Electron spin resonance magnetic field sensors for the B-Train systems
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CERN
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Abstract: For Iron dominated magnets, the magnetic models cannot be always used to predict the field within the required reproducibility, which may be as low as 10^(-5), due to non-linear effects (eddy currents, saturation and hysteresis). Therefore, most of the CERN's synchrotrons are equipped with a real time magnetic field measurement system, so called "B-Train". The magnetic field measurement devices are composed of absolute field sensors (called "markers"), field tracking sensors (called "induction coils"), an acquisition system, a control system that calculates the magnetic field from the sensors, and a distribution system that delivers the field value to the users. The markers are critical devices for operations and must be carefully developed to fulfil the high performance and reliability requirements of the B-Train systems. In this seminar we present new designs for electron spin resonance (ESR) field markers. We discuss in details the design, the operation, and performance of the ESR sensors based on resonator and oscillator structures including comparison between paramagnetic and ferrimagnetic samples. We propose four field marker levels at 36 mT, 106 mT, 360 mT and 710 mT that corresponds to resonance frequencies of 1GHz, 3GHz, 10GHz and 20 GHz. Those markers can measure the absolute field with ramps as fast as 5 T/s and field gradients as strong as 12 T/m.
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