KARATE - a setup for high rate tests of the CMS Outer Tracker 2S module readout chain

KARATE (KArlsruhe high RAte TEst) is a new test system to stress test the readout chain of detector modules for the upgrade of the CMS Outer Tracker for the high-luminosity LHC. Modules consisting of two silicon strip sensors, called 2S modules, are deployed in the outer regions of the Outer Tracker. The readout chain of a 2S module consists of 16 CMS Binary Chips~(CBC) each connected to two stacked silicon strip sensors. The CBC contributes data to the first trigger level by identifying particles with large transverse momenta. The output is sparsified on two concentrator chips which in turn are connected to a Gigabit transceiver that prepares the data for output through an optical module. Standard test systems such as test beams or radioactive source measurements need a track reconstruction or do have Gaussian distributed hit profiles and do not reach the occupancy or trigger rates expected in the future Outer Tracker of CMS. KARATE uses a combination of LEDs and photodiodes to inject hit patterns with varying pulse heights, occupancies and trigger rates into the front-end of the CBC, giving full control on 48 channels at 40\,MHz. This offers the opportunity to directly compare injection patterns with readout patterns. This contribution introduces the test system and summarizes measurements on a CBC that is read out electrically.