Imagine a high-precision integrator a hundred times faster than what is available today. Imagine it with a hundred times higher resolution, and enhanced stability and reproducibility...

You can open your eyes, your dream has come true: this product now exists and can be found in Metrolab’s catalogue. Equipped with a high-performance Analogue-to-Digital Converter (ADC), the brand new FDI2056 (Fast Digital Integrator) boasts a maximum trigger rate of 250 kHz – 100 times faster than the PDI5025, the previous state-of-the art solution. Its SINAD (signal-to-noise and distortion ratio) is improved by 40 dB, giving it a resolution... 100 times greater than that of its predecessor, along with a 24-hour stability of ±3 ppm and an unrivalled repeatability of ±1 ppm.

Destined to replace the PDI5025 in the near future, the FDI2056 covers the same fields of application more effectively... and opens up new perspectives. It is likely to be of great interest for all research programmes using accelerators where transient fields need to be measured – "as is the case with eddy currents in switching magnets, which are a headache for accelerator tuning as they cause dynamic magnetic field disturbances," explains Philip Keller, Metrolab's Maketing and Product manager.

Fifteenth order
The LHC (Large Hadron Collider) in Geneva is where this revolutionary integrator came into being, in 2007. During the superconducting magnet measurement campaign, the engineers at CERN strove to control "decay and snapback", magnetic field inertia effects occurring at the beginning (decay) and end (snapback) of a plateau in the acceleration ramp. "To quantify these phenomena accurately they needed a very fast measurement,” Philip Keller explains. “They built a coil spinning at a speed of 10 rps, and they decompose the result of a single turn into a sum of dipoles, quadrupoles, hexapoles, etc. up to at least the fifteenth order, so they required an integrator that produces enough flux samples to stay under the Nyquist limit – resulting in an unheard-of sample rate!"

It seems that nothing is impossible for CERN and the University of Sannio, which systematically analyzed the requirements and developed their FDI over the space of approximately two years. Its cutting-edge ADC, which digitizes the signal at a maximum sample rate of 500 kHz, is a major technological breakthrough. But a number of other significant advances went into the FDI. In particular, it is equipped with a PXI bus, to transfer data in real time to the computer – which was generally not the case on the PDI. Also worthy of mention are the high-precision programmable-gain amplifier, the UTC (Universal Time Counter), which measures the exact arrival time of the trigger pulse, and the DSP (Digital Signal Processor), which computes a partial integral at each trigger pulse.

Intelligent development
For Metrolab, which developed the PDI5025 more than 20 years ago on the basis of CERN's PDI, it was natural to take a licence to market the FDI, naming it the FDI2056. CERN continued – and is continuing – to develop the FDI in close collaboration with its partner. "We have requested features that expand the product’s utility in a broad range of applications,” stresses Philip Keller. “CERN has been very open to addressing our needs – for example to enable the firmware to be updated in the field."

The FDI incorporates practical features that were introduced with Metrolab's PDI5025 – specifically, programmable-gain amplifiers to adapt to a wide range of input signal levels, a level meter to give quick feedback on the amplification required, and a status display. "That is why we have decided to manufacture the FDI card exactly as designed by CERN and the University of Sannio," explains Philip Keller. “Our current contribution is to supply the other components required to make a complete system: crate, computer interface, software, manual, and of course continuing support." The product is proposed with a LabVIEW Application Programming Interface (API).

The first shipping release of the FDI2056 is operational, and Metrolab has already produced ten units. Also note that the integrator will be accompanied by a range of standard coils produced by Magnet-Physik and adapted for the FDI2056. Philip Keller explains: "We intend to offer different coil types to cover a wide range of conventional measurements, such as Helmholtz coils, which are used in magnetic block quality control."