Bernhard Lauss

1
Magnetic Fields in and around MuCAP
Bernhard Lauss
MuCAP Collaboration Meeting PNPI, Gatchina, Ru,
June 14-18, 2004
2
2 different issues 1) MuCAP magnet ? good /
reduces systematic error 2) COBRA magnet ? bad
/ increase systematic error kepp in mind only
relevant for the m measurement
MuCAP Collaboration Meeting PNPI, Gatchina, Ru,
June 14-18, 2004
3
1) new MuCAP mSR magnet made with Aluminum
tubing 200 Amps - 80 Gauss field ? ?
MuCAP Collaboration Meeting PNPI, Gatchina, Ru,
June 14-18, 2004
4
Simulation
Co Al stacked Al no magnet no
frame
2003 ePC1 data Co magnet
MuCAP Collaboration Meeting PNPI, Gatchina, Ru,
June 14-18, 2004
5
ePC1 ePC2
no TPC frames in simulation
Cu Al Cu Al
MuCAP Collaboration Meeting PNPI, Gatchina, Ru,
June 14-18, 2004
6
Arrival at PSI
MuCAP Collaboration Meeting PNPI, Gatchina, Ru,
June 14-18, 2004
7
- needs performance test at PSI - will get 10
degrees warmer
MuCAP Collaboration Meeting PNPI, Gatchina, Ru,
June 14-18, 2004
8
2) COBRA Magnet (COnstant Bending RAdius)
m ? e g experiment in pE5
diameter of compensation coils 240cm
MuCAP Collaboration Meeting PNPI, Gatchina, Ru,
June 14-18, 2004
9
MuCAP Collaboration Meeting PNPI, Gatchina, Ru,
June 14-18, 2004
10
COBRA Magnet fringe field
10 gauss 1 gauss
Longitudinal Fringe Field in pE3 of a few gauss
!!!
MuCAP Collaboration Meeting PNPI, Gatchina, Ru,
June 14-18, 2004
11
Profile of fringe field
along beam axis
orthogonal axis
MuCAP Collaboration Meeting PNPI, Gatchina, Ru,
June 14-18, 2004
12
What is the real influence of a small
longitudinal field on the lifetime ? ?
Workgroup Possible solutions 1) Measure the
longitudinal component of the field 3-axis Gauss
meter (1800 ) 3-axis fluxgate (4000) 2)
Small Bucking Helmholtz coils or solenoid around
the TPC vessel to compensate the longitudinal
field -gt bad homogeneity 3) Large Bucking
Helmholtz coils to compensate the longitudinal
field (around ePCs, around eSC, -gt all
iron/steel parts influence the field distribution,
beam pipes, large base plate and rails, might
make things worse. 4) Control the longitudinal
field with a solenoid making the same field
magnitude as transvers (40-80 Gauss) with 1
winding per cm on the TPC vessel one gets
approximately 1 Gauss / Cooling !
MuCAP Collaboration Meeting PNPI, Gatchina, Ru,
June 14-18, 2004
13
MuCAP Collaboration Meeting PNPI, Gatchina, Ru,
June 14-18, 2004