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Author: Subject: X-Ray tubes
Elemental Phosphorus
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[*] posted on 22-10-2018 at 11:44
X-Ray tubes


I have a friend working on a project requiring irradiating foods with 0.2 to 0.5 grays (absorbed dose) of radiation. I am not an expert on x-ray tubes and so I am not aware of a few things, like whether or not the tube which my friend is looking at buying is suitable for continued use at about 1-1.8 kw or what the overall radiation dose would be near a tube operating at a voltage around 18kv. Anyone have some expertise regarding this? The project is measuring growth of fungi and bacteria on irradiated vs. non-irradiated foods, somewhat standard high school science project stuff. Would continued use require a rotating anode perhaps?

Here's the link: https://www.ebay.com/itm/Vintage-USSR-X-RAY-roentgen-tube-2-...
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[*] posted on 22-10-2018 at 15:30


Well anything using a kilowatt of power for more than a few seconds needs cooling




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[*] posted on 23-10-2018 at 10:56


Anything using a kilowatt of power to generate Xrays needs, at the very least, serious shielding + interlocks.
Probably, what it needs is forgetting about- especially as " high school science project stuff. "
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wg48
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[*] posted on 23-10-2018 at 12:47


Quote: Originally posted by Elemental Phosphorus  
I have a friend working on a project requiring irradiating foods with 0.2 to 0.5 grays (absorbed dose) of radiation. I am not an expert on x-ray tubes and so I am not aware of a few things, like whether or not the tube which my friend is looking at buying is suitable for continued use at about 1-1.8 kw or what the overall radiation dose would be near a tube operating at a voltage around 18kv. Anyone have some expertise regarding this? The project is measuring growth of fungi and bacteria on irradiated vs. non-irradiated foods, somewhat standard high school science project stuff. Would continued use require a rotating anode perhaps?

Here's the link: https://www.ebay.com/itm/Vintage-USSR-X-RAY-roentgen-tube-2-...


Your friend is considering buying a technical item without out a detailed specification/operating manual or an understandable one ,and the condition of the item is specified as NOS (not otherwise specified) and it costs $149 seems foolish at the very least.

I don’t know much about X rays or the generation of them however I can comment on the power supply. Just designing and constructing the power supply to use the tube would be a serous project. The tube must be operated with a series resistance of 20kohmes so to operate at 17kV@100mA requires a 37kV supply and a heater supply that must operate at that common mode voltage range. That’s a plug power of at least 4kW. A potentially very dangerous system for a high school project from the lethal voltages/current and X ray exposure. The cost of the X ray tube is probably less than 5% of the total power supply cost and less that 10% of the technical expertise required for the power supply.



Oops! got the sums wrong the voltage drop across the series power supply resistor is 2kV @ 100mA so the supply voltage must be 19kV with a plug power of 2kW+, however still a major task. X ray machines and parts do occasionally appear on ebay.

[Edited on 23-10-2018 by wg48]




Borosilicate glass:
Good temperature resistance and good thermal shock resistance but finite.
For normal, standard service typically 200-230°C, for short-term (minutes) service max 400°C
Maximum thermal shock resistance is 160°C
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[*] posted on 25-10-2018 at 13:33


Yes, I am aware it's a bad idea, I talked him out of the project a few days ago for the reason that the amount off radiation he needed would require a lot of shielding, and the amount of time and effort required to avoid accidental exposure would be far too much. As far as I am concerned, the issue is resolved. (And wg48, not that it matters at this point, but the power supply was already available, he'd made arrangements with someone who had a power supply to use it.) He did talk to the seller of the tube (for what that's worth, the seller was in Ukraine and probably just wants to make the sale).
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