Development of Low Vibration Cryocooler

KEK Tomiyoshi Haruyama

1. Cooling requirements2. GM/Pulse Cryocooler3. Vibration measurement4. R&D of low vibration cryocooler

2003.2.6-7 TAMA Symposium, ICRR, Kashiwa

1. Cooling Requirements -CLIO

Cooling Requirements-Cryostat concept

4K Pulse tube Cryocooler

K４

Compressor

RT suspension

10K

20K

80K Pulse tube Cryocooler

Heat link

80K shield5m

Mirror

Buffer mass

4K shield

Seismic displacement

Cooling requirement

COOLING POWER-Mirror cooling

0.5W at 4.2K20W at 40K

-5m Shield cooling50W at 80K

VIBRATION at COLDENDS

-<10-7 m at 1Hz

CRYOCOOLER

Advantages-Easy to operate-Maintenance free (for 1-2 years)-No danger in tunnel (no cryogen)

Disadvantages-Sound + vibration

→Origin?

Driving mechanism

GM Cryocooler Pulse Tube Cryocooler

Compressor CompressorRegenerator Regenerator

CompressorPulse tube

Rotary valveRotary valve

Displacer

Motor

Origin and level of vibration

Solid piston

Driving motor

Pressure wave

GM~ ~ ~ ~

~Severe

~ ~ ~Intrinsic

Pulse tube Quiet

~ ~ ~Intrinsic

Commercially available 4K cryocooler

GM-Sumitomo Pulse-Cryomech Pulse-Sumitomo

Driving motor Buffer tank only

Vibration measurement at low temperature

CryocoolerAccelerometer

Reflector

Opt sensor

Sustaining post

Cryostat

Reflection displacement sensor

Sensor setup (single stage PT)

Photo sensorSustaining post

Cold end withreflection box

Vibration -real time

Vibration (GM)

Vibration (PT)

GM→ Pulse

Cryomech and Sumitomo 4K PT cryocooler

Pulse-Cryomech Pulse-Sumitomo

Driving motor+buffer tank

Buffer tank only(separated motor)

Final problem?-Pressure wave

x=pRL

6kt

k: bulk modulus E/3(1-2 ）

Example:SUSφ40X200,t=1Δp ＝ 2MPaΔx ＝ ~8μm（ Experiment ： 6~30μm ）

圧縮機

L

2R

t

Soft thermal link at cold stage

25μm→ ＜ 3μm ＠ RT 1HzSingle stage, 77 K6μm→0.5μm

CRYOMECH Giessen Univ.

R&D results of KEK-Sumitomo4K Pulse

1st stage

Flexible link

2nd stage

Flexible link

Concluding Remarks

-Pulse tube cryocooler: Final solution for mirror cooling

-Thermal link (vibration free stage):Key technology (R&D is going on)

-Innovative idea for vibration-free cold end: Prepare for testing

Concluding Remarks-Schedule

-April 2003 R&D cryocoolers will be dispatched-July 2003 Vibration/Cooling performance test-September 2003 Production will be started-March 2004 All the coolers will be available

Vibration image

GM Cryocooler Pulse Tube Cryocooler