timing counter status @ sept. 2004

CSN I, Assisi 2004 Giorgio Cecchet 1

Genova/Pavia/Roma

Timing Counterstatus @ Sept. 2004


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


Genova/Pavia/Roma

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 (tL- tR)]/2= 124 ps FWHM

Scintillator

Light guide

248 ps FWHM(tL- tR)

Low Thr.

High Thr.

Delaycoinc

PM


Genova/Pavia/Roma


• 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 : 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

APD

Scint. Fiber Spot SizeTime spread ~25ps


Genova/Pavia/Roma


1. 1,2,3 electron events are resolved in the charge spectrum2. (tL- tR) is selected in the 1e peak Our Best Results :

2.35x (tL- tR)]/2= 1042ps FWHM

1e2e

3e


Genova/Pavia/Roma

Characterisation in MagField


Genova/Pavia/Roma


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.


Genova/Pavia/Roma

Gain Vs Bias at several angles

Same gain

Max gain curvein magn. field

+10º

+10º


Genova/Pavia/Roma

RMS timing resolution vs p.e.

60ps pulsedblue Laser

attenuator

100um Fiber

PM

Laser beam illuminates thewhole photocatode


Genova/Pavia/Roma


Genova/Pavia/Roma

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.


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

BB

0.75 T 1.05 T


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 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


Genova/Pavia/Roma


Genova/Pavia/RomaSingle Counter Response Study


Genova/Pavia/RomaSingle 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


Genova/Pavia/Roma

Mechanical design


Genova/Pavia/Roma

30º 30º8.5º

From COBRA center

105 cm

10º

25 cm

BB


Genova/Pavia/Roma


Genova/Pavia/Roma

3D view of TC


Genova/Pavia/Roma

Transverse Timing Counter


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


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


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


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


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

timing counter status @ sept. 2004

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