Upgrade of the ATLAS Thin Gap Chamber Electronics for HL-LHC

The High-Luminosity LHC (HL-LHC) is planned to start its operation in 2026 with an instantaneous luminosity of $7.5\times 10^{34}\,\mathrm{cm}^{-2} \mathrm {s}^{-1}$ . Studies with data taken by ATLAS indicate that the upgraded first level trigger with fast tracking for HL-LHC can reduce the rate of a single muon trigger by 25% for the $p_{\mathrm {T}}$ threshold of 20 GeV while maintaining similar efficiency. First prototype of the ATLAS Thin Gap Chamber frontend board has been developed with most of the functions required for HL-LHC implemented. Performance of data transfer has been demonstrated with charged particle beams at the CERN SPS beam facility.