1. „Cryogen-free“ Dilution Refrigerators
50 Years of Dilution Refrigeration, Manchester, 16 September 2015
„Cryogen-free“ Dilution Refrigerators
Kurt Uhlig
Walther Meissner Institute
Garching, Germany

2. 1990: Patrick Pari, Adv Cryog Eng 35: 1079 first cryogen-free DR
precooled by GM cryocooler
1999: delivery of PT4-05 (#2 in CRYOMECH production line)
2002: Cryogenics 42: 73
„ 3He/4He DR with pulse tube precooling “
2007: Prouvé et al., JLTP 148: 909
„Pulse-Tube Dilution Refrigeration Below 10 mK“

3. „Cryogen-free“ dilution refrigerators
Cryomech
PT405
T(mc2) = 4.3 mK
trap
PT1
heat leak:
Q(tot) = 70 nW
GM-precool:
Q(GM) = 170 nW
PT2
shield
cfhx
flow
restriction
IVC
Cryogenics 44 (2004) 53
hx‘s
double mc
3He melting
curve therm.

4. „Cryogen-free“ dilution refrigerators
VeriCold Inc.:
no inner vacuum can (IVC)
big mixing chamber plate
separate pulse tubes from rotary valve
all electrical 300K
precool circuit
(or gas heat switches, BlueFors)
High refrigeration powers
( mK)
(1.75 mK)
Superconducting magnets
(up to 18 T)
Clear shots
Top loading
Bottom loading (cold sample exchange)
Automatic cooldown
~ 75% of newly sold DRs are CF

5. CF-DR with 1K-stage 4He-1K-stage: PT Q = 100 mW @ 1.3 K
(80 m3/h pump)
T(min) = 1.05 K
CF-DR with 1K-stage
(exp. on sc quantum circuits) PT
405
Cryomech PT405 RM:
1st stage: 32 K
40 75 K
2nd stage: 2.5 K
0.5 K
DR-stage: mK
T(min) = 4.0 mK
(CMN + fixed point device)
CMN
sc FPD

6. Vibrational heat leak:
run fridge at base temperature
fill 1K-stage with 4He(liq)
operate 1K-pot in single cycle mode
turn off pulse tube cryocooler
see if mixing chamber temperature drops
(and make sure, still temperature and inlet pressure remain unchanged)
Cryogenics !

7. J. Hoehne, Cryocoolers 18 (2014) 319
piston
cylinder
oil
90 mm
gear pump
ν = 1 Hz
el. motor
pV - efficiency: η ~ 70%
J. Hoehne, Cryocoolers 18 (2014) 319
J. Hoehne: arXiv: (CEC/ICMC 2015)

8. Thanks for
your attention!

11. AUTOMATION! Characteristics of dry fridge:
„Cryogen-free“ dilution refrigerators
Characteristics of dry fridge:
Wide geometry, no He, no 1K-pot,
automatic cooldown and warmup
AUTOMATION!
2004:
helium: 5 €/l
power 9c / kWh
PTR: 25,000 €
compare with
He-cryostat
20 l (liq) / day )
2015:
helium: 7.50 €/l
power €/kWh
PTR: 33,500 €
amortization:
280 days 5kW-PTR
(320 days 10 kW-PTR)
amortization:
266 days 5kW-PTR
(330 days 10kW-PTR)

12. „Cryogen-free“ dilution refrigerators
J. Hoehne:
arXiv:
(CEC/ICMC 2015)