Spectrometer Solenoid Test Plan Workshop Spectrometer Solenoid Overview

Spectrometer Solenoid Test Plan Workshop: Spectrometer Solenoid Overview Steve Virostek - LBNL February 17, 2012

Topics • Overview of the Spectrometer Solenoids • Key magnet requirements • Recent magnet operation • Design modifications § Heat reduction to 4. 2 K § Radiation shield improvements § Cryocooling power § Other improvements LBNL Spectrometer Solenoid Test Magnet Overview Steve Virostek LBNL Plan Workshop - 2/17/2012 -2 -

MICE Cooling Channel Layout Spectrometer Solenoid #1 Spectrometer Solenoid #2 LBNL Spectrometer Solenoid Test Magnet Overview Steve Virostek LBNL Plan Workshop - 2/17/2012 -3 -

Performance Overview • Key magnet requirements: § All five coils must be trained to 275 amps § The cryocoolers must maintain the LHe in the cold mass (no boil-off) Not yet achieved for either magnet LBNL Spectrometer Solenoid Test Magnet Overview Steve Virostek LBNL Plan Workshop - 2/17/2012 -4 -

Magnet 2 B Operation • A single-stage cooler had been added to increase cooling at the HTS lead upper ends and to help reduce the shield temperature • Magnet 2 B was trained in series to 258 amps when a coil lead was found to contain an open circuit • The failure was traced to the M 2 coil close to the He/vacuum feedthru • Training on the Center, E 1 and E 2 coils in series continued, reaching 270 amps • During operation, the 3+1 cooler configuration could not maintain a closed LHe system LBNL Spectrometer Solenoid Test Magnet Overview Steve Virostek LBNL Plan Workshop - 2/17/2012 -5 -

Magnet 2 B Cross Section LBNL Spectrometer Solenoid Test Magnet Overview Steve Virostek LBNL Plan Workshop - 2/17/2012 -6 -

Added Single Stage Cooler LBNL Spectrometer Solenoid Test Magnet Overview Steve Virostek LBNL Plan Workshop - 2/17/2012 -7 -

Magnet 2 B Disassembly • After warm-up, the cold mass was removed from the vacuum vessel and opened • The failed lead was located just inside the cold mass feedthrough • Analysis indicated that the conductor adjacent to the feedthru needed stabilization against movement and for enhanced cooling • The internal quench resistors in Magnet 2 B were found to be damaged due to overheating • Magnet 1 resistors were not damaged LBNL Spectrometer Solenoid Test Magnet Overview Steve Virostek LBNL Plan Workshop - 2/17/2012 -8 -

Subsequent Analyses • The heat leaks from dominant static sources were re-evaluated, focusing on heat leaks to 4. 2 K (LHe boil-off issue) • Other operational aspects considered: heat loads on the shield and vacuum insulation • The design of the passive magnet protection system design was also analyzed under various operational regimes LBNL Spectrometer Solenoid Test Magnet Overview Steve Virostek LBNL Plan Workshop - 2/17/2012 -9 -

Design Modification Approach • The design and assembly modification plan was developed based on the following: § reduction of heat leaks to the cold mass § the addition of more cryo cooling power § modification of the cold leads near the feedthroughs to prevent burn-out § thermal heat sinking of the quench resistors • Details provided on the following slides LBNL Spectrometer Solenoid Test Magnet Overview Steve Virostek LBNL Plan Workshop - 2/17/2012 - 10 -

4. 2 K Heat Load Reduction • Improved vacuum pumping and instrumentation • 4 K areas covered with actively cooled shield where possible • Baffles added to vent lines to prevent radiation shine to 4. 2 K • Possible thermal acoustic oscillations in vent/fill lines to be monitored w/pressure gauges • Improved application of MLI on cold mass • Sensor wires optimized & w/proper heat sinking LBNL Spectrometer Solenoid Test Magnet Overview Steve Virostek LBNL Plan Workshop - 2/17/2012 - 11 -

Radiation Shield Improvements • Radiation shield remade w/6. 35 mm thick 1100 series aluminum (except for the inner bore) – previously 6061 • Improved thermal connection between cooler first stage and radiation shield (copper sheets vs. aluminum tubes) • Application of MLI on shield improved • Heat loads decreased as possible: shield pass-through holes for the cold mass supports, intermediate cold mass support heat intercepts, and shielding of the warm end of the supports LBNL Spectrometer Solenoid Test Magnet Overview Steve Virostek LBNL Plan Workshop - 2/17/2012 -

Quench Resistor Heat Sinking LBNL Spectrometer Solenoid Test Magnet Overview Steve Virostek LBNL Plan Workshop - 2/17/2012 - 13 -

Other Design Modifications • Other key improvements: § Total cooling power increased to five 2 -stage pulsed tube coolers and one single-stage cooler § Extra copper/superconductor added near cold mass feedthroughs for increased cold lead stability • Other improvements/additions: § LBNL/MICE personnel assisting with magnet reassembly § Detailed MLI inspection carried out during assembly § Fast DAQ system will continuously monitor voltage taps § Additional temperature sensors added to the logging system LBNL Spectrometer Solenoid Test Magnet Overview Steve Virostek LBNL Plan Workshop - 2/17/2012 - 14 -

5 + 1 Cryocooler Layout LBNL Spectrometer Solenoid Test Magnet Overview Steve Virostek LBNL Plan Workshop - 2/17/2012 - 15 -