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CM ReviewMagneticsPage 1

Magnetization options for the calibration module

Jeff Nelson & Bob WandsCalibration module review (8/00)

• Simulations: status and impact• 2 concepts

– Pro/Con– Designs– Magnetics– Coil and steel requirements

• Conclusion– Probably the last talk you’ll ever

see on this subject!

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CM ReviewMagneticsPage 2Simulations

• Peter’s Monte Carlo study found that fields in steel have negligible effect on showers

– The air field is not implemented in GMINOS -- It should be studied

– The air field is roughly

» B = 100 gauss / r (r in [m])

– Low energy particles won’t make it from the steel to the scintillator

<0.3 MeV @ inner radii

• A CDHS NIM article also shows little effect on hadronic response

• Peter’s conclusion (in Jeff’s words)– “If it’s so small... let’s just make the

spectral measurement in the near detector with & without field”

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CM ReviewMagneticsPage 32 Options

• Need a magnetic circuit• Box Option

– Connect the tops & bottoms of two plates

– Use one plate as the flux return for the other

– Wrap power coils on the short legs » 2 coils per pair of planes

• Flux Return Option– Use a larger steel plane

put a hole off center and wrap a coil on it» Like the near detector!

– Flux stays in a plane– Can power 2 planes with

the same coil (more later)

edge-on view

face-on view

scint area

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CM ReviewMagneticsPage 4Pros & Cons

• Pro– Box

» Shape of planes nearly the same as the standard plane

» Less steel, better access– Flux return

» Fewer coils and lower power

» The air field is in the right direction (parallel to the steel planes)

• Con– Box

» The air field is in the wrong direction (normal to the planes)

– Flux return» Mechanical headache» Air field is at the low end unless

substantial power employed

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CM ReviewMagneticsPage 5

Box Option:Integration with Scintillator

• 2 horizontal plates connect 2 planes making an open-sided “box”

• A module is slipped into the box and the next is connected to the outside of the box

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CM ReviewMagneticsPage 6

Box OptionField in Steel

• The required current is roughly 1500 a-turns per coil

• Either design can repeated for as many pairs of planes as required

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CM ReviewMagneticsPage 7Coil Design

• Coils can be made like our test toroid– 300 turns of 10 gauge insulated wire – 15A power supply

• Repeat for each coil• Readout system and coils

for ~ $3500, existing supplies?

400 turn coil

15A power supply

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CM ReviewMagneticsPage 8The Flux Return Option

• Add 3 (thicker) plates to the edges to make a flux path

• 2 planes can be tied together using the same power coil

• Some manifolds are buried in the flux return

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CM ReviewMagneticsPage 9

Flux Return OptionFields in Steel

• This design can yield lower fields at lower currents• This plot shows the field with higher current to produce more air field

– 3000A-turns yields ~1.3T

Instrumented Area

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CM ReviewMagneticsPage 10

Air fields in the Flux Return Option

• Fields between planes ~ 9 to 11 gauss » 3000 A-turns

• To get 100 gauss need » 100 times the power -- Ouch!

Half of the instrumented area

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CM ReviewMagneticsPage 11

• System based on that used for the 4PP and the table top toroids

• Automated readout via PC & Labview – Waveform digitizes integration-coil signals – Monitors power supply – Automated current control

» Presets for hysteresis loop, degauss…– Expandable for multiple supplies

Control and Monitoring

V(t)B= A V(t)dt

I(t)

B vs I

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CM ReviewMagneticsPage 12Conclusions

• 2 options make reasonable fields in steel– Both use cheap coils & existing control

systems

• Simulations show that the field in the steel in probably unimportant

• The field in the air may or may not be important– If it is… the flux return option is the

only one that’s close» Many drawbacks

– Size and shape makes issues for the mechanical support

– Poor access to the manifolds if they are 1m modules

– The actual field in the air is low

– If not... flush this talk