Automatic Shielding-Shimming Magnetic Field Compensator for Excluded Volume Applications

Application of field-cycling NMR relaxometry to the study of ultrasound-induced effects in the molecular dynamics and order of mesomorphic materials

“…A revision of these experiments is currently in progress. Scanning the spin-lattice relaxation at the ultra low frequency (ULF) limit demands of two new insights: an improved lowfrequency magnetic field compensation [39,40], and the study of local fields by other experimental set-up avoiding the cycle of the magnetic field [41]. Summarizing, from experimental facts we may observe:…”

Active Magnetic-Field Stabilization with Atomic Magnetometer

“…Compared with passive magnetic shielding, the most attractive aspect of the active magnetic-field stabilization is the relatively low cost and large dimension. The demonstrated noise rejection ratio of the active magnetic-field stabilization is typically smaller than that of the magnetic shield and ranges from 10 to 1000 [6,29,33,36], depending on the noise level and response properties of the magnetometer and the parameter settings of the feedback controller. It is important to understand how these factors affect and how to improve the performance of active magnetic-field stabilization in a quantitative way.…”

“…The basic idea is to measure the magnetic-field noise with a magnetometer, compare the measured result with a reference, and generate an error signal to feedback control the current in a magnetic-field generator (solenoid or Helmholtz coil) and compensate for the magnetic-field noise. Many types of magnetometers have been used for active magnetic-field stabilization, including, but not limited to, optically-pumped atomic magnetometer (OPM) [ 32 ], superconducting quantum interference device (SQUID) [ 29 ], Hall sensor [ 33 ], fluxgate [ 34 ], and anisotropic magnetoresistive sensor [ 35 ]. In [ 21 ], the magnetic field outside the magnetic shield is monitored with SQUID sensors and actively stabilized, realizing a 30-fold improved noise rejection ratio of 2 at 0.01 Hz compared with that of the same magnetic shield without field stabilization.…”

A simple geomagnetic field compensation system for uniform magnetic field applications

“…On the other hand, the magnetic field control systems attempt to compensate the ambient magnetic field components capable of generating changes on the desired magnetic field distribution on a specific volume, this compensation can be achieved through an active or passive (shielding) system [9]. Active compensation consists in generating a magnetic field in opposite direction to the reference magnetic field in order to compensate the ambient magnetic field components [10], including the geomagnetic field [11], resulting in the desired magnetic field without interference.…”