BESIII TOF Monitoring System UH: Fred Harris, Jim Kennedy, Qian Liu, Steve Olsen, Marc Rosen, Chengping Shen, and Gary Varner
TOF Crucial for particle ID and for fast trigger. • Barrel – 50mm x 60mm x 2320 mm (inner layer). Endcap – BC408 – 2 layers – 88 in each – Radius from 810 to 930 mm. • Endcap – 48 fan shaped pieces – each end. – BC404 • PMT: Hamamatsu R5942 fine mesh – 2 on each barrel scintillator – 1 on each endcap counter • Resolution – Barrel: σ T = 100 ps – Endcap: σ T = 110 ps TOF – IHEP TOF group Barrel TOF electronics - USTC
TOF Status Oct. 23, 2007
BESIII TOF Calibration System (Fred Harris, Jim Kennedy, Qian Liu, Steve Olsen, Marc Rosen, Chengping Shen, and Gary Varner) • Hawaii is building a state-of-the-art TOF calibration system for BESIII. • Important as system monitor and for calibration. • UH built such systems for both BESII and Belle. • Major improvements: – Diode Laser – High quality multi fiber – fiber optic cable
BESIII TOF Monitoring System � Monitor the amplitude and time performance of each channel including PMTs and electronics. � Concept: � Use fiber cable bundles (2 cables) to distribute light to barrel and endcap TOF counters. � Use light splitter to illuminate one bundle at a time. Electronic switch Fiber bundles TOF barrel 176 fibers Laser Light splitter TOF endcap 48 fibers Diode TOF barrel 176 fibers Beam splitter TOF endcap 48 fibers connector To TOF Ref. PMTs electronics fiber Fiber PMT TOF barrel PMT
BESIII TOF Monitoring System • State-of-the-art TOF monitoring system built by Hawaii. • Major improvements: – Diode Laser – High quality multi fiber – fiber optic cables Use PicoQuant 440M Laser Diode. – Simple to use and maintain. – Long lifetime (6 k hours at full power). – Peak power: ~1W – Pulse width < 70 ps. – Wavelength 440 ± 10 nm. PicoQuant LDH-P-440M – Power stability 1% RMS.
Fiber Bundle Cables (need 2) Barrel TOF EC TOF
Fiber Bundles Design done by UH in conjunction with vendors. Manufactured by RoMack Fiberoptics. Distribution boxes built at UH. Barrel fibers – each box Endcap fibers supplies ½ of one end.
Fiber relative time measurement Delivery fibers 1” x 3” Measurement tube fiber PMTs Pulsed light Bundle Reference source fiber Dark box Flexible common end Neutral density filters Scheme: measure relative times between each delivery fiber and a reference fiber with two reference PMTs.
Time difference measurement setup Diffuser Common end Laser diode illuminating Two distribution fibers common end of bundle through connected to diffuser. reference PMTs.
Time difference measurement results Barrel Endcap Time diff. Time diff. σ = 83 ps σ = 66 ps All other Ref. PMT PMTs Pulse height Pulse height σ = 0.8% σ = 3.4% Measures PH stability of laser and length and light transmission uniformity of bundle fibers. Also illumination uniformity.
TOF Monitor System – Light Coupling Marc Rosen 5% 95% 1. Laser diode 2. Beam splitter (5%-95%) 3. Prismatic beam splitters (50-50) 4. Shutters 5. Reference PMTs 6. Diffusers 7. Fiber bundles
Laser Box
Control Box – J. Kennedy Supplies PMT voltages, solenoid currents, laser interlock, and laser pulse train. Accepts control pulses from USTC VME module. Interfaces to PC. Power supplies Xilinx programable board
All fibers successfully installed on east side of detector – Nov. 10, 2007.
Fibers 2 layers of tubes
Workers installing the fibers. Liu Qian (Hawaii) supervised installation at IHEP.
TOF Monitoring 10,000 laser pulses @ 1kHz ~75 ps West Barrel TOF’s Tmean and Tsigma vs. PMT number. NIM A593, 255 (2008).
Barrel Time of Flight – last run. ~5 % resolution Liu Qian Barrel TOF’s Qm and Qsigma vs. PMT number.
Data Base Information for BIE01 Liu Qian
History Database (BIE01) Liu Qian
TOF monitoring status • Liu Qian developed monitoring software and has developed a nice web user interface for people to check the results. • Results can be correlated with run number, B, and HV. Will allow monitoring system performance with time. The collaboration between IHEP TOF group, USTC (interface), and Hawaii on the TOF monitoring system has worked extremely well.
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