1. Review of PANDA Magnet Designs Reviewers A. Dael, D. Tommasini, and A. Yamamoto Held at GSI, 19 - 20th April, 2007

2. Acknowledgements Reviewers would thank all presentors and the review organizers/secretaries for their hard work to prepare for the review and for their hospitalities. We wish further successful cooperation to reach the PANDA magnet to be successfully completed.

3. Task given Review of two designs –Pro. & Con., and evaluation, Advise a design adequate for PANDA –Can we find a best, unified design, and the reasons, Suggest further work to be done –Further optimization, and –Necessary works in balance of other systems

4. Recommendations (1) Superconductor: –Al-stabilized NbTi-superconductor Mechanical and electrical properties to be further optimized, Coil-winding and support-shell configuration –Single or multi-layer winding Operational current to be optimized in balance of quench protection and cryogenics operation, –Thin support shell adequate for less mechanical- stress consentration between coil and shell, –Energy/Cold-mass (E/M) ratio of 5 (~10) kJ/kg may be a convenient guide-line,

5. Recommendations (2) Thermal insulation –Further studies suggested on Radiation heat load to be minimized by pure-Al coated cold surface, Conduction support Current leads (conduction, gas-cooled), Cooling –Indirect cooling with both 2-phase force flow and thermo-syphon to be available,

6. Recommendation (3) Cryogenics –He Refrigerator would be the primary option, Efficient and flexible in various operational mode (pre- cooling, powering, quench recovery, power failure recovery.. ) –Comment: Cryo-cooler would be convenient, –if no additional operational effort required, and –If no Lhe systems available, »Pre-cooling system for safe cooling required, »Combination with Lhe reservoir would not be smart, »Extra, operational effort required, if the system design not well considered, »System not be so much redundant against emergency and/or failure modes

7. Recommendation (4) Electromagnetic design with Iron Yoke –Smaller dF-z is encouraged from the magnet design and safety view point, – Further optimization advised in balance of dF-z, yoke-demensional constraint, and accessbility,

8. Recommendation (5) Safety –Conductor Load-line ratio of ~ 50 % adequate to keep a temperature margin of > 1.5 K ( @ T-op = 5 K) –Coil E/M ratio of 5 (= 10 kJ/lg) adequate for the thermal stress free condition in case of quench, Connections between split windings to be pursued –Cooling Indirect cooling with pure-Al strips temperature equalization adequate, in stability and high pressure (Liquid gas) handling,

9. Recommendation (6) Quench Protection –Energy extraction with PS switch-off, –Quench back from support shell, –Quench-propagation by using heater may be advised for redundant safety. –Current leads need to be redundant against quench (specially in case of HTS current leads) >> back-up leads required,

10. Recommendation (7) High-pressure gas safety –High pressure design should be adaptable for He-refrigerator max. pressure (10 ~ 20 bars).

11. Summary of Comments The magnet parameters are clearly in the range of state of the art Aluminum stabilised solenoids. Also the indirect cooling has decisive advantages and is recommended. So the basic options of existing solenoids for HEP are recommended. The reasonable axial force equilibrium is better; The magnetic configuration from DUBNA has better optimisation

12. COMMENTS on the budgetary offers: The two offers are difficult to compare: –different questions have been asked to the companies by different people. If collaboration needs consolidated industrial budgetary estimations same global specifications and definition drawings with clear scope of supply must be sent from unique authority to several companies in the world and may include a technical questionnaire; This phase needs also a first definition by the collaboration –of the responsibility limit of the companies and of the procurement scheme that will be used ( Is there any in kind contribution for subparts,Who is giving the orders, who is doing follow up…?)

13. Conclusion Seeing the extensive design work still to be done, we strongly recommend to converge in one unified reference design with following concept, –Al-stab. NbTi conductor, –Indirect cooling –Cryogenics system with Refrigerator It is encouraged to seek further optimum yoke design to reduce axial difference force.

14. For Collaboration : Clearly define: –interface with Cryogenics FAIR system –Handling capacity ( –Magnetic measurements –Field time stability requirement and ramping time constraint –acceptable total height of the magnet (thermo siphon case) –Fixed specifications allowed the space available for the coil and YOKE with view of reasonable equilibrium of the forces Define work packages to allow team working in synergy on a unified design. We encourage a superferic dipole.

16. Design Reviewed Magnet –Superconductor: Cu or Al stabilized? –Coil: Single or multi-layer coil? –Support: –Cooling: Indirect (2  -flow or thermo-syphon) or bath-cooling? –Safety: thermal and mechanical stress, quench protection, high-pressure, residual magnetic field Cryogenics –Pre-cooling: refrigerator, or pre-cooler? –Steady state: refrigerator or cryo-cooler? –Quench recovery: refrigerator or LHe, LN2,

17. Design-Work Looked at Strucutre design –Electromagnetic force Coil itself, – Interaction of Iron-Yoke and coil –Gravity and Acceleratrion Force Support and safety condition, –Asembly, Acess, Maitenance

18. Design Looked at Operation and Maintenance Cryogenics Power system Monitoring, Controlling, Safety and Protection