The New Small Wheel electronics

The increase in luminosity, and consequent higherbackgrounds, of the LHC upgrades require improved rejection of faketracks in the forward region of the ATLAS Muon Spectrometer. TheNew Small Wheel upgrade of the Muon Spectrometer aims to reduce thelarge background of fake triggers from track segments that don'toriginate from the interaction point. The New Small Wheel employstwo detector technologies, the resistive strip Micromegas detectorsand the “small” Thin Gap Chambers, with a total of 2.45 millionelectrodes to be sensed. The two technologies require the design ofa complex electronics system given that it consists of two differentdetector technologies and is required to provide both precisionreadout and a fast trigger. It will operate in a high backgroundradiation region up to about 20 kHz/cm$^{2}$ at the expected HL-LHCluminosity ofℒ = 7.5 × 10$^{34}$ cm$^{-2}$ s$^{-1}$. Thearchitecture of the system is strongly defined by the GBTx dataaggregation ASIC, the newly-introduced FELIX data router and thesoftware based data handler of the ATLAS detector. The electronicscomplex of this new detector was designed and developed in the lastten years and consists of multiple radiation tolerant ApplicationSpecific Integrated Circuits, multiple front-end boards, denseboards with FPGA's and purpose-built Trigger Processor boards withinthe ATCA standard. The New Small Wheel has been installed in 2021and is undergoing integration within ATLAS for LHC Run 3. It shouldoperate through the end of Run 4 (December 2032). In thismanuscript, the overall design of the New Small Wheel electronics ispresented.