Pankaj,

The only realistic viable insulation option is a vacuum - unless you can afford a lot of Helium, or have access to a very powerful refrigerator.

How big is the chamber, and what unusual requirements (feed-throughs, windows) do you have?

If it's small (10cc) then simply attach it to the cold end of a GM or pulse-tube refigerator. In a hard vacuum (of course).

It also depends on what is inside the chamber, and what vibration levels it can tolerate.

Classic books on Low temp techniques: Guy White's "Experimental Techniques in Low Temperature Physics (pub by Oxford) and Robert Richardson and Eric Smith's "Experimental Techniques in Condensed Matter Physics at Low Temperatures" See if you can borrow those

Hi James,

I need provision for RF feed-through and the sensors feed-through as i am working on a test chamber for testing RF losses of SRF cavities. I am thinking of using a pulsetube cryocooler, but 10cc is too small a volume me. Thank you for that valuable insight.

Pankaj,

I was wrong to give you the impression of a size limitation via cryocoolers. There is no limit as to the size of an object that a cryocooler can cool - what matters is their cooling power and the radiative heating received by your test chamber and the quality of the vacuum. I was simply going by the area of the contact - and generally one wants the cooled article to be small so as to have fast cooldown and low equilibrium temperatures.

So, the goal is to acquire a vacuum chamber with suitable ports.

Ebay even.

I once bought a 200l vessel from eBay with CF ports for only 1k Euro.

Find a cryocooler supplier, and then do terrible things to a mating CF flange so that the cryocooler is mounted to the chamber. The rest of the chamber can be capped off with 'O' rings - just be careful with contamination control and lock away the acetone.

Mount the test chamber (which may not be necessary any more) to the cold head of the cryocooler, and evacuate the 'outer' chamber with a turbo backed by a simple rotary or diaphragm pump.

With careful use of MLI and perhaps even a LN2-cooled radiation shield, you should be able to cool kg-mass objects to a few K in a matter of hours.

I've used a GM cooler to take an RF amplifier (size of a paperback book) down to 4K using a chamber that was around 50l in size.

Getting RF into the outer chamber may or may not be easy - depending on the frequency of interest. The sensor harness can probably use a stock CF multiway flange.

So, what's inside the test chamber? A pressurized gas? If not, then perhaps there is no reason to have a second 'test' chamber within the outer one. You will simply need a copper baseplate to bolt to the cryocooler. Mount all of the exciting parts onto that plate, and then offer the whole thing up to the larger outer chamber.

Let's see:

http://www.ebay.com/itm/VARIAN-MDC-HIGH-VACUUM-CHAMBER-STAINLESS-STEEL-TORR-CONFLAT-FUSOR-/221423898208?pt=BI_Pumps&hash=item338de48e60

http://www.ebay.com/itm/12-5-ID-14-5-deep-chamber-set-up-for-CVD-vacuum-deposition-with-gas-shower-/251257553026?pt=LH_DefaultDomain_0&hash=item3a801e0082

Dear James,

Thank you so much for your advice. I really required such an input. As a budding researcher, diving into cryogenics coming from instrumentation background is tough.

Expect many more such question from me and i will be following you closely. And I am testing (inside test chamber) RF heat dissipation by thin film Superconducting RF resonator.

Pankaj,

Ah, in that case then the test chamber need only be an RF-tight assembly - I had had visions of you wanting to test some exotic gas property that *required* a hermetic cell.

So, you have some electronics, on a brassboard, and wish to test its efficiency at deep cryogenic temperatures.

I always favour four-wire resistance thermometers for cold work, but in this case some calibrated silicon diodes might be best. Lakeshore sells them, and a few other places.

Otherwise, the only tricky part might be providing the RF - what frequency are you hoping to drive the resonator at?

3.4Ghz is the standard frequency. May go for something lower just for testing sake.

Dear Pankaj,

although the post is a bit older it could be of interest (If not for you for people who search the old posts) be careful about the generated heat in the resonator. 3.4 GHz is quite a high frequency, so you will probably have considerable losses. We (Superconducting RF group at CERN) used always helium cryostats for our resonator tests so we could allow higher losses for short periods (rf on).

As a book I would recomend:

Experimental Techniques for Low-Temperature Measurements: Cryostat Design, Material Properties and Superconductor Critical-Current Testing by Ekin