1. Genova/Pavia/Roma Flavio Gatti, PSI, 11 February, 20041 Timing Counter: status @ january 2004

2. Genova/Pavia/Roma Flavio Gatti, PSI, 11 February, 20042 Timing Counter Activities Timing resolution (Ge-Pv-Rm) PMs characteristics in magnetic field(Ge-Pv) APD for the counter (Ge) MC simulation activities(Pv-Rm) Helium(Ge-Pv)

3. Genova/Pavia/Roma Flavio Gatti, PSI, 11 February, 20043 Timing resolution The spread  of the time distribution of the positron impact,T 0, is evaluated as:  (T 0 )  (T L - T R )]/2 where (T L - T R )] is the delay spread between the L and R PM ------------------------------------------------------------------------- T 0 =(T L +T R )/2 +L/(2V eff )   (T 0 )    [(T L +T R )/2] ;   [(T L +T R )]=   [(T L -T R )] TLTL TRTR T0T0

4. Genova/Pavia/Roma Flavio Gatti, PSI, 11 February, 20044 Timing resolution Main parameters to be evaluated and matched in the TC: 1.Scintillation time, attenuation length, PM coupling 2.PM’s Transit Time Spread, Quantum Efficiency, Gain 3.Signal Slew Rate, Bandwidth and Noise 4.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. PMTTS (FWHM) Typ.TTS Measured R7761-70(1.5”)350 ps470 ps R5924 (2”)440 ps650 ps XP2020 UR (2”)350 ps

5. Genova/Pavia/Roma Flavio Gatti, PSI, 11 February, 20045 Timing resolution measurements First test(PSI-E5)- may 03: -BC404 (1X5x80 cm 3 ) – 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 (t L - t R )]/2= 124 ps FWHM Scintillator Light guide 248 ps FWHM (t L - t R ) Low Thr. High Thr. Delay coinc PM

6. Genova/Pavia/Roma Flavio Gatti, PSI, 11 February, 20046 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 10 10 particles (Allowed Current 10 3 particles/second) Beam spot :  x =2mm  y =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

7. Genova/Pavia/Roma Flavio Gatti, PSI, 11 February, 20047 Timing resolution measurements BC404 and BC408 (2X5x80 cm 3 ) directly coupled to 1.5” and 2” Hamamatsu Fine Mesh PMs Digital electronic readout (CAMAC) Beam Approx. Beam Focus Position APD Cross and Preamplifier TC BTF Beam line

8. Genova/Pavia/Roma Flavio Gatti, PSI, 11 February, 20048 Timing resolution measurements 1.1,2,3 electron events are resolved in the charge spectrum 2.(t L - t R ) is selected in the 1e peak Our Best Results : 2.35x (t L - t R )]/2= 1042ps FWHM 1e 2e 3e

9. Genova/Pavia/Roma Flavio Gatti, PSI, 11 February, 20049 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

10. Genova/Pavia/Roma Flavio Gatti, PSI, 11 February, 200410 Timing resolution measurements The plastic slab acts as a light guide with V eff =12.6 cm/ns The time resolution is proportional to the inverse of the sqrt(path length) 2x(distance from center) [cm]

11. Genova/Pavia/Roma Flavio Gatti, PSI, 11 February, 200411 2” PM in Magnetic Field (Data presented in July 03) 2” PM Transit time spread respect to B=0 Magnetic field [ T ] Gain respect to B=0 0º0º 10º 20º Note: no charge/amplitude corrected

12. Genova/Pavia/Roma Flavio Gatti, PSI, 11 February, 200412 Timing resolution measurements Conclusions: –2” PMs allow to obtain the target resolution –We are still 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) –In these tests there is no evidence of limits due to the electronics (slew rate, noise, …) –No evidence of differences between BC404 and BC408 To be done: –Geometrical arrangement that provide the same efficiency of positron collection and same timing resolution in Magn. Field (see exe. in figures ->) - Selection of 2” PMs with respect the Q.E. and gain may be needed. –Improvements & fine tuning will be done in the next beam times –Finalize the design of TC from now 50x20 mm 39x30 mm

13. Genova/Pavia/Roma Flavio Gatti, PSI, 11 February, 200413 Guideline for Operation in Magnetic Field Impact angles: 60º in the orthogonal plane, 40º in the longitudinal plane Magn. Field at radius 29<R<31 in figure. Minimal Cross Section 39x30 mm 60º PM section PM active diameter 20º 8.5º From COBRA center 105 cm 10º 25 cm B B 0.75 T 1.05 T Reductio 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 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….) *Note: data not corrected for time-walk effect

14. Genova/Pavia/Roma Flavio Gatti, PSI, 11 February, 200414 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.

15. Genova/Pavia/Roma Flavio Gatti, PSI, 11 February, 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, 11 February, 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, 11 February, 200417 Schedule Beam Test 2002200320042005 Test Milestone AssemblyDesignManufactoring Design Assembly PMT EvaluationPMT procur. Procur & Manuf. 2” Fine Mesh 19 dyn. R5924 APD EvaluationAPD testAPD procur. 5x5 mm APD Hmamatsu