Timing Counter: progress report Flavio Gatti, CSNI, May 17th , 2004

Timing Counter Activities Timing resolution: 100 ps FWHM have been achieved. PM’s characteristics in the COBRA magnet: gain and timing. TC – Design: first engineering design. APD: measurement and status of procurement Flavio Gatti, CSNI, May 17th , 2004

Timing resolution The spread s of the time distribution of the positron impact,T0, is evaluated as: s(T0)  s[(TL- TR)]/2 where s[(TL- TR)] is the delay spread between the L and R PM ------------------------------------------------------------------------- T0 =(TL+TR)/2 +L/(2Veff) s2(T0)  s2[(TL+TR)/2] ; s2[(TL+TR)]= s2[(TL-TR)] TL TR T0 Flavio Gatti, CSNI, May 17th , 2004

Timing resolution Main parameters to be evaluated and matched in the TC: Scintillation time, attenuation length, PM coupling PM’s Transit Time Spread, Quantum Efficiency, Gain Signal Slew Rate, Bandwidth and Noise Particle trajectory length(=light output) and its spread High Luminosity Event, High Quantum Efficiency and PM Collecting Area, High Slew Rate Signal (dV/dt), High S/N ratio, High Bandwidth. PM TTS (FWHM) Typ. TTS Measured R7761-70(1.5”) 350 ps 470 ps R5924 (2”) 440 ps 650 ps XP2020 UR (2”) Flavio Gatti, CSNI, May 17th , 2004

Timing resolution measurements 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 Low Thr. High Thr. Delay coinc 248 ps FWHM Scintillator Light guide PM (tL- tR) Flavio Gatti, CSNI, May 17th , 2004

Timing resolution measurements Last test (LNF-Frascati-Beam Test Facility –BTF-) January 04: Energy Range 25-800 MeV e- 25-550 MeV e+ Max. Repetition Rate 50 Hz Pulse Duration: ~ 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 5x5 mmScint. Fiber Spot Size Time Spread ~25ps Flavio Gatti, CSNI, May 17th , 2004

Timing resolution measurements BC404 and BC408 (2X5x80 cm3) directly coupled to 1.5” and 2” Hamamatsu Fine Mesh PMs Digital electronic readout (CAMAC) Approx. Beam Focus Position BTF Beam line TC Beam APD Cross and Preamplifier Flavio Gatti, CSNI, May 17th , 2004

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= 1042ps FWHM 2e 1e 3e Flavio Gatti, CSNI, May 17th , 2004

Timing resolution measurements We don’t see walk-effect (time/amplitude correlation). The thresholds have been set to 0.5% of the average pulse height (3 V) at about 7 (rms noise level) from the baseline. TDC Thr. ADC off-line selection Flavio Gatti, CSNI, May 17th , 2004

Timing resolution measurements The plastic slab acts as a light guide with Veff=12.6 cm/ns The time resolution is proportional to the inverse of the sqrt(path length) 2x(distance from center) [cm] Flavio Gatti, CSNI, May 17th , 2004

2” PM in Magnetic Field 2” PM 2” PM Gain respect to B=0 (Data presented in July 03) Gain respect to B=0 Transit time spread respect to B=0 Note: no charge/amplitude corrected 2” PM 2” PM 20º 10º 0º Magnetic field [ T ] Magnetic field [ T ] Flavio Gatti, CSNI, May 17th , 2004

Guideline for Operation in Magnetic Field Scintillator Cross Section 39x30 mm or 39x50 mm 60º PM section PM active diameter Impact angles: 60º in the orthogonal plane, 40º in the longitudinal plane Magn. Field at radius 29<R<31 in figure. Reductio 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 30º 8.5º From COBRA center 105 cm 10º 25 cm B *Note: data not corrected for time-walk effect Expected Positron Path-Length: ~7cm (factor ~ 1.4) Geom. Matching Improv.: ~ 1.5 Total increase of light yield:~ 2.1 Better situation @ 30º PM tilt angle MC comparison of different config. (Rotated Slab, ..) under study for further impr. (coincidence….) 0.75 T 1.05 T Flavio Gatti, CSNI, May 17th , 2004

Gain and TTS in the COBRA Magnet (April 04) Test of PM’s gain and timing resolution in the final operating conditions PM Drift Chamber assembly Scintillator slab COBRA Magnet Flavio Gatti, CSNI, May 17th , 2004

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 and 27.5º at 2100 V. Unallowable increase of biasing voltage are needed at 0º. Flavio Gatti, CSNI, May 17th , 2004

Gain Vs Bias at several angles Max gain curve in magn. field +10º Same gain +10º Flavio Gatti, CSNI, May 17th , 2004

RMS timing resolution vs p.e. attenuator 60ps pulsed blue Laser 100um Fiber Laser beam illuminates the whole photocatode PM Flavio Gatti, CSNI, May 17th , 2004

Conclusions 50x39 mm 39x30 mm 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 improves 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 6x105. An increase of a factor 2 can be easily obtained. To be done: Systematic tests of single element of TC are foreseen in the next run (May, 26 – June, 16) Define the final shape and sizes of scintillators Finalize the design of TC 50x39 mm 39x30 mm Flavio Gatti, CSNI, May 17th , 2004

TC inside the COBRA Flavio Gatti, CSNI, May 17th , 2004

3D view of TC Flavio Gatti, CSNI, May 17th , 2004

Curved detector (triggering) Problem: curved thin scintillators orthogonal to the field Proposal: 5mmx5mm scintillating fibers coupled with APD. *APD high efficiency 95% *Optimal Matching of fibers/detectors *No relevant results published result on fast scintillator results ( 0.5 ns claimed) *Preliminary results in which we observed light pulses in plastic with Advanced Photonics and Hamamatsu APDs are obtained in the last summer. November 03: received first batch of APDs selected for CMS We made our selection, which is based on static parameters measurements (I-dark and Gain vs Vbias, Vbkd…), in order to calculate the expected Signal/Noise at the working point. Flavio Gatti, CSNI, May 17th , 2004

- detector (triggering) We found good APDs with high S/N ratio that we tested at PSI and LNF (Frascati) e- beam Pure e-beam Flavio Gatti, CSNI, May 17th , 2004

- 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 Flavio Gatti, CSNI, May 17th , 2004

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 banch in Genoa About 10% can be accepted Flavio Gatti, CSNI, May 17th , 2004

Schedule 2002 2003 2004 2005 Flavio Gatti, CSNI, May 17th , 2004 2” Fine Mesh 19 dyn. R5924 PMT Evaluation Beam Test COBRA test PMT procur. APD Evaluation APD procur. APD test Design Procur & Manuf. 5x5 mm APD Hmamatsu Assembly Test Milestone Assembly Design Manufactoring Flavio Gatti, CSNI, May 17th , 2004