The NA48 LKr calorimeter readout electronics

Abstract

The NA48 experiment at the CERN SPS accelerator is making a measurement of thc direct CP violation paramctcr E I / C by compering thc four rates of decay of IQ and K, . into 2x0 and K + K -. To reconstruct the dccliys into 2x0 the information from the almost 13500 channels of ii qiiasi-hornogeneous liquid krypton elcctromagnetic calorimeter is used. The readout electronics of the calorimeter has been designed to provide a dynamic range from a Cew McV to about 50 GeV eiiergy deposition per cell, and to sustain a high rate of incident particles. The system is made by cold charge preamplifiers (working at 120°K). low-noise fast shapers followed by digitizer electronics at 40 MHz sampling rate that employs a gain switching technique to expand the dyilainic range, where the gain can bc selected for each sample individually (i.e. cvery 25 ns). To reduce the amount of data cullected the system contains a zero suppression circuit based on halo cxpaosion.

The NA62 Liquid Krypton calorimeter readout architecture

“…Each of the 13,248 readout cells has a cross-section of about 2 × 2 cm 2 and consist (along the horizontal direction) of a central anode (kept at high voltage) in the middle of two cathodes (kept at the ground). More details about the LKr calorimeter structure can be found in [4].…”

The New Readout System of the NA62 LKr Calorimeter

“…It consists of a daughterboard, where the analog input signals are shaped and digitised, and a motherboard, where the data is processed and eventually sent out if the required trigger conditions are met. A CREAM-based readout system has replaced the old LKr readout system [10], unable to cope with the demanding NA62 requests in terms of rate sustainability and trigger logic.…”

The NA62 Liquid Krypton calorimeter readout module

“…The required signal to noise ratio is 15000 to 1. The back-end part of the readout chain, CPD [3], performed final signal shaping and digitization. At the design time in 1995, only a few low cost 10-bit 40 MS/s FADC were available and a custom dynamic range switching ASIC was developed to fulfil the experiment requirements.…”

“…The high resolution Liquid Krypton (LKr) calorimeter of the former NA48 experiment [2], together with other detectors, will provide a photon-veto with hermetic coverage from zero out to large angles from the decay region. The old backend electronics [3] does not satisfy the NA62 specifications and the study of a new readout system began in 2008.This paper presents the Calorimeter REAdout Module (CREAM), an upgrade project for the backend part of the LKr data acquisition chain [3]. The CREAMs will provide 40 MHz sampling of 13248 calorimeter channels, data buffering during the SPS spill, zero suppression, and programmable trigger sums for the experiment trigger processor.…”

“…This paper presents the Calorimeter REAdout Module (CREAM), an upgrade project for the backend part of the LKr data acquisition chain [3]. The CREAMs will provide 40 MHz sampling of 13248 calorimeter channels, data buffering during the SPS spill, zero suppression, and programmable trigger sums for the experiment trigger processor.…”