1. Genova/Pavia/Roma Flavio Gatti, PSI, July 1st, 20041 Timing Counter status @ july 2004

2. Genova/Pavia/Roma Flavio Gatti, PSI, July 1st, 20042 Timing Counter Activities Timing resolution: 100 ps FWHM have been achieved. PM’s characteristics in the COBRA magnet: gain and timing. Full charactherisation of single TC’s counter is started Final design and integration with DC is started Ф-detector : APD directly from Hamamatsu

3. Genova/Pavia/Roma Flavio Gatti, PSI, July 1st, 20043 TC key features Scintillator Cross Section 39x39 mm 70º PM section PM active diameter 30º 8.5º From COBRA center 105 cm 10º 25 cm B B 0.75 T 1.05 T Expected Reduction factor Ext. PMInt. PM Gain12 @ 8.5º 5 @ 20º 35 @ 10º 15 @ 20º TTS1.2* @ 8.5º 1.2* @ 20º 1.8* @ 10º 1.6* @ 20º ☺ Increase Positron Path-Length ~ 5 cm ☺ Improve Geom. Matching Scint.- PMT ☺ Tilt the PM @ ~ 30º respect Magn. Field → Rotated Scint. Slab improves response uniformity and timing performance due to coincidences. *Note: data not corrected for time-walk effect

4. Genova/Pavia/Roma Flavio Gatti, PSI, July 1st, 20044 Gain and TTS in the COBRA Magnet (April 04) PM Drift Chamber assembly Scintillator slab COBRA Magnet Test of PM’s gain and timing resolution in the final operating conditions

5. Genova/Pavia/Roma Flavio Gatti, PSI, July 1st, 20045 Gain vs Rate Zero field 1.05 T 27.5º The Gain vs Rate at 1500 V in zero field is fully recovered at 1.05 T and 27.5º at 2100 V. Unallowable increase of biasing voltage are needed at 0º.

6. Genova/Pavia/Roma Flavio Gatti, PSI, July 1st, 20046 Gain Vs Bias at several angles Same gain Max gain curve in magn. field +10º

7. Genova/Pavia/Roma Flavio Gatti, PSI, July 1st, 20047 RMS timing resolution vs p.e. 60ps pulsed blue Laser attenuator 100um Fiber PM Laser beam illuminates the whole photocatode

8. Genova/Pavia/Roma Flavio Gatti, PSI, July 1st, 20048 Conclusions: –2” PMs allow to obtain the target resolution –At first order, the resolution is limited by the number of photoelectrons (light output from scintillator, quantum efficiency of PM, coupling scintillator-PM[2”], which has 39 mm dia. active area) –At second order, the slew rate could be used to improve the resolution in small signal regime: we have demonstrated that amplification recovers the timing resolution. – 2” PMs can supply 100uA -maximum- current ( 10uA for 1.5” PMs) –2” PMs Lifetime=100uAx100h which correspond to 2.3 years at the event rate of 50kHz @ gain of 6x10 5. An increase of a factor 2 can be easily obtained. To be done: -First systematic tests of single element of TC started in the run (May, 31 – June, 12) and will continue in the Frascati BTF –Finalize the design of TC and integration with DC 50x39 mm 39x39 mm

9. Genova/Pavia/Roma Flavio Gatti, PSI, July 1st, 20049 Single Counter Response Study

10. Genova/Pavia/Roma Flavio Gatti, PSI, July 1st, 200410 Single Counter Response Study 39x39 slab in rotated configuration simulating a positron trajectory @ 40.5° along z and 70°in radial plane Very Preliminary Position (mm) Time Resolution FWHM (ps) BC408 BC404

11. Genova/Pavia/Roma Flavio Gatti, PSI, July 1st, 200411 TC inside the COBRA

12. Genova/Pavia/Roma Flavio Gatti, PSI, July 1st, 200412 3D view of TC

13. Genova/Pavia/Roma Flavio Gatti, PSI, July 1st, 200413 Curved detector (triggering) The design of the curved detectors has been modified in order to match the budget limits for procurement of virgin APD form Hamamatsu (159 Euro/each). ~ 80 scintillating fibers and 160 APD per each TC. Procurement preliminary procedure started APD Scint. Fibers 5 x 10 mm

14. Genova/Pavia/Roma Flavio Gatti, PSI, July 1st, 200414 Timing Counter Schedule Test Milestone AssemblyDesignManufactoring Full installation 2002200320042005 COBRA Test Beam Test Design Assembly PMT EvaluationPMT procur. Procur & Manuf. APD EvaluationAPD testAPD procur. Beam Test Design PMT EvaluationPMT procur. Procur & Manuf. APD EvaluationAPD testAPD procur. Mechanical matching BG test APD procur. New APDs

15. Genova/Pavia/Roma Flavio Gatti, PSI, July 1st, 200415  - detector (triggering) We found good APDs with high S/N ratio that we tested at PSI and LNF (Frascati) e-  beam Pure e-beam

16. Genova/Pavia/Roma Flavio Gatti, PSI, July 1st, 200416  - detector (triggering) But, only about 10% of the selected APDs are good enough Huge spread in dynamic parameters not predictable from static parameters [left figure] The CMS selection and conditioning of the first batch of APDs is not applicable to MEG (we are working at few Volts from Vbkd – high gain- and we are interested to high slew rate and high S/N for timing purpose) For comparison new APDs from Hamamatsu have similar response[right figure] More work is needed to better understand the correlation between static and dynamic parameters of CMS APDs. From Hamamatsu from CMS selection

17. Genova/Pavia/Roma Flavio Gatti, PSI, July 1st, 200417 Status of test and procurements of APD Pulsed Laser Integrating Calibrated Photometer Fast Photodiode Photomult iplier 1/1000 attenuator Splitters APD Copper block Peltier Cell About 10% can be accepted APD test bench in Genoa