, 10:09PM
Location:
Posts: 792

You may want to check out this thread that popped up a while back.

He used a 6vs-1 tube. I also have some standard 40kv tube rectafiers that have a xray warning sticker on them. My particular tube t was a 1b3gt.

Dragon64

Wed Aug 06 2008, 04:26AM

Registered Member #1438 Joined: Sat Apr 12 2008, 12:57AM
Location: Canada
Posts: 218

A couple question came into mind.

Is it possible to turn a light bulb into a Vacuum tube without re-vacuuming?

Could I use a xeon flash tubes in camera's to generate x-ray? Since that there are two contacts that can serve as anode and cathod and the slight vacuum.

Lastly, is there a way to vacuum a glass bottle without having a vacuum pump? ie, chemical reaction or steam in bottle then freeze it?

I will be going to a music store soon and I'll look for a tube.

By the way, thank you for your help.

Myke

Wed Aug 06 2008, 05:55AM

Registered Member #540 Joined: Mon Feb 19 2007, 07:49PM
Location: MIT
Posts: 969

X-ray tubes have to be high vacuum so a xenon flash tube wouldn't work. I would assume that they would stop using xenon flash tubes if evry time they flashed, they would emit a pulse of x-rays too...

uzzors2k

Wed Aug 06 2008, 10:04AM

Registered Member #95 Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308

There's no cheap way to create a vacuum with sufficiently low pressure for x-rays to be created. You'll need to acquire a vacuum tube from somewhere, then a 50kV+ voltage source, and finally some means of detecting the radiation. I've been wanting to make an x-ray setup for a few years now, and I just recently got my hands on a real x-ray tube through ebay (only 50 bucks!). I have made an x-ray setup which produces x-rays using a Marx generator and HV rectifier, but currently the radiation can only be used to trigger my Geiger counter, not make images.

Fabio

Wed Aug 06 2008, 01:22PM

Registered Member #122 Joined: Fri Feb 10 2006, 12:55PM
Location: Milano Italy
Posts: 148

Making really simple and small Xray tubes isn't so difficoult but require at least some basic glassblowing equipment (thorches, cylinders, graphite pieces and an anealing oven) plus a spotwelder, a REALLY GOOD dual stage high vacuum pump and some unused getters..... ordinary pumps and compressors cannot reach useful grade of vacuum., a special pump is required.

Valves and lightbulbs usually offer a really bad results, so i suggest a REAL surplus Xray tube, end of story

Proud Mary

Wed Aug 06 2008, 02:04PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

The readily available EHT shunt stabilizer triode PD500 or the similar American colour TV valve 6BK4 are popular and successful with amateur radiographers.

Care should be taken in the selection of 6BK4s, as the two early iterations 6BK4A and 6BK4B are suitable, whilst the later 6BK4C is not, due to radiation-shielding heavy elements having been added to the glass envelope in response to the X-ray TV hazard uproar of the late 1960s. In amateur X-ray work, these triodes are usually operated at anode voltages of 40 - 60kV, and anode currents between 500uA and about 2mA, when copious X-rays are produced. Anode current may be controlled by varying the heater current, or by manipulating the control grid voltage or both. Bare in mind that the recommended maximum dissipation of these valves is about 30W.

EHT diodes such as GY501 and DY802 will also produce good results with 30 - 45kV anode voltage, and 50 - 100 uA or so anode current. These should be operated in 'cold cathode' mode - i.e. without any heater current for successful operation.

Flashover, surface leakage problems, and overheating of the glass and anode seals may be overcome by immersing the tube in an oil-filled plastic pipe, remembering to leave an overflow or other pressure relief system so that the case will not start to leak - or even burst - as the oil expands as the valve heats it.

Remember that roughly two thirds of X-ray output will be in the lower third of the energy spectrum - i.e. if you have 60kV anode voltage then two thirds of the output will be at 20keV or less. Soft X-rays are easily absorbed by the human body, and so are much the most dangerous.

Make sure you have an effective means of detecting and measuring low energy X-rays - not just an old military geiger counter designed for a completely different purpose - never take chances, ensure more than generous shielding of both direct and reflected X-rays, and above all, never ever do anything that might put the health or safety of other people at risk.

Hon1nbo

Sun Aug 10 2008, 11:20PM

Registered Member #902 Joined: Sun Jul 15 2007, 08:17PM
Location: North Texas
Posts: 1040

forgot to mention, unitednuclear.com sells a kit ($30) that comes with shielding, and tubes that are tested for being good with radiography... even if you don't get the tube from there, at least get plenty of shielding and a geiger...

Steven Busic

Fri Sept 12 2008, 04:00AM

Registered Member #147 Joined: Sun Feb 12 2006, 06:35AM
Location: my house!
Posts: 8

I have a pd500 and a few others laying around, I'll check what kind of shape they're in and if you're interested, I just give them to you.... you just take care of shipping.

Steve

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