Genova/Pavia/Roma Flavio Gatti, PSI, July 1st, Timing Counter july 2004

Genova/Pavia/Roma Flavio Gatti, PSI, July 1st, 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

Genova/Pavia/Roma Flavio Gatti, PSI, July 1st, 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 8.5º 20º 10º 20º 8.5º 20º 10º 20º ☺ Increase Positron Path-Length ~ 5 cm ☺ Improve Geom. Matching Scint.- PMT ☺ Tilt the ~ 30º respect Magn. Field → Rotated Scint. Slab improves response uniformity and timing performance due to coincidences. *Note: data not corrected for time-walk effect

Genova/Pavia/Roma Flavio Gatti, PSI, July 1st, 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

Genova/Pavia/Roma Flavio Gatti, PSI, July 1st, 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.

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

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

Genova/Pavia/Roma Flavio Gatti, PSI, July 1st, 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 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

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

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

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

Genova/Pavia/Roma Flavio Gatti, PSI, July 1st, D view of TC

Genova/Pavia/Roma Flavio Gatti, PSI, July 1st, 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

Genova/Pavia/Roma Flavio Gatti, PSI, July 1st, Timing Counter Schedule Test Milestone AssemblyDesignManufactoring Full installation 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

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

Genova/Pavia/Roma Flavio Gatti, PSI, July 1st,  - 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

Genova/Pavia/Roma Flavio Gatti, PSI, July 1st, 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