Vibration-Free Pulse Tube Cryocooler Systems for Gravitational Wave Detectors II II --Cooling Performance and Vibration -- Rui Li A, Y. Ikushima A, T. Koyama A, T. Tomaru B, T. Suzuki B, T. Haruyama B,T. Shintomi B and A. Yamamoto B A Cryogenics Division, Sumitomo Heavy Industries, Ltd. B High Energy Accelerator Research Organization (KEK) 1
Background 1. 1. 4K 4K pulse tube cryocooler was was chosen for for the the Cryogenic Laser Interferometer Observatory (CLIO).. Because of 1) Long Interval Observation 2) Remote Area 3) Highly Sensitive Detectors 2. 2. 4 K PT PT has has lower vibration, but but not not enough for for the the CLIO. Acceleration : Two Orders of Magnitude Lower than GM Displacement : The Same Order as GM Laser beam 10K 20K Sapphire mirror 4.2K Vibration isolator Heat link Cryocooler Low Low vibration PT PT system is is necessary 2
Basic Idea Basic Idea 1 To Make Use of a Commercially Available 4K PT Cryocooler Basic Idea 2 To Introduce Vibration Reduction Components for Separating Overall Cold Head Vibration Cold Stage Vibration for Reducing Them Effectively. 3
Schematic Diagram Cold Head Connecting Tube Upper Flange Bellows FRP pipes Valve Unit Lower Flange 1st Cold Stage 1st VR Stage Heatlinks Supporting Frame Cryostat 2nd Cold Stage 2nd VR Stage Valve Unit Table (Compressor and flexible Hoses are not shown) 4
Major Component -4K PT Cryocooler 1. 1. 4K 4K Pulse Tube Cryocooler 1. Model : SRP-052A Commercialized by Sumitomo Heavy Industries, Ltd. 2. Specification 0.5W@4.2K / 20W@45K with a 7kW compressor 3. Standard System Configuration of SRP-052A, without connecting tube Valve Unit Cold Head 4. Advantage Valve Unit Separated from Cold Head Easy for Maintenance, Short Down Time Flexibility for Vibration Reduction Cold Head Compressor 5
Major Component - VR Stage 2. 2. Vibration Reduction Stages 1. Introduced for the 1st stage and the 2nd stage 2. Interface for delivering cooling capacity 3. Linked to the original cold stages with braided wires 4. Supported by eight FRP pipes fixed to the top flange of cryostat 6
Major Component - Supporting Frame 3. 3. Cold Head Supporting Frame 1. Introduced for separating overall cold head vibration and cold stage vibration 2. Cold head was supported by the upper flange and the supporting frame 3. VR stages was supported by the lower flange and the cryostat 7
Major Component - Valve Unit Table 4. 4. Valve Unit Unit Mounting Table 1. The Isolation of the vibration from compressor and valve unit 2. A steel table weighted more than 140 kg 3. A connecting tube of 40 cm between the cold head and the table 8
Impact to Cooling Performance 1. 1. 4K 4K Pulse Tube Cryocooler 2. 2. Vibration Reduction Stages Influence of Braided Wires 3. 3. Cold Head Supporting Frame 4. 4. Valve Unit Unit Mounting Table Influence of Connecting Tube 9
Influence of Valve Unit Separation Second Clod Stage Temperature (K) 5.0 4.5 4.0 3.5 3.0 2.5 60 Hz 2.0 Standard Setup Valve Unit 40 cm Separated (0W, 0.5W) (20W, 0.5W) (0W, 0W) (20W, 0W) 25 30 35 40 45 50 First Cold Stage Temperature (K) Load Map for Standard Setup of SRP-052A without a Connecting Tube Load Map for VU 40 cm Separated The The specification of of SRP-052A (0.5W@4.2K (0.5W@4.2K /20W@45K) /20W@45K) was was kept, kept, with with a connecting tube tube of of 40 40 cm cm 10
Load Map of VR Stage 2nd Stage Temperature [K] 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 60 Hz (1st) Cu-wire / (2nd) Al-wire 0.7W 0.5W 0.3W 0W 15W 30 35 40 45 50 1st Stage Temperature [K] 20W Cold Stage VR Stage 0.7W 0.5W 0.3W 0W 15W 20W Load Map of Cold Stage Load Map of VR Stage At At VR VR stage, stage, 0.5W@4.4K & 15W@43.7K are are available 11
Setup for Vibration Measurement 15 degrees Y (Top View) Upper Flange Supporting Frame X Pressure Sensor Valve Unit Valve Unit Table Laser Displacement Sensor Lower Flange Supporting Frame Personal Computer Z Air Dumper Spectrum Analyzer 12
Displacement of 2nd Stage COLD STAGE VR STAGE 10 10 10 8 8 8 6 4 2 0-2 -4-6 6 4 2 0-2 -4-6 6 4 2 0-2 -4-6 -8-10 X-axis 0 0.5 1 1.5 2 TIME, sec. -8-10 Y-axis 0 0.5 1 1.5 2 TIME, sec. -8-10 Z-axis 0 0.5 1 1.5 2 TIME, sec. 13
Displacement of 2nd VR Stage ON OFF PRESSURE 1.2 1.0 0.8 0.6 0.4 0.2 0.0-0.2-0.4-0.6-0.8 X-axis 0 1 2 TIME, sec. 3.0 2.0 1.0 0.0-1.0-2.0-3.0 PRESSURE, MPa 1.2 1.0 0.8 0.6 0.4 0.2 0.0-0.2-0.4-0.6-0.8 Y-axis 0 1 2 TIME, sec. 3.0 2.0 1.0 0.0-1.0-2.0-3.0 PRESSURE, MPa 0.12 0.10 0.08 0.06 0.04 0.02 0.00-0.02-0.04-0.06-0.08 Z-axis 0 1 2 TIME, sec. 3.0 2.0 1.0 0.0-1.0-2.0-3.0 PRESSURE, MPa 14
Spectrums of Displacement Cold Stage / ON VR Stage / ON Background (VR Stage) 1.E+01 1.E+01 1.E+01 1.E+00 1.E-01 1.E-02 1.E-03 1.E-04 1.E+00 1.E-01 1.E-02 1.E-03 1.E-04 1.E+00 1.E-01 1.E-02 1.E-03 1.E-04 1.E-05 X-axis 0.1 1 10 100 FREQUENCY,Hz 1.E-05 Y-axis 0.1 1 10 100 FREQUENCY, Hz 1.E-05 Z-axis 0.1 1 10 100 FREQUENCY, Hz X-axis @1.2Hz 2.6 m 120nm 120nm Y-axis @1.2Hz 4.6 m 310nm 310nm Z-axis @1.2Hz 6.4 m 10nm 10nm 15
Conclusions 1. 1. A vibration-free pulse tube tube cryocooler system has has been developed for for gravitational wave detectors. 2. 2. The The major components of of the the system are are :: a commercially available 4 K PT PT two two vibration reduction stages a cold cold head supporting frame a valve unit unitmounting table 3. 3. The The cryocooler system was was able able to to deliver net net cooling capacities of of 15 15 W at at 45 45 K and and 0.4 0.4 W at at 4.2 4.2 K simultaneously 4. 4. The The displacement was was reduced by by 1 to to 2 orders of of magnitude for for horizontal direction (max. 0.65 m) by by 2 to to 3 orders of of magnitude for for vertical direction (( 0.05 m) 16