1. SNS PPU Cryomodule Magnetic Shields
SNS PPU CRYOMODULE PDR
SNS PPU Cryomodule Magnetic Shields
Gary Cheng
Wednesday, February 27, 2019

2. Introduction
The HB spare CM magnetic shield model and related drawings are reviewed and minor modifications are made mainly to clean up the model. The end caps on both the inner and outer shields are re- designed. This report will address the following:
Modifications to Inner Magnetic Shield
Assembly of Inner Magnetic Shield
Modifications to Outer Magnetic Shield
Assembly of Outer Magnetic Shield
Review of the Original Cryomodule Magnetic Shield Design
Possible Design Changes
Remaining work

3. Modifications to Inner Magnetic Shield
Highlighted (in yellow) parts are modified.
Door supports are opened up slightly to facilitate door sliding in assembly.
End caps are re-designed to eliminate the hole for piezo, merge a couple pieces that do not need a slit any more and split the opposite part to ease assembly.

4. Assembly of the Inner Magnetic Shield
Install the reducer shield patches onto the helium vessel heads. Tape the two halves of shields together.
Install interconnection region shields. Tape & rivet shields together.

5. Assembly of the Inner Magnetic Shield (Cont’d)
Install shields onto the helium vessels. Tape & rivet shields together.
Install the end caps. Tape & rivet shields together.

6. Modifications to Outer Magnetic Shield
Shield not concentric to FPC
Highlighted (in yellow) parts are modified.
Door supports are opened up slightly to facilitate door sliding in assembly.
End caps are re-designed due to changes at both ends inside the vacuum vessel.
Found that magnetic shield openings not concentric with FPC. Now corrected.
Shield concentric to FPC

7. Assembly of the Outer Magnetic Shield
The outer magnetic shield patches are designed to be in a clam shell configuration. They are installed onto the spaceframe.
The shields are anchored to the spaceframe with a series of screws. Slotted holes allow assembly adjustments.

8. Assembly of the Outer Magnetic Shield (Cont’d)
Outer magnetic shield end caps are still under design currently. They will be installed upon finishing the work at the ends of the vacuum vessel (shown translucent).
DOWNSTREAM
UPSTREAM
Slot will be removed

9. Review of the Original Cryomodule Magnetic Shield Design
Dec. 6, 2000 FDR T. Hiatt report indicates that the original SNS cryomodule magnetic shield design goal is to achieve a shielding factor of 100 and attenuated field < 10 mG.
The ambient field is assumed to be 1.0 G.
Sun An’s Dec. 22, 2003 report states that analyses show that the transverse shielding factor can be > 100, however, the axial shielding factor for the HB CM is in the range of 7-21, depending on which algorithm is applied.
Axial shielding factor is low.
SNS has a pulsed machine so that the dynamic heat load is not so high. Despite the axial shielding factor being low, the overall shield design seems to be adequate to meet the SNS Qo requirements.
Nevertheless, SNS PPU CM magnetic shield design has room to improve.

10. Possible Design Changes
Based on our most recent magnetic shielding design experiences, we propose:
Inner magnetic shield material to use Cryoperm 10, which has better permeability at cryogenic temperature than a generic mumetal.
Add top-hat shape magnetic shields to the outer magnetic shield to attenuate the field leaked through FPC openings. See illustration of the proposed design.
Design changes may be evaluated analytically and the influence on cost can be investigated.

11. Remaining Work
Drawings for new and modified shield parts, mainly the end caps, need to be created.
If there is enough interest in the top hat shield design for FPCs, analyses to compare the shielding performance w & w/o the top- hat shield can be done.
For procurement, the statement of work needs to be developed.

12. Questions? Comments, Suggestions?
THE END
Questions? Comments, Suggestions?
Thank you!