Danning Di

University of Virginia

Jan.19.2017

SBS GEM Test

Hall A collaboration meeting

01/19/17 2

● Test setup

● Two crucial GEM characteristics for high occupancy situation– Charge sharing

– Time correlation

● Hit reconstruction method– Tracking

– Charge correlation of test data

– Timing correlation of test data

● GEM efficiency

● GEM spacial resolution

● Summary

Overview

01/19/17 3

GEMs

Scintillator

Calorimeter

Target chamber direction

● Parastic test at 70° from beam in Hall A during DVCS/GMP experiment in Fall 2016.

● 5 60x50 cm SBS GEM modules spaced by ~13 cm

● Gas mixture: Ar/CO2 (75/25%) at flow rate ~5L/h

● GEM HV: ~4100V● Calorimeter size: 30x30 cm● The occupancy of GEMs during test was

around 1.5%.● DAQ rate was about 40Hz(MPD 3.0) reading

about 15k channels, data rate ~12MB/s

Setup in Hall A at JLab

01/19/17 4

Scintillator

5 SBS GEMs

Calorimeter

Setup in Hall A at JLab

● Parastic test at 70° from beam in Hall A during DVCS/GMP experiment in Fall 2016.

● 5 60x50 cm SBS GEM modules spaced by ~13 cm

● Gas mixture: Ar/CO2 (75/25%) at flow rate ~5L/h

● GEM HV: ~4100V● Calorimeter size: 30x30 cm● The occupancy of GEMs during test was

around 1.5%.● DAQ rate was about 40Hz(MPD 3.0) reading

about 15k channels, data rate ~12MB/s

01/19/17 5

Charge sharing and time correlation of GEM

σ~10 ns

Signal arrive time in Y plane

10 ns wide band

Sig

na

l arr

ive

tim

e in

X p

lan

e

Signal arrive time in Y plane

Sig

na

l arr

ive

tim

e in

X p

lan

e

Signal arrive time in x(y) plane

Signal arrive time in x/y planeCluster charge ratio X/Y

Charge sharing Time correlation

BeforeAfter correct trigger phase in APV clock

Plots are from cosmic data in 2015

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Real hits buried in accidental hits and cross-talk clusters and mismatching clusters(incorrectly paired x/y clusters)

Real hits, small part of accidental hits, cross-talk clusters andpart of mismatching clusters

cut in charge correlation and timing correlation

Hit Reconstruction

Do tracking in x/y plane

Real hits

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GEM 3

GEM 4

GEM 2

GEM 1

GEM 0

Tracking Snapshots

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Charge Correlation

Due to electronics cross talk

Due to Mismatching of clusters

Tracking remove most of mismatching clusters

Not showing up here because cross talk happens mainly in Y direction

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Charge Correlation

Due to Mismatching of clusters

Electronics cross talk removed

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Correcting the phase of trigger in APV clock Cut off weakly timing

correlated clusters

Timing Correlation

From fit of 6 time sample

σ~6 ns

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Efficiency

HV: 4100V

HV from 4000 V to 4150 V with step of 25 V

Efficiency drop due to spacer

Overall efficiency HV scan

X Plane(mm)

Y P

lan

e(m

m)

01/19/17 12

Spatial Resolution

σ~80 μm

σ~233μm

Inclusive residual in X

Exclusive residual in XExclusive residual in X

σ~230μm

Slope of tracks

● Tracks varies in direction● Work in progress to get better offsets

to align the GEM modules

Cosmic data results(preliminary)

mm

mm

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Spatial Resolution

σ~110 μm

Inclusive residual in X

Exclusive residual in X

σ~44 μm σ~69μm

σ~170μm

Inclusive residual in X

Exclusive residual in X

perpendicular tracks Non-perpendicular tracks

Simulation resultsAssuming resolution of 70 μm

mm

mmmm

mm

01/19/17 14

Summary

● A GEM tracker of 5 modules are tested at about 1.5% occupancy. By combining tracking and cuts on charge correlation and timing correlation can successfully remove the accidental hits and mismatching clusters.

● The spacial resolution is calculated and needs further work on finding more accurate offsets to better align GEM modules for better results.

● It is definitely beneficial to our knowledge and experience on dealing with high occupancy in future if there is chance to take data with this simple tracker under higher occupancy that is comparable with the expected SBS run condition.