Proton Driver Test Cryostat: Discussion of Possible Changes for Magnetic Shielding and Ease of Manuf

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Proton Driver Test Cryostat Discussion of
Possible Changes for Magnetic Shielding and Ease
of Manufacturing

• Michael White
• Technical Division E F
• Fermi National Accelerator Laboratory
• November 1, 2005

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Topics For Today

• SMTF Flow Schematic
• He Reservoir
• Neck
• MLI around 80 K shield
• Magnetic Shielding

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He Reservoir

• Present
• Two 48 ASME FD heads with 4 x 10 holes and
  1.5 straight flanges
• Volume 46.3 gallons
• Surface Area6,490 sq. in.
• Possible change
• Two 42 ASME FD heads with no holes and 1.5
  straight flanges
• Volume 53.4 gallons
• Surface Area2,990 sq. in.

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He Reservoir

• 48 case
• Total External Surface Area 13,401 in2
• Distance from He to VV 1 in.
• Fire Relief Diameter 3.6 in.
• 42 case
• Total External Surface Area 10,652 in2
• Distance from He to VV 9 in.
• Fire Relief Diameter 1.1 in.
• CGA mentions nothing about conduction through
  vessel connections. Should it be included?

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He Reservoir (Benefits of Change)

• Increased access to Phase Separator, Heat
  Exchanger, Valves, Bayonets, and Plumbing
• 2 Holes were used already
• Pressure Vessel Code goes from Division II to
  Division I (simpler)
• Reduced Surface Area and increased distance to
  vacuum vessel lead to smaller reliefs

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Layout of Ports (42 Reservoir)
2 K Valve
HX Support
4 K He Out Bayonet
4 K Valve
Phase Separator Bayonet
N2 In Bayonet
Vacuum Header Valve
Heat Exchanger
Phase Separator Relief
Vacuum Header Relief
He In Bayonet
Vacuum Header Bayonet
Reservoir Outlet
Reservoir Relief
Reservoir Inlet
Phase Separator
N2 Out C-Seal
Neck Bleed Flowmeter
2 K Operation
N2 Jumper
4 K Operation
Temperature and Pressure Readouts
Cool Down Valve and Relief
Vacuum Vessel Relief and Pumpout
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Layout of Ports (48 Reservoir)
Reservoir Outlet
2 K Valve
4 K He Out Bayonet
4 K Valve
Phase Separator Bayonet
N2 In Bayonet
Vacuum Header Valve
Phase Separator Relief
Vacuum Header Relief
He In Bayonet
Vacuum Header Bayonet
Reservoir Relief
Phase Separator
Heat Exchanger
HX Support
N2 Out C-Seal
Reservoir Inlet
Neck Bleed Flowmeter
2 K Operation
N2 Jumper
4 K Operation
Temperature and Pressure Readouts
Cool Down Valve and Relief
Vacuum Vessel Relief and Pumpout
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He Reservoir (Drawbacks to Change)

• Less access through central portion of cryostat
• All plumbing and instrumentation can be easily be
  rerouted around He reservoir
• May make it more difficult to hang objects below
  cryostat
• Other reasons?

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Neck

• There are three areas of concern about the neck
• Helium Heat Leak
• Nitrogen Heat Leak
• Formation of Ice Balls

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Neck

• Proposed changes
• I spent a fair amount of time trying to develop a
  removable neck
• All my ideas ended up too complex
• Idea Abandoned

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Neck

• However, vertically dropping both the helium
  vessel and the nitrogen intercept for the
  Fermilab design will reduce heat leaks and the
  chance of frost balls
• Ample room since Fermilab is only testing
  horizontal cavities
• Very easy design change (dimensions only)

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80 K Shield
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80 K Shield

• A small amount of MLI goes a long way towards
  saving Nitrogen (and will help to create a more
  even temperature distribution)
• The original goal of keeping entire 80 K system
  under 90 K does not depend on MLI
• With at least 15 layers of MLI, almost all
  boiloff is used for intercepting conduction heat

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Magnetic Shielding

• The following is based off of conversations with
  Larry Maltin of Amuneal
• Please remember the following
• I am not a magnetic shielding expert
• I made many remarks on different options
• The remarks are intended solely to promote
  discussion leading to a greater understanding of
  magnetic shielding and greater confidence that
  our shielding strategy will work

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Magnetic Shielding

• Assumption Magnetic Shielding Requirements
  similar to that of Single Module Test Cryostat
• SMTC measured magnetic flux densities
• 0.9 Gauss vertically
• 0.2 Gauss horizontally
• SMTC requires
• lt0.02 Gauss, roughly a factor of 50 reduction

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Magnetic Shield

• Four Possible Options
• Shield the cavity
• Shield the inside of the vacuum vessel
• Using cylinders and heads
• Using cylinders and cones
• Shield the outside of the vessel

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Materials

• The properties we are concerned with are
• Permeability
• Saturation
• Reluctance (geometry dependent)
• There are essentially two choices of material
• 80 Ni Mumetal (room temp)
• Cryoperm (cryogenic temp)

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Materials (cont.)

• 80 Ni Mumetal
• Saturation 8,000 gauss
• µ40 60,000
• µdesign 15,000
• Cryoperm (at cryogenic temperatures)
• Saturation 9,000 Gauss
• µ40 65,000
• µdesign 15,000
• Can be annealed to have optimum permeability at
  77 K or 4 K (4 K slightly better)

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mA/cm
C
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Shield Placement Comparison Study

• For Simplicity, End Effects and Holes were
  Ignored
• One Layer of 0.040 Material was Used
• Cavity Radius 20
• Inside Vacuum Vessel Radius 60
• Outside Vacuum Vessel Radius 70

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Magnetic Attenuation

• Cavity Attenuation 16
• Inside Attenuation 6
• Outside Attenuation 5.3

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Magnetic Saturation

• Using an applied field of 0.9 Gauss, saturation
  doesnt appear to be an issue (ltlt 15,000 Gauss)
• Cavity Flux 900 Gauss
• Inside Flux 2,700 Gauss
• Outside Flux 3,150 Gauss

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Pros and Cons of Cavity Shield

• Pros
• Less Material
• Easily Replaced/Repaired
• Easily Manufactured
• One layer closer in replaces two layers further
  out

• Cons
• At least three different shields needed (single,
  double, triple)
• May need to be cooled prior to cooling cavity,
  and will at least need to be cooled
  simultaneously

Question Does the cavity need to be magnetically
shielded from the solenoid/quadrupole? Does this
make it easier or harder to install a shield from
earths magnetic field?
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Pros and Cons of Inside Shield

• Pros
• Less Material than Outside
• Shield is not Cavity Dependent
• Vacuum Vessel does Provide some Protection

• Cons
• Easily Damaged at Connection between Upper and
  Lower Assemblies (treat like glass)
• Not Easily Replaced
• Many Penetrations
• One Layer Probably not Adequate
• Far more Material than Cavity Shield
• Harder to Manufacture

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Pros and Cons of Outside Shield

• Pros
• Easy to manufacture
• Shield is not cavity dependent
• Can be easily repaired/replaced

• Cons
• Easily Damaged (treat like glass)
• One layer probably not adequate
• Large amount of material

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Formed Head vs. Cone

• Formed Head
• Saves space in cryostat, (not as much of an issue
  for Fermilab)
• Much more expensive, will require shipping
  between magnetic shield supplier, head
  manufacturer, and annealer
• Cone
• Takes up more space (which become available if I
  drop the He reservoir)
• Could all be done at magnetic shield supplier for
  much cheaper

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Magnetic Shielding

• Questions, comments, concerns?

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Last Discussion Point

• To what level do we want to detail He system?
• We probably want AD/Cryo to build our bayonets
  and some control valves, vendors would be much
  more expensive
• Modeling could take as much time as installing
  components

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