Author Topic: X-Ray tube insulation  (Read 2851 times)

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Offline NeukyhmTopic starter

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X-Ray tube insulation
« on: September 26, 2017, 04:52:23 pm »
Good afternoon (here in Europe). I have an x-ray tube I want to isolate. I was planning to use a good epoxy resin I got from RS. The cathode is grounded so the anode will be working at 60kV, and I'm worried about the anode itself heating, expanding and pushing the epoxy towards the tube & cracking it, see picture.

I know there are some x-ray users here that are much more experienced than me, I would really like to avoid a liquid isolator, I have this epoxy with a dielectric strenght of 12kV/mm and it is indicated for applications where there are different materials with different expansion coefficients.
 

Offline calexanian

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Re: X-Ray tube insulation
« Reply #1 on: September 26, 2017, 05:42:18 pm »
I would not use any epoxy anywhere near an X ray tube. Nothing should come in contact with the bulb that is not a thermal expansion match to the glass, otherwise bad things can happen. You should construct a proper holder.
Charles Alexanian
Alex-Tronix Control Systems
 

Offline calexanian

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Re: X-Ray tube insulation
« Reply #2 on: September 26, 2017, 05:52:28 pm »
Typically in this kind of tube they will use an anode connector that is a heatsink as well. Typically copper or aluminum alloy. That is turn is mounted in a properly shielded housing typically with a fan or something to provide overall cooling. That looks to be a 50 watt model or so. What will your duty cycle be? How long will each exposure be? You may be able to just get away with a large copper or aluminum piece as a heat sink if its infrequent short exposures. As for the voltage isolation the high voltage transformer, or switching supply leads should safety integrate into your tube housing in a manner to prevent breakdown and arcing. Epoxy is terrible for this. It may have good dielectric properties, but can suffer surface breakdown easily from stuff landing on it or chemical breakdown from corona effects. Ceramic, glass, mica, and the like should be considered first.
Charles Alexanian
Alex-Tronix Control Systems
 

Offline NeukyhmTopic starter

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Re: X-Ray tube insulation
« Reply #3 on: September 26, 2017, 06:54:15 pm »
The main problem I have with insulating oil is that I have look for it and been unable to find it here in Spain/Europe in small quantities.

Does anyone know where can I find it?
 

Offline NeukyhmTopic starter

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Re: X-Ray tube insulation
« Reply #4 on: September 26, 2017, 08:10:10 pm »
The main problem I have with insulating oil is that I have look for it and been unable to find it here in Spain/Europe in small quantities.

Does anyone know where can I find it?

I have read that regular mineral oil works, as well as canola oil.

Plase HV users, I need your help xD
 

Offline calexanian

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Re: X-Ray tube insulation
« Reply #5 on: September 26, 2017, 09:37:29 pm »
Once again. What type of duty cycle and usage do you have in mind?
Charles Alexanian
Alex-Tronix Control Systems
 

Offline NeukyhmTopic starter

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Re: X-Ray tube insulation
« Reply #6 on: September 26, 2017, 09:48:14 pm »
Once again. What type of duty cycle and usage do you have in mind?
For now, exposures of no more than 5 seconds every 5 minutes or so, just a few times, I mean, the machine won't be operating 24/7.

Definitely industrial transformer oil is not an option for me, it is sold in very very large quantities in my country. I see a lot of people in youtube using
mineral, canola or sunflower oil.
« Last Edit: September 26, 2017, 09:55:14 pm by Neukyhm »
 

Offline calexanian

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Re: X-Ray tube insulation
« Reply #7 on: September 26, 2017, 11:10:49 pm »
Then a simple heat sink of copper strap should do well. No need for coolant. are you driving it with a x ray transformer or a voltage multiplier?
Charles Alexanian
Alex-Tronix Control Systems
 

Offline NeukyhmTopic starter

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Re: X-Ray tube insulation
« Reply #8 on: September 27, 2017, 09:34:06 am »
Then a simple heat sink of copper strap should do well. No need for coolant. are you driving it with a x ray transformer or a voltage multiplier?
I will use a 6 stages multiplier and a 5kv transformer. But the problem is, how do I isolate the HV parts if I cannot use epoxy because it may crack the tube?
« Last Edit: September 27, 2017, 09:37:47 am by Neukyhm »
 

Offline ptricks

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Re: X-Ray tube insulation
« Reply #9 on: September 29, 2017, 11:43:25 am »
If you use any mineral oil make sure it is not flammable, there is a lot of products out there that may be labeled mineral oil but there is no standard for how the product is made.

Vegetable based oils like canola will tend to become rancid over time and you don't want that  :--

Protecting HV circuits I would use HV silicone putty . Easy to remove and stays flexible.

 

Offline grifftech

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Re: X-Ray tube insulation
« Reply #10 on: September 29, 2017, 07:20:04 pm »
hot glue or liquid electrical tape
 

Offline CM800

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Re: X-Ray tube insulation
« Reply #11 on: September 30, 2017, 12:57:55 am »
Check about for companies that service medical equipment, X-Ray machines etc.

They usually take the X-Ray transformers apart to scrap the copper & Iron separately

They will usually happily sell you the oil. I have a load of the oil from a friend who got it there.
 

Offline NeukyhmTopic starter

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Re: X-Ray tube insulation
« Reply #12 on: September 30, 2017, 09:39:10 pm »
I'm now planning to use mineral oil, previously dehydrated in vacuum. I will use the epoxy not to insulate but to fix the tube inside a cylindrical container. Is epoxy resistant to mineral oil?
 


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