Radiation Sensor Characterization for the LHC Experiments Federico Ravotti, Maurice Glaser, Michael Moll CERN PH/DT2 and TS/LEA

Outline Sensor Catalogue; Quality Assurance (QA) procedure for sensors; RadFETs packaging; Sensors readout board for LHC Experiments; Sensors R&D: Readout procedure optimization for BPW34 p-i-n diodes; New p-i-n diodes from Czech Republic (LBSD); On-line dosimeter based on fibred OSL. Conclusion. F.Ravotti 5th LHC Radiation Day 29-11-2005

Sensor Catalogue (www.cern.ch/lhc-expt-radmon/) 2 x RadFETs (TID); Specifies sensors suitable for dosimetry in the LHC experiments environment: Mixed-LET radiation field; ~ 5 orders of magnitude in intensity. Many devices tested but only a few selected (e.g. only 2 out of 9 RadFETs) 2 x RadFETs (TID); [REM, UK and LASS, France] 2 x p-i-n diodes (1-MeV Feq); [CMRP, AU and OSRAM BPW34] 1 x Silicon detectors (1-MeV Feq). [CERN RD-50 Mask] Detailed discussion on the sensors selection criteria  see talk at 4th LHC Radiation Day! F.Ravotti 5th LHC Radiation Day 29-11-2005

Sensors QA Procedure Suitable radiation response and intrinsic stability are not enough to guarantee reliable measurements over a long time (e.g. 10 y. LHC). Example of different radiation response curves for Thin Oxide RadFETs from REM (see Catalogue). Example of Annealing Behaviour at different doses for Thick Oxide RadFETs from LAAS (see Catalogue). Compliance with electrical specifications to keep working correctly under irradiation; Homogeneous initial values to insure reproducible measurements; Sensors must be identified one by one using their pre-irradiation characteristics! F.Ravotti 5th LHC Radiation Day 29-11-2005

Delivery to the LHC Experiments Sensors QA Procedure Electrical Tests on the purchased sensor batches to complies with specifications Acceptance Tests For the Experiments with proper readout boards Mounting bare-die sensors in a proper packaging Issue for TID Measurement (RadFETs Packaging) Functional Verification Test Integration in a specific PCB circuit “sensor carrier” For the Experiments that need a readout board Functional Verification Test Delivery to the LHC Experiments F.Ravotti 5th LHC Radiation Day 29-11-2005

Electrical Tests RadFETs: Ids – Vgs in linear and saturation regime; Ids – Vds in function of Vgs; Read-time stability of Vth; p-i-n diodes: I-V in forward bias; Stability of VF  (t); Silicon Detectors: I-V & C-V in reverse bias; Stability of bulk IL  (t). Example of I/V characteristics of not-irradiated BPW34 diodes. Example of I/V and C/V characteristics of not-irradiated Detectors. F.Ravotti 5th LHC Radiation Day 29-11-2005

RadFETs Characteristics Idss VT Sensors Acceptance/Rejection based on: Vth,0 Idss Ids-Vds immune to kink effects Stability of Vth (t).  Tech. Spec. document existent F.Ravotti 5th LHC Radiation Day 29-11-2005

RadFETs Packaging ~10 mm2 36-pin Al2O3 carrier Commercial Packaging (i.e. TO-5, DIL) cannot satisfy all Experiment Requirements (dimensions/materials) Development / study in-house at CERN High Integration level: up to 10 devices covering from mGy to kGy dose range; Customizable internal layout; Standard external connectivity; 1.8 mm ~10 mm2 36-pin Al2O3 carrier Calculated Radiation Transport Characteristics (0.4 mm Al2O3): X = 3-4 % X0; e cut-off  550 KeV; p cut-off  10 MeV; photons transmission  20 KeV; n attenuation  2-3 %; Packaging under validation (including lids effect) with GEANT4 model in collaboration with Genova INFN (Riccardo Capra) Full-Package Geometry designed in GEANT4 F.Ravotti 5th LHC Radiation Day 29-11-2005

Integration Issues ATLAS ID (RMSB Hybrid) CMS (BCM 1) Rest of ATLAS 4 x RADFETs DMILL structure (nth damage) CMS (BCM 1) BPW34 diodes PCB with T control PAD diode PT1000 p-i-n diode [I. Mandic, JSI] ELMB (ADC) + DAQ [A. Macpherson, CERN] Rest of ATLAS General-purpose plug-on I/O module for the monitoring and control of sub-detector front-end equipment F.Ravotti 5th LHC Radiation Day 29-11-2005

Sensors Readout Board PCB designed to host: 1 x RadFETs Packaging (5 channels) 5 x p-i-n sensors; 1 x Temperature sensor; Fully customizable; Small size (15 mm x 25 mm x 5 mm); Signals available on a standard connector plug (12 pins) or direct wire connection. Board readable with commercial electronics: Keithley Source-Meter 2400 and Agilent Switch Matrix; Price ~ 130 CHF/channel (if > 60 channels) PCB can be used as passive dosimeter. F.Ravotti 5th LHC Radiation Day 29-11-2005

Outline Sensor Catalogue; Quality Assurance (QA) procedure for sensors; RadFETs packaging; Sensors readout board for LHC Experiments; Sensors R&D: Readout procedure optimization for BPW34 p-i-n diodes; New p-i-n diodes from Czech Republic (LBSD); On-line dosimeter based on fibred OSL. Conclusion. F.Ravotti 5th LHC Radiation Day 29-11-2005

BPW34 Readout Optimization 1) Devices not manufactured to be dosimeters (e.g. not sensitive to low F); 2) Pre-irradiation helps to shift operation point (see our last years talk); To be studied in more detail: Influence of readout parameters (current density and pulse length) on diode’s response; Long-term annealing of VF as function of IF and Temperature. iF = 1 mA  200 ms Current density: Feq > 21013 cm-2  “thyristor - like” behaviour; Keep IF < 50 mA is a good precaution! Tested readout currents 1 mA, 10 mA, 25 mA Feq (1x1011 to 1x1015 cm-2) F.Ravotti 5th LHC Radiation Day 29-11-2005

BPW34 Readout Optimization Current density (radiation response at 25 mA vs. 1 mA): Feq < 21012 cm-2 negligible sensitivity increase; Feq > 21012 cm-2; S (25 mA) > 36 % S (1 mA); Signs of heating effects Feq ~ 11014 cm-2; iF = 25 mA  100 ms Pulse Length:  Keep the readout-time  200 ms is advisable;  “optimized” pulse-length of 50 ms. after ~ 11013 cm-2 IF = 1 mA; VF = 6.7 V Conclusion: Current density and pulse length have to be adopted to the user requirements (fluence range, current density limitations in electronics, etc….) F.Ravotti 5th LHC Radiation Day 29-11-2005

BPW34 Readout Optimization Annealing of VF (IF): Relative change of the voltage less significant at high injection levels! (detailed study ongoing in the Temperature range 20 – 100 ºC) F.Ravotti 5th LHC Radiation Day 29-11-2005

Czech p-i-n diodes (LBSD) Long Base Silicon Diodes from CMI, Prague Cheaper compared to the High Sensitivity diodes currently presented in the Catalogue; Two types are produced: one MORE SENSITIVE than the currently used devices; Recommended IF pulse for readout: 25 mA x 40 ms. Type “Si-1”: KERMA: 0.1-30 Gy (Feq ~ 1.2x1012 cm-2) nF sensitivity: ~ 3 mV/109 cm-2 Type “Si-2”: KERMA: 0.01-5 Gy (Feq ~ 2x1011 cm-2) nF sensitivity: ~ 3 mV/108 cm-2 Annealing studies ongoing to include these products into Sensor Catalogue! F.Ravotti 5th LHC Radiation Day 29-11-2005

Fibred OSLs System Quartz Radhard Fibers Laser System Driver Laser Light 60 mW Visible light ~ 5 mg OSL Crystal Oscilloscope 1 mA/nW (@ OSL l) 5 V/div 1 MW DC 50 ms/div Tested at the TRIGA Reactor of the JSI, Ljubljana (Slovenia) F.Ravotti 5th LHC Radiation Day 29-11-2005

Dose integrated in 6 sec time. Fibred OSLs System Preliminary Results (last week!!!) show the feasibility of such a system in harsh and intense environment; Test condition ~200 mGy/s with feq ~1.9x109 cm-2s-1 (values referred to 250 W reactor power at Z = 0). Dose integrated in 6 sec time. Sensitivity of the tested prototype ~ 0.1 mGy, but minimal sensitivity probably higher; probe edge dimension < 1 mm2 F.Ravotti 5th LHC Radiation Day 29-11-2005

Conclusion Over 1200 sensors have been procured and ~ 1/3 have been tested following the QA procedure here described. About 100 samples have been delivered to LHC Experiments; A dedicate packaging and a readout board for the sensors have been produced; R&D on sensors is carried out in parallel: Improvement in the BPW34 readout protocol; More sensitive p-i-n diodes are under studies  added soon to the Sensor Catalogue; Very promising results obtained in OSL on-line dosimetry! F.Ravotti 5th LHC Radiation Day 29-11-2005