Magnetic Field Studies
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Transcript of Magnetic Field Studies
![Page 1: Magnetic Field Studies](https://reader034.fdocuments.in/reader034/viewer/2022051315/56812be3550346895d90571f/html5/thumbnails/1.jpg)
Magnetic Field Studies
Dan Karmgard
for the
HCAL RBX Group
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1 Mar 01 2RBX Production Readiness Review - D. Karmgard, University of Notre Dame
Outline
• Introduction
• Limitations and Programming Notes
• HB Field Angle
• HE Field Angle
• HO Field Studies
• HO RBX Placement
• Where to go from here
• Conclusions
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1 Mar 01 3RBX Production Readiness Review - D. Karmgard, University of Notre Dame
Introduction
• HPDs accelerate electrons across a gap– gap is 3 – 4 mm.– Aligns with a 10kV E field
• If there is a substantial local B field– electrons deviate from the path– could wind up in the wrong pixel
• It is critical that we align the HPD axis with the local B field direction
• To do this, we have to map the local field
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1 Mar 01 4RBX Production Readiness Review - D. Karmgard, University of Notre Dame
Limitations
• This study uses Slavas’ field map and code– it is only as accurate as they are
• The field map is based on 1/8 of the detector– assumes a reflection symmetry about each axis
• Also uses a series of planes to define the field– if the field for a point not on a predefined plane is
requested code interpolates between the nearest planes
• Original code is for points only
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1 Mar 01 5RBX Production Readiness Review - D. Karmgard, University of Notre Dame
Programming Notes
• Change & Refinement– converted original to C
– embedded into a loop• allows automated
calculation in a region
– created a GUI control
– Added automated checking for HO RBX locations
• feature can be turned off on the fly or from a configuration file
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1 Mar 01 6RBX Production Readiness Review - D. Karmgard, University of Notre Dame
Program Tests
4T Axial Field 3.5T Axial Field
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1 Mar 01 7RBX Production Readiness Review - D. Karmgard, University of Notre Dame
Programming Notes
• Why do you care?– Turning off the RBX location routines makes
the program general enough to be of use outside the RBX group
– Program designed and built for Linux• kernel 2.2.12-20, glibc 2.1, gcc, gtk+ 1.28
• may work on other Unices with recompilation
• port to Windows problematic and not planned
– Anyone interested should let me know• binary or source distribution available
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1 Mar 01 8RBX Production Readiness Review - D. Karmgard, University of Notre Dame
HB Field Angle
• The local field angle in HB is about 4.5º– Well known for some time– Calculations made with earlier versions of code– confirmed by the new versions
• This means that the HPDs are mounted at an angle– aligns the HPD axis with the local field
• Field changes in HB– changes are small enough to set one angle
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1 Mar 01 9RBX Production Readiness Review - D. Karmgard, University of Notre Dame
HB Field Angle
arc t
a n(B
x/By)
(d e
g ree
s )
x (meters)
z (meters)
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1 Mar 01 10RBX Production Readiness Review - D. Karmgard, University of Notre Dame
HE Field Angle
• The situation in HE is similar to HB– local angle is 8½ º
• Calculation done with old code– confirmed with new code
• The field is not uniform here either– again, small enough to set
a single angle for HPDs
angl
e (
degr
ees)
x (meters)
z (meters)
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1 Mar 01 11RBX Production Readiness Review - D. Karmgard, University of Notre Dame
HO Field Studies
• HO very different from HB and HE– Placing RBXs in Yoke means shorter fiber– Also means worse B field to deal with
• Field is weaker– generally around 2T in this region
• but it changes much more rapidly– can have significant Bx and By components
• Probably have to build many variants of the HPD mounting to accommodate it
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1 Mar 01 12RBX Production Readiness Review - D. Karmgard, University of Notre Dame
B Field in the HO Region
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1 Mar 01 13RBX Production Readiness Review - D. Karmgard, University of Notre Dame
B Field in the HO Region
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1 Mar 01 14RBX Production Readiness Review - D. Karmgard, University of Notre Dame
HO RBX Placement
• Assumptions– (x,y) positions obtained from survey of YB-2
• CMS-SY-UR-0017
• assume that other yokes are symmetric
– RBX has a regular design• HPDs are in the same location in each RBX
– Placement checks use a rotation in • 30º rotation per position
• all RBX are transformed to check position against the survey line
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1 Mar 01 15RBX Production Readiness Review - D. Karmgard, University of Notre Dame
HO RBX Placement
• Requirements– Fits in the allowed volume– RBX doesn’t come within 1cm of survey line– local field is well behaved
• variation is less than 5º over each HPD location
• rough calculation indicates ±7° is acceptable
• requiring ±2½° allows a reasonable margin of safety
• Following plots show 1 point in the RBX– centered in (x,y) and 125mm from front in z
• center of the HPD compartment in z
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1 Mar 01 16RBX Production Readiness Review - D. Karmgard, University of Notre Dame
Positions for RBX 0
Ring 1 Ring 2
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1 Mar 01 17RBX Production Readiness Review - D. Karmgard, University of Notre Dame
Positions for RBX 6
Ring 1 Ring 2
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1 Mar 01 18RBX Production Readiness Review - D. Karmgard, University of Notre Dame
RBX 0 with B = 3.5T
Ring 1 Ring 2
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1 Mar 01 19RBX Production Readiness Review - D. Karmgard, University of Notre Dame
RBX 6 with B = 3.5T
Ring 1 Ring 2
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1 Mar 01 20RBX Production Readiness Review - D. Karmgard, University of Notre Dame
HO RBX Placement
• Gives a set of points– acceptable in terms of field and survey lines– other considerations can’t be programmed
• in Ring 2 prefer to have RBX at high z facing out– easier access when detector is opened
– Once placement is decided• define the angles at which HPDs are mounted
– It is preferable to have regular placement• don’t know yet if this is possible
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1 Mar 01 21RBX Production Readiness Review - D. Karmgard, University of Notre Dame
HO RBX Placement Example• Pick a consistent location for the RBX
– rings 1 and 2, RBX 0 and 6– z location is ½ m from high–z edge of the yoke– table below shows results of the program for these RBX
RBX ID(Ring-RBX)
X(m)
Y(m)
Z(m)
y
x1
B
Btan
(degrees)
z
x1
B
Btan
(degrees)
z
y1
B
Btan
(degrees)
1-0 -0.5 4.7 3.5 -35 4.1 -5.8
1-6 0.5 -4.7 3.5 -34 4.0 5.8
2-0 -0.5 4.7 6.1 -28 12 -21
2-6 0.5 -4.7 6.1 -28 11 21
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1 Mar 01 22RBX Production Readiness Review - D. Karmgard, University of Notre Dame
HO RBX Placement
• May not be possible to pick a consistent location for all HO RBX– a location in which each RBX occupies the
same position relative to it’s volume
• May not be possible to pick a single angle– HPD mounts may have to be custom built for
numerous positions– As table above shows, there needn’t be a
unique HPD mount for every one
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1 Mar 01 23RBX Production Readiness Review - D. Karmgard, University of Notre Dame
Where do we go from here?
• Obviously this study is far from complete– would like to verify the results independently
• any ideas would be welcome
• We need to get at least a preliminary location settled for our Indian colleagues– should be able to settle this quickly
• Rest of the locations need to be checked– in progress but not yet complete
• Finalization requires full HO RBX design
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1 Mar 01 24RBX Production Readiness Review - D. Karmgard, University of Notre Dame
Conclusions
• We have a preliminary understanding of the field in the muon yoke– informs HO RBX placement
• Field in this region can change rapidly– simple RBX placement may not be possible
• Some details remain to understood– initial placement of RBX possible quickly– necessary so fiber lengths can be determined
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1 Mar 01 25RBX Production Readiness Review - D. Karmgard, University of Notre Dame
Conclusions
• Further study is in progress– results will be made available as soon as
possible• as they are completed
– finalization of the study requires final design for the RBX
• need to know where the HPDs are
• because the field can change rapidly
– Once this is known the study should be quick