What the study found
65 nm CMOS analog pixel test structures kept strong performance after radiation exposure, with DC-coupled designs maintaining time resolution below 70 ps and detection efficiency above 99% up to 10^15 NIEL. AC-coupled designs also performed well, especially at high reverse bias.
Why the authors say this matters
The authors say these results support the suitability of 65 nm monolithic active pixel sensors for future collider detectors that need radiation tolerance, efficiency, and timing precision. The study suggests that combining the low capacitance of DC-coupled designs with the higher-bias capability of AC coupling could further improve time resolution.
What the researchers tested
The researchers evaluated Analog Pixel Test Structures fabricated in the TPSCo 65 nm CMOS imaging process as part of the ALICE ITS3 R&D program and CERN R&D. The prototypes used 10 um pitch pixels and an operational amplifier-based buffering stage, and were tested with minimum ionizing particles in beam tests. They compared DC- and AC-coupled designs, including devices exposed to 10^14 NIEL and 10^15 NIEL.
What worked and what didn't
DC-coupled sensors showed stable performance, with time resolution below 70 ps and efficiency greater than 99% up to 10^15 NIEL. AC-coupled sensors had a wide operational margin and efficiency above 99% for clusterization thresholds below 150 electrons, but the lower signal amplitude reduced the signal-to-noise ratio and increased jitter. At high reverse bias, the AC-coupled sensors reached time resolutions comparable to the DC-coupled version.
What to keep in mind
The abstract does not describe detailed limitations beyond the tested designs, radiation levels, and beam-test conditions. The reported results apply to these specific 65 nm pixel test structures and the conditions stated in the summary.
Key points
- DC-coupled sensors kept time resolution below 70 ps and efficiency above 99% up to 10^15 NIEL.
- AC-coupled sensors showed efficiency above 99% for clusterization thresholds below 150 electrons.
- Lower signal amplitude in AC-coupled sensors reduced signal-to-noise ratio and increased jitter.
- At high reverse bias, AC-coupled sensors reached timing performance comparable to DC-coupled sensors.
- The authors say the results support 65 nm MAPS for future collider detectors.
Disclosure
- Research title:
- 65 nm pixel sensors stayed efficient and timed well after radiation
- Image credit:
- Photo by Nennieinszweidrei on Pixabay
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