PID PC 7th Sept 2005 1 MICE MAGNETIC FIELDS & SHIELDS J. H. Cobb & H. Witte Oxford University et fields for MICE (VI) calculated including magnetic shield discs equest of software people r adjustments to end-coil currents to get uniform field in spectrome lculate fields at positions of PID detectors with shields All documented in MICE Note 119, q.v. for details comments on possibility of lighter shield minor amendments/additions for PID meeting 7/9/05
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PID PC 7th Sept 20051 MICE MAGNETIC FIELDS & SHIELDS J. H. Cobb & H. Witte Oxford University Magnet fields for MICE (VI) calculated including magnetic.
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PID PC 7th Sept 2005 1
MICE MAGNETIC FIELDS & SHIELDS
J. H. Cobb & H. Witte
Oxford University
Magnet fields for MICE (VI) calculated including magnetic shield discsat request of software people
Minor adjustments to end-coil currents to get uniform field in spectrometers
Recalculate fields at positions of PID detectors with shields
All documented in MICE Note 119, q.v. for details
Some comments on possibility of lighter shield
Some minor amendments/additions for PID meeting 7/9/05
PID PC 7th Sept 2005 2
Shield:100 mm soft iron400 mm from end coil
Spectrometersolenoid
PID PC 7th Sept 2005 3
Calculations made with FemLab after comparison with OPERA
B in solenoid – no visible differencebetween FemLab & OPERA
Used OPERA default B – Hcurve for soft iron
PID PC 7th Sept 2005 4
Field in ironAverage ~ 1.5 T – not saturatedHot Spot is artefact of FEA calc.
OUTSIDE
INSIDE SOLENOID
Z
r
Bz in channel, r = 0Minimal difference iron/no ironexcept at ends
PID PC 7th Sept 2005 5
External B (obviously) less with ironBeam less confined Problem ?? TBD (software folk)
Shi
eld
Adjust end-coil current only by ~2.5% to give dB / B < 1% in solenoidi.e. like no iron
PID PC 7th Sept 2005 6
Shielding efficiency – summary table follows
TOF
Ckov
EMCal
|B|
r
Black = No Iron
Red = with Iron
Residual B @ EMCAL ~2x higherthan shown in TDR ~ 38mT
PID PC 7th Sept 2005 7
• Fields with currents adjusted for the iron are calculated & available as z – r map
• Fields at positions of TOF, Ckov & EMCAL calculated S/W & PID people must see if they are OK• This Shield does little for EMCAL
• NOTE No allowance for ‘Tunnel’ (shielding around hall)
• Investigate if it’s possible to reduce amount of iron for same shielding efficiency by subdividing shield....