1. DPF 2002, May 26 th Williamsburg, VA Triple GEM Tracking Detectors for COMPASS Klaus Dehmelt This presentation will probably involve audience discussion, which will create action items. Use PowerPoint to keep track of these action items during your presentation In Slide Show, click on the right mouse button Select “Meeting Minder” Select the “Action Items” tab Type in action items as they come up Click OK to dismiss this box This will automatically create an Action Item slide at the end of your presentation with your points entered.

2. DPF 2002 – K. Dehmelt – May, 26 th COMPA SS A COmmon Muon and Proton Apparatus for Structure and Spectroscopy  COMPASS Measurement of Gluon polarization  G/G due to cross-section differences (asymmetry) of open charm production (among other things) ECAL1+2  -Wall 1+2 RICH SM1+2 HCAL Tracking Polarized target DC MicroMegas

3. DPF 2002 – K. Dehmelt – May, 26 th COMPA SS A COmmon Muon and Proton Apparatus for Structure and Spectroscopy  COMPASS Fixed Target Experiment at SPS-CERN ECAL1+2  -Wall 1+2 RICH SM1+2 HCAL Tracking Polarized target DC MicroMegas

4. DPF 2002 – K. Dehmelt – May, 26 th ECAL1+2  -Wall 1+2 RICH SM1+2 HCAL Tracking Polarized target DC MicroMegas COMPA SS A COmmon Muon and Proton Apparatus for Structure and Spectroscopy  COMPASS

5. DPF 2002 – K. Dehmelt – May, 26 th  Cover area up to ~20 cm around beam  7 stations with 14 detectors in 2001  10 stations with 20 detectors in 2002  Each station equipped with two Triple-GEM-detectors, rotated by 45º with respect to each other Small Area Tracking (SAT) GEM (Gas Electron Multiplier)

6. DPF 2002 – K. Dehmelt – May, 26 th GEM - Basics GEM structure: photolithography – etching (A. Gandi, R. de Oliveira)

7. DPF 2002 – K. Dehmelt – May, 26 th Applied potential difference  U ~ 500V between electrodes GEM - Basics

8. DPF 2002 – K. Dehmelt – May, 26 th COMPASS - GEMs GEM: COMPASS design Ar/CO 2 (70/30)

9. DPF 2002 – K. Dehmelt – May, 26 th GEM: COMPASS design COMPASS - GEMs 2-Dim Readout structure   

10. DPF 2002 – K. Dehmelt – May, 26 th COMPASS - GEMs GEM: COMPASS design

11. DPF 2002 – K. Dehmelt – May, 26 th  Single cluster @ U 0 =4050 V G ~ 8000 Triple-GEM properties COMPASS - GEMs

12. DPF 2002 – K. Dehmelt – May, 26 th COMPASS - GEMs Triple-GEM properties

13. DPF 2002 – K. Dehmelt – May, 26 th COMPASS - GEMs Triple-GEM properties  Charge correlation ~ 1 Narrow correlation  ~ 0.1  Resolve hit ambiguities

14. DPF 2002 – K. Dehmelt – May, 26 th COMPASS - GEMs Triple-GEM properties  Absolute efficiency >98% @ G ~ 8000

15. DPF 2002 – K. Dehmelt – May, 26 th Triple-GEM properties COMPASS - GEMs  Spatial resolution  < 50  m

16. DPF 2002 – K. Dehmelt – May, 26 th Hit map: Positions of maximum clusters for each event (2.1 x 10 8  per spill) COMPASS – GEMs Performance

17. DPF 2002 – K. Dehmelt – May, 26 th Hit map: Correlation between two different detectors, 0.5 m apart in beam direction (2.1 x 10 8  per spill) COMPASS – GEMs Performance

18. DPF 2002 – K. Dehmelt – May, 26 th Summary GEM detectors meet requirements for tracking devices in modern HEP experiments: High rate capability High spatial resolution Large active area Low material budget No aging observed for COMPASS Triple GEM GEM detectors will contribute to success of COMPASS

19. DPF 2002 – K. Dehmelt – May, 26 th The Group B. Ketzer, M.C. Altunbas, K. Dehmelt, J. Ehlers, J. Friedrich, B. Grube, S. Kappler, I. Konorov, S. Paul, A. Placci, L. Ropelewski, and F. Sauli