ITk Pixel Demonstrators

The ATLAS upgrade programme for the high-luminosity large hadron collider (HL-LHC) includes the replacement of the inner tracking detector with an all-silicon system (ITk). The outer layers of the new tracker consist of strip sensors and the inner region is made up of pixel sensors. Due to the increased channel count and power density in the pixel detector, a serial powering scheme has been chosen for the ITk Pixel Detector. In this scheme, the readout chips of the pixel modules are powered in series; however, in much of the detector, the sensors of several modules will be connected in parallel to a common supply line for the depletion voltage. Details of the serial powering scheme along with a description of various demonstrators that test powering, data readout and cooling for the ITk Pixel detector are presented here.