In-orbit Performance of the Silicon-Tungsten Tracker of the DAMPE Mission

Abstract

The DArk Matter Particle Explorer (DAMPE) is a high energy astroparticle satellite mission designed to detect electron, photon and cosmic rays with high precision for Dark Matter search, cosmic ray flux and composition measurement and gamma-ray astronomy. One of the key components of the DAMPE payload is the Silicon-Tungsten Tracker (STK), consisting of 6 tracking planes, each plane is made of 2 orthogonal layers of single-sided silicon micro-strip detectors. Three layers of 1 mm thick tungsten plates are interleaved with the tracking planes to serve as photon converter. Besides precise track reconstruction for charge particles and converted photons, the STK will also measure the charge of the incoming cosmic ray, and provide pre-shower information to improve particle identification. After intensive design, prototyping, test and production efforts by the STK collaboration, the construction of the STK has been completed in April 2015 and successfully integrated into the DAMPE payload in June 2015, after passing the environmental acceptance test. The DAMPE satellite was launched on December 17th 2015. After the launch the STK has been commissioned rapidly in orbit and has ben functioning extremely well since, which allows it to play a key role in the first physics results coming out of the DAMPE collaboration. In this contribution, a brief overview on the development, qualification and beam tests of the STK Engineering and Qualification Model and the Flight Model will be provided. Then the STK in-orbit calibration and performance will be presented in details, including the noise behavior, the thermal and mechanical stability, the alignment procedure, the position resolution, and the tracking efficiency.