Coax for vacuum applications

I'd consider semirigid coax (Google "semirigid coax") Solid wire center conductor, solid Teflon dielectric, solid copper tube for the shield. May be low enough outgasing for all but EHV.

0.141" od is common, but there are smaller and larger diameters. Might be an arcing issue at the ends of small diameters? Pasternack has some, but 50-foot minimum.

Steve Noll | The Used Equipment Dealer Directory: |

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what power, what frequency?

Try MDC Vacuum,

This is bakeable to 260°C and claims it is designed for HV and UHV.

Bret Cannon

On Fri, 14 Apr 2006 00:53:10 GMT, Steve Noll Gave us:

The slightly less rigid, tinned braid outer sheath versions are out there as well.

Thanks people. The signal is not more than few mVolts and the bandwidth is 10MHz. I saw at MDC but they don't sell less than 30ft. I need only may be

10ft and yes inexpensive the better.

Looks promising. Ultra-high vacuum is all about pumping rates and baking, so I''d think about making my own connections by stretching the centre wire between UH -coaxial feedthroughs (tricky enough - you need parts with glass-to-metal seals on the centre pin) and mechnicallly locating a thoroughly rigid copper outer around it (assembled in reverse order).

Not as conveninet as the store-bought cable, but it might pump down faster.

--=20 Bill Sloman, Nijmegen

Thanks Bill, If i don't get something inexpensive store - made , i will go the route you told me to. I dont think i get the glass-to-metal seals for the center conductor part? Can we buy such wires with glass- insulator on them?

you need the glass to metal seal at the vacuum chamber interface to keep the atmosphere out and vacuum in you chamber. Usually a vacuum rated feedthrough at the chamber wall is used. you also need to consider contamination from the coax if it has not been vacuum baked previously.

Soitenly! ;-)

Cheers! Rich

Thanks guys, I have some feedthrough for ultra high vacuum so i am planning to use them. So to make a coax, i will take some stainless steel wire (prferably stranded). Now, before i put the copper around for EMI , i need a insulator? Are there any ultra-high vacuum insulators which won't break at cryogenic temperatures. Teflon may be the right choice?

How about vacum?

As in an empty void instead of an insulator.

At your voltage level it should be fine. You will have to adjust the geometry and velocity factor slightly compared to popular dielectrics, but that may not matter either.

We use "coax" shielded cable that's made with ceramic disks spaced every so often. No problem for bakeout or ultra-high vacuum. It's not 50 ohms, and it has a higher capacitance than any coax you're used to in air.

--
 Thanks,
    - Win