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R&D Status and Plan on The Cryostat. N. Ohuchi, K. Tsuchiya, A. Terashima, H. Hisamatsu, M. Masuzawa, T. Okamura, H. Hayano. STF-Cryostat Design Construction Status of Cryostat R&D Studies of Cryostat Components Summary. Gaining the experience of the long cryostat for the S.C. cavity.

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r d status and plan on the cryostat

R&D Status and Plan on The Cryostat

N. Ohuchi, K. Tsuchiya, A. Terashima,

H. Hisamatsu, M. Masuzawa, T. Okamura, H. Hayano

STF-Cryostat Design

Construction Status of Cryostat

R&D Studies of Cryostat Components

Summary

stf cryostat design 1
Gaining the experience of the long cryostat for the S.C. cavity.

R&D of the high performance and the low cost ILC cryostat.

Cooling two types of the cavities of 35 MV/m and 45 MV/m down to 2 K in STF, and measuring the thermal characteristics.

Starting point of the STF cryostat design: TESLA TYPE III Cryomodule

R&D and study items for the STF cryostat

Understanding the TESLA design from the thermal and mechanical points of view.

Temperature profile and heat load of the components, and construction errors.

R&D component

SUS-Ti joint between the helium vessel and cryogenic lines.

Magnetic shield

Measurement of the remnant field in the shield and the magnetic characteristics of the shield material.

Survey of the low cost quadrupole magnet system (conduction cooling)

STF-Cryostat Design (1)

Target of the cryostat R&D in KEK

Strategy of the cryostat R&D

stf cryostat design 2
STF-Cryostat Design (2)

Design Overview of STF Cryostat

Two cryomodules are connected with bellow tubes.

  • Four cavities designed for 35 MV/m and 45 MV/m are assembled in the individual cryostat.
  • The total length of two cryostats is 13.2 m.
    • The vacuum vessel of the TESLA TYPE III cryomodule has the length of 11.4 m including one quadrupole.
stf cryostat design 3
STF-Cryostat Design (3)

Cross sections of STF Cryostat

Alignment

Target

80 K Thermal

Radiation Shield

5 K Thermal

Radiation Shield

Gas Return

Pipe (GRP)

  • The design of the cold mass are same as the TESLA TYPE III cryomodule.
    • Cold mass : support post, gas return pipe, thermal radiation shields (5 K, 80 K), cooling channels
    • The diameter of the vacuum vessel is 965.2 mm, same as the TESLA cryomodule.
  • The helium vessels, frequency tuners and input couplers between the cavities of 35 MV/m and 45 MV/m have different configurations.

Input Coupler

35MV/m Cavity

45MV/m Cavity

stf cryostat design 4
STF-Cryostat Design (4)

Cooling scheme and heat loads

STF-Phase-1

Cryogenic system : 20 W @ 2K

(Cold box : 600 W @ 4.4 K)

Calculated Heat Load for STF-Cryomodule (W)

Heat loads via signal wires are not included.

stf cryostat design 5
STF-Cryostat Design (5)

Calculated pressure distribution

Calculation model

Qc: 10/8 W or 30/8 W

m: evaporated helium gas

  • Pressure drop along the system = 2.27 Pa for 10 W, 17.59 Pa for 30W
  • Temperature at each cavity = 2.000 K for 10/8 W, 2.002 K for 30/8 W
construction of stf cryostat 1
Construction of STF-Cryostat (1)
  • Gas return pipes (GRP) are connected with the support posts which have the alignment targets.
  • The helium vessels for cavities are supported from the GRPs.
  • The surfaces for the connection are processed by a milling machine with the target precision of 0.05 mm.

Cryostat

Connection

Bellows

Gas Return Pipe

construction of stf cryostat 2
Construction of STF-Cryostat (2)
  • Thermal radiation shield : aluminum, vacuum vessel : carbon steel (used for magnetic shield)
  • These components have been delivered from the company (Hitachi) on 24th March.

Thermal radiation shield

Vacuum vessel for 45 MV/m cavities

construction of stf cryostat 3
Construction of STF-Cryostat (3)

Slide:8.4mm

Slide:8.4mm

Fixed

Fixed

Invar rod

Slide:1.4mm

Fixed

Slide:1.4mm

Fixed

  • The four support posts for the STF-cryomodules have been delivered from INFN Milano on March 3 under the research collaboration between INFN and KEK.
  • The support post on the inlet side is fixed to the vacuum vessel, and the other one has a sliding function.
    • The position change of the sliding support post by thermal contraction is calculated to be 8.4 mm.
  • The cavity helium vessels are hold with sliding supports from the Gas Return Pipes.
    • The axial positions of the helium vessels are decided by the invar rods.

Support post

Sliding cavity support

r d studies of cryostat components 1
R&D Studies of Cryostat Components (1)

SUS-Ti junction (35 MV/m cavity helium vessel)

SUS-pipe

Ti helium vessel

SUS

Ti

SUS-Ti junction by HIP

  • Material of helium vessel for the 35 MV/m cavity and the TESLA cavity : Ti
    • The SUS-Ti junction is being studied for the connection between the cooling channel pipes (SUS) and the helium vessels (Ti).
  • Samples of two types (Hot Isostatic Pressure, Friction Pressure Welding) have been manufactured. Mechanical strength tests have been completed.
    • For both methods, the mechanical strength at the junction was almost same as Ti at room temperature.
  • Helium leak test at 2 K (super-leak) will be performed next week.
r d studies of cryostat components 2
R&D Studies of Cryostat Components (2)

Heat Loss Measurement

  • The heat losses of the components in the cryomodule will be estimated by the temperature profile and the FEM calculation.
    • Temperature sensors
      • 2K~ 5K (input coupler, helium vessel etc) : Cernox temperature sensor (54 points)
      • 4K ~ 300 K (support post, thermal radiation shield etc) : PtCo temperature sensor (44 points)
      • > 80K : Copper-Constantan thermo-couple temperature sensor (58 points)
  • The heat loss of the system at the 2 K region will be measured by the attainable saturated pressure value of the He-II with the pump system.
r d studies of cryostat components 3
R&D Studies of Cryostat Components (3)

Wire Position Monitor

GRP

Cavity

Helium

Vessel

  • From the test results of the TESLA cryomodule, the 1st thermal cycle induced the position change of GRP with respect to the original position.
  • Measurement of cavity position during cool-down and warm-up : WPM sensors
    • Helium vessel : 2 sensors in axial direction

16 sensors for cavity helium vessels

    • GRP : 5 sensors for one cryostat

10 sensors for GRPs

summary
Summary
  • The cryomodule design for the STF phase-1 is based on the TESLA type III cryomodule.
      • Calculated heat loss of the cryostat at 2 K : 12.1 W
      • Cooling power of cryogenic system at 2 K : 20 W
  • Manufacturing the cryostat components have been completed, and they have been delivered from the company.
      • The four support post were delivered from INFN under the research collaboration between INFN and KEK.
      • The assembly of these components and the cavities will start in this summer.
  • R&D studies of the cryostat components;
      • SUS-Ti junction

The junctions have been manufactured by two methods (HIP, friction pressure welding). The helium leak test at 2 K will start next week.

      • WPM

The performance test will start in April.