GenovaPaviaRoma Timing Counter status Sept 2004 CSN I

Genova/Pavia/Roma Timing Counter status @ Sept. 2004 CSN I, Assisi 2004 Giorgio Cecchet 1

Genova/Pavia/Roma 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 2

Genova/Pavia/Roma Timing resolution measurements • First test(PSI- E 5)- may 03: -BC 404 (1 X 5 x 80 cm 3) – light guides and 1” 1/2 and 2” Hamamatsu Fine Mesh PMs -passive beam collimation (6 mm diameter) -5 cm positron path length. -Analogic electronics - Double Threshold Discriminator-MCA 2. 35 x s[(t. L- t. R)]/2= 124 ps FWHM Low Thr. High Thr. Delay coinc Scintillator PM (t. L- t. R) 248 ps FWHM Light guide CSN I, Assisi 2004 Giorgio Cecchet 3

Genova/Pavia/Roma Timing resolution measurements • Last test (LNF-Frascati-Beam Test Facility) January 04: Energy Range 25 -800 Me. V e- 25 -550 Me. V 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=2 mm sy=4 mm (in the focus) • Further geometrical selection of 5 mmx 5 mm spot by two scintillating fibers with APD read-out. Time spread due to the spot size ~25 ps. • Coincidence with “APD cross” and the LINAC trigger allow to reject most of the bck. Events. Scint. Fiber APD beam CSN I, Assisi 2004 Giorgio Cecchet Spot Size Time spread ~25 ps APD 4

Genova/Pavia/Roma Timing resolution measurements 1. 1, 2, 3 electron events are resolved in the charge spectrum 2. (t. L- t. R) is selected in the 1 e peak Our Best Results : 2. 35 x s[(t. L- t. R)]/2= 104 2 ps FWHM 1 e 2 e CSN I, Assisi 2004 3 e Giorgio Cecchet 5

Genova/Pavia/Roma Characterisation in Mag. Field CSN I, Assisi 2004 Giorgio Cecchet 6

Genova/Pavia/Roma CSN I, Assisi 2004 Giorgio Cecchet 7

Genova/Pavia/Roma CSN I, Assisi 2004 Giorgio Cecchet 8

Genova/Pavia/Roma 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 9

Genova/Pavia/Roma Gain Vs Bias at several angles +10º Max gain curve in magn. field Same gain +10º CSN I, Assisi 2004 Giorgio Cecchet 10

Genova/Pavia/Roma RMS timing resolution vs p. e. attenuator 60 ps pulsed blue Laser 100 um Fiber Laser beam illuminates the whole photocatode PM CSN I, Assisi 2004 Giorgio Cecchet 11

Genova/Pavia/Roma CSN I, Assisi 2004 Giorgio Cecchet 12

Genova/Pavia/Roma Expecte d. Reduc tion factor Gain TTS Ext. PM Int. PM ☺ Increase Positron Path-Length ~ 5 cm ☺ Improve Geom. Matching PMT 12 @ 8. 5º 35 @ 10º 5 @ 20º 1. 2* @ 8. 5º 1. 2* @ 20º CSN I, Assisi 2004 Scint. - ☺ Tilt the PM @ ~ 30º respect Magn. Field → Rotated Scint. Slab improves response uniformity and timing performance due to coincidences. 1. 8* @ 10º 1. 6* @ 20º Giorgio Cecchet 13

Genova/Pavia/Roma TC key features PM active diameter Scintillator Cross Section 39 x 39 mm 70º PM section From COBRA center 105 cm 25 cm 8. 5º 30º B 0. 75 T CSN I, Assisi 2004 30º 10º B 1. 05 T Giorgio Cecchet 14

Genova/Pavia/Roma • 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 100 u. A -maximum- current ( 10 u. A for 1. 5” PMs) – 2” PMs lifetime correspond to 2. 3 years at the event rate of 50 k. Hz @ gain of 6 x 105. 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 50 x 39 mm 39 x 39 mm CSN I, Assisi 2004 Giorgio Cecchet 15

Genova/Pavia/Roma CSN I, Assisi 2004 Giorgio Cecchet 16

Genova/Pavia/Roma Single Counter Response Study CSN I, Assisi 2004 Giorgio Cecchet 17

Genova/Pavia/Roma Time Resolution FWHM (ps) Single Counter Response Study BC 408 Very Preliminary BC 404 • 39 x 39 slab in rotated configuration simulating a positron trajectory @ 40. 5° along z and 70°in radial plane Position (mm) CSN I, Assisi 2004 Giorgio Cecchet 18

Genova/Pavia/Roma Mechanical design CSN I, Assisi 2004 Giorgio Cecchet 19

Genova/Pavia/Roma From COBRA center 105 cm 8. 5º 30º B CSN I, Assisi 2004 25 cm 30º 10º B Giorgio Cecchet 20

Genova/Pavia/Roma CSN I, Assisi 2004 Giorgio Cecchet 21

Genova/Pavia/Roma 3 D view of TC CSN I, Assisi 2004 Giorgio Cecchet 22

Genova/Pavia/Roma Transverse Timing Counter CSN I, Assisi 2004 Giorgio Cecchet 23

Genova/Pavia/Roma 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 Scint. Fibers 5 x 10 mm APD CSN I, Assisi 2004 Giorgio Cecchet 24

Genova/Pavia/Roma Timing Counter Schedule 2002 2003 PMT Evaluation APD Evaluation 2004 Beam Test PMT procur. APD test Design 2005 Procur & Manuf. Assembly PMT Evaluation Beam Test COBRA Test PMT procur. New APDs APD Evaluation APD procur. APD test APD procur. Design Procur & Manuf. Mechanical matching Design Manufactoring CSN I, Assisi 2004 Assembly Test Milestone Giorgio Cecchet BG test Full installation 25

Genova/Pavia/Roma - detector (triggering) • We found good APDs with high S/N ratio that we tested at PSI and LNF (Frascati) e- beam CSN I, Assisi 2004 Pure e-beam Giorgio Cecchet 26

Genova/Pavia/Roma - 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 CSN I, Assisi 2004 From Hamamatsu Giorgio Cecchet 27

Genova/Pavia/Roma Status of test and procurements of APD Copper block Splitters Pulsed Laser APD test bench in Genoa Peltier Cell Integrating Calibrated Photometer Fast Photodiode 1/1000 attenuator Photomultiplier About 10% can be accepted CSN I, Assisi 2004 Giorgio Cecchet 28