Flavio Gatti, PSI, July 1st , 2004 1

Genova/Pavia/Roma

Timing Counterstatus @ july 2004

Flavio Gatti, PSI, July 1st , 2004 2

Genova/Pavia/Roma

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

Flavio Gatti, PSI, July 1st , 2004 3

Genova/Pavia/Roma

TC key featuresScintillator CrossSection 39x39 mm 70º

PM section

PM activediameter

30º 30º8.5º

From COBRA center

105 cm

10º

25 cm

BB0.75 T 1.05 T

ExpectedReduction

factor

Ext. PM Int. PM

Gain 12 @ 8.5º 5 @ 20º

35 @ 10º15 @ 20º

TTS 1.2* @ 8.5º1.2* @ 20º

1.8* @ 10º1.6* @ 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.

*Note: data not corrected for time-walk effect

Flavio Gatti, PSI, July 1st , 2004 4

Genova/Pavia/Roma

Gain and TTS in the COBRA Magnet (April 04)

PMDrift

Chamberassembly

Scintillator slab

COBRAMagnet

Test of PM’s gain and timing resolution in the final operating conditions

Flavio Gatti, PSI, July 1st , 2004 5

Genova/Pavia/Roma

Gain vs Rate

Zero field

1.05 T27.5º

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.

Flavio Gatti, PSI, July 1st , 2004 6

Genova/Pavia/Roma

Gain Vs Bias at several angles

Same gain

Max gain curvein magn. field

+10º

+10º

Flavio Gatti, PSI, July 1st , 2004 7

Genova/Pavia/Roma

RMS timing resolution vs p.e.

60ps pulsedblue Laser

attenuator

100um Fiber

PM

Laser beam illuminates thewhole photocatode

Flavio Gatti, PSI, July 1st , 2004 8

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 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:- 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

Flavio Gatti, PSI, July 1st , 2004 9

Genova/Pavia/Roma

Single Counter Response Study

Flavio Gatti, PSI, July 1st , 2004 10

Genova/Pavia/Roma

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)

Tim

e R

esol

utio

n F

WH

M (

ps)

BC408

BC404

Flavio Gatti, PSI, July 1st , 2004 11

Genova/Pavia/Roma

TC inside the COBRA

Flavio Gatti, PSI, July 1st , 2004 12

Genova/Pavia/Roma

3D view of TC

Flavio Gatti, PSI, July 1st , 2004 13

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

APD

Scint. Fibers5 x 10 mm

Flavio Gatti, PSI, July 1st , 2004 14

Genova/Pavia/Roma

Timing Counter Schedule

Test MilestoneAssemblyDesign Manufactoring

Fullinstallation

2002 2003 2004 2005

COBRA Test

Beam Test

Design

Assembly

PMT Evaluation PMT procur.

Procur & Manuf.

APD Evaluation APD test APD procur.

Beam Test

Design

PMT Evaluation PMT procur.

Procur & Manuf.

APD Evaluation APD test APD procur.

Mechanicalmatching

BGtest

APD procur.

New APDs

Flavio Gatti, PSI, July 1st , 2004 15

Genova/Pavia/Roma

- 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, PSI, July 1st , 2004 16

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.

FromHamamatsu

from CMSselection

Flavio Gatti, PSI, July 1st , 2004 17

Genova/Pavia/Roma

Status of test and procurements of APD

Pulsed Laser

Integrating CalibratedPhotometer

Fast Photodiode

Photomultiplier

1/1000 attenuator

Splitters

APDCopper block

Peltier Cell

peak-to-noise ratio @ 250 photons signal

0.00

10.00

20.00

30.00

1 11 21 31 41 51 61 71 81 91

S/N ratioAbout 10% can be accepted

APD test bench in Genoa