TIMING COUNTER: status report. Flavio Gatti - Lecce, Sept 23, INFN Genova, Pavia, Roma1

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1 TIMING COUNTER: status report Flavio Gatti - Lecce, Sept 23, INFN Genova, Pavia, Roma1

2 Timing counter Activities Preliminary results of May test (Ge-Pv-Rm1) Tests on PM characteristics (Pv) and Tests in magnetic field (Pv-Ge) New solution for the Φ counter using APDs(Ge) MC simulation activities(pv-rm1) Helium(Ge-Pv)

3 May test at PSI Aims: Measure the count rate in a set-up similar to the final inside the cobra. Measure the time resolution.

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7 Main results Position similar to final in the Cobra (30 cm off beam axis) Rates: Beam off -> Bck: 25evs/s Beam on, no mu stopper -> 0.5 Mhz Beam on, with mu stopper -> 5 Mhz PMT saturation: 25Hz->10KHz : 1.8 V/pulse 20KHz: 1.7V/pulse 200KHz: 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?

8 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.

9 Tests on PM characteristics and test in Mag Field Basic tests on gain and TTS. Photomultiplier used Hamamatsu fine mesh 1,5, 19 dynodes H mod. Preliminary test at LASA in a room temperature Magnet. Test in Genova in the MARISA facility have been re-scheduled in october.

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13 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.

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16 PMT tra le espansioni polari

17 Set-up misure di Timing

18 Variazioni di gain in campo magnetico assiale Red: PMT 2

19 Variazioni di gain in campo magnetico a 0, 10, 20 deg PMT 2 PMT 1.5

20 Transit time, diversa intensità

21 TTS normalizzato al valore in assenza di campo magnetico

22 Transit time ad intensità fissa, vari angoli

23 TTS ad intensità fissa, vari angoli

24 Results and limits La riduzione del segnale in campo magnetico presenta un andamento indipendente dalla tensione di alimentazione del PM L effetto risulta meno evidente al crescere dell angolo tra l asse del PM e le linee del campo magnetico L andamento in perfetto accordo con le specifiche date da Hamamatsu catodo non illuminato uniformmente Impossibilità di ridurre la soglia a causa del rumore del laser Impossibilità di effettuare una correzione di time walk dovuto alla variabilità della carica degli impulsi : E necessario acquisire carica e tempo per ciascun impulso

25 B field measurements Rotable support for 1-2 PMT/MCP for MARISA magnet under construction. B= T Measurement of single PMT parameters (gain/tts vs B) at different angles with B 2-PMTs and scintillators assembly.

26 New ideas Investigate the possibility of using a 5x5 mm2 APD from Hamamatsu to readout optical fibers as transverse (trigger) counter. Few samples made available from PSI and under investigation in Genoa.

27 Questions: Is the APD gain high enough to produce a signal / noise ratio high enough for triggering purpose? Is the light yield of a thin fiber 5x5 or 3x3 mm enough to be read by APD? Can we use the low cost APDs from PSI?

28 Hamamtsu APD 5x5 mm2 active area. Gain up to 1000 (reasonable value 400/500) Easy optical match with fibers. Tests have been performed with a 3x3 fiber 10 cm long composed by 9 fibers 1x1 mm glued with optical grease. Amplifiers: charge Amplifier Silena and home made voltage amplifier.

29 APD gain

30 Set-up 3x3 mm multifibers BCF20 APD Shield Bi-207

31 First observation impulso formato 3.00E E E E-01 uscita (mvolts) 1.00E E E E E E E E E E E E E E E-06 tempo (s)

32 Typical charges IMPULSI CON SORGENTE PREAMPLIFICATI x10^5 Series2 Series3 Series4 Series6 Volts (V) x10^5 2.9x10^5 e x10^5 e E E E E E E E E E-07 Time (s)

33 Noise vs gain noise with apd at different biases counts HV372 HV383 HV384 HV385.5 HV386, channel

34 Shot noise APD signal Electronic noise gain Optimal bias point

35 APD and fibers give rise to good signals for implementing the phi-detectors. A z-phi array can be built to give an impact point resolution in principle better then 5mm or 3 mm. 3mm fiber can be used without increase of number of channels.

36 Increase the segmentation?

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

40 Length 70 cm Angle (-140,10) Radius

41 Sezioni Genova - Pavia MEG Hamamatsu PMT

42 Sezioni Genova - Pavia MEG Hamamatsu PMT

43 Sezioni Genova - Pavia MEG Hamamatsu PMT

44 Sezioni Genova - Pavia Helium Diffusion Measures Two kinds of measures PMT Steel Chamber Flange Steel Chamber Membrane Mass Spectrometer Vacuum Pump Mass Spectrometer Vacuum Pump

45 Sezioni Genova - Pavia Hamamatsu PMT Glass Type Gas diffusion through plane membrane q= K A p / d q = gas quantity / time unit K = permeation constant A = cross-section area p = pressure difference d = thickness Permeation rate K of helium through various glasses. Log K vs. 1000/Temperature K. Units of K are cc(stp)/sec/cm 2 area/mm thickness/cm Hg pressure difference. Ref. [5] Glass plate is Corning 7056 thickness: 3.0 mm (glass PMT), 2.4 mm (metal PMT) Side material: Kovar powder glass, 1.1 mm thick (glass PMT) Kovar metal mm thick (metal PMT) Stem part is Kovar powder glass thickness: 3.0 mm (glass and metal PMT) Pins are made of Kovar Ref. [1], [2], and [3]

46 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.

47 Fixed points and future Timing resolution within a factor 2 from 100 ps The APD solution have been tested succesfully. 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.

48 PMT Evaluation PMT Design Design Manufactoring Assembly Test Milestone