The Latest Status of the KAGRA Cryogenics

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The Latest Status of the KAGRA Cryogenics
N. KIMURA A, D. CHEN B, T. KUME A, S. KOIKE A, Y.
SAKAKIBARA B, T. SUZUKI A, C. TOKOKU B, K.
YAMAMOTO B, M. OHASHI B, and K. KURODA B
A High Energy Accelerator Research Organization,
KEK B ICRR, University of Tokyo,
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Outline

• Over View of KAGRA Cryogenics
• Time Line
• Performance Tests
• Cryostat with Cryocooler-units
• 1/2 Dummy Payload
• Vibration in the cryostat
• ( Mr. D. Chen presented at poster
  session)
• Prototype Duct Shield
• ( Preliminary results )
• Summary

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Overview of KAGRA Cryogenics
Seismic Attenuation System (SAS)
Radiation Shields
Cryogenic Payload
5 m Duct Shield
Sapphire Mirror (?-alumina crystal)
5 m Duct Shield
Main Laser Beam
Four Cryocooler Units
S.Koike
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The requirements for KAGRA Cryogenic

• Temperature of the test mass/mirror lt 23 K
• Inner radiation shield have to be cooled to lt 8
  K
• The test mass have to be cooled without
  introducing
• excess noise, especially vibration due to
  cryocoolers.
• Easy access and enough capacity
• to installation work around the mirror.
• Allowable size as large as possible under public
• transport regulation and KAGRA tunnel.
• Meets ultra high vacuum specification lt 10-7
  Pa

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Conceptual Design of the Cryogenics
Low vibration in U. H. Vacuum Stop propagation of
300K radiation Prevent heating by scattered beam
80K PTC with Vibration reduction
4K PTC with Vibration reduction
Baffles
two units
Cooling Cryo-Payload
1W
Main Beam
400kW
4W?
8K shield
two units
300K Radiation lt 1.0 W (lt 0.5 W x 2)
80K shield
Duct Shield
Cryostat
Cooling 8K shield
2 units for cool cryo-payload 2 units cool for 8K
shield 4 units cool for 80K shield

• Four 4K cryocooler units per one cryostat
• Baffles against wide scattering is cooled via 8K
  shield.

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Valve Unit
Structure view of the Low Vibration Cryo-cooler
Unit
Bellows
Flexible Heat Links
????
1m
Part of Vibration Reduction Stage
5N8 8K Conduction Bar
Support Frame (Support Cold Head)
80K Cooling passage
Vacuum Vessel (Support Conduction Paths)
2m
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Cooling Time Reduction with Black Coating
To accelerate cooling down by radiation, plated
black coating with Diamond Like Carbon on outer
surface of the payload and inner surface of 8K
shield.
TM Test Mass RM Recoil Mass IM Intermediate
Mass
S.Koike
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Time Line of KAGRA Cryogenics
2011 Jfy
2012 Jfy
2013 Jfy
Apr./12
Apr./13
Apr./14
Apr./11.
We are here 22th/Oct.
Four Mirror Cryostats
Manufacture components
Design by KEK
Assemble and factory test with cryo-coolers
Transport to storage near Kamioka
Bidding
Cryo-cooler units
Performance test
Design by KEK
Transport to Kamioka
Production of seven cryo-cooler units with
performance test
Custody at Kamioka
Production of nine cryo-cooler units with
performance test
Duct shield units
Production of three ducts shield units without
cryo-coolers
Design by KEK
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Performance of the Cryostat
Performance test at Toshiba Keihin Product

• It took 12.5 days to cool down from 300 K to 8K.
• Cool down time of the cryostat was almost
  consistent with the predicted cooing time by
  Calculation model.

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Results (with copper heat links)

• Cryo-coolers for payloads didnt cool down
  completely (2nd stage stayed at 20 K)
• Thermal conductivity of heat links calculated
  from results one fifth of literature!
• Thermal contact resistance between payloads and
  heat links, etc.

Emissivity Sapphire 0.5 Platform
0.3(T/300K) IM 0.4(T/300K)
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Cooling test in Toshiba
Heat Load Response Test
Heater and thermometer
Pulse tube cryocoolers
Pulse tube cryocoolers
Sapphire mirror
Pulse tube cryocoolers
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Cooling test _at_ Toshiba
It is confirmed that 25 ppm (10 W) _at_400 kW of
scattered loss is acceptable as heat load for
the cryocoolers via the 8 K radiation shield.
Scatted light power is 4 W _at_400 kW beam
power when scattered loss on the mirror surface
is 10 ppm.
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Measurement of thermal radiation
Performance Test of the Prototype Duct Shield

1. Thermal Radiation

1. 40 K

1. 150 K

1. 250 K

1. 600 mm

1. 250 mm

1. 17 m

• Two aluminum plates suspended
• 600 mm plate (Left side) is heated up to 300 K
  and emits thermal radiation
• 250 mm plate (Right side) absorbs radiation and
  is heated up
• Calibration is conducted using heater on 250 mm
  plate
• Coated with Solblack to enhance emissivity or
  absorptivity

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Preliminary Results
courtesy
Preliminary
Reduced by Duct Shield
Reflectivity at 10 um Duct 0.940.02 Solblack 0.3
0.1

• Calculated value has error of several times
• Measured reflectivity at 10 µm of shield has
  error
• Rays are reflected by shield many times
• Measured value is within the error

It was confirmed duct shield could reduce 99.9
of heat to cryogenic payload.
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Measurement of scattered light
635 nm, 4.5 mW
200 ppm of laser light came back to camera

• Red light from laser diode
• Photographs of scattered light when angle changes
• Calibration by changing exposure time
• Future work Vibration measurement, calculation
  of equivalent GW amplitude

Background
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Shape of duct shield at each resonant frequency.
Resonant Frequency F1 18.85 Hz F2 25.48 Hz F3
38.52 Hz F4 40.28 Hz F5 40.99 Hz F6 43.65 Hz
F7 44.20 Hz F8 46.31 Hz F9 49.01 Hz F10 59.07
Hz F11 63.66 Hz F12 64.58 Hz F13 68.25 Hz F14
68.69 Hz F15 73.87 Hz F16 77.00 Hz F17 77.16
Hz F18 94.00 Hz F19 96.18 Hz F20 99.86 Hz
F17 77.16 Hz
F18 94.00 Hz
F20 99.86 Hz
F19 96.18 Hz
It was confirmed that the most of resonant
frequencies are cause of strength of the vacuum
chamber, and weaker than that of inner
shield. These results have been feedback to the
duct shield design.
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Structure view of the Production Duct Shield
Specification L5 m -gt Qinput lt 0.5 W
Baffles
80 K Duct Shield
Bellows
Support Frame
Vacuum Vessel
5 m
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Summary

• 1. KAGRA cryogenics consisting of cryostat and
  cryo-
• cooler units was designed, fabricated, and
  tested
• their performances during 2011JFY and 2012JFY.
• 2. At the performance test, following items were
• confirmed and verified
• The cooling and vibration performance of sixteen
  cryocooler units.
• The cooling performance of all the four
  cryostats.
• Vibration on the surface of inner radiation
  shield.
• Experiment with half size of dummy cryo-payload
• 3. Experiment with proto type duct shield
• was conducted, and result was agreed with
  predicted
• heat load. But, need more analysis work.
• 4. Design of the production of duct shield were
  almost
• finished. Now, We are focusing our work on
• fabrication of the duct shields and preparing
  
• performance test.

Finally, we could achieve the big mile
stone which completed the cryostats on time!