Cosmic ray susceptibility of the Terahertz Intensity Mapper detector arrays

TL;DR

This study investigates how cosmic rays impact the performance of KID-based detector arrays in the TIM experiment, showing low dead fractions and robustness against high-energy particle interference.

Contribution

It provides detailed measurements of cosmic ray interactions with large KID arrays and demonstrates the array's resilience, addressing calibration challenges at high multiplexing densities.

Findings

Cosmic ray rate of 2.1 events/min/cm^2 in the array.

66% of events affect a single pixel, 33% affect fewer than 5 KIDs.

Total cosmic ray dead fraction of 0.0011%, with an estimated maximum of 0.165%.

Abstract

We report on the effects of cosmic ray interactions with the Kinetic Inductance Detector (KID) based focal plane array for the Terahertz Intensity Mapper (TIM). TIM is a NASA-funded balloon-borne experiment designed to probe the peak of the star formation in the Universe. It employs two spectroscopic bands, each equipped with a focal plane of four $\sim\,$900-pixel, KID-based array chips. Measurements of an 864-pixel TIM array shows 791 resonators in a 0.5$\,$GHz bandwidth. We discuss challenges with resonator calibration caused by this high multiplexing density. We robustly identify the physical positions of 788 (99.6$\,$%) detectors using a custom LED-based identification scheme. Using this information we show that cosmic ray events occur at a rate of 2.1$\,\mathrm{events/min/cm^2}$ in our array. 66$\,$% of the events affect a single pixel, and another 33$\,$% affect $<\,$5 KIDs per event spread over a 0.66$\,\mathrm{cm^2}$ region (2 pixel pitches in radius). We observe a total cosmic ray dead fraction of 0.0011$\,$%, and predict that the maximum possible in-flight dead fraction is $\sim\,$0.165$\,$%, which demonstrates our design will be robust against these high-energy events.