A low mass pixel detector upgrade for CMS

TL;DR

This paper presents an upgrade to the CMS pixel detector aimed at reducing material and improving performance to cope with increased luminosity and radiation damage at the LHC.

Contribution

The paper introduces a new low mass pixel detector design with four barrel layers and three end cap disks, utilizing thin modules and lightweight support structures.

Findings

Design of a 4-layer barrel and 3-disk end cap pixel system

Implementation of thin detector modules and CO2 cooling

Material reduction in services and support structures

Abstract

The CMS pixel detector has been designed for a peak luminosity of 10^34cm-2s-1 and a total dose corresponding to 2 years of LHC operation at a radius of 4 cm from the interaction region. Parts of the pixel detector will have to be replaced until 2015. The detector performance will be degraded for two reasons: radiation damage of the innermost layers and the planned increase of the LHC peak luminosity by a factor of 2-3. Based on the experience in planning, constructing and commissioning of the present pixel detector, we intend to upgrade the whole pixel detector in 2015. The main focus is on lowering the material budget and adding more tracking points. We will present the design of a new low mass pixel system consisting of 4 barrel layers and 3 end cap disks on each side. The design comprises of thin detector modules and a lightweight mechanical support structure using CO2 cooling. In addition, large efforts have been made to move material from the services out of the tracking region.