Thermal runaway characteristics of silicon microstrip module designed for ATLAS upgrade inner tracker at super LHC

In accordance with the super LHC program, which plans to increase a collision rate of LHC by tenfold, the ATLAS silicon strip trackers need to be upgraded to overcome proportionally higher data rate and harsher radiation environment. Immediate concern is an increase of leakage current induced by radiation damage under such a severe condition. Without proper thermal management increase of the leakage current might lead silicon tracker modules to a catastrophic thermal runaway. Considering that the ATLAS inner trackers are strictly required to be as thin as possible in radiation length, careful optimization is imperative to cope with a robust thermal performance against thermal runaway. Based on the present ATLAS silicon strip modules (SCT), we have designed an upgrade silicon module, which consists of large area silicon sensors with short readout strips and densely populated readout ASIC’s. Thermal performance of such a module is investigated employing three dimensional FEA thermal analyses as well as a prototype thermal module. Although the upgrade module is about five times denser in readout channels than the present SCT, it shows a good thermal performance even with module materials comparable to the present SCT.