1. PID electronics for
FDIRC (Focusing Detector of Internally Reflected Cherenkov light) and FTOF (Forward Time of Flight)
Christophe Beigbeder and Dominique Breton for the SuperB PID group, presented by Nicolas Arnaud (LAL).
From BABAR DIRC to SuperB FDIRC
The PID group is designing two different detectors for the particle identification for the Barrel (FDIRC) and Forward region (FTOF). The two are based on time measurement respectively in 100 ps and 10 ps resolution domain.
The FDIRC can be seen as an upgrade of the electronics of the BABAR DIRC, with a new design of the mechanics , the optics and the associated electronics to collect the Cherenkov light coming from the inner region of the detector.
The electronics will equip the 18,432 channels of the 12 sectors. Its main requirements are 99% efficiency with a count rate of 500 kHz per channel, 100 ps rms hit time resolution, a trigger rate of 150 KHz with a minimum distance of 50 ns.
PMTs are arranged as a matrix of 6 in vertical x 8 in horizontal direction. Each column of 6 PMTs will be readout by two FE boards. In horizontal direction, the resolution is reduced by connecting 2 adjacent pixels to get 32 channels per PMT. The crate houses 16 FE boards, one crate controller board for data transfer, plus control and readout links.
The electronics chain is based on :
Hamamatsu H channel MaPMT
High resolution/ high count rate TDC chip
One analog chip housing a low walk discriminator and a track /peak detector
FBlock
Front end Analog Chip (PIF).
Track /peak detector for external charge measurement over 10 bits (dynamics of 15)
Analog derandomizer FIFO synchronized with the TDC readout
Low walk discriminator ( < 50 ps ) based on a pseudo CFD with 2 mV min threshold
Technology : AMS CMOS 0.35 um. Submission end 2012
TDC chip (SCATS)
dead time limited to 25ns.
500kHz input rate /channel with 1% dead time.
Data-push architecture
Technology : AMS .35 um. Submitted.
Simulation of the discriminator part
45 ps
PIF
SCATS

2. SuperB forward region is not covered by the FDIRC
SuperB forward region is not covered by the FDIRC. A dedicated detector would improve the PID coverage => Forward Time-Of-Flight (FTOF)
12 thin quartz tiles equipped with fast MCPPMTs to read the Cherenkov photons
56 channels per tile
Flight path 2m => 30ps total accuracy needed to separate π/K => ultra-fast electronics is required (resolution as good as 10 ps rms).
A prototype of the FTOF has been tested in the SLAC cosmic ray telescope in 2010 using WaveCatcher boards. Those are 12-bit 3.2 GS/s low power and low cost waveform digitizers based on the SAMLONG ultra-fast analog memory commonly developed by LAL Orsay and CEA/Irfu Saclay. Sampling time precision is a good as 10 ps rms at the crate level. Photon arrival time is extracted via digital Constant Fraction Discrimination (CFD).
A new 16-channel board have then been designed and characterized and exhibits the same performances.
The
16-channel
prototype crate
The
16-channel WaveCatcher
board
The final electronics for the FTOF will be highly integrated and based on a new principle of TDC, called SAMPIC. The latter, designed in AMS CMOS 0.18µm technology, will be able to tag the arrival time of 16 analog signals with a precision of a few ps thanks to its embedded analog memory (running between 5 and 10 GS/s) and its embedded ADC.
FINAL FTOF ELECTRONICS
SAMPIC TDC