CMS Hadron Calorimeter front-end upgrade for SLHC Phase I

We present an upgrade plan for the CMS HCAL detector. The HCAL upgrade is required for the increased luminosity (3×1034) of SLHC Phase I, which is targeted for 2014. A key aspect of the HCAL upgrade is to add longitudinal segmentation to improve background rejection, energy resolution, and electron isolation at L1 trigger. The increased segmentation is achieved by replacing the hybrid photodiodes (HPDs) with silicon PMTs (SIPMs). We plan to instrument each fiber of the calorimeter with an SIPM (103,000 total). We will then electrically sum outputs from selected SIPMs to form the longitudinal readout segments. In addition to having more longitudinal information, the upgrade plans include a new custom ADC with matched sensitivity and timing information. The increased data volume requires higher speed transmitters. The additional power dissipation for the readout electronics requires better thermal design, since much of the on-detector infrastructure (front-end electronics crates, cooling pipes, optical fiber plant, etc.) will remain the same. We will report on the preliminary designs for these upgraded systems, along with performance requirements and initial design studies.