Magnetic Fields in s/f/ePHENIX John Haggerty Brookhaven National Laboratory

BaBar solenoid Built by Ansaldo, delivered to SLAC ~ T solenoid Major parameters of the cryostat: –Inner radius: 140 cm –Outer radius: 173 cm –Length: 385 cm I visited the coil in End Station A at SLAC on May 17, 2013 –It is packed in transfer frame for shipping –Power supply, quench detection, and dump resistor available –Some cryo components available (but most going to FRIB) –Freight cost $33k 7/29/20132

BaBar solenoid 7/29/20133

4

ePHENX LOI Internal Discussions Jin Huang, et. al.5 RICH GEM Station4 EMCal HCal GEM Station2 z (cm) R (cm) HCal p/A EMCal GEMs EMCal & Preshower μ-TPC DIRC η~1 η~ R (cm) GEM Station3 GEMs Station1 η~-1 e-e- e-e- AreoGel

7/29/20136

Magnetic field 2D magnetic field calculations have been done for some geometries 3D models and optimization still to come 7/29/20137

Questions about magnet acquisition What tests should we make before the magnet is trucked across the US? How worried should we be about vibration? What tests should we make on arrival? How feasible is a cold test of the coil? 7/29/20138

Questions about the sPHENIX design The sPHENIX HCAL is the barrel part of the flux return and consists of steel plates running along the axis of the solenoid with plastic scintillator tiles in slots between plates Do you see any difficulties with this design? How can we quickly evaluate the forces on the plates? We’d like to modify the “chimney” to stay out of the acceptance (now it is vertical, we’d like it to come out at about 37°); are there any fundamental problems with doing that? We don’t have a good analysis of the static forces, but we have no analysis of the dynamic forces (during a quench, for example); are there any shortcuts to understanding those forces? 7/29/20139

Future additions Some ideas for the future include additional field elements, both passive and active: Forward piston which increase the transverse field in the forward direction A dipole on one side only Air core toroids on one side Are these ideas likely to be practical? They presumably create asymmetric forces on the solenoid, but how can we make some preliminary analysis of those situations? 7/29/201310

ePHENXI Internal Discussions Jin Huang, et. al.11 RICH GEM Station4 EMCal HCal GEM Station2 z (cm) R (cm) HCal p/A EMCal GEMs EMCal & Preshower μ-TPC DIRC η~1 η~ R (cm) GEM Station3 GEMs Station1 η~-1 e-e- e-e- AreoGel

Without much optimization: net force on coil = 65T towards left  How much Z and internal force can be tolerated?  How to further minimize? ePHENXI Internal Discussions Jin Huang, et. al.12 Could further add a trim ring 640T 10T 690T Longitudinal Ton force on three segments of coils. Net force = -65T Longitudinal Ton force on three segments of coils. Net force = -65T z (cm) R (cm)

Net force on coil = 3T, which seems mechanically OK. In real device we can have a movable z=-270cm to fine tune the force with measurement  How much Z and internal force on coil can be tolerated?  What’s the requirement for dynamic balancing? ePHENXI Internal Discussions Jin Huang, et. al.13 Trim ring 640T 2T 630T Longitudinal Ton force on three segments of coils. Net force = -3T Longitudinal Ton force on three segments of coils. Net force = -3T z (cm) R (cm)

How we plan to proceed We are planning on help from BNL’s Superconducting Magnet Division, but they are fairly small and very busy, so I would like to focus their efforts on the most critical questions. 7/29/201314