1. Technical Summary - ANL
Part 1: Cryostat (J. Fuerst) Part 2: Magnet (Y. Ivanyushenkov) for the APS SCU Team: S. Bettenhausen, C. Doose, M. Kasa, Q. Hasse, I. Kesgin, D. Jensen, S. Kim, G. Pile, D. Skiadopoulos, E. Trakhtenberg, Y. Shiroyanagi, M. White Mar. 3, 2016

2. SCUs in operation at the APS
SCU0 installed in APS January 2013
(0.3 m magnetic length)
SCU1 installed in APS April 2015
(1.1 m magnetic length)
LCLS SCU R&D leveraged a mature cryostat design to save development costs.
Design was originally developed at the Budker Institute of Nuclear Physics and brought to ANL through a cooperative effort.

3. Cryostat Layout – from 0.3 to 1.5 meter magnets
Cryostat thermal performance is essentially independent of magnetic length.
The same cryostat is used to test both LCLS R&D magnets.

4. Cryogenic System Design
Closed cycle (zero boil-off) liquid helium bath-cooled magnets with cryocooler-based recondensation. Excess 4 K capacity is about 0.5 W.
Helium bath pressure/temperature is regulated using a heater.
Beam chamber is cooled at a higher temperature level due to high beam-induced heat loads (up to 20 W) in storage ring applications.
Numerical simulations verify existing design and guide future effort.

5. Vendor-Supplied Components
Vacuum vessel, thermal radiation shields, and liquid helium tank are built-to-print following a detailed SOW.
To date, three units have been ordered from two separate vendors.
Cold mass components (magnets, piping, beam chamber, support frame, etc.) are separately sourced or fabricated in-house.

6. NbTi Magnet - Cold Mass Assembly (1)
Magnets & beam chamber are installed and pre-aligned to the support strong-back
Magnetic gap and chamber clearance are established

7. NbTi Magnet - Cold Mass Assembly (2)
The liquid helium tank is mounted and connecting pipes between tank & magnets are routed.
Current leads, voltage taps, temperature sensors etc are added.

8. NbTi Magnet - Cold Mass Installation
Wiring checkout & end loading

9. Nb3Sn Magnet - Cold Mass Assembly (1)
Magnet envelope is similar to NbTi version.
Additional tuning and cooling features need to be accommodated.
Alignment between beam chamber and magnet is critical.

10. Nb3Sn Magnet - Cold Mass Assembly (2)
The project purchased two cold mass support frames so LBNL could do pre-assembly prior to shipment to ANL.
ANL activity upon receipt consisted of alignment check, LHe tank installation, and wiring

11. Final Assembly, Cooldown, Measurement
Final electrical connections are made between the cold mass and the current lead/cryocooler turrets.
Vacuum vessel turret and end covers are installed.
Cryostat is moved to the measurement bench and aligned.

12. Cryostat Performance – NbTi Magnet

13. Cryostat Performance – Nb3Sn Magnet
Dots represent NbTi magnet cooldown
Nb3Sn cooldown profile is very similar
Subtle differences reflect variations in design and assembly.

14. Typical NbTi Magnet Quench Response
Initial spike indicates rapid boiling, after which liquid and vapor return to equilibrium. System remains closed throughout, with no helium venting.
Slow linear reduction in temperature/pressure reflect the available excess cooling capacity of the cryocoolers.

15. Summary/Future Work Mature cryostat design performed as expected.
Prior assembly experience reduced risk & enabled the project to focus on magnet development.
This project has jump-started future cryostat R&D for both storage ring and FEL light source applications.
OLD
NEW
5-meter FEL SCU concepts
with QTY3 1.5-m magnets
New APS cryostat concepts are being developed based on experience and further analysis.