Timing Counter status @ Sept. 2004 CSN I, Assisi 2004 Giorgio Cecchet
Timing Counter Activities Timing resolution: 100 ps FWHM have been achieved. PM’s characterised in the COBRA magnet for gain and timing. Full characterisation of single TC’s counter is started Final design and integration with DC is started Ф-detector : APD directly from Hamamatsu CSN I, Assisi 2004 Giorgio Cecchet
Timing resolution measurements Low Thr. High Thr. Delay coinc First test(PSI-E5)- may 03: -BC404 (1X5x80 cm3) – light guides and 1”1/2 and 2” Hamamatsu Fine Mesh PMs -passive beam collimation (6mm diameter) -5 cm positron path length. -Analogic electronics - Double Threshold Discriminator-MCA 2.35x s[(tL- tR)]/2= 124 ps FWHM 248 ps FWHM Scintillator Light guide PM (tL- tR) CSN I, Assisi 2004 Giorgio Cecchet
Timing resolution measurements Last test (LNF-Frascati-Beam Test Facility) January 04: Energy Range 25-800 MeV e- 25-550 MeV e+ Max. Repetition Rate 50 Hz Pulse Duration 1-10 ns Current/pulse 1 to 1010 particles (Allowed Current 103 particles/second) Beam spot : sx=2mm sy=4mm (in the focus) Further geometrical selection of 5mmx5mm spot by two scintillating fibers with APD read-out. Time spread due to the spot size ~25ps. Coincidence with “APD cross” and the LINAC trigger allow to reject most of the bck. Events. beam APD Scint. Fiber Spot Size Time spread ~25ps CSN I, Assisi 2004 Giorgio Cecchet
Timing resolution measurements 1,2,3 electron events are resolved in the charge spectrum (tL- tR) is selected in the 1e peak Our Best Results : 2.35x s[(tL- tR)]/2= 1042ps FWHM 2e 1e 3e CSN I, Assisi 2004 Giorgio Cecchet
Characterisation in MagField CSN I, Assisi 2004 Giorgio Cecchet
CSN I, Assisi 2004 Giorgio Cecchet
CSN I, Assisi 2004 Giorgio Cecchet
Unallowable increase of biasing voltage are needed at 0º. 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. CSN I, Assisi 2004 Giorgio Cecchet
Gain Vs Bias at several angles +10º Max gain curve in magn. field Same gain +10º CSN I, Assisi 2004 Giorgio Cecchet
RMS timing resolution vs p.e. attenuator 60ps pulsed blue Laser 100um Fiber Laser beam illuminates the whole photocatode PM CSN I, Assisi 2004 Giorgio Cecchet
CSN I, Assisi 2004 Giorgio Cecchet
ExpectedReduction factor Ext. PM Int. PM Gain 12 @ 8.5º 5 @ 20º 35 @ 10º 15 @ 20º TTS 1.2* @ 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. CSN I, Assisi 2004 Giorgio Cecchet
TC key features 30º 8.5º 105 cm 10º 25 cm B 0.75 T 1.05 T 70º Scintillator Cross Section 39x39 mm PM active diameter 70º PM section 30º 8.5º From COBRA center 105 cm 10º 25 cm B 0.75 T 1.05 T CSN I, Assisi 2004 Giorgio Cecchet
Conclusions: To be done: 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 correspond to 2.3 years at the event rate of 50kHz @ gain of 6x105. 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 CSN I, Assisi 2004 Giorgio Cecchet
CSN I, Assisi 2004 Giorgio Cecchet
Single Counter Response Study CSN I, Assisi 2004 Giorgio Cecchet
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 CSN I, Assisi 2004 Giorgio Cecchet
Mechanical design CSN I, Assisi 2004 Giorgio Cecchet
30º 8.5º 105 cm 10º 25 cm B From COBRA center CSN I, Assisi 2004 Giorgio Cecchet
CSN I, Assisi 2004 Giorgio Cecchet
3D view of TC CSN I, Assisi 2004 Giorgio Cecchet
Transverse Timing Counter CSN I, Assisi 2004 Giorgio Cecchet
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 CSN I, Assisi 2004 Giorgio Cecchet
Timing Counter Schedule 2002 2003 2004 2005 COBRA Test Beam Test Design Assembly PMT Evaluation PMT procur. Procur & Manuf. APD Evaluation APD test APD procur. Mechanical matching BG test New APDs Full installation Test Milestone Assembly Design Manufactoring CSN I, Assisi 2004 Giorgio Cecchet
- detector (triggering) We found good APDs with high S/N ratio that we tested at PSI and LNF (Frascati) e- beam Pure e-beam CSN I, Assisi 2004 Giorgio Cecchet
- 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 CMS selection From Hamamatsu CSN I, Assisi 2004 Giorgio Cecchet
Status of test and procurements of APD Pulsed Laser Integrating Calibrated Photometer Fast Photodiode Photomultiplier 1/1000 attenuator Splitters APD Copper block Peltier Cell APD test bench in Genoa About 10% can be accepted CSN I, Assisi 2004 Giorgio Cecchet