low temperature techniques course 2008

Dr Kurt HaselwimmerCambridge Magnetic Refrigeration

Notes to a Low Temperature Physicist

or, what I wished I'd have known when I started

LT Techniques course, 26th Nov 2008

Time

PhD = 1000 days

LT is difficult

A Cabinet of Curiosities ?Ole Worm (1588-1654)

Helium

Another Curiosity ?

http://www.flickr.com/photos/noyespictures/2289512991

Try Dry

Pulse tubes now to 2.7K

Dryogenic – DMS-1000 system

Wiring

“God hangs the greatest weights upon the smallest wires”

Francis Bacon

http://www.flickr.com/photos/andrewmckaskill/16531297

Don’t build if you can buy

Rewiring a cryostat properly costs less than getting a powersocket installed. Do it right and do it only once.

http://www.cmr-direct.com

Pumps andplumbing

http://www.flickr.com/photos/arcanegazebo/445426559/

“A vacuum is a hell of a lot better than some of the stuff thatnature replaces it with”

Tennessee Williams

• Always clean and grease o-rings• Only Use Viton O-rings – buna-N cracks

• Paint your KF-fittings

• Don't use poppet relief valves on vacuum cans

• Always boil-off flux on HS joints

• Buy SS flexibles from Kurt J Lesker

• Use plastic KF clamps from BOC edwards

• Use only bellows sealed valves on He-3

Millikelvin work

http://www.flickr.com/photos/arcanegazebo/3299089

The dilution fridge – the mainframe ofmK machines

Keep it simple,stupid !

http://www.flickr.com/photos/hynkle/2587828754

Simplicity means achieving themaximum effect with the minimummeans.

Koichi Kawana

Entropy, S

Temperature

Entropy, S

T MIN<50mK

B min = 0.1 T

B max = 6T

T BATH = 4.2K, 1.5K

Temperature

Refrigerant

Entropy, SB min = 0.1 T

B max = 6T

Temperature

Refrigerant

SuperconductingMagnet

Entropy, SB min = 0.1 T

B max = 6T

Temperature

1

T BATH = 4.2K, 1.5K

Thermal Contact

Bath

RefrigerantPill

SuperconductingMagnet

Entropy, SB min = 0.1 T

B max = 6T

Temperature

1

T BATH = 4.2K, 1.5K

2

T MIN<50mK

Heat Switch

Bath

RefrigerantPill

SuperconductingMagnet

Practical Refrigerators

Connection to Bath

Heatswitch

Sample Region (Double axis rotator)

Refrigerant

LT is difficulta

http://www.flickr.com/photos/rakkar/574407246

Cambridge Magnetic Refrigeration

www.cmr.uk.com

Cryoconsumables - wiring, connectors etc

www.cmr-direct.com

Completely Dry systems -Dryogenic Ltd

www.dryogenic.com

Dr Kurt HaselwimmerKurt@cmr.uk.com