characterization of double sided silicon micro-strip sensors with a pulsed infra- red laser system...

Characterization of double sided Characterization of double sided silicon micro-strip sensors with a silicon micro-strip sensors with a pulsed infra-red laser system for pulsed infra-red laser system for

the CBM experimentthe CBM experiment

Pradeep Ghosh1,2 & Jürgen Eschke2,3

1Goethe-Universität, Frankfurt am Main2GSI Helmholtzzentrum für Schwerionenforschung GmbH,

Darmstadt3Facility for Antiproton and Ion Research GmbH, Darmstadt

ContentsContentsMotivationIntroductionMeasurement setupCalibration of focuserSilicon sensor under testMeasurements and resultsPlanned activities and future

work

05-Mar-13 Laser Test Stand: P.Ghosh & J.Eschke 2

1. Motivation1. MotivationBand gap in silicon ~ 1.1 eV and Infrared

light (1060nm) is equivalent to 1.17 eVAbsorption depth of infrared light in silicon

is around 500 µm. Silicon sensor is 300 µm thick.


Infrared light (1060nm ~ 1.17 eV) induces charge of about 24 kilo electrons and is equivalent to 1 Minimum Ionizing Particle.

Idea is to mimic in-beam scenario and investigate sensor performanceArnaud Darmont, Aphesa, white paper, 04/2009

2. Introduction2. IntroductionPulsed infrared Laser with

◦ Wavelength : 1060 nm ; Pulse duration : 10ns◦ Laser current : 41mA ; Laser Power < 5mW◦ Multi lens focuser: spot-size ~ 13 µm (1

strip/side)

◦Fully depleted CBM02 double sided strip sensor

Initial Goals◦ To create 24 kilo electrons in the sensor with the

help of LASER to mimic the MIP(~176 ADC) and observe sensor response.

◦ Focus the laser spot to fire only1 strip/side and able to scan the whole sensor with step motor.

◦ Understand the charge sharing function in the interstrip region 05-Mar-13 Laser Test Stand: P.Ghosh & J.Eschke 4

3. Set up: Laser test stand3. Set up: Laser test stand


3. Set up : Laser Test 3. Set up : Laser Test Stand Stand


Focuser

CBM02 sensor

Optical fiber

Coupling: Laser and Optical fiber

Laser

Nside-nx2Nside-nx0

Pside-nx2

Pside-nx2

Laser spot

4. Calibration of Focuser4. Calibration of FocuserCalibration of the Laser

focuser was done at various heights(z-position above sensor surface) at different laser currents43mA ; 45 mA and 48 mA

Minimum number of fired strips/side was achieved at point 7 above the reference level.

Furthermore, laser can be tuned to focus to 1 strip/side firing position by reducing the laser current.


5. Sensor under test 5. Sensor under test CBM02 SPID 0-b 006 sensor non irradiatedDouble sided, 256 strips with

50µm strip pitch.Size : 1.5 cm x 1.5 cm x 300 µm1 dc pad and 4 ac pads per

stripFull depletion Voltage: 70VOperating Voltage: 100 VLeakage current at V(op): 0.5µAReadout via self triggering

nXYTER based FEE



6. Measurements with Pulsed Laser

Strip number

Num

ber

of

hit

s

Strip number

Num

ber

of

hit

s

p-side

ADC values

Num

ber

of

hit

s

Channel hits(fired strips) Channel hits(fired strips) per side per side


Digital amplitude with position Digital amplitude with position per side per side

Equal number of hits on both p and n side of the microstrip sensor Strip nr.132 on p-side and Strip nr. 122 on n-side is fired. One strip cluster on both sides of sensor proves that charge

collected only by one strip and not been shared by neighboring strips.

ADC counts suggest we are able to induce charge eqv. of 1 MIP.

n-side

ADC values

Num

ber

of

hit

s

Hit position in the Hit position in the detectordetector


Sensor Size : 1.5 x 1.5 cm2

Strip width is 18 µm; Strip pitch is 50 µm.

Laser spot size ~ 13 µmStep motor attached to the Laser

system has a pitch of few µm. Enabling to investigate the interstrip region.


18 µm

50 µm

Cha

rge

colle

cted

in A

DC

Distance from the Strip, µm0 50

1 MIP

Charge Collected at Strip 1Charge Collected at Strip 2

Charge sharing function- Charge sharing function- measurementmeasurement

The curve above is just a cartoon

Charge sharing function-Charge sharing function-resultsresultsRed and Green curves

shows the charge collected by individual strip when laser moves in the interstrip region.

Blue curve shows the charge sharing function.

Results shows a plateau region (10-12 µm) where charge is always shared equally with neighboring strip.


Preliminary result

Planned activities & future Planned activities & future workworkStrip-by-strip characterization of silicon

sensors by scanning over it.Preparing and pre-testing prototype

sensors for the in-beam measurement.Charge sharing function will be

investigated for more prototype sensors.Coupling capacitances will be determined

to understand the charge loss to neighboring strips.

To run data acquisition (DAQ) for laser scanning of sensors over EPICS.


Thank you for your Thank you for your attention!attention!


H35.6 ; A. Lymanets

Detector module development for the CBM-STS

H35.7 ; M. Singla

Study of low mass readout cables for the CBM-STS

H35.8 ; T. Balog

Performance of prototype module for the CBM-STS

H63.1 ; C. Pauly

The CBM experiment : Status and outlook

H68.7 ; A . Senger

FLUKA calculations for the CBM experiment

Tue

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characterization of double sided silicon micro-strip sensors with a pulsed infra- red laser system...

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