Construction and Quality control of large scale GEM detectors

On behalf on the collaboration GEM for CMS

Status

Prototype I Prototype IINew NS2 technic assembly

4 prototypes produced

NS2 assembly technic

10 to 15mm

Readout connector

O-ring

Drift electrode

Free to slide

External screws to adjuststretching

GND

GND

GEM attaching structure(4 pieces defining gaps)Embedded nutO-ring

Rui De Oliveira GEM workshop IV

GEM stack ready

Inserting drift board

Install pulling screws

• Install 50 pulling screws

Oring installation

Closing with readout board

• Colsing with the readout board 50 screws.

Producing 6 new NS2 Large scale detectors

External frame

Produced in several pieces, then glued together.

GEM foils ready, waiting for the readout and drift boards. Assembly next week.

GEM foils quality control

• Sector to test from -50V to -500V by step of 50V.

• High voltage applied on the top, bottom and first neighbors sectors connected to ground.

• Measuring the leakage current

Expected leakage current

HV (-500V)

Leakage current

• Kapton resisitvity ~1019ohm.m• Air resistivity ~1016ohm.m

• R// = Rkapton x Rair / (Rkapton +Rair )

• R//(60µm)~1016 x 60.10-6 = 6. 1011ohm

• Iexpected~ 500/ R//(60µm) = 0.8 nA

RKaptonRair

RESULTS0 100 200 300 400 500 600

-0.4

-0.35

-0.3

-0.25

-0.2

-0.15

-0.1

-0.05

0

sector1sector2secteur3secteur4secteur5secteur6secteur7secteur8secteur9secteur10

0 100 200 300 400 500 600

-0.8

-0.7

-0.6

-0.5

-0.4

-0.3

-0.2

-0.1

0

sector2secteur3secteur4secteur5secteur6secteur7secteur8secteur9

GEM1

GEM2

0 100 200 300 400 500 600

-5

-4.5

-4

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

sector1sector2secteur3secteur4secteur5secteur6secteur7secteur8secteur9secteur10

GEM3

0 100 200 300 400 500 600

-2.5

-2

-1.5

-1

-0.5

0

sector1sector2secteur3secteur4secteur5secteur6secteur7secteur8secteur9secteur10

GEM4

HV (Volts) HV (Volts)

HV (Volts)HV (Volts)

I (nA)

I (nA) I (nA)

I (nA)

Gain Uniformity Control Set up

Eta Sector 4

X Position (mm)

Peak Position (ADC counts) 15 slices ->1 slice ~ 3cm

Eta Sector 5

X Position (mm)

Peak Position (ADC counts)

Eta Sector 6

X Position (mm)

Peak Position (ADC counts)

Eta Sector 7

X Position (mm)

Peak Position (ADC counts)

Eta Sector 8

X Position (mm)

Peak Position (ADC counts)

Slice N°1

Slice N°2

PeakPosition Variation (%)

Uniformity Plot

Uniformity TOP view

Conclusion

• Construction of 6 large scale production prototypes is going on

• Improvements made on mechanical assembly (NS2 technic and flat boards)

• Powerfull tool to check gain uniformity is available