Radiation hardened ADC chip power Atlas particle detector

Inside CERN’s Large Hadron Collider, protons collided almost at the speed of light, and the radiation was so intense that fries could be traditional electronics in seconds.

However, a team of Colombian engineers designed a silicon chip that thrives in this hostile environment, capturing precise data from each subatomic explosion. Their new radiation training, 8-channel analog to digital converter (ADC) will be the core of the Atlas detector liquid argon calorimeter, powering the next decade of an upgraded high-photometric LHC (HL-LHC).

Why particle physics requires custom chips

HL-LHC is set to increase the particle collision rate ten times, generating a large amount of data and radiation. Each collision in the atlas detector leaves an electrical feature in the ultracooled argon. These exquisite pulses must be digitized at 40 million times per second (MSP) and have almost perfect fidelity.

“We tested standard commercial components, and they just died. The radiation was too intense,” said Rui (Ray) Xu, a PhD student in engineering in Columbia. “We realized that if we wanted something that worked, we had to design ourselves.”

This work resulted in a custom ADC chip:

• 15-bit resolution and 14.2-bit dynamic range
• 40 MSP sampling rate
• Radiation tolerances for a 12-year mission
• Built-in foreground calibration and error correction

How ADCs Stay Stable in Particle Storm

The chip is designed using RHBD technology: triple module redundancy (TMR) for control logic, reliable metal insulators-metal capacitors and conservative circuit layout to mitigate ionization damage. It operates entirely on 1.2V supplies and integrates all the necessary digital and analog systems on chip to minimize external vulnerabilities.

“The next discovery of LHC will be triggered by one Columbia chip and measured by another chip,” said Peter Kinget, a professor of electrical engineering in Columbia. “The real-time selection of the most interesting collision triggered ADCs are already in use. This new data acquisition ADC processes the precise digitization of the selected signal.

One chip, 365,000 times

The Atlas Calorimeter contains over 180,000 channels, each requiring a dual gain path to capture the full range of dynamic energy signals. This means that despite the strong radiation and temperature fluctuations, there are still more than 364,000 ADC channels that have to function perfectly.

The team’s chips passed rigorous radiation tests at Massachusetts General Hospital and encountered a lifetime dose threshold for CERN. The single event UPSESS (SEUS) (digital erectile malfunction caused by particle hit rate) is within a tolerable range and does not require electric drive equipment.

According to performance tests, the chip exceeds the signal-to-noise ratio (SNDR) required by the calorimeter and even maintains high resolution near the Nyquist limit. The measured performance includes 11.4 significant bits and 70.3 dB SNDR, which is rare in radiation hardening designs.

Physics designed by physicists and engineers

Apart from its technical specifications, chips are a case study of interdisciplinary innovation. Electrical engineers from Columbia and the University of Texas work closely with Atlas physicists to ensure that designs meet physical goals and demanding hardware reality.

“As an engineer, there is an opportunity to make such a direct contribution to basic science directly,” Xu said. Xu joined the project and became an undergraduate student and regarded it as full production.

With the currently proven final ADC design and mass production in progress, these Colombian-designed chips will play a central role in the HL-LHC upgrade. They hope to help researchers explore the lingering mysteries of the Higgs boson and may discover new physical phenomena that have not yet been imagined.

Magazine: IEEE Solid State Circuit Association Public Magazine
doi: 10.1109/ojsscs.2025.3573904
Publication date: May 28, 2025

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