Test Beam Analysis of Czochralski Silicon Strip Detector John Kennedy, Alison Bates, Chris Parkes, Paula Collins, Juan Palacios & Doris Eckstein
Overview LHCb Detector and Motivation Radiation Hard Material? Czochralski Silicon Test Beam 2002/CERN PS Irradiation/2003 Conclusions and Future Work AIMS: To develop detectors that may be used for the LHCb VELO upgrade, that offer increased radiation hardness and resolution. November 4 John Kennedy 2
LHCb VErtex LOcator Stations - A dedicated CP Violation measuring experiment 21 diffusion oxygenated FZ silicon sensors. Silicon detectors start 7mm from beam axis but 1mm of guard ring structure silicon detection begins at 8mm November 4 John Kennedy 3
Extreme Radiation Environment Middle station Far station Strongly non-uniform dependence on 1/r 2 and station (z) Maximum Fluence 1.3x10 14 1MeV n eq /cm 2 /year. Predominantly charged particles. Maintain a good S/N performance for several years (replacement). Extensive R&D program to select Sensor and Front-End chip. November 4 John Kennedy 4
Czochralski Silicon Single crystal pulled out of melt (High resistivity 7 available) standard FZ 6 neutrons 400 pions 5 protons oxygen rich FZ Oxygen content: neutrons 300 Standard silicon ~1e15cm -3 DOFZ silicon ~1e17cm -3 Cz silicon ~1e18cm -3 0 0.5 1 1.5 2 2.5 3 3.5 Φ eq [10 14 cm -2 ] Oxygen thought to increase radiation hardness N eff [10 12 cm -3 ] 4 3 2 1 (to charged particles only) pions protons 200 100 V dep [V] (300µm) November 4 John Kennedy 5
Czochralski Detector Thanks to Jaakko Harkonen Helsinki Institute of Physics First ever Czochralski Silicon detector equipped with LHC speed electronics p on n Czochralski material Area read out = 6.1 x 1.92 cm Strips run along x axis (6.1 cm) 2 SCT128A chips for readout Procedure: 2002 test beam (non-irradiated) Irradiate detector (May 2003) 2003 test beam (June 2003) November 4 John Kennedy 6
2002 Test Beam Unirradiated Cz Extrapolated Residuals aligned Detector 10 300 250 200 ExtrapResidsAligned10 Entries 3327 Mean 7.828e-05 RMS 0.004698 Underflow 6 Overflow 0 150 100 50 0-0.03-0.02-0.01 0 0.01 0.02 0.03 Test beam of 120 GeV/c muon & pions Initially nice clear signals from detector November 4 John Kennedy 7
Irradiations May 2003 Max. fluence 5 x10 14 1 MeV n. eq./cm 2 PS CERN- 24GeV p Already bonded => tricky mounting! November 4 John Kennedy 8
June 2003 Test Beam Beam Profile from irradiation (max = 8x10 14 p/cm 2 [24 GeV/c] ) No. of reconstructed clusters 167V bias shown x [cm] November 4 John Kennedy 9
First performance indications 4. green 3. black 0.6x10 14 p/cm 2 2.52x10 14 p/cm 2 2. red 1. blue 5.85x10 14 p/cm 2 7.65x10 14 p/cm 2 Find point of track interception. Integrate charge around intercept point. Fit Landau convoluted with gaussian (noise). Split detector into irradiation regions. Repeat for several applied voltages. November 4 John Kennedy 10
First performance indications Mean Fluence 0.6x10 14 p/cm 2 Least irradiated 2.52x10 14 p/cm 2 5.85x10 14 p/cm 2 7.65x10 14 p/cm 2 Most irradiated November 4 John Kennedy 11
Simulation 2000 With available temperature measurements/estimates Vdep [V] 1500 1000 500 FZ Si 0 0.0E+00 2.0E+01 4.0E+01 6.0E+01 8.0E+01 1.0E+02 1.2E+02 1.4E+02 1.6E+02 1.8E+02 time [hours] Float Zone Silicon Expect 1400 V full depletion Using ROSE (Hamburg) model November 4 John Kennedy 12
Conclusions Ran the 2003 test beam of the 1 st ever irradiated Czochralski detector equipped with LHC speed electronics. Initial results appear promising! Currently analysing/re-analysing and comparing the non-irradiated and irradiated data to understand Czochralski performance. November 4 John Kennedy 13
6 th International Workshop on Radiation Imaging Detectors 25-29 th July 2004 University of Glasgow Glasgow, SCOTLAND to be hosted by: Department of Physics and Astronomy University of Glasgow Glasgow, Scotland http://www.iworid2004.ph.gla.ac.uk November 4 John Kennedy 14