Spectrometer Solenoid Test Plan Workshop: Spectrometer Solenoid Overview Steve Virostek - LBNL...

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

Slide 1Spectrometer Solenoid Overview
Steve Virostek - LBNL
February 17, 2012
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Topics
Key magnet requirements
Recent magnet operation
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MICE Cooling Channel Layout
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Performance Overview
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
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Magnet 2B 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 2B was trained in series to 258 amps when a coil lead was found to contain an open circuit
The failure was traced to the M2 coil close to the He/vacuum feedthru
Training on the Center, E1 and E2 coils in series continued, reaching 270 amps
During operation, the 3+1 cooler configuration could not maintain a closed LHe system
LBNL
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Magnet 2B Cross Section
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Added Single Stage Cooler
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Magnet 2B 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 2B were found to be damaged due to overheating
Magnet 1 resistors were not damaged
LBNL
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Subsequent Analyses
The heat leaks from dominant static sources were re-evaluated, focusing on heat leaks to 4.2K (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
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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
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4.2K Heat Load Reduction
4K areas covered with actively cooled shield where possible
Baffles added to vent lines to prevent radiation shine to 4.2K
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
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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
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Quench Resistor Heat Sinking
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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:
Detailed MLI inspection carried out during assembly
Fast DAQ system will continuously monitor voltage taps
Additional temperature sensors added to the logging system
LBNL
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5 + 1 Cryocooler Layout