Transcript ipac_ss_posterx

UPDATE ON THE MODIFICATION AND TESTING OF THE MICE
*
SUPERCONDUCTING SPECTROMETER SOLENOIDS
S. Virostek, M. Green, N. Li, T. Niinikoski, H. Pan, S. Prestemon and M. Zisman
Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
on behalf of the MICE Collaboration
BERKELEY LAB
Abstract: The Muon Ionization Cooling Experiment (MICE) is an international effort sited at Rutherford Appleton Laboratory, which will
demonstrate ionization cooling in a segment of a realistic cooling channel using a muon beam. A pair of identical, 3-m long spectrometer solenoids
will provide a 4-tesla uniform field region at each end of the cooling channel. The emittance of the beam as it enters and exits the cooling channel
will be measured within the 400 mm diameter magnet bores. The magnets incorporate a three-coil spectrometer magnet section and a two-coil
section that matches the solenoid uniform field into the MICE cooling channel. The cold mass, radiation shield and leads are kept cold by means of
a series of two-stage cryocoolers and one single-stage cryocooler.
Previous testing of the magnets had revealed several operational issues related to heat leak and quench protection. A quench analysis using Vector
Fields software and detailed heat leak calculations have been carried out in order to assess and improve the magnet design. Detailed analyses of the
eddy currents, temperature distribution and stresses in a modified radiation shield design have been carried out as well. Details of the analyses and
resulting magnet design modifications along with an update of the magnet assembly progress will be presented here.
INTRODUCTION
COLD MASS COIL ASSEMBLY
• Each magnet consists of five superconducting coils
wound on a common 2923 mm long aluminum mandrel
• Match Coils 1 and 2 operate as a focusing doublet to
match the beam to the adjacent AFC modules
• The spectrometer (End 1, Center, End 2 Coils) generate
a 4T uniform field over a 1m long, 0.3m dia. volume
MICE consists of two spectrometer solenoids and a cooling
channel. Muon ionization cooling occurs in three LH2 absorbers
in the cooling channel, and the muons are reaccelerated by eight
RF cavities. Scintillating fiber detectors in the solenoid bores
measure the incoming and outgoing muon emittance.
SHIELD ANALYSES
Several analyses were carried out to
assess the integrity of the new 1100
aluminum radiation shield
Spectrometer
Solenoid #1
Eddy currents during quench
MAGNET QUENCH ANALYSIS
Stress during quench and shipping
Magnet quench during a training run
Steady state temperature distribution
QUENCH RESISTOR COOLING
• The internal passive quench resistors were thermally
damaged during previous testing
• A larger than expected amount of energy was
deposited in the resistors when one of the cold leads
burned out at a 257 amp current
• A scheme to cool the
resistors conductively
was developed and
tested off line
• An insulated copper
clamp conducts the
resistor heat to the
coil winding mandrel
* This
3D quench model of the spectrometer solenoid coils
• 3D analyses carried out using Opera-3D/QUENCH module
• The 3D model provides detailed results for the quench
process (quenchback, layer-to-layer voltages, etc.)
• The analysis also considers the impact of a quench on critical
components such as the LTS and HTS leads
SUMMARY
• A coil quench analysis has been
completed, and the final magnet
protection design developed
• Thermal analyses have resulted in
design modifications to reduce the
heat leak into the cold mass and
increase the cryocooling power
• Reassembly of the first of the two
magnets is currently under way
Cooling clamp test setup
Current decay in coils during quench Field distribution in the MICE coils
work was supported by the Office of Science, U.S. Department of Energy under DOE contract number DE-AC02-05CH11231.
Paper ID:
WEPO033