MECO Cryogenic System

1
MECO Cryogenic System
2
Overview

• Helium System
• Steady state 4.5 k system
• Steady state heat loads and operating points
• Thermal design of Dewars TS and DS
• Thermal Design of PS Dewar
• Liquid N2 System
• Quench
• Recool after Quench

3
Component Overview

• Four Separate Cryostats (PS, TS1, TS2 and DS)
• One Liquefier/Refrigerator
• Pressurized Liquid Nitrogen Tank-(Truck filled)
• Forced Convection cooling in 3 dewars (TS1, TS2
  and DS)
• Conduction cooling from He tubes to the coils (No
  He bath)
• PS is pool cooled- Natural convection and/or
  Forced flow cooling.
• Two storage/control dewars
• Vacuum insulated LN2 traced MLI.

4
Design and Operation Overview

• All active components are outside the shield
  wall.
• Many interconnections and valves to allow for
  flexible operation.
• Dewars can be cooled separately.
• Cooling of one dewar does not affect the state of
  other dewars.
• Valves allow the isolation of cryostats during a
  quench.
• Cool down with He circulated from and LN2 heat
  exchanger for Tgt80 K.
• Cool down with He from the liquefier for Tlt80K.
• Dewars are protected against overpressure during
  a quench.

5
Steady State Operation
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Estimated Heat Loads
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States in Cooling System
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Cryostat 4.5 K Cooling
All cryostats have stainless steel vacuum shells
and LN2-cooled thermal radiation shields.

• PS
• Bath cooled with 6700 liter LHe volume to safely
  remove 192 W of nuclear heat load at 4.5 K
• 25 cm diameter quench vent stack keeps quench
  pressure below 5 atmospheres
• TS and DS
• Lack of nuclear heat load enables conduction
  cooling
• Inner and outer copper shells intercept radiation
  heat load and take it to He-traced copper heat
  sinks at the top of each coil

9
He Vessel Pressure for PS Quench
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Cooldown
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Liquid Nitrogen System

• Tank filled by commercial vendor
• LN2 distribution lines cool shields in 4.5 K
  conduits.
• LN2 cools heat stations on valves and vacuum
  separators.
• Commercial MLI systems combined with an LN2
  shield is used for lines, cryostat and dewars.
• LN2 cooled heat stations on mechanical supports
  in PS, DS and TS.
• More details on the Ozone issue in a later
  talk