1. Development of a TPC for the Future Linear Collider on behalf of the LC TPC groups Aachen, Berkeley, Carleton, Cracow, DESY, Hamburg, Karlsruhe, MIT, Montreal, MPI Munich, NIKHEF, Novosibirsk, Orsay, St.Petersburg, Rostock, Saclay, Victoria Stefan Roth, RWTH Aachen Europhysics Conference on High Energy Physics 17 – 23 July 2003 Aachen

2. Stefan Roth, Development of a TPC for the future Linear Collider - HEP 2003 Aachen 2 Outline: 1. The e + e - Linear Collider Project 2. Design of the Time Projection Chamber 3. Micropattern Readout of the TPC 4. Ongoing R&D efforts

3. Stefan Roth, Development of a TPC for the future Linear Collider - HEP 2003 Aachen 3 TESLA-Project (DESY): Acceleration gradient 35 MV/m   s = 800 GeV Superconductive cavities with improved manufacturing (electropolishing)

4. Stefan Roth, Development of a TPC for the future Linear Collider - HEP 2003 Aachen 4 Detector for the Linear Collider Why new & improved e + e – detector? Higher particle energies from GeV to TeV More complex final states e + e –  ZHH  6 jets/leptons e + e –  H + H –  tb tb  8 jets Resolution e + e –  ZH  e + e – (  +  – ) + X SUSY (missing energy) Accelerator background, luminosity, bunch separation...we want to build the best apparatus...

5. Stefan Roth, Development of a TPC for the future Linear Collider - HEP 2003 Aachen 5 Precise measurement of charged particle momenta: Study of Higgs production independent of Higgs decay  lepton momenta ideally: recoil mass resolution only limited by Z width  Momentum resolution  (1/p t ) < 5 × 10 -5 GeV -1 (full tracker) Tracker: Momentum Resolution

6. Stefan Roth, Development of a TPC for the future Linear Collider - HEP 2003 Aachen 6 Large Silicon-Tracker à la LHC experiments? much lower particle rates at linear collider keep material budget low Large TPC 1.7 m radius 3% X 0 barrel 30% X 0 endcap 4 T magnetic field Goals 200 points (3-dim.) per track 100 µm single point resolution dE/dx 5% resolution 10 times better performance than at LEP A Time Projection Chamber for the LC

7. Stefan Roth, Development of a TPC for the future Linear Collider - HEP 2003 Aachen 7 New concept for gas amplification at the end flanges: Replace proportional wires with Micro Pattern Gas Detectors GEM or Micromegas: Smaller structures Two-dimensional symmetry (no E×B effects) Only fast electron signal Intrinsic ion feedback suppression Wires GEM Gas Amplification System

8. Stefan Roth, Development of a TPC for the future Linear Collider - HEP 2003 Aachen 8 Gas Electron Multiplier - GEM (F. Sauli 1996) 140  mØ 75  m 50 µm kapton foil, double sided copper coated 75 µm holes, 140 µm pitch GEM voltages up to 500 V yield 10 4 gas amplification Use GEM towers for safe operation (COMPASS)

9. Stefan Roth, Development of a TPC for the future Linear Collider - HEP 2003 Aachen 9 Micromegas (Y. Giomataris 1995) asymmetric parallel plate chamber with micromesh saturation of Townsend coefficient mild dependence of amplification on gap variations ion feedback suppression 50  m pitch

10. Stefan Roth, Development of a TPC for the future Linear Collider - HEP 2003 Aachen 10 Studies on drift gas Understand the charge transfer and gain of micropattern detectors in strong magnetic field Demonstrate feasibility with large prototype in test beam Obtain optimal position resolution Study dE/dx resolution Get in touch with industry for large scale production and detector manufacturing (GEMs, Micromegas, thin frames, grids, field cage) Goals of the R&D Project

11. Stefan Roth, Development of a TPC for the future Linear Collider - HEP 2003 Aachen 11 Gas Studies Traditional TPC gas P10: Ar/CH 4 (90/10) might be problematic because of expected high neutron background at linear collider Other possible quenchers are CO 2 and CF 4 CF 4 :  >20 -> potential transverse diffusion less than 200  m at 1m attachment is small below 400 V/cm » TDR-Gas « : Ar/CH 4 /CO 2 (93/5/2)

12. Stefan Roth, Development of a TPC for the future Linear Collider - HEP 2003 Aachen 12 Magnetic Field Langevin equation: Aleph: B = 1.5 T  9 Tesla: B = 4 T  24 Impact on electron collection ?  cyclotron frequency  mean free time

13. Stefan Roth, Development of a TPC for the future Linear Collider - HEP 2003 Aachen 13 DESY: 5 T superconducting magnet 28 cm bore diameter Total length 187 cm Saclay: 2 T superconducting magnet 53 cm bore diameter Total length 150 cm Test Magnets

14. Stefan Roth, Development of a TPC for the future Linear Collider - HEP 2003 Aachen 14 Orsay-Saclay: no change observed in the iron 55 peak position beween 0 and 2T Electron Transparency in Magnetic Field

15. Stefan Roth, Development of a TPC for the future Linear Collider - HEP 2003 Aachen 15 Charge Transfer Measurements in Magnetic Field - Anode current rises with magnetic field - Effect can be explained with improved extraction efficiency - Triple GEM structure with current readout - Put into superconducting magnet at DESY

16. Stefan Roth, Development of a TPC for the future Linear Collider - HEP 2003 Aachen 16 Ion Feedback in Magnetic Field GEM: Ion feedback improves with magnetic field Micromegas: No dependence of ion feedback on the magnetic field Finer mesh (1000 lpi) should allow reaching the optimal feedback

17. Stefan Roth, Development of a TPC for the future Linear Collider - HEP 2003 Aachen 17 - Simulation of electric fieldmap using MAXWELL - Input fieldmap into GARFIELD - Monte Carlo simulation of electron drift paths Simulation of Charge Transfer in GEM Structures - Calculation of transfer coefficients (like extraction efficiency)

18. Stefan Roth, Development of a TPC for the future Linear Collider - HEP 2003 Aachen 18 Measured resolution: 124 µm TPC Cosmic Tests Karlsruhe: GEM TPC STAR readout electronics

19. Stefan Roth, Development of a TPC for the future Linear Collider - HEP 2003 Aachen 19 TPC Cosmic Tests Berkeley, Orsay, Saclay: Micromegas TPC STAR readout electronics Magnetic field run end of year

20. Stefan Roth, Development of a TPC for the future Linear Collider - HEP 2003 Aachen 20 Carleton, Montreal, Victoria: Prototype TPC with GEM tower STAR readout electronics Cosmics test stand in 1 T magnet (TRIUMF) Gas: P10 B = 0 T,  = 2.3 mm B = 0.45 T,  = 1.2 mmB = 0.9 T,  = 0.8 mm Cosmic Tests with 1 T Magnet

21. Stefan Roth, Development of a TPC for the future Linear Collider - HEP 2003 Aachen 21 3cm 30 cm TDR spec. goal B = 0 B = 0.45 T B = 0.9 T Track Resolution

22. Stefan Roth, Development of a TPC for the future Linear Collider - HEP 2003 Aachen 22 Readout Structure Disadvantage of electron signal: No broadening by induction Signal collected on one pad No centre-of-gravity Possible Solutions: Charge spread within GEM structure Capacitive or resistive coupling of adjacent pads Alternative pad geometries Smaller pads ( Replace pads by pixel readout chips) chevrons strip coupling

23. Stefan Roth, Development of a TPC for the future Linear Collider - HEP 2003 Aachen 23 Carleton/Orsay/Saclay: Resistive film on readout board Micromesh on frame Charge Dispersion Pulses in a Resistive Anode Resistive foil signal Charge dispersion signal Direct signal on centre strip

24. Stefan Roth, Development of a TPC for the future Linear Collider - HEP 2003 Aachen 24 Cathode foil base plate MediPix 2 Drift Space GEM foils Silicon readout NIKHEF: Use MediPix 2 pixel detector (Jan Visschers et al.) Remove sensor chip Use readout chip to detect signal of GEM tower

25. Stefan Roth, Development of a TPC for the future Linear Collider - HEP 2003 Aachen 25 Summary ↔ Outlook Measurements in high B-field have started, with encouraging results for the charge-transfer coefficients for GEM and Micromegas Better understanding of amplification and resolution achieved Test-stand infrastructure now functioning Resolution in high B-fields must be measured for all technologies, GEM, Micromegas and wires Design and operation of large prototypes should follow promptly, including test beam Mechanics and field cage design should start now