We describe the principles and measured performance of custom configurable 32-channel shaper/digitizer Front End Electronics (FEE) cards with 14-bit dynamic range for gain-adjustable photon detectors. The electronics has been designed for the PHOS calorimeter of ALICE with avalanche photodiode (APD) readout operated at -25 o C ambient temperature and a signal shaping time of 1 μs. The electronics has also been adopted by the EMCal detector of ALICE with the same APD readout, but operated at an ambient temperature of +20 o C and with a shaping time of 100ns. The CR-RC2 signal shapers on the FEE cards are implemented in discrete logic on a 10-layer board with two shaper sections for each input channel. The two shaper sections with gain ratio of 16:1 are digitized by 10-bit ADCs and provide an effective dynamic range of 14 bits. Gain adjustment for each individual APD is available through 32 bias voltage control registers of 10-bit range. The fixed gains and shaping times of the pole-zero compensated shapers are defined prior to FEE production by the values of a few R and C components. For trigger purposes, "fast OR" outputs with 12-bit dynamic range are available. FPGA based slave logic, combined with a USB processor supports a variety of remote control and monitoring features, including APD gain calibration. The measurements presented here for APDs at -25 o C ambient temperature and 1 μs shaping time achieve an average RMS noise level of 0.25 ADC counts or 290 electrons.The linearity over the dynamic range is better than 1%, as is the uniformity of shaping time and gain over 32 channels. Due to the excellent correspondence of the output pulse shape with offline fit, a differential timing resolution of less than 1.5 ns between channels has been achieved at ca. 2 GeV, i.e. at 1.5% of the dynamic range of PHOS.
Abstract-TheThis article will give an overview of the trigger system from trigger generation with the Photon Spectrometer to trigger reception of the Front End Electronics of both detectors. How to deal with the possible effects of the radiation environment on the electronics that do trigger handling will be evaluated.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.