CERN Summer Student 2010 Student Sessions August 17

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CERN Summer Student 2010 Student Sessions, August 17 th 2010 Sensor R&D for ATLAS-IBL

CERN Summer Student 2010 Student Sessions, August 17 th 2010 Sensor R&D for ATLAS-IBL and s. LHC Student Theresa Obermann Supervisors A. La Rosa and H. Pernegger

Overview Aim of the project Characterization of 3 D/FBK Silicon Pixel detectors Thematics Interaction

Overview Aim of the project Characterization of 3 D/FBK Silicon Pixel detectors Thematics Interaction of radiation and particles with matter, silicon detector properties, lab characterization, irradiation induced effects Work Study of ATLAS Pixel front-end chip (FE-I 3), FE tuning and calibration, sensor source-tests and automatization of the measurements, testbeam data taking This project has been supported by CERN ATLAS Team (CAT) and PH-DT in the framework of White-Paper/ WP 4 Rad Hard Detectors studies https: //twiki. cern. ch/twiki/bin/view/Main/Cern. Atlas. Pixel. Sensors. RD 17. 08. 2010 Theresa Obermann 2

Motivation for radiation-hard detectors s. LHC versus LHC higher radiation level -> higher radiation

Motivation for radiation-hard detectors s. LHC versus LHC higher radiation level -> higher radiation tolerance needed higher multiplicity -> higher granularity needed sensor issues increase of full depletion voltage -> limited by maximum operation voltage increase of leakage current -> sensor dissipates significant power charge trapping -> smaller signal after irradiation -> R & D is needed 17. 08. 2010 Theresa Obermann 3

Two geometries for Silicon pixel detectors planar sensors • • well known technology high

Two geometries for Silicon pixel detectors planar sensors • • well known technology high availability (high) depletion voltage new n-in-n and n-in-p technology 17. 08. 2010 3 D silicon sensor • • • Theresa Obermann decoupling of substrate thickness from electrode distance low depletion voltage, larger active area smaller trapping probability fast signal collection larger capacitance reliable production (yield) 4

More about 3 D sensors • double side double type column • three different

More about 3 D sensors • double side double type column • three different electrode distances • some properties Substrate thickness 200 µm Overlap 95 µm Full depletion voltage 12 V Breakdown voltage 70 V • connection sensor-frontend sensor size 400 µm x 50 µm INFN Trento, Genova, FBK 17. 08. 2010 Theresa Obermann 5

Experimental Setup DAQ based on ATLAS Pixel USBPix set-up advantages - no changing in

Experimental Setup DAQ based on ATLAS Pixel USBPix set-up advantages - no changing in relative positions - source is placed directly above the sensor 17. 08. 2010 Ameritium Strontium Photon E=59. 9 ke. V Electron E=546 ke. V Theresa Obermann 6

Front-End electronics and evaluation methods • To. T triangular signal shape - measurable value

Front-End electronics and evaluation methods • To. T triangular signal shape - measurable value - is proportional to the deposited energy in the sensor • S-Curve sensor - convolution of a stepfunction and a gaussian - defines the threshold and noise • • • Injection of a known charge via Charge=Capacitance*applied Voltage Feedback current can be set with two DACs -> slope of To. T Threshold can be set with two DACs-> height of diskriminator 17. 08. 2010 Theresa Obermann 7

Measurements list • leakage current versus bias voltage • threshold and noise scans •

Measurements list • leakage current versus bias voltage • threshold and noise scans • noise versus bias voltage • gamma and beta source-tests at different bias voltages 17. 08. 2010 Theresa Obermann up to now have been performed individually from now on by automatization 8

I-V curve of the 3 D sensors General behaviour of the I-V-curve of a

I-V curve of the 3 D sensors General behaviour of the I-V-curve of a diode • rise • plateau • breakdown region T=20°C Properties of the 3 D I-V-curve • rise • plateau from 10 V to 50 V • breakdown region at 60 V/70 V 17. 08. 2010 Theresa Obermann 9

Threshold and noise behaviour Noise of 3 D sensors before irradiation 4 E-type 50

Threshold and noise behaviour Noise of 3 D sensors before irradiation 4 E-type 50 V Some values: 17. 08. 2010 Threshold [e] Noise [e] HV [V] 3 D-4 E 3292± 60 232± 12 50 3 D-2 E 3288± 43 200± 10 50 Planar-n-in-n 3237± 33 173± 9 150 Theresa Obermann 10

Energy spectrum of Am 241 • Gaussian fit 3 D-2 E-30 V • •

Energy spectrum of Am 241 • Gaussian fit 3 D-2 E-30 V • • 17. 08. 2010 Charge [ke] Expected value 16. 6 Planar n-in-n 14. 8± 0. 7 3 D-4 E 14. 06± 0. 90 Charge collection in dependence of bias voltage 150 V Results Ameritium not all the charge is collected performance is in agreement with planar n-in-n sensor Theresa Obermann 11

Energy spectrum of Sr 90 65 ± 4 [e/µm] 86 ± 6 [e/µm] n-in-n-150

Energy spectrum of Sr 90 65 ± 4 [e/µm] 86 ± 6 [e/µm] n-in-n-150 V d=250 µm 3 D-2 E-20 V d=200 µm • percentage of cluster size • measured at different HV • fitted with a Landau-Gaussian distribution 17. 08. 2010 Theresa Obermann 12

Outlook • characterization of unirradiated sensors has been performed • automatization of the measurements

Outlook • characterization of unirradiated sensors has been performed • automatization of the measurements including programming with C++ • characterization of proton irradiated sensors up to a fluence of f=1 x 1015[1/cm 2] • testbeam involvement with a diamond pixel detector Special thanks to Christian Gallrapp who helped me a lot taking the data. 17. 08. 2010 Theresa Obermann 13

Thanks for your attention and have a nice break 17. 08. 2010 Theresa Obermann

Thanks for your attention and have a nice break 17. 08. 2010 Theresa Obermann 14

BACK-UP 17. 08. 2010 Theresa Obermann 15

BACK-UP 17. 08. 2010 Theresa Obermann 15

Physics of a silicon detector pn-junction 17. 08. 2010 • particle/radiation that passes the

Physics of a silicon detector pn-junction 17. 08. 2010 • particle/radiation that passes the depleted area creates electron-holes pairs with a cost of 3. 61 e. V • this charge is collected by the electrodes • height of signal is proportional to collected charge and therefore to depsited energy Theresa Obermann 16

Bandgap and energy level of doped detectors 17. 08. 2010 Theresa Obermann 17

Bandgap and energy level of doped detectors 17. 08. 2010 Theresa Obermann 17

Radiation induced effects – bulk damage • increase of leakage current • change of

Radiation induced effects – bulk damage • increase of leakage current • change of space charge – type inversion • charge trapping 17. 08. 2010 Theresa Obermann 18

Tuning of a sensor • • 17. 08. 2010 Threshold: 3200 e To. T:

Tuning of a sensor • • 17. 08. 2010 Threshold: 3200 e To. T: 60 (*25 ns) @ 20 ke 20°C System: Durbo. DAQ Theresa Obermann 19

Some formulas • • d=epsilon*A/c_depleted E_max=e*N_D/epsilon v=mu*E_max t=d/v 17. 08. 2010 Theresa Obermann 20

Some formulas • • d=epsilon*A/c_depleted E_max=e*N_D/epsilon v=mu*E_max t=d/v 17. 08. 2010 Theresa Obermann 20

Method of measurements I - Turbo. DAQ Scanprogram 17. 08. 2010 Theresa Obermann 21

Method of measurements I - Turbo. DAQ Scanprogram 17. 08. 2010 Theresa Obermann 21

Noise and Capacitance 17. 08. 2010 Theresa Obermann 22

Noise and Capacitance 17. 08. 2010 Theresa Obermann 22

Results of 3 D-sensors • Threshold • Noise - independent of voltage 17. 08.

Results of 3 D-sensors • Threshold • Noise - independent of voltage 17. 08. 2010 - decreasing with increasing voltage Theresa Obermann 23

3 D-types 17. 08. 2010 Theresa Obermann 24

3 D-types 17. 08. 2010 Theresa Obermann 24