Spatial Resolution of Gas Electron Multiplier (GEM) Detectors Using

GEM
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Spatial Resolution of
Gas Electron Multiplier (GEM) Detectors
Using Prototype Readout Boards
Analysis from October 2013 Beam Test at Fermilab
M.Phipps, V. Bhopatkar, J. Twigger, A. Zhang, M. Hohlmann
Florida Academy of Sciences Conference
Indian River State College
March 7, 2014
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GEM
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Outline
1 Motivation
Cost Reduction for the Electron Ion Collider (EIC)
2 FNAL Beam Test
Beam Test Objectives
Detector Resolution Methods
Tracking and Alignment
Spatial Resolution Results
3 Future Work
4 Summary
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GEM
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Motivation
Cost Reduction for the Electron Ion Collider (EIC)
Outline
1 Motivation
Cost Reduction for the Electron Ion Collider (EIC)
2 FNAL Beam Test
Beam Test Objectives
Detector Resolution Methods
Tracking and Alignment
Spatial Resolution Results
3 Future Work
4 Summary
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GEM
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Motivation
Cost Reduction for the Electron Ion Collider (EIC)
Where does mass come from?
EIC Mission
What makes up normal matter?
Atomic mass: 99.9% from nucleons
Nucleon mass: Energy of massless gluons and nearly massless quarks
Quark-Gluon interactions and dynamics (not the Higgs!) responsible
for 99.9% of mass in visible universe
Goal of EIC: Understand the role of sea quarks and gluons in the
nucleus
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GEM
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Motivation
Cost Reduction for the Electron Ion Collider (EIC)
EIC Proposals: eRHIC (BNL) and ELIC (J Lab)
Construction planned 2020-2024
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GEM
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Motivation
Cost Reduction for the Electron Ion Collider (EIC)
Large Area Tracker Proposals
Challenge: Expand GEM detector size while reducing cost and
retaining high spatial resolution
Approach: Use radial zigzag readout to reduce number of readout
channels by factor of 3
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GEM
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FNAL Beam Test
Beam Test Objectives
Outline
1 Motivation
Cost Reduction for the Electron Ion Collider (EIC)
2 FNAL Beam Test
Beam Test Objectives
Detector Resolution Methods
Tracking and Alignment
Spatial Resolution Results
3 Future Work
4 Summary
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GEM
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FNAL Beam Test
Beam Test Objectives
Beam Test Objectives
Characterize 1 meter CMS radial straight strip prototype
(CMS oriented; Vallary’s presentation)
Successfully use four reference detectors for alignment and
tracking studies
Compare the spatial resolution of radial straight strip readout
to radial zigzag readout
Test performance of various radial zigzag prototype boards to
optimize future design (EIC oriented)
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GEM
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FNAL Beam Test
Detector Resolution Methods
Outline
1 Motivation
Cost Reduction for the Electron Ion Collider (EIC)
2 FNAL Beam Test
Beam Test Objectives
Detector Resolution Methods
Tracking and Alignment
Spatial Resolution Results
3 Future Work
4 Summary
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GEM
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FNAL Beam Test
Detector Resolution Methods
Methods for Determining Detector Resolution
∆ Y distribution: Rough, initial estimate that requires two
identical boards close together and coarsely aligned in the
beamline (See: Jessie’s presentation)
Residual distributions: Fine techique (Post-alignment;
post-tracking)
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GEM
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FNAL Beam Test
Detector Resolution Methods
Resolution Measurement through Residual Distribution
Spatial Resolution: σ 2 = σin σex
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GEM
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FNAL Beam Test
Tracking and Alignment
Outline
1 Motivation
Cost Reduction for the Electron Ion Collider (EIC)
2 FNAL Beam Test
Beam Test Objectives
Detector Resolution Methods
Tracking and Alignment
Spatial Resolution Results
3 Future Work
4 Summary
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GEM
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FNAL Beam Test
Tracking and Alignment
Alignment of Straight Strip, 2d GEM Detectors
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1
Center the position distribution. Mean
values (multiplied by scale factor of 0.2)
used as shift parameters.
2
Minimize the residual mean. Fine
translational and rotational alignment
technique
3
Minimize χ2 of linear track fits. Fine
translational and rotational alignment
technique
GEM
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FNAL Beam Test
Tracking and Alignment
Resolution of GEM Trackers
Resolutions between 40-60
µm is a strong result and in
line with expectation
Exclusive residuals
predictably biased up at end
detectors
Inclusive residuals
overestimate the true
resolution; exclusive
residuals underestimate the
true resolution; the
geometric mean gives the
best approximation
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GEM
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FNAL Beam Test
Tracking and Alignment
Alignment of Radial GEM Detectors: Method
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p
r = x2 + y2
Φ = atan( yx )
Φ : (−20mrad, +20mrad)
Transfer tracker coordinates from (x,y) to (r,Φ)
Both CMS readout boards (straight strip and zigzag) have fixed
angle pitch and if origin shown above is adopted, the strips can be
expressed in terms of Φ
The distance to the origin of the CMS detector not measured in
terms of (x,y) for trackers → Must align tracker detectors through
optimization algorithm
GEM
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FNAL Beam Test
Tracking and Alignment
Alignment of Radial GEM Detectors: Method
Iterative optimization algorithms:
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1
Coarse align through χ2 minimization of
inclusive linear fits in X,Y, and Φ
2
Fine align translation and rotation
through minimization of residual means
GEM
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FNAL Beam Test
Spatial Resolution Results
Outline
1 Motivation
Cost Reduction for the Electron Ion Collider (EIC)
2 FNAL Beam Test
Beam Test Objectives
Detector Resolution Methods
Tracking and Alignment
Spatial Resolution Results
3 Future Work
4 Summary
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GEM
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FNAL Beam Test
Spatial Resolution Results
Spatial Resolution: Initial Results
Optimization of radial
alignment is ongoing!
Distribution for current
alignment parameters still too
wide ... shows an inflated
resolution
From the geometric acceptance
of the detector, we can predict
an upper bound on our
resolution of 250 µm. Further
optimization should bring our
results down to at least that
level
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GEM
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Future Work
Future Work
Finalize radial alignment parameters
Compare spatial resolution for straight strip CMS readout to
radial zigzag readout
Compare different radial zigzag boards and optimize design for
future beam test
Test pixel and chevron readout boards (Liz’s presentation)
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GEM
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Summary
Summary
Spatial resolution for straight-strip trackers between 40-60
µm. This should allow good resolution measurements for the
prototype detectors
Final spatial resolution results for CMS radial straight strip
and radial zigzag boards to be finished soon. Expectation:
radial straight strip resolution below 200µm and slightly
higher radial zigzag resolution
Future Work: Optimize GEM detector readout design
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