Speaker
Nick Lumb
(Universite Claude Bernard-Lyon I (FR))
Description
The extreme pile-up conditions expected in the CMS detector during operation in the High Luminosity LHC (HL-LHC) necessitate the replacement of the entire tracking system during long shutdown 3 (LS3). New silicon modules with higher radiation tolerance and enhanced functionality will be installed. To further improve radiation resistance, the tracker will be operated at a lower temperature (-20°C) with respect to the current detector. In addition, it is highly desirable that the overall mass of the tracker be reduced. Progress towards achieving these aims for the endcap region of the outer tracker will be presented. To reduce mass, the silicon modules will be attached directly to the endcap disks, rather than to intermediate structures (‘petals’) as in the current endcaps. Individual lightweight conductors will replace relatively heavy printed circuit boards. Furthermore, cooling of the modules will be achieved using two-phase CO2, a low-density fluid which allows the use of small diameter pipework. The status of the endcap mechanics, including disk design, module layout, services routing and cooling, will be presented, together with results from initial prototyping of the disk mechanics and cooling circuits.
