A/D Converters Help Researchers Measure Magnetic Fields

The European Organization for Nuclear Research (CERN) in Switzerland and the University of Sannio, Benevento, Italy, have collaborated on the design of an instrument for measuring magnetic fields in CERN’s Large Hadron Collider (LHC) superconducting magnets. Called the Fast Digital Integrator (FDI) board, this measurement device uses Analog Devices’ A/D converters, analog multiplexers and DSP components to provide the LHC with the highest possible performance achieved to-date in measuring magnetic fields.

The new FDI board enables 100 times the resolution and frequency bandwidth of the previous generation digital integrator. This improvement in dynamic range enables scientists to detect even more minute artifacts that contribute to magnetic field variations, field decay, and other time dependent phenomena typical in high-field superconducting accelerator magnets that all negatively affect the quality of particle beams under study. The new FDI boards are used at CERN to measure magnetic flux at 10 revolutions per second through fast-rotating calibrated coils that evaluate the magnetic field produced by the LHC’s 8 Tesla accelerator magnets.

CERN technician connects superconducting magnets in the Large Hadron Collider (LHC) tunnel. Analog Devices’ processing technology helps CERN’s LHC achieve the highest possible superconducting magnet performance. The LHC is the world’s largest and highest-energy particle accelerator, as well as the biggest machine ever built by humans. Its mission is to probe some of the most fundamental questions of physics. (Photo Credit: CERN)

“Prior to the FDI board, the available electronic components were not suitable in terms of accuracy or resolution, which, in the case of the Large Hadron Collider easily approaches 10 parts per million,” said Pasquale Arpaia, professor of engineering at the University of Sannio. “The components from Analog Devices helped make it possible for the FDI to reveal new magnetic investigation regions that we were not able to explore before.”

The LHC is the world’s largest and highest-energy particle accelerator, as well as the biggest machine ever built by humans. Construction started in 2003 and the LHC was operational in 2008. Its mission is to probe some of the most fundamental questions of physics and advance the understanding of the most fundamental laws of nature.

Researchers specified the following ADI components for use on the FDI board:

A/D converter (AD7634): this 18-bit analog-to-digital converter delivers superior 101-dB signal-to-noise and distortion ratio (SINAD) at the maximum sampling rate of 670 kS/s (thousand samples per second).

Multiplexer (ADG406): this multiplexer features a combination of high switching speed, low power dissipation and low on-resistance.

SHARC DSP (ADSP-21262): this 32-bit/40-bit floating-point processor is optimized for high-performance signal processing applications with two computational units, 2-Mbit dual-port on-chip SRAM, multiple internal buses to eliminate I/O bottlenecks, and an innovative digital applications interface.

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