MB1 T.O.F. II Precise timing Electron ID Eliminate muons that decay Tracking devices T.O.F. 0 & I Pion /muon ID precise timing 201 MHz RF cavities Liquid H2 absorbers or LiH ? SC Solenoids; Spectrometer, focus pair, compensation coil TOF 0, I-II positions 1.Trigger 2.PID 3.Timing respect to RF TOF system in MICE

MB2 Tof detector structure Conventional fast scintillator bars, read by PMTs at both ends, arranged in planes (Y or X/Y for better performances) for 3 stations: T0,T1,T2 Aimed performance  70 ps Bars are staggered and overlapped at the edges (for cross calibrations with incoming particles) Calibration: beam particles impinging on overlaps + dedicated fast laser system (a la Harp)

MB3 A layout of the Laser calibration system (Harp system) Laser Nd-YAG with passive Q-switch (dye), active/passive mode locking and 10 Hz repetition rate IR emission converted to a second harmonic ( =532 nm) by a KD*P SHG crystal Pulse: width 60 ps energy 6 mJ Beam splitter:  To ultra-fast (30 ps rise/fall) InGaAs MSM photodiode = START  To detector slabs through custom-made optical fibre system = STOP Foreseen mod: introduction of an optical switch to deliver signal to single channel

MB4 Main experimental problems: T0: high incoming particle rate (at least some MHz). Solution: R4998 PMTs with modified divider circuit (it can sustain up to 1.6 MHz, but small tolerance to B fiels) T1,T2: high magnetic fields. Solution: global iron shield+ fine-mesh PMTs (R7761, R5505) Tests under way: laboratory rate tests for PMTs, fine-mesh PMTs tests in B field

MB5 PMT rate studies Hamamatsu PLP-10 fast laser (35 FWHM, 1Hz- 1MHz rate, 415 nm) Fiber launching system into IR multimode fiber (Ceram OPTEC UV 50/100, measured spread 15 ps/m) PMT signal read by QVT (35 ps resolution) R4998 with modified divider circuit: booster for last dynodes Lab rate tests to be done with: Nominal: up to 1.5 MHz

MB6 Preliminary rate effects tests Please insert here.prn file available

MB7 PMTs for TOF1,TOF2: problems with high magnetic field Figure shows |B| from the cooling and measurement solenoids. The phototubes are placed in a place with high field. B may be bigger than 1 T -> problems TOF II ? Fine-mesh PMTs may not be enough

MB8 First step: global soft iron shield for downstream detector (GG)

MB9 Solution from Ghislain: single iron slab 15-cm thick with a central hole of 40 cm- diameter Z (cm) r (cm) Field map covers the domain 0 < z < 135 cm and 0 < r < 100 cm (dashed rectangle) O B is greatly reduced well below 1 T No problem for PMTs

MB10 Second step: systematic fine-mesh PMTs test in B-field (up to 1.2T) PMT under test Light source: Laser diode Hitachi DL (  635nm) pulsed by a pulser (Lecroy 9210, risetime 300 ps) FWHM laser pulse 300 ps. Injection in a short optical fiber to a prism, giving light to the PMT Output PMT signal to a Silena QVT

MB11 Fine-mesh phototube Properties Under test

MB12 Test magnet at LASA. First typical results. 1.Timing measurements 2.Gain measurements As a function of B,  More measurements under way