Does metal film resistor work at cryogenic temperature (3K)?

[Sandbo]

I am trying to use a metal film resistor to limit the current inside a dilution fridge (to reduce noise power from it), but I couldn't confirm if the metal film resistor is going to survive (or it goes superconducting) at ~3 Kelvin, searching a bit on the web but still I couldn't find the answer, much appreciated if you don't mind providing me with some references.

 

[Sandbo]

Looking up on the manufacturer's website for the composition, it said the resistive elements are mainly Nickel(97.72%) and Chromium(2.28%).

Nickel is not superconducting at 3K, however Chromium just goes superconducting at 3K.
Nickel is magnetic which would surpass superconductivity, still there is an uncertainty about how the Chromium would behave.

 

[f95toli]

It will work fine (I am talking from experience) . However, note that the resistance will change. How much, will depend on the initial resistance value (or small values it be something like a factor of two) so your best bet is to test a few resistors at 4K in a dipping dewar.
Also, it is usually best to use surface mounted resistors. The reason is that larger resistors can -if you are unlucky- eventually break due to the thermal cycling.

 

[f95toli]

Btw. some Cr alloys will indeed become superconducting; but at much lower temperatures (a couple of hundred mK), so be careful if you are mounting resistors on the mixing chamber.

 

[Sandbo]

Thanks a lot for your replies,

I talked to my supervisor, he said the NiCr alloy is used also in the cryogenic microwave attenuators we are using in the fridge, which means they can stand low temperature without going superconducting. In this case I will go ahead and use it for now, and as you suggested I think I should get some panel connectors and use the surface mount in the future.

 

[Windadct]

Biggest issue in my mind is what happens to the dielectric at 3K...since caps are E field devices, the dielectric is more important then the conductors.

 

[f95toli]

Thanks a lot for your replies,

I talked to my supervisor, he said the NiCr alloy is used also in the cryogenic microwave attenuators we are using in the fridge, which means they can stand low temperature without going superconducting. In this case I will go ahead and use it for now, and as you suggested I think I should get some panel connectors and use the surface mount in the future.

Tell your supervisor to be careful. It is true that virtually all attenuators work at 4K, but only some work at mK temperatures since most become superconducting. Hence, be careful if you are installing attentuators at the mixing chamber (which you usually have to do). It used to be that standard attenuators from some companies worked well (e.g. attenuators from XMA) meaning you only needed to know which brand to buy. However, in the past few years they all seemed to have changed something so nowadays you usually have to buy special cryogenic attenuators (which are quite a bit more expensive) if you want to be sure that it will work.