# Presentation: 857139

## 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

## Topics For Today

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

## He Reservoir

- Present
- Two 48” ASME F&D heads with 4 x 10” holes and 1.5” straight flanges
- Volume= 46.3 gallons
- Surface Area=6,490 sq. in.
- Possible change
- Two 42” ASME F&D heads with no holes and 1.5” straight flanges
- Volume= 53.4 gallons
- Surface Area=2,990 sq. in.

## 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?

## 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

## Layout of Ports (42” Reservoir)

- N2 Jumper

- N2 In Bayonet

- He In Bayonet

- Phase Separator Relief

- Phase Separator Bayonet

- Reservoir Relief

- Vacuum Vessel Relief and Pumpout

- Temperature and Pressure Readouts

- N2 Out C-Seal

- Vacuum Header Bayonet

- 4 K He Out Bayonet

- Vacuum Header Valve

- Cool Down Valve and Relief

- Neck Bleed Flowmeter

- Vacuum Header Relief

- Heat Exchanger

- Phase Separator

- 4 K Valve

- 2 K Valve

- HX Support

- Reservoir Inlet

- Reservoir Outlet

- 2 K Operation

- 4 K Operation

## Layout of Ports (48” Reservoir)

- N2 Jumper

- N2 In Bayonet

- He In Bayonet

- Phase Separator Relief

- Phase Separator Bayonet

- Reservoir Relief

- Vacuum Vessel Relief and Pumpout

- Temperature and Pressure Readouts

- N2 Out C-Seal

- Vacuum Header Bayonet

- 4 K He Out Bayonet

- Vacuum Header Valve

- Cool Down Valve and Relief

- Neck Bleed Flowmeter

- Vacuum Header Relief

- Heat Exchanger

- Phase Separator

- 4 K Valve

- 2 K Valve

- HX Support

- Reservoir Inlet

- Reservoir Outlet

- 2 K Operation

- 4 K Operation

## 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?

## Neck

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

## 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

## 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)

## 80 K Shield

|  |
| --- |

| Layers of MLI | Radiant Heat Leak | N2 Boiloff | N2 Boiloff |
| --- | --- | --- | --- |
|   | [W] | [g/s] | [L/hr] |
| 0 | 1432 | 7.3 | 33 |
| 15 | 13.25 | 0.07 | 0.33 |
| 30 | 6.8 | 0.035 | 0.16 |
| 60 | 3.42 | 0.017 | 0.08 |

## 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

## 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

## 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
- <0.02 Gauss, roughly a factor of 50 reduction

## 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

## 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)

## 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)

## °C

- mA/cm

## 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”

## Magnetic Attenuation

- Cavity Attenuation: 16
- Inside Attenuation: 6
- Outside Attenuation: 5.3

## Slide 23

## Magnetic Saturation

- Using an applied field of 0.9 Gauss, saturation doesn’t appear to be an issue (<< 15,000 Gauss)
- Cavity Flux: 900 Gauss
- Inside Flux: 2,700 Gauss
- Outside Flux: 3,150 Gauss

## 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 earth’s magnetic field?

## 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

## 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

## 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

## Magnetic Shielding

- Questions, comments, concerns?

## 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