High-accuracy absolute magnetometry with application to the Fermilab Muon g-2 experiment

We present details of a high-accuracy absolute scalar magnetometer based on pulsed proton NMR. The B-field magnitude is determined from the precession frequency of proton spins in a cylindrical sample of water after accounting for field perturbations from probe materials, sample shape, and other corrections. Features of the design, testing procedures, and corrections necessary for qualification as an absolute scalar magnetometer are described. The device was tested at B = 1.45 T but can be modified for a range exceeding 1–3 T. The magnetometer was used to calibrate other NMR magnetometers and measure absolute magnetic field magnitudes to an accuracy of 19 parts per billion as part of a measurement of the muon magnetic moment anomaly at Fermilab.

Spherical calibration and quality control of ground and UAV vector magnetometer data

Ground traverse and unmanned aerial vehicle (UAV) airborne magnetic mapping results covering an urban landfill are compared for a picoTesla-resolution fluxgate vector magnetometer (FVM). Rural and urban system noise tests are undertaken first to develop FVM quality assessment and control methods that are then used for processing the landfill survey data. The FVM ground and UAV survey results are subsequently compared with a femtoTesla-resolution alkali-vapor scalar magnetometer ground survey that provides a scalar total magnetic intensity image reference standard.

Swarm Mission: instruments performance, data availability, quality and future evolutions

<p>The European Space Agency (ESA) Swarm mission, launched on November 2013, continue to provide very accurate measurements of the strength, direction and variation of the Earth’s magnetic field. These data together with precise navigation, accelerometer, electric field, plasma density and temperature measurements, are crucial for a better understanding of the Earth’s interior and its environment. This paper will provide a status update of the Swarm Instrument performance after seven years of operations. Moreover, we will provide full details on the new Swarm Level 1b product baseline of Magnet and Plasma data which will be generated and distributed soon to the whole Swarm Community.  Please note that the main evolutions to be introduced in the Swarm L1B Algorithm are: i) computation of the Sun induced magnetic disturbance (dB_Sun) on the Absolute Scalar Magnetometer (ASM) and Vector Field Magnetometer (VFM) data; ii) computation of systematic offset between Langmuir Probes (LP) measurements ad ground observations derived from Incoherent Scatter Radars (IRS) located at middle, low, and equatorial latitudes. These and further improvements are planned to be included in the upcoming versions of the Swarm Level 1b products, aiming at achieving the best data quality for scientific applications.</p>

Magnetic field turbulence studies aboard the China Seismo-Electromagnetic Satellite and related ground based phenomena

<p>With a new type of a scalar magnetometer, the Coupled Dark State Magnetometer (CDSM) aboard the China Seismo-Electromagnetic Satellite (CSES) mission, we observed magnetic field fluctuations in the period mid July 2018 until mid November 2018. <br>The measurement range of the CDSM is from 1000 nT up to 100000 nT and the accuracy 0.19 nT (1), the operational performance is discussed in (2). We are using 1 Hz data in the latitude range -65 degree to +65 degree, CSES has an altitude of approx. 507 km in Sun synchronous polar configuration with 97.4 degree inclination. <br>We analyzed the total magnetic field turbulence by converting the time series into thermodynamic parameters, e.g. entropy, finally these results have been compared with ground based seismic and volcanic events.</p><p>Ref:<br>(1) Pollinger, A., et al.: Coupled dark state magnetometer for the China Seismo-Electromagnetic Satellite, Measurement Science and Technology, 29, 9, 2018. https://doi.org/10.1088/1361-6501/aacde4<br>(2) Pollinger, A., et al.: In-orbit results of the Coupled Dark State Magnetometer aboard the China Seismo-Electromagnetic Satellite, Geosci. Instrum. Method. Data Syst., 9, 275–291, 2020. https://doi.org/10.5194/gi-9-275-2020</p>

In-orbit results of the Coupled Dark State Magnetometer aboard the China Seismo-Electromagnetic Satellite

The China Seismo-Electromagnetic Satellite (CSES) was launched in February 2018 into a polar, sun-synchronous, low Earth orbit. It provides the first demonstration of the Coupled Dark State Magnetometer (CDSM) measurement principle in space. The CDSM is an optical scalar magnetometer based on the coherent population trapping (CPT) effect and measures the scalar field with the lowest absolute error aboard CSES. Therefore, it serves as the reference instrument for the measurements done by the fluxgate sensors within the High Precision Magnetometer instrument package. In this paper several correction steps are discussed in order to improve the accuracy of the CDSM data. This includes the extraction of valid 1 Hz data, the application of the sensor heading characteristic, the handling of discontinuities, which occur when switching between the CPT resonance superpositions, and the removal of fluxgate and satellite interferences. The in-orbit performance is compared to the Absolute Scalar Magnetometer aboard the Swarm satellite Bravo via the CHAOS magnetic field model. Additionally, an uncertainty of the magnetic field measurement is derived from unexpected parametric changes of the CDSM in orbit in combination with performance measurements on the ground.

An Novel Atomic Scalar Magnetometer Using Laser

The measurement precision of commercial atom scalar magnetometer is relatively backward compared with that of quantum magnetometer. However, the application of quantum magnetometers such as SERF requires more stringent environmental background requirements, which is not suitable for magnetic field measurement in the geomagnetic environment. The purpose of this paper is to design a 4He atom scalar magnetometer using ECDL laser. Compared with the conventional atomic scalar magnetometer, this magnetometer has higher measuring precision and can work normally in the geomagnetic environment. In order to achieve the above goals, the sensitivity formula of the atomic scalar magnetometer is first deduced and calculated, and the key physical factors that directly affect the sensitivity are the optical pumping rate, transverse relaxation rate, and longitudinal relaxation rate. Then, the light source and 4He cell are determined as key components which affect sensitivity. On this basis, the optical path of the 4He atomic scalar magnetometer using laser is designed in this paper. The light path ensures the stability of the laser wavelength of 1083.207nm by the saturation absorption spectrum method, and it ensures the circularly polarized light enters the 4He cell through the combination of various optical components. This paper also studies the electric excitation technology of the 4He cell. And, combined with simulation experiments, the High-Frequency discharge excitation circuit with high energy transfer efficiency and corresponding matching network are determined. Through the optical wavelength meter, it can be determined that the optical path designed in this paper can guarantee the wavelength stability of 1083.207nm for a long time. By analyzing the detection signals of PD, the circularly polarized light enters the 4He cell in the light circuit designed in this paper has a higher degree of polarization. The High-Frequency discharge excitation circuit designed in this paper can light up the cell smoothly, and the input power when the circuit works stably is about 6W. Finally, the static sensitivity of the magnetometer is 5pT/Hz1/2. The 4He atom scalar magnetometer using ECDL laser designed in this paper has high static sensitivity, which basically meets the design requirements, and the instrument can be used normally in the geomagnetic environment. However, the instrument still has a lot of room for improvement, including optical path and cell performance optimization, and we will continue to study in this direction.

In-orbit results of the Coupled Dark State Magnetometer aboard the China Seismo-Electromagnetic Satellite

The China Seismo-Electromagnetic Satellite (CSES) was launched in February 2018 into a polar, sun-synchronous, low Earth orbit. It provides the first demonstration of the Coupled Dark State Magnetometer (CDSM) measurement principle in space. The CDSM is an optical scalar magnetometer based on the Coherent Population Trapping (CPT) effect and measures the scalar field with the lowest absolute error aboard CSES. Therefore, it serves as the reference instrument for the measurements done by the fluxgate sensors within the High Precision Magnetometer instrument package. In this paper several correction steps are discussed in order to improve the accuracy of the CDSM data. This includes the extraction of valid 1 Hz data, the application of the sensor heading characteristic, the handling of discontinuities at CPT resonance transitions as well as the removal of fluxgate and satellite interferences. The in-orbit performance is compared to the Absolute Scalar Magnetometer aboard the SWARM satellite Bravo via the CHAOS-6 magnetic field model. Additionally, an uncertainty of the magnetic field measurement is derived from unexpected parametric changes of the CDSM in orbit in combination with performance measurements on ground.