Proton and Neutron Irradiation Tests of Readout Electronics of the ATLAS Hadronic Endcap Calorimeter

TL;DR

This study evaluates the radiation tolerance of ATLAS Hadronic Endcap Calorimeter readout electronics, specifically GaAs ASICs, under neutron and proton irradiation to ensure reliable operation in the high-radiation environment of the HL-LHC.

Contribution

It provides the first comprehensive irradiation tests of the ASICs using neutron and proton beams at fluences exceeding HL-LHC expectations, assessing performance degradation.

Findings

ASIC performance degrades with increased fluence, but remains within acceptable limits for HL-LHC operation.

In-situ S-parameter measurements reveal frequency-dependent performance changes.

Linearity tests show how the ASIC response varies under radiation exposure.

Abstract

The readout electronics of the ATLAS Hadronic Endcap Calorimeter will have to withstand the about ten times larger radiation environment of the future high-luminosity LHC (HL-LHC) compared to their design values. The GaAs ASIC which comprises the heart of the readout electronics has been exposed to neutron and proton radiation with fluences up to ten times the total expected fluences for ten years of running of the HL-LHC. Neutron tests were performed at the NPI in Rez, Czech Republic, where a 36 MeV proton beam is directed on a thick heavy water target to produce neutrons. The proton irradiation was done with 200 MeV protons at the PROSCAN area of the Proton Irradiation Facility at the PSI in Villigen, Switzerland. In-situ measurements of S-parameters in both tests allow the evaluation of frequency dependent performance parameters - like gain and input impedance - as a function of the fluence. The linearity of the ASIC response has been measured directly in the neutron tests with a triangular input pulse of varying amplitude. The performance measurements and expected performance degradations under HL-LHC conditions are presented.