Application specific integrated circuits for ANTARES offshore front-end electronics

The ANTARES undersea neutrino telescope will consist of an array of mooring lines carrying photomultiplier tubes enclosed in pressure resistant glass spheres (optical modules). They detect the Cherenkov light emitted by the muon produced by the charged current interaction of the parent neutrino. The data are transmitted to the shore through an electro-optical cable. Two ASICs have been developed in order to process the photomultiplier tube signals. The SPE_PSD chip discriminates between single-photoelectron pulses for which the integrated charge and the arrival time are measured, and more complex pulses to be processed by the ARS0 chip. The ARS0 is a five-channel 128-memory-cell 1GS/s analogue sampler, read out by a 1 MHz ADC. This array of switched capacitors is equivalent to a 1 GHz flash ADC of several orders of magnitude less power consumption. Since single-photoelectron pulses amount to 99% of the total, this dual path of the signal processing provides a strong reduction of the power consumption as well as of the amount of transmitted data.