the ATLAS Pixel Detector: Overview and Status Sven Vahsen, LBNL for the ATLAS Pixel collaboration DPF 2006 Meeting, Honolulu, Hawaii October 30, 2006 Honolulu, October Sven Vahsen, LBNL2 Large Hadron Collider (LHC) under construction near Geneva, Switzerland Eventually 7-TeV proton-on-proton Beam crossings every 25 ns L = cm -2 s -1 (ATLAS / CMS) Near Geneva, Switzerland, underground Full physics run (14TeV) First beams and collisions (0.9TeV) Honolulu, October Sven Vahsen, LBNL3 Length = 55 m Width= 32 m Height= 35 m Weight = 7000 T ATLAS: multi-purpose particle detector Optimized for study of Electroweak symmetry breaking and search for physics beyond SM at the LHC Under construction around one of the LHC interaction points To be completed in time for first beam in 2007 * ATLAS = A Toroidal LHC Apparatus ATLAS! Honolulu, October Sven Vahsen, LBNL4 Detection of charged particles takes place in 1744 identical ATLAS Pixel Modules 6 cm Pixel 50 x 400 m x46080 ATLAS ATLAS Pixel Detector Innermost tracking detector, surrounding beam pipe 1.3 m 1744 modules x pixels = 80 million channels! From ATLAS to Pixels: Mechanical Overview physicist Honolulu, October Sven Vahsen, LBNL5 Pixel Project Overview Pixel Detector is last sub- detector to be installed in ATLAS April 2007 as the 7m Pixel Package, which includes Service panels (connections for electrical, optical, cooling) Be beam pipe Remaining work at CERN Final stages of integration Connection of service panels Testing Remaining slides Overview of the pixel detector and how it works Status of the project Trial insertion of pixel frame into support tube Honolulu, October Sven Vahsen, LBNL6 The LHC Tracking Challenge Only tracks with P T >1Gev, 0 0 shown Pixel Detector design constraints from LHC timing / event-environment physics, ATLAS design Tracking in high multiplicity environment high granularity Good impact parameter resolution high granularity + low mass Distinguishing hits 25ns apart fast preamp rise time 3.2 s trigger latency (LVL2) on detector buffering of hits High radiation dose low temp., high radiation tolerance ATLAS tracking : three sub-detectors from r = 5 cm m, inside 2T magnetic field. Pixel Detector innermost highest granularity and radiation tolerance (3 sp) (4 sp) (36 sp) H bb interaction With pile-up at design luminosity Honolulu, October Sven Vahsen, LBNL7 Modules overlap on the support structure to provide hermetic coverage: 3 space points for || 99.8% fully functional Process variation across FE chips, preamps differ need tuning to make response of all pixels uniform Each preamp has digitial knobs for tuning the preamp behavior,.e.g. Tuning = find the settings for each pixel that give uniform response across module untuned moduletuned module Adjust threshold of each pixel Honolulu, October Sven Vahsen, LBNL28 Actual ATLAS Pixel Sensor A diode junction forms wherever p-doped and n-doped regions touch. Depletion always begins at the diode junction as reverse external voltage is applied. Hadron irradiation introduced p-type defects. Eventually this will cause the bulk to type invert and become p-type. At this point the diode junction shifts to the top. This was chosen on purpose because it allows to operate without fully depleting the bulk. Leakage current increases drastically with irradiation! Lightly n-doped bulk Heavily n-doped pixel implants (doping too heavy to deplete) Heavily p-doped back side contact Guard rings P-spray doping to isolate individual pixels Diode junction Bumps connect to implants Honolulu, October Sven Vahsen, LBNL29 Pixel Chip Front End comparator Input from Pixel sensor (bump goes here) preamp Honolulu, October Sven Vahsen, LBNL30 The MOS transistor schematic of the FE-I3 charge amplifier Above is just one pixel! 2880 pixels / readout chip ~3M (MOS) transistors / chip FE-I3). Honolulu, October Sven Vahsen, LBNL31 Front End Features Programmable threshold = Global Threshold + Pixel Threshold Calibration charge injection Ability to measure leakage current Time over Threshold (TOT) charge measurement How long the red curve says above threshold depends on the size of the input charge Can easily change threshold for whole chip Can fine tune each pixel to compensate for response differences (Tuning) V1 V2 switch Input from detector Good old charge amplifier Injection capacitor (must be small)