Optical Links for the ATLAS SCT and Pixel

Optical Links for the ATLAS SCT and Pixel Detector Ingrid-Maria Gregor (University Wuppertal) for the ATLAS collaboration June 6 th, 2000 International Workshop on Semiconductor Pixel Detectors for Particles and X-Rays Genova, Italy June 2000

Overview Ingrid-Maria Gregor ä ä University of Wuppertal ATLAS Inner Detector Optical Link Architecture System Tests Conclusion Pixel 2000 Genova, Italy 2

ATLAS Inner Detector Ingrid-Maria Gregor Pixel 2000 Genova, Italy University of Wuppertal 3

Data Transfer Ingrid-Maria Gregor University of Wuppertal ä Control and clock information must be transferred from acquisition system to the silicon detectors ä Hit data must be transferred from the modules to a remote acquisition system ä use of copper links unfeasible â large amount of dead material which would be introduced â problems from cross-talk and ground loops ä it is proposed to use custom optical links to transfer data to and from the detector modules (SCT and Pixel Detector) Pixel 2000 Genova, Italy 4

Special Requirements (1) Ingrid-Maria Gregor University of Wuppertal ä radiation hardness â ionizing radiation : 100 k. Gy (SCT) to 550 k. Gy (Pixel detector) â 1 billion lung x-rays â neutron radiation : ã Si-devices: 1*1015 n(1 Me. V)/cm 2 ã Ga. As-devices: up to 6. 4*1015 n(1 Me. V)/cm 2 â expected over the 10 year lifetime of ATLAS (1 st layer) Pixel 2000 Genova, Italy 5

Special Requirements (2) Ingrid-Maria Gregor University of Wuppertal ä non-magnetic to avoid perturbing the inner detector magnetic field ä low mass â additional interactions in non-instrumented regions of the detector would compromise the quality of momentum measurements â particle conversion ä reasonably low cost Pixel 2000 Genova, Italy 6

Read-Out Link Architecture Ingrid-Maria Gregor University of Wuppertal Vertical Cavity Surface Emitting Laser Pixel 2000 Genova, Italy 7

Timing Triggering and Control (TTC link) Ingrid-Maria Gregor University of Wuppertal ä VCSEL Driver Bi. Phase Mark Encoder ä driver chip for VCSEL on acquisition side (12 way) ä 40 MHz-Clock and Commands on one link Pixel 2000 Genova, Italy 8

TTC Link Ingrid-Maria Gregor University of Wuppertal ä ä Digital Optical Receiver IC decodes the signals received by the PIN recovers commands and 40 MHz-clock LVDS output ä 2 versions: bipolar (SCT) and CMOS (Pixel) ä SCT redundancy system: TTC data can be taken from redundancy link from a neighbouring data Pixel 2000 Genova, Italy 9

Data Link Ingrid-Maria Gregor University of Wuppertal ä VCSEL Driver Chip ä LVDS input ä 40 Mbit/s (SCT), 80 Mbit/s (Pixel 1 st and 2 nd layer) or 160 Mbit/s (B-layer) ä NRZ (20 MHz = 40 Mbit/s) ä 2 versions: bipolar (SCT) and CMOS (Pixel) ä SCT: in the event of failure, the data can be rerouted through the second link ä Pixel: one link for outer layers, two for Blayer (160 MBit/sec) Pixel 2000 Genova, Italy 10

Opto-Package Specs Ingrid-Maria Gregor University of Wuppertal ä Custom package made of material with low Z, nonmagnetic, with 2 VCSELs and 1 PIN ä Fibres attached without standard connector ä not larger than 5. 5 mm x 1. 6 mm ä package and including devices have to stand radiation levels ä operation temperature during testing: -25 o. C to 40 o. C ä operation temperature during ATLAS: -25 o. C to 15 o. C ä three different designs under survey Pixel 2000 Genova, Italy 11

Taiwan Opto-Package Ingrid-Maria Gregor Pixel 2000 Genova, Italy University of Wuppertal 12

Taiwan Opto-Package Ingrid-Maria Gregor University of Wuppertal 5. 5 mm Pixel 2000 Genova, Italy 13

Taiwan Opto-Package Ingrid-Maria Gregor Pixel 2000 Genova, Italy University of Wuppertal 14

Opto-Elbow (Pixel) Ingrid-Maria Gregor DORIC VDC University of Wuppertal Opto-Package Opto Elbow Bending Zone Solder Connection Single Side Module Pigtail Glue Attachment & Wire Bonding Pixel 2000 Genova, Italy 15

Opto Package Support (SCT) Ingrid-Maria Gregor Module Connector Opto Hybrid University of Wuppertal VDC (VCSEL Driver Chip) DORIC (Receiver Chip) VCSEL/PIN Package Kapton Cable ZIF Connector Pixel 2000 Genova, Italy 16

System Tests Ingrid-Maria Gregor University of Wuppertal ä Characteristics of opto-link for this system under test: â â Radiation and Annealing studies Lifetime studies Bit Error Rate Single Event Upsets Pixel 2000 Genova, Italy 17

Annealing Studies of VCSEL Ingrid-Maria Gregor University of Wuppertal Average Relative Light Output (RLO) 1, 0 0, 8 Radiation levels: 0, 6 Light Output after Irradiation RLO = 0, 4 0, 2 0, 0 00: 00 Light Output before Irradiation RLO of VCSEL (group A) annealed at 10 m. A RLO of VCSEL (group A) annealed at 20 m. A RLO of VCSEL (group B) annealed at 10 m. A RLO of VCSEL (group B) annealed at 20 m. A 24: 00 48: 00 72: 00 96: 00 Annealing time [h] Pixel 2000 Genova, Italy 18

VCSEL tests Ingrid-Maria Gregor University of Wuppertal ä VCSELs were not powered during irradiation ä radiation induced damages can be annealed up to 90% over a period of days/weeks ä results suggest brief 20 m. A current annealing sessions ä following aging tests showed an expected lifetime of a few hundred years (irradiated) ä further irradiation and lifetime tests are under way (up to Pixel level of 6. 4*1015 n(1 Me. V)/cm 2) Pixel 2000 Genova, Italy 19

Bit Error Rate (BER) Ingrid-Maria Gregor University of Wuppertal ä BER: good parameter to evaluate the performance of the optolink ä Good results with SCT link ä Pixel test under way Pixel 2000 Genova, Italy 20

Single Event Upsets Ingrid-Maria Gregor University of Wuppertal ä Single Event Upsets caused by a very high energy deposition in a small volume of electronics chips ä most sensitive region: reverse-biased p/n junction where high electric field is very effective in collecting the charge by drift ä PIN = reverse biased p/n junction ä 100 mm x 50 mm ! ä First SEU appearance : NPL neutron beam ä test with pions at PSI Pixel 2000 Genova, Italy 21

SEU at PSI Ingrid-Maria Gregor University of Wuppertal ä Sensitive power around 100 m. W ä for P>350 m. W, BER <10 -10 s-1 ä discrepancy between counter and Al foil ä repeat next week Pixel 2000 Genova, Italy 22

Conclusion Ingrid-Maria Gregor University of Wuppertal ä data transfer using optical links ä custom packaging developments for the 40 Mb/s optical link show good physical results ä design of complete Pixel opto-link under way ä radiation induced damages can be annealed up to 90% over a period of days ä results suggest brief 20 m. A current annealing sessions ä SEU problems can be fixed by sending more light Pixel 2000 Genova, Italy 23

Conclusion Ingrid-Maria Gregor University of Wuppertal ä http: //www. atlas. uni-wuppertal. de/ Optolink/Pix_Optolink. html Pixel 2000 Genova, Italy 24