Building a CRT and bathing yourself in x-rays

For the Milan design week held last April, [Patrick Stevenson Keating] made a cathode ray tube and exhibited it in a department store.

The glass envelope of [Keating]’s tube is a very thick hand-blown piece of glass. After coating the inside of the tube with  a phosphorescent lining, [Keating] installed an electrode in a rubber plug and evacuated all the air out of the tube. When 45,000 Volts is applied to the electrode, a brilliant purple glow fills the tube and illuminates the phosphor.

Since the days of our grandfathers, CRTs have usually been made out of thick leaded glass. The reasoning behind this – and why your old computer monitor weighed a ton – is that electron guns can give off a substantial amount of x-rays. This usually isn’t much of a problem for simple devices such as a Crookes tube and monochrome CRTs. Even though [Keating] doesn’t give us any indication of what is being emitted from his tube, we’re fairly confident it’s safe for short-term exposure.

Despite being a one-pixel CRT, we can imagine using the same process to make a few very interesting pieces of hardware. The Magic Eye tube found in a few exceptionally high-end radios and televisions of the 40s, 50s, and 60s could be replicated using the same processes. Alternatively, this CRT could be used as a Williams tube and serve as a few bits of RAM in a homebrew computer.

You can check out the tube in action while on display after the break, along with a very nice video showing off the construction.

13 thoughts on “Building a CRT and bathing yourself in x-rays

  1. FTA:

    “For Milan Design Week, I teamed up with Super/Collider to create the world’s first handcrafted glass particle accelerator and set it up inside Milan’s poshest department store…”

    World’s first I’m sure, Mr. Blowhard.

    1. they call that Theft Of Patents! this man did NOT invent the CROOKES TUBE… MR CROOKE INVENTED IT!!!

      this man is a thief and any revenue generated is 100% patent theft

      this man will not be accepted by any university or collage in the entire world.


  2. You exceed 21 kV into a vacuum tube, you’re generating X-Rays. 45 kV (yes, 45,000 Volts) generates HARD X-Rays.

    The amount of lead in a CRT is a minor fraction of the glass weight … the front surface can be as much as an inch thick … for mechanical stability, not shielding.

    Early color TVs had tube rectifiers that, while capable of handling in excess of 21.5 kV, had the input (flyback voltage) adjustment to ensure you didn’t turn the rectifier into an X-Ray generator.

    I’ll dig up my old RCA tube manual and send you the details on the magic eye tube theory of operation.

  3. The penetrating power of x-rays is directly related to the acceleration voltage.

    X-rays can be produced at voltages as low as a few kV.

    Crookes tubes typically operate at 10kV.

    I think 15kV is the point at which x-rays are considered to significantly penetrate unleaded glass.

    This “art” exhibit operates at 45kV. Producing x-rays with penetration on par with the old shoe-fitting fluoroscopes; that operated at 50kV and would display a real-time x-ray image of your bones on a phosphor screen.

    The quantity of x-rays are less, and the distances greater. So I think Brian’s right, and for all practical purposes, it’s safe for the typical viewer; though a regulatory agency might not agree.

    But the sheer naivety of the “artist” both for putting an x-ray source in a department store, and falsely claiming it as a world first, is still appalling.

    One can only hope he spends many hours admiring the greatness of his own creation, thus removing another egotistical “artist” from the gene pool.

  4. “Magic Eye” tubes (in all their various configurations) were not limited to a few exceptionally high-end radios and tv’s… they were quite prolific not only in high-end sites, but also in mid-range gear. Sets with them were marketed as being “better” (and they were helpful in getting a look at signal strength/modulation/etc…), but their value to the various TVs & Radios that used them was in the user interface, not in the actual electromechanical functionality of the device (with a limited few exceptions).

    The marketing was very effective, and if you went to a friend’s house and their radio or TV had a “Magic Eye” on it, it has serious Cred. But, they certainly were not rare. They showed up in instrumentation used in a variety of fields (laboratory, industrial, military, audio & video production, art, etc…).

    The website link in the article ( is quite informative and very complete in its scope… worth doing some reading if you’d like to learn more about how things were done back when Hector was a pup.

    1. I visited the site in the link, while he’s got a nice collection, it doesn’t seem to address how they actually work! Sure there’s the diagrams, but how was the beam deflected? And what did that mean? How would you use it to tune in a radio? I’m only curious, but I’d like to know how they actually work and what they do, just for that reason.

  5. – is that electron guns can give off a substantial amount of x-rays.

    Totally not so. Only after they have been accelerated by the HV and hit the target do they produce X-Rays. Higher the voltage the faster they hit the target the more penetrating the X-Ray is.

    Pure tungsten is used in medical X=Ray tubes. The electrons hit the W surface and the X-Ray are emitted. In medical / dental tubes the anode is angled to allow a more uniform intensity field.

    Old Bio Medical Imaging guy

  6. I have an old Grundig three band tabletop radio with a 6E1p¤, 6BR5, 19BR5, EM80, UM80, Y119 type magic eye tube, positioned with the round end down.

    IIRC it’s from around the time when FM radio first started. It also has AM and shortwave.

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