TIMING COUNTER status report Giorgio CECCHET PSI July

TIMING COUNTER: status report Giorgio CECCHET, PSI July 11 th, 2003

Timing counter • • • MC activities Tests on PM characteristics Preliminary results of May test Tests in magnetic field Possible new ideas on “transverse counter”

Montecarlo activities • Reorganization of code repository • Critical revision of TC code • Rievaluation of main geometrical parameters of TC

Length 70 cm Angle (-140, 10)° Radius 28. 2 0. 5 29. 0 2. 0

Tests on PM characteristics • Basic tests on gain and TTS • Photomultiplier used Hamamatsu fine mesh 1, 5”, 19 dynodes H 8409 -70 mod

MMICRO CHANNEL PLATE PMT Serial n. Q. E. % (500 nm) VMCP (10^6) Noise (0. 5 p. e. ) 3256 19, 2 2450 V 100 k. Hz 7237 18, 5 2160 V 140 k. Hz Active diameter: Test wavelength Ligh spot diameter 20 mm 670 nm 8 mm

May 2003 test • On May 2003 two scintillators (80 x 5 x 1) assembled with 1. 5” and 2” PM’s and taken to p. E 5 area • Aim: measure rough count rate in conditions similar to final

Main results Position similar to final in the Cobra (30 cm off beam axis) Rates: Beam off -> Bck: 25 evs/s Beam on, no mu stopper -> 0. 5 Mhz Beam on, with mu stopper -> 5 Mhz PMT saturation: 25 Hz->10 KHz : 1. 8 V/pulse 20 KHz: 1. 7 V/pulse 200 KHz: 0. 4 V/ pulse PMT with higher anode current are nedeed (2” PM better than 1. 5”) Need to design a higher current voltage divider?

With collimated beam (10 mm dia. ): measure of arrival time differences between 2 PMTs and calculation of time resolution FWHM using the formula: Sigma*2. 35/sqrt(2) We obtain 175 ps FWHM for the single PMT, in absence of magnetic field.

Magnetic field tests • One week ago magfield tests started • Conventional magnet in LASA (Milan) with 12 cm headroom and field up to 1. 2 Tesla water cooled

Setup used • A very simple setup was used to take the light from a blue diode to the photocathode

New ideas • Investigate the possibility of using a 5 x 5 mm 2 APD from Hamamatsu to readout optical fibers as transverse (trigger) counter. • Few samples made available from PSI and under investigation in Genoa

More work to be done • Complete timing test on single PM in magnetic field • Test scintillator coupled to PM’s in magfield (MARISA) • Full testing of APD’s and optical fibers • Exploit the full capabilities of fine mesh PM’s (new voltage divider? . . ) • Engineering test of 3 -4 scintillators and similar number of fibers during Oct-Nov beam time

B field measurements: planned form july 15 to 30 • • Rotable support for 1 -2 PMT/MCP for MARISA magnet under construction. B= 0 -1. 6 T Measurement of single PMT parameters (gain/TTS vs B) at different angles with B 2 -PMTs and scintillators assembly.

Not to mention work going on Helium bag!

Schedule • We think now we do not have yet enough infos to make a correct choice of the PM to be used in the TC. We are confident that the new tests will lend us to a reliable decision.

2002 2003 2004 PMT Evaluation 2005 PMT Design Manufactoring Assembly Test Milestone