The front-end electronics of the NA48 liquid krypton calorimeter

Abstract
The NA48 Collaboration has built a quasi-homogeneous liquid krypton calorimeter with 13500 channels for its experimental apparatus aiming to measure CP violation in the decays of neutral kaons. Stringent requirements in terms of energy, time and position resolution as well as uniformity of response and calibration accuracy led to the installation of charge integrating preamplifiers based on Si-JFETs and mounted on the electrode structure in the liquid krypton. The electronic calibration circuit is based on DMOS switches that generate through an RC circuit pulses to be injected in the channels, according to a simple pattern scheme. All the components of the calibration circuits are mounted on a 18 layer PCB, which contains also the distribution of power supplies for the preamplifier, of the reference voltages for the pulsers and of the trigger signals. Calibration capacitors are built inside the PCB. 64 channel connectors made with Stesalite connect to the readout structure and house the HV blocking capacitor, HV distribution and the above mentioned PCB with connectors for the preamplifier. A mechanical protection system against HV discharges during HV ramping has been included. Finally, a new design of HV blocking capacitors and HV resistors, based on PCB techniques, has been tested and implemented.