Gamma-ray Large Area Space Telescope 15th INTERNATIONAL WORKSHOP ON VERTEX DETECTORS September , 2006 Perugia, Italy GLAST Silicon Tracker beam test results Stefano Germani INFN Perugia

S. Germani - INFN Perugia September Perugia, Italy Outline GLAST: mission and science The LAT instrument The LAT Tracker Beam test motivations The LAT Calibration Unit Beam test description –Preliminary results Conclusions

S. Germani - INFN Perugia September Perugia, Italy The GLAST mission High energy Gamma Ray observatory 2 instruments: --Large Area Telescope (LAT) --Gamma Ray Burst Monitor (GBM) GBM: GBM: ~10 keV – 30 MeV LAT: LAT: ~20 MeV - >300 GeV  Observe γ ray sky (10 keV –300 GeV) All sky survay Pointed observations  Answer to important question in high energy astrophysics raised by results from EGRET  Lifetime 5 years (minimum) LAT assembly completed Environmental tests completed LAT is being integrated on spacecraft Tests will continue (termal, vibrational …) Launch end 2007

S. Germani - INFN Perugia September Perugia, Italy LAT science and performances AGN spectrum GRB emission time structure All sky survey with large field of vew (2.4 sr) Large energy range (20 MeV – 300 GeV) GeV: unexplored energy window Small dead time ~ 25 μs

S. Germani - INFN Perugia September Perugia, Italy The Large Area Telescope (LAT) γ e+e+ e-e- ACD Thermal Blanket Calorimeter DAQ Electronics Tracker 4x4 Towers Array ACD (Aanti Coincidence Detector) : segmented plastic scintillator surrounding the 4x4 Traker Towers array Tracker: silicon microstrip 18 XY layers interleaved with W converters ~ 1.5 X 0 Calorimeter: 8 CsI(Tl) hodoscopic array layers ~ 8.5 X 0

S. Germani - INFN Perugia September Perugia, Italy Space Environment Limitations and Requirements Total mass budget: 3000 Kg Total power budget 650 W –Tracker 160 W Temperature Range +45  -15 °C Vibrations at Launch No consumables Limited Data Flow (8-10 min 40 Mbps ) –Trigger rate: ~ 4 kHz –Downlink rate: ~ 370 Hz –Photon rate : few Hz

S. Germani - INFN Perugia September Perugia, Italy Tracker Design Overview 16 tower modules 37  37cm 2 active cross section/layer 83m 2 of Si SSD, ~ 1M channels strip pitch: 228 μm 18 xy layers per tower –19 “tray” structures 12 with 3% X 0 W on top 4 with 18% X 0 W on bottom 3 with no converter foils –every tray is rotated by 90° wrt the previous one: W foils followed by x,y plane of detectors 2mm gap between x and y oriented detectors Trays stack and align at their corners Electronics on sides of trays: –Minimize gap between towers x x x x y y y y xy plane Tkr Tower Tray

S. Germani - INFN Perugia September Perugia, Italy Tracker Readout Electronics  24 GLAST Tracker Fornt End (GTFE) chips mounted on Multi-Chip Module (MCM) on tray side  9 GLAST Tracker Readout Controllers (GTRC) per cable  Time Over Threshold (TOT) from layer-OR trigger signal Any single component (GTFE, GTRC, cable) can fail without affecting the other

S. Germani - INFN Perugia September Perugia, Italy Tracker Highlights Wafers Yeld ~ 99.5% MCM MCM-SSD right-angle interconenction Kapton cables  4 layers flexible circuit  each cable in the tower module is different  cm long Each Layer passed several Electrical Tests Each Tray passed thermal-cycle tests Each Tower passed  vibrational tests  thermal vacuum tests Difficult work but now the Tracker is complete and working well

S. Germani - INFN Perugia September Perugia, Italy Why Beamtest ? LAT performances have been studied with MC (GEANT4) and cosmic muons The whole energy, angle, position phase space will be available only in orbit Need to verify MC with real data Sample critical/typical points for detector performances and background rejection with particle Beam Check basic quantities (energy deposit, hit multiplicities) Check high level quantities (energy and direction reconstruction) Eventually tune MC

S. Germani - INFN Perugia September Perugia, Italy Photons: what to check ? γ Energy Spectrum γ Angular Distribution wrt LAT axis Most of γ will cross 2 Towers Most of γ will have very low Energy Energy and Direction reconstruction performances scale with energy Check absolute values and scaling especially in the low energy region Direction reconstruction performances scales with angle Check absolute values and scaling especially in the most probable region Check two towers effects Check passive material description

S. Germani - INFN Perugia September Perugia, Italy Background: what to check ? Photons Photons coming backword and hitting the CAL can mimic a track Protons ACD can miss some p Check efficiency Protons hitting the CAL side can mimic a track Check hadron reactions Check efficiencies MMS e+ γ γ Positrons e+ can annihilate in MicroMeteorite Shild Check efficiency

S. Germani - INFN Perugia September Perugia, Italy Check BackSplash High energy γ /electrons produce backsplash from calorimeter Can affect direction reconstruction High multiplicity can saturate cables FIFO Check hit multiplicity Most backsplash hits in bottom layers Direction informations in firsts track hits Study optimal FIFO configurations (Max allowed hits/layer) and dead time Tracker Towers readout by flex cables Max read hits (strips) / Cable = 128 Layer read from bottom to top (FIFO) Flex Cable

S. Germani - INFN Perugia September Perugia, Italy The Calibration Unit The LAT could not be tested on beam (environmental tests at NRL during beam time) anyway: Use Calibration Unit (2 complete Towers + 2 CAL) To scan and test each single Tower for all configuartions is not feasible Most of of the events are contained in 2 towers Calibration Unit allows to test all the geometry related configurations Impact position and angle 2 Towers crossing The aim of the Beamtest is to check and eventually tune MC response

S. Germani - INFN Perugia September Perugia, Italy The Calibration Unit tower 3 tower 2tower 1bay 0 ~ 820 mm ~ 1500 mm

S. Germani - INFN Perugia September Perugia, Italy Where ? Need wide energy range (50 MeV – 300 GeV) Need several particle types ( γ e± protons) CERN T9 line – extracted from PS e±, p, π 0.5 – 10 GeV H4 line – extracted from SPS e-, p, π 10 – 280 GeV Beam time: 24/7 – 22/8 Beam time: 4–15/9

S. Germani - INFN Perugia September Perugia, Italy Analysis Status Beamtest is finished 10 days ago data analysis started but ALL PLOTS shown in the following slides are PRELIMINARY

S. Germani - INFN Perugia September Perugia, Italy Setup at T9 (CERN - PS) GLAST CU C1 C2 S0 Sh S1 S2 Dump Magnet S4 SSDs Photons (Magnet ON) and Charged Particles (Magnet OFF) S4 GLAST CU C1 C2 S0 Sh S1 S2 Dump Magnet SSDs Positrons

S. Germani - INFN Perugia September Perugia, Italy Setup at T9 Picture Magnet Scintillators SSDs Dump CU

S. Germani - INFN Perugia September Perugia, Italy T9 data - Photons Tagged γ Full bremsstrahlung Use tagger to measure photon direction and energy  Small momentum range and limited rate Fixed tagger position use different beam energies (and Magnet B) to cover the needed energy spectrum Ebeam: 0.5, GeV No momentum or rate limitations  Assume gamma direction from beam PRELIMINARY For both cases measurements at several angles (0, 30, 50 deg)

S. Germani - INFN Perugia September Perugia, Italy Tagged Photons Photon Energy measured by Tagger e- beam energy: 0.5 GeV 1 GeV 1.5 GeV 2.5 GeV Electron Energy measured by Tagger+CU Full range covered: 50 MeV  1.4 GeV PRELIMINARY

S. Germani - INFN Perugia September Perugia, Italy First look at Beam Data vs MC I Full bremsstrahlung  Beam Data  MC Conversion Point PRELIMINARY

S. Germani - INFN Perugia September Perugia, Italy First look at Beam Data vs MC II Full bremsstrahlung  Beam Data  MC CAL Energy vs Layer Direction Error PRELIMINARY

S. Germani - INFN Perugia September Perugia, Italy Event Display γ

S. Germani - INFN Perugia September Perugia, Italy T9 data – charged particles Electrons: All the γ configurations for comparison Several other positions energies and angles Protons: E = 10, 6 GeV Small angles on MMS Angle 30, 60, 90 deg CU Positrons: Only a small angle on MMS CU

S. Germani - INFN Perugia September Perugia, Italy Setup at H4 (CERN – SPS) GLAST CU C1 C2 S1 S2 CU Cherenkov upstream GOLIATH BEAM Scintillators

S. Germani - INFN Perugia September Perugia, Italy H4 data Electrons: E 10  280 GeV (10, 20, 50, 100, 200, 280 GeV) Angle 0  90 deg (0, 10, 20, 30, 45, deg) Several impact points Several FIFO configurations Protons: E 10  150 GeV (10, 20, 100, 150 GeV) Angle 0  90 deg (0, 30, 45, 60, 90 deg) Number of Hits in thick W converter layers Number of reconstructed tracks PRELIMINARY

S. Germani - INFN Perugia September Perugia, Italy First look at Beam Data vs MC 20 GeV electrons  Beam Data  MC Number of Tracker Hits PRELIMINARY

S. Germani - INFN Perugia September Perugia, Italy Conclusions Program completed both at T9 and H4 We have a lot of data –CU configurations –Energies –Particles Data analysis is started –Tagger performances –Beam systematics –Hit multiplicity –FIFO configurations –Direction reconstruction –Efficiency –Background –… under study First look analysis show reasonable agreement with MC Heavy Ions test beam scheduled for November at GSI

S. Germani - INFN Perugia September Perugia, Italy Backup Slides

S. Germani - INFN Perugia September Perugia, Italy Italian contribution to the Tracker INFN/ASI responsabilities for the LAT-TKR construction ASI Tracker Tower built and tested in Italy

S. Germani - INFN Perugia September Perugia, Italy LAT Science Requiremnts Large Energy Range: 20 MeV -300 GeV Large Effective Area: > 8000 cm cm 2 (at 10 GeV) Wide Field of View: > 2 sr 2.4 sr Dead Time: < 100 μs/event 25 μs/event Energy Resolution : < 10 % 9 % (at 100 MeV) Point Source Sensitivity: < 6x10 -9 cm -2 s -1 3x10 -9 cm -2 s -1 (>100 MeV) (on axis 100 MeV - 10 GeV) Angular Resolution – 68%: < 0.15° 0.086° (thin) (on axis E>10 GeV) 0.115° (total) Spectral coverage and ground based observations overlap Bright sources variability and GRBs monitor Transient sources emission time structures Spectral studies Good Source localization and minimize sources confusion Requirement - Present Value

S. Germani - INFN Perugia September Perugia, Italy EGRET – LAT properties EGRET LAT Energy range20 Mev – 30 GeV20 Mev – 300 GeV Energy resolution10 %9 % Effective Area1500 cm cm 2 Angular resolution Field of View0.5 sr2.4 sr Flux sensitivity (E>100 MeV) cm -2 s -1 3 · cm -2 s -1 Dead Time 100 ms 25  s

S. Germani - INFN Perugia September Perugia, Italy LAT Performances

S. Germani - INFN Perugia September Perugia, Italy Data Downlink and Commands White Sands Complex/GFEP TDRS Ground Stations USN: Hawaii;Australia GPS GPS Timing & Position Data TLM: Ku-band 40 Mbps S-band 1,2,4,8 kbps 1 kbps CMD: S-band 4 kbps 0.25 kbps TLM: 2.5 Mbps CMD: 2 kbps GLAST

S. Germani - INFN Perugia September Perugia, Italy Tracker Features Conversion Efficiency > 58% Aspect (H/W) ratio < 0.45 (wide field of view) Active area > 19,000 cm 2 (Fraction > 88%) 6-in-a-row tracker trigger –Efficiency > 90% –Single layer trigger rate < 50 kHz Average Noise occupancy < 5x10 -5 Hit efficiency > 98%

S. Germani - INFN Perugia September Perugia, Italy Layer assembly

S. Germani - INFN Perugia September Perugia, Italy Silicon Sensor Devices Specifications Wafer size6” Sensor size (cmXcm) 8.95X8.95 Thickness (mm)400 Dopingn-type Implantp+ Read-outSingle-sided CouplingAC BiasPoly-Si Strips384 Strip pitch (mm)228 Implant width (mm)56 Bias voltage< 120V Breakdown< 175V AND <200nA (averaged any 100 SSD) Bad strips rate0.2 % Hamamatsu Photonics