A through-casing formation monitoring system may include a casing string positioned within a wellbore, a power source electrically coupled to a first transmitter configured to produce a magnetic field, a magnetic induction sensor positioned within the casing string such that the magnetic induction sensor allows a continued operation of the wellbore, a fiber optic cable coupled to an electro-optical transducer within the magnetic induction sensor, and an optical interrogation system configured to receive measurements from the magnetic induction sensor via the fiber optic cable.

A fiber optic sensor for measuring electromagnetic phenomena, including electrical and magnetic fields, voltage, and current is disclosed. The sensor includes an optical fiber probe containing a transmitting fiber and at least one receiving fiber, and a reflective surface or body. The reflective surface or body may be part of or attached to a material exhibiting a physical displacement from a force exerted upon the material due to electromagnetic phenomena, such as an electrical field, a magnetic field, voltage, and current. The reflective surface may be spaced apart from the ends of the fibers in the probe, and positioned so that light transmitted through the transmitting fiber is reflected by that surface into at least one receiving fiber. A light sensing means is coupled to the at least one receiving fiber, so light from a light reflected by the reflector body back into the receiving fibers is detected.

A magnetometer can include a single, integrated, unitary structure that has a gas cell defining a cavity having a vapor or vaporizable material disposed therein, a collimating element coupled to the gas cell and configured for collimating light directed toward the gas cell, and a lens element coupled the gas cell and configured for redirecting at least a portion of light that has passed through the gas cell. Additionally or alternatively, a gas cell of a magnetometer may be made of sapphire.

A magnetometer can include a single, integrated, unitary structure that has a gas cell defining a cavity having a vapor or vaporizable material disposed therein, a collimating element coupled to the gas cell and configured for collimating light directed toward the gas cell, and a lens element coupled the gas cell and configured for redirecting at least a portion of light that has passed through the gas cell. Additionally or alternatively, a gas cell of a magnetometer may be made of sapphire.

A thin film has a band gap of 2.2 eV or more and in which a crystal includes an atomic vacancy and an electron, a microwave irradiation system configured to irradiate the thin film with a microwave in response to driving from outside, an excitation unit configured to excite the electron included in the thin film in response to driving from outside, and a detector configured to detect, as an electric signal, at least either one of an intensity of light outputted from the thin film when the electron transitions from an excited state to a ground state and a change in conductivity of the thin film based on excitation.

A magnetic field measurement apparatus includes at least one first magnetic sensor that measures a magnetic field including a magnetic field to be measured and an environmental magnetic field, a plurality of second magnetic sensors that measure the environmental magnetic field, and a magnetic field calculation unit that estimates distribution of the environmental magnetic field on the basis of measured values of the second magnetic sensors, and calculates the magnetic field to be measured on the basis of a measured value of the first magnetic sensor and the estimated distribution of the environmental magnetic field.

A magnetic field measurement apparatus includes at least one first magnetic sensor that measures a magnetic field including a magnetic field to be measured and an environmental magnetic field, a plurality of second magnetic sensors that measure the environmental magnetic field, and a magnetic field calculation unit that estimates distribution of the environmental magnetic field on the basis of measured values of the second magnetic sensors, and calculates the magnetic field to be measured on the basis of a measured value of the first magnetic sensor and the estimated distribution of the environmental magnetic field.

A method for measuring magnetic field gradients that includes laser cooling atoms in a dark spot magneto-optical trap with an illuminated part, releasing the atoms, laser cooling the sample of atoms a second time, dividing the sample of atoms in half such that the first half of atoms are in the illuminated part of the trap, tossing the first half of atoms, leaving the second half of atoms behind, obtaining a RamanRaman spectrum from the first half of atoms and the second half of atoms and obtaining magnetic field measurements of the first half of atoms and the second half of atoms, and calculating a magnetic field gradient by subtracting the magnetic field measurements of the first half of atoms from the second half of atoms, then dividing the difference by the separation of the first half of atoms and the second half of atoms.

A method for measuring magnetic field gradients that includes laser cooling atoms in a dark spot magneto-optical trap with an illuminated part, releasing the atoms, laser cooling the sample of atoms a second time, dividing the sample of atoms in half such that the first half of atoms are in the illuminated part of the trap, tossing the first half of atoms, leaving the second half of atoms behind, obtaining a RamanRaman spectrum from the first half of atoms and the second half of atoms and obtaining magnetic field measurements of the first half of atoms and the second half of atoms, and calculating a magnetic field gradient by subtracting the magnetic field measurements of the first half of atoms from the second half of atoms, then dividing the difference by the separation of the first half of atoms and the second half of atoms.

A high-frequency magnetic field generating device includes two coils arranged with a predetermined gap in parallel with each other, the two coils (a) in between which electron spin resonance material is arranged or (b) arranged at one side from electron spin resonance material; a high-frequency power supply that generates microwave current that flows in the two coils; and a transmission line part connected to the two coils, that sets a current distribution so as to locate the two coils at positions other than a node of a stationary wave.