Development of a tracking detector for physics at the Large Hadron Collider Geoff Hall

1. Development of a tracking detector for physics atthe Large Hadron ColliderGeoff Hall

2. missing element in current theoretical framework - mass CMS = Compact Muon Solenoid detector Total weight 12,500 tons Diameter 15m Length 21.6m Magnetic field 4T Tracking system 10 million microstrips Diameter 2.6m Length 7m Power ~50kW G Hall

3. Consequences High speed signal processing Signal pile-up High (low) radiation exposure High (low) B field operation Very large data volumes New technologies LHC parameters (CMS) G Hall

4. Large solenoidal (4T) magnet iron yoke - returns B field, absorbs particles technically challenging but smaller detector, p resolution, trigger, cost Muon detection high pT lepton signatures for new physics Electromagnetic calorimeter high (DE) resolution, for H => gg (low mass mode) Tracking system momentum measurements of charged particles pattern recognition & efficiency complex, multi-particle events complement muon & ECAL measurements improved p measurement (high p) E/p for e/g identification Design philosophy G Hall

5. E, p, cosq, f prefer variables which easily Lorentz transform e.g E, pT, pL, f pT divergences from simple behaviour could imply new physics eg heavy particle decay => high pT lepton (or hadron) rapidity Lorentz boost pseudorapidity Parameters for hadronic collider physics invariant => LHC H~ 6 |h| < 2.5 G Hall

6. Mass peak - one means of discovery => small s(pT) eg H => ZZ or ZZ* => 4l± typical pT(µ) ~ 5-50GeV/c Background suppression measure lepton charges good geometrical acceptance - 4 leptons background channel t => b => l require m(l+l-) = mZ GZ ~ 2.5GeV precise vertex measurement identify b decays, or reduce fraction in data Physics requirements (I) G Hall

7. p resolution large B and L high precision space points detector with small intrinsic smeas well separated particles good time resolution low occupancy => many channels good pattern recognition minimise multiple scattering minimal bremsstrahlung, photon conversions material in tracker most precise points close to beam Physics requirements (II) G Hall

8. Spatial measurement precision defined by strip dimensions ultimately limited by charge diffusion s ~ 5-10µm Silicon diodes as position detectors G Hall

9. Vertex detector ~1990 G Hall

10. Interactions in CMS 7 TeV p 7 TeV p G Hall

11. Microstrip tracker system 2.4m ~10M detector channels ~ 6m G Hall

12. Event in the tracker G Hall

13. Constraints on tracker minimal material high spatial precision sensitive detectors requiring low noise readout power dissipation ~50kW in 4T magnetic field radiation hard Budget Silicon detector modules • Requirements • large number of channels • limited energy resolution • limited dynamic range G Hall

14. Particle fluxes Charged and neutral particles from interactions ~ 1/r2 Neutrons from calorimeter nuclear backsplash + thermalisation ≈ more uniform gas only E > 100keV damaging Dose energy deposit per unit volume Gray = 1Joule/kg = 100rad mostly due to charged particles Radiation environment G Hall

15. Imperial College contributions to Tracker APV25 APVMUX/PLL • Hardware development • Hardware construction • Beam tests & studies • Preparation for physics FED G Hall

16. APV25 0.25µm CMOS 1 of the 128 channels programmable gain signal processing & MUX Analogue unity gain inverter pipeline memory Differential current O/P 128:1 MUX 192-cell analogue pipeline amplifiers S/H SF SF APSP Low noise charge preamplifier 50 ns CR-RC shaper control logic APV25-S1 (Aug 2000) Chip Size7.1 x 8.1 mm Final APV25-S0 (Oct 1999) G Hall

17. Chip testing Automated on-wafer testing ~1min/site ~100,000 to test G Hall

18. Extensive studies CMS tracker data from IC, Padova, CERN ALL POSITIVE and well beyond LHC range CMOS hard against bulk damage Qualify chips from wafers with ionising sources Typical irradiation conditions 50kV X-ray source Dose rate ~ 0.5Mrad/Hour to 10, 20, 30 & 50Mrad Irradiations of 0.25µm technology PMOS PMOS 2000/0.36 400µA G Hall

19. APV25 irradiations (IC & Padova) IC x-ray source Normal operational bias during irradiation clocked & triggered also 10 MeV linac electrons(80Mrad) and 2.1x1014 reactor n.cm-2 Post irradiation noise change insignificant APV25-S1 pre-rad 10 Mrad G Hall

20. Detectors operated as reverse biased diode dark current = noise source signals small typical H.E. particle ~ 25000 e 300µm Si 10keV x-ray photon ~ 2800e Deplete entire wafer thickness Vbias ~ NDd2 ND ~ 1012 cm-3 =>Vbias ~ 50V for 300µm ND : NSi ~ 1 : 1013 ultra high purity Further refining required Float Zone: local crystal melting with RF heating coil Silicon as a detector material G Hall

21. Silicon atoms dislodged from lattice sites… causing more damage as they come to rest... Radiation effects in (bulk) silicon after irradiation increased dark currents altered substrate doping primary defects = V & I diffuse and become trapped influenced by O & C impurity levels G Hall

22. 12 12 12 12 12 12 12 12 CMS Silicon Strip Tracker Front End Driver 96 Tracker Opto Fibres CERN Opto- Rx 9U VME64x Data Rates 9U VME64x Form Factor Modularity matched Opto Links Analogue: 96 ADC channels (10-bit @ 40 MHz ) @ L1 Trigger : processes 25K MUXed silicon strips / FED Raw Input: 3 Gbytes/sec* after Zero Suppression... DAQ Output: ~ 200 MBytes/sec ~440 FEDs required for entire SST Readout System *(@ L1 max rate = 100 kHz) Analogue/Digital JTAG FE-FPGA Cluster Finder FPGA Configuration VME Interface VME-FPGA BE-FPGA Event Builder TCS TTC TTCrx DAQ Interface Buffers Power DC-DC Temp Monitor Front-End Modules x 8 Double-sided board Xilinx Virtex-II FPGA TCS : Trigger Control System G Hall

23. CMS Silicon Strip Tracker FED Front-End FPGA Logic 1x per adc channel phase compensation required to bring data into step Cluster Finding FPGA VERILOG Firmware Clock 40 MHz 2x DLL 4x Synch in Synch out 2 x 256 cycles 256 cycles nx256x16 Synch emulator in trig2 trig3 trig4 trig1 Synch error Re-order cm sub Phase Registers 10 11 11 s-data 16 10 10 Hit finding 8 sync 16 ADC 1 Ped sub d d DPM Global reset 8 s-addr hit Sub resets 8 8 Sequencer-mux a a Control No hits Full flags 8 header status averages control mux 4x data 4 Packetiser 256 cycles 256 cycles nx256x16 160 MHz trig1 trig2 trig3 Re-order cm sub Phase Registers 10 11 11 s-data 16 10 10 8 sync 16 Hit finding Ped sub d d DPM ADC 12 8 s-addr Serial I/O hit Sequencer-mux 8 8 a a Serial Int No hits 8 header status averages Temp Sensor Local IO Opto Rx Delay Line + Raw Data mode, Scope mode, Test modes... B’Scan Config G Hall

24. The CMS Tracking Strategy 2-3 Silicon Pixel 10 - 14 Silicon Strip Layers • Rely on “few” measurement layers, • each able to provide robust (clean) and precise coordinate determination Number of hits by tracks: Total number of hits Double-side hits Double-side hits in thin detectors Double-side hits in thick detectors Radius ~ 110cm, Length/2 ~ 270cm 6 layers TOB 4 layers TIB 3 disks TID 9 disks TEC G Hall

25. Vertex Reconstruction Primary vertices: use pixels! At high luminosity, the trigger primary vertex is found in >95% of the events G Hall

26. High Level Trigger & Tracker • In High Level trigger reconstruction only 0.1% • of the events should survive. • “How can I kill these events using the least • CPU time?” • This can be interpreted as: • The fastest (most approx.) reconstruction • The minimal amount of precise reconstruction • A mixture of the two DAQ 40 MHZ 100 KHz 100 Hz HLT Track finding • Same SW would be use in HLT and off-line : • algorithms should be high quality • algorithms should be fast enough Events rejected at HLT are irrecoverably lost! G Hall

27. References • A. Litke & A. Schwarz Scientific American May 1995 • T. Liss & P. Tipton Scientific American September 1997 • N. Ellis & T. Virdee. Experimental Challenges in High Luminosity Collider Physics. Ann. Rev. Nucl. Part. Sci 44 (1994) 609-653. • G.Hall Modern charged particle detectors Contemporary Physics 33 (1992) 1-14 & refs therein • G.Hall Semiconductor particle tracking detectors Reports on Progress in Physics.57 (1994) 481-531 • A. Schwarz 1993 Heavy Flavour Physics at Colliders with silicon strip vertex detectors. Physics Reports 238 (1994) 1-133. • C. Damerell Vertex detectors: The state of the art and future prospects. Rutherford Appleton Laboratory report RAL-P-95-008 A pdf version is available on the CERN library Web site.(Search preprints) • CMS Web pages http://cmsdoc.cern.ch/cmsnice.html • http://cmsinfo.cern.ch/Welcome.html Letter of Intent (most readable) and and Technical proposal • http://cmsdoc.cern.ch/cms/TDR/TRACKER/tracker.html CMS Tracker Technical Design Report (even more detail on many aspects) of the tracker. G Hall