Radiation Hard 3D Silicon Pixel Sensors for use in the ATLAS Detector at the HL-LHC

TL;DR

This paper evaluates 3D silicon pixel sensors' radiation tolerance for the HL-LHC ATLAS detector, demonstrating high efficiency at extreme radiation levels, suitable for inner detector regions.

Contribution

It presents the design, fabrication, and testing of 3D silicon pixel sensors with RD53A readout, showing their superior radiation hardness for high-fluence environments.

Findings

Achieved over 96% efficiency at $1\times10^{16}$ $n_{eq}cm^{-2}$ fluence

Demonstrated effective operation at 80 V bias after heavy irradiation

Validated the suitability of 3D sensors for HL-LHC inner detector upgrades

Abstract

The High Luminosity LHC (HL-LHC) upgrade requires the planned Inner Tracker (ITk) of the ATLAS detector to tolerate extremely high radiation doses. Specifically, the innermost parts of the pixel system will have to withstand radiation fluences above $1\times10^{16}$ $n_{eq}cm^{-2}$. Novel 3D silicon pixel sensors offer a superior radiation tolerance compared to conventional planar pixel sensors, and are thus excellent candidates for the innermost parts of the ITk. This paper presents studies of 3D pixel sensors with pixel size $50 \times 50$ $\mu m^2$ mounted on the RD53A prototype readout chip. Following a description of the design and fabrication steps, Test Beam results are presented for unirradiated as well as heavily irradiated sensors. For particles passing at perpendicular incidence, it is shown that average efficiencies above 96% are reached for sensors exposed to fluences of $1\times10^{16}$ $n_{eq}cm^{-2}$ when biased to 80 $V$.