X-Ray tube insulation - Page 1
Forum section: electronics / projects

author: Neukyhm
author_rank: Contributor
timestamp: September 26, 2017, 04:52:23 pm
content: 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.

author: calexanian
author_rank: Super Contributor
timestamp: September 26, 2017, 05:42:18 pm
content: 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.

author: calexanian
author_rank: Super Contributor
timestamp: September 26, 2017, 05:52:28 pm
content: 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.

author: calexanian
author_rank: Super Contributor
timestamp: September 26, 2017, 09:37:29 pm
content: Once again. What type of duty cycle and usage do you have in mind?

author: calexanian
author_rank: Super Contributor
timestamp: September 26, 2017, 11:10:49 pm
content: 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?

author: ptricks
author_rank: Frequent Contributor
timestamp: September 29, 2017, 11:43:25 am
content: 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 thatProtecting HV circuits I would use HV silicone putty . Easy to remove and stays flexible.

author: grifftech
author_rank: Frequent Contributor
timestamp: September 29, 2017, 07:20:04 pm
content: hot glue or liquid electrical tape

author: CM800
author_rank: Frequent Contributor
timestamp: September 30, 2017, 12:57:55 am
content: 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 separatelyThey will usually happily sell you the oil. I have a load of the oil from a friend who got it there.