Soft-errors in FPGAs at the SuperKEKB interaction point

Abstract

In February 2016, the SuperKEKB positron-electron high-luminosity collider of the KEK laboratory (Tsukuba, Japan) started being commissioned. A dedicated commissioning detector, named BEAST2, has been used to characterize beam backgrounds before the Belle2 detector is rolled into the beams and to provide tuning parameters for Monte Carlo simulations. BEAST2 consists of a fiberglass support structure and several subdetectors mounted onto it, including time projection chambers (TPCs) and He-3 tubes. In this work, we present direct measurements of radiation-induced single event upsets in a SRAM-based FPGA device installed in BEAST2 at a distance of ∼1 m from the beam interaction point. Our goal is to provide experimental results of the expected radiation-induced configuration upset rate and power consumption variation at Belle2 and at other experiments operating in similar radiation conditions. For this study, we designed a dedicated board hosting a Xilinx Kintex-7 325T FPGA without additional active components, in such a way to be able to decouple FPGA failures from those of other devices. During the commissioning of the collider, we periodically read back the FPGA configuration in order to detect errors and we logged the power consumption on the different power domains of the device. Currents for both electron and positron rings spanned a range between 50 and 500 mA, therefore providing data about the FPGA operation in different radiation conditions.