HIGH KV / mm INSULATION 1

[Todd619]

I am searching for insulator materials with the highest dielectric strength per thickness possible. The best ones I've found seem to be Teflon @ about 40-80 kV / mm (short time) and CPVC @ about 40 kV / mm (short time).
My problem is that all the values I find say "short time", but this is not going to be a "short time" kind of thing, so I'm trying to find where I can find the "long time" values.
I also would like any suggestions as far as other materials go. I would like to use something that is bondable (not Teflon)
The application is basically for a ion mass spectrometer. It will be two anode plates @ 50-100kV separated by just a few mm, on the other side the plates must be insulated from magnetic pole faces with neutral potential. The insulation must be kept thin so that the magnetic dipole gap can be small for a greater field across the gap.
I appreciate any feedback
-Todd

 

[Warpspeed]

I guess you would need something that was a solid material with no porosity or gaps within its micro structure. Something non hygroscopic that will not absorb moisture or air, or deteriorate from ozone or other chemical attack.

How about glass ?

 

[itsmoked]

There are also epoxy resins that are specifically for high voltage so you could use that as is or cast it into whatever shape you need. Same goes for some silicon potting materials that are flexible.

 

[Todd619]

I may have found the material to use, it's called Pyrolytic Boron Nitride (PBN)and it is supposed to have the highest dielectric strength known: 200,000v/mm
I would still be interested to hear input on other materials as I would assume that the PBN is probably pricey and doesn't seem like it's the easiest to machine although it's supposed to be machinable. I also will need some high voltage adhesives also, as itsmoked mentioned, so if there are any brand names or specific products that anyone can recommend that would be helpful also.

-Todd

 

[Timelord]

Todd619,

After years of experience with HV and pulse power, I have yet to find a better bulk insulator than plain acrylic. Easy to machine, available in tube, rod, sheet, billet etc. It will easily withstand 1kV per mil (.001") in thicker sections.
For real thin applications, Kapton is the material of choice, but it is not available in anything but thin sheet form.

Timelord

 

[Todd619]

Thanks for the tip on the acrylic, I had no idea! It just might work for my application. Normally a materials dielectric strength / thickness goes down with greater thickness due to more impurities and flaws in a thicker part, but you seem to say it's the other way around here(?)
Also, can you tell me if that 1KV / mil rating is good for long periods of time? How about in the presence of A/C or pulse DC?

Thanks again
-Todd