Optical Links for the ATLAS SCT and Pixel Detector Ingrid-Maria Gregor (University Wuppertal) for the ATLAS June 6th, 2000 collaboration International Workshop on Semiconductor Pixel Detectors for Particles and X-Rays Genova, Italy June 2000
Overview Ingrid-Maria Gregor University of Wuppertal ➤ ATLAS Inner Detector ➤ Optical Link Architecture ➤ System Tests ➤ Conclusion Pixel2000 Genova, Italy 2
ATLAS Inner Detector Ingrid-Maria Gregor University of Wuppertal Barrel SCT Forward SCT TRT Pixel Detectors Pixel2000 Genova, Italy 3
Data Transfer Ingrid-Maria Gregor University of Wuppertal ➤ Control and clock information must be transferred from acquisition system to the silicon detectors ➤ Hit data must be transferred from the modules to a remote acquisition system ➤ use of copper links unfeasible ➢ large amount of dead material which would be introduced ➢ problems from cross-talk and ground loops ➤ it is proposed to use custom optical links to transfer data to and from the detector modules (SCT and Pixel Detector) Pixel2000 Genova, Italy 4
Special Requirements (1) Ingrid-Maria Gregor University of Wuppertal ➤ radiation hardness ➢ ionizing radiation : 100kGy (SCT) to 550kGy (Pixel detector) ➢ 1 billion lung x-rays ➢ neutron radiation : ➣ Si-devices: 1*10 15 n(1MeV)/cm 2 ➣ GaAs-devices: up to 6.4*10 15 n(1MeV)/cm 2 ➢ expected over the 10 year lifetime of ATLAS (1 st layer) Pixel2000 Genova, Italy 5
Special Requirements (2) Ingrid-Maria Gregor University of Wuppertal ➤ non-magnetic to avoid perturbing the inner detector magnetic field ➤ low mass ➢ additional interactions in non-instrumented regions of the detector would compromise the quality of momentum measurements ➢ particle conversion ➤ reasonably low cost Pixel2000 Genova, Italy 6
Read-Out Link Architecture Ingrid-Maria Gregor University of Wuppertal Vertical Cavity Surface Emitting Laser Pixel2000 Genova, Italy 7
Timing Triggering and Control (TTC link) Ingrid-Maria Gregor University of Wuppertal ➤ VCSEL Driver BiPhase Mark Encoder ➤ driver chip for VCSEL on acquisition side (12 way) ➤ 40MHz-Clock and Commands on one link Pixel2000 Genova, Italy 8
TTC Link Ingrid-Maria Gregor University of Wuppertal ➤ Digital Optical Receiver IC ➤ decodes the signals received by the PIN ➤ recovers commands and 40MHz-clock ➤ LVDS output ➤ 2 versions: bipolar (SCT) and CMOS (Pixel) ➤ SCT redundancy system: TTC data can be taken from redundancy link from a neighbouring data Pixel2000 Genova, Italy 9
Data Link Ingrid-Maria Gregor University of Wuppertal ➤ VCSEL Driver Chip ➤ LVDS input ➤ 40Mbit/s (SCT), 80Mbit/s (Pixel 1st and 2nd layer) or 160Mbit/s (B-layer) ➤ NRZ (20MHz = 40Mbit/s) ➤ 2 versions: bipolar (SCT) and CMOS (Pixel) ➤ SCT: in the event of failure, the data can be rerouted through the second link ➤ Pixel: one link for outer layers, two for B-layer (160MBit/sec) Pixel2000 Genova, Italy 10
Opto-Package Specs Ingrid-Maria Gregor University of Wuppertal ➤ Custom package made of material with low Z, non-magnetic, with 2 VCSELs and 1 PIN ➤ Fibres attached without standard connector ➤ not larger than 5.5 mm x 5.5 mm x 1.6 mm ➤ package and including devices have to stand radiation levels ➤ operation temperature during testing: -25 o C to 40 o C ➤ operation temperature during ATLAS: -25 o C to 15 o C ➤ three different designs under survey Pixel2000 Genova, Italy 11
Taiwan Opto-Package Ingrid-Maria Gregor University of Wuppertal Pixel2000 Genova, Italy 12
Taiwan Opto-Package Ingrid-Maria Gregor University of Wuppertal 5.5 mm Pixel2000 Genova, Italy 13
Taiwan Opto-Package Ingrid-Maria Gregor University of Wuppertal Pixel2000 Genova, Italy 14
Opto-Elbow (Pixel) Ingrid-Maria Gregor University of Wuppertal DORIC VDC Opto-Package Opto Elbow Bending Zone Solder Connection Single Side Module Pigtail Glue Attachment & Wire Bonding Pixel2000 Genova, Italy 15
Opto Package Support (SCT) Ingrid-Maria Gregor University of Wuppertal VDC (VCSEL Driver Chip) DORIC Module Connector (Receiver Chip) VCSEL/PIN Package Opto Hybrid Kapton Cable ZIF Connector Pixel2000 Genova, Italy 16
System Tests Ingrid-Maria Gregor University of Wuppertal ➤ Characteristics of opto-link for this system under test: ➢ Radiation and Annealing studies ➢ Lifetime studies ➢ Bit Error Rate ➢ Single Event Upsets Pixel2000 Genova, Italy 17
Annealing Studies of VCSEL Ingrid-Maria Gregor University of Wuppertal 1,0 Average Relative Light Output (RLO) 0,8 Radiation levels: = 14 n A 8 * 10 0,6 2 cm Light Output after Irradiation = 14 RLO = n B 5 * 10 Light Output before Irradiation 2 0,4 cm RLO of VCSEL (group A) annealed at 10mA 0,2 RLO of VCSEL (group A) annealed at 20mA RLO of VCSEL (group B) annealed at 10mA RLO of VCSEL (group B) annealed at 20mA 0,0 00:00 24:00 48:00 72:00 96:00 Annealing time [h] Pixel2000 Genova, Italy 18
VCSEL tests Ingrid-Maria Gregor University of Wuppertal ➤ VCSELs were not powered during irradiation ➤ radiation induced damages can be annealed up to 90% over a period of days/weeks ➤ results suggest brief 20 mA current annealing sessions ➤ following aging tests showed an expected lifetime of a few hundred years (irradiated) ➤ further irradiation and lifetime tests are under way (up to Pixel level of 6.4*10 15 n(1MeV)/cm2) Pixel2000 Genova, Italy 19
Bit Error Rate (BER) Ingrid-Maria Gregor University of Wuppertal ➤ BER: good parameter to evaluate the performance of the optolink BER vs lightinput 1 .E+ 0 1 PIN-BIAS = 5V 1 .E+ 0 0 N − PIN-BIAS = 0V = < 9 error 1 .E-0 1 BER 10 N 1 .E-0 2 bits 1 .E-0 3 1 .E-0 4 BER 1 .E-0 5 1 .E-0 6 1 .E-0 7 1 .E-0 8 1 .E-0 9 ➤ Good results with SCT link 1 .E-1 0 1 .E-1 1 ➤ Pixel test under way 8 0 1 0 0 1 2 0 1 4 0 1 6 0 1 8 0 2 0 0 2 2 0 2 4 0 Lightinput ( m W ) Pixel2000 Genova, Italy 20
Single Event Upsets Ingrid-Maria Gregor University of Wuppertal ➤ Single Event Upsets caused by a very high energy deposition in a small volume of electronics chips ➤ most sensitive region: reverse-biased p/n junction where high electric field is very effective in collecting the charge by drift ➤ PIN = reverse biased p/n junction ➤ 100 µ m x 50 µ m x 50 µ m ! ➤ First SEU appearance : NPL neutron beam ➤ test with pions at PSI Pixel2000 Genova, Italy 21
SEU at PSI Ingrid-Maria Gregor University of Wuppertal ➤ Sensitive power around 100 µ W ➤ for P>350 µ W, BER <10 -10 s -1 ➤ discrepancy between counter and Al foil ➤ repeat next week Pixel2000 Genova, Italy 22
Conclusion Ingrid-Maria Gregor University of Wuppertal ➤ data transfer using optical links ➤ custom packaging developments for the 40 Mb/s optical link show good physical results ➤ design of complete Pixel opto-link under way ➤ radiation induced damages can be annealed up to 90% over a period of days ➤ results suggest brief 20 mA current annealing sessions ➤ SEU problems can be fixed by sending more light Pixel2000 Genova, Italy 23
Conclusion Ingrid-Maria Gregor University of Wuppertal ➤ http://www.atlas.uni-wuppertal.de/ Optolink/Pix_Optolink.html Pixel2000 Genova, Italy 24
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