Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 1410.2681

Comparison of adjustable permanent magnetic field sources

R. Bjørk·C. R. H. Bahl·A. Smith·N. Pryds
View original source ↗Read source document ↗Export metadata ↓

Abstract

A permanent magnet assembly in which the flux density can be altered by a mechanical operation is often significantly smaller than comparable electromagnets and also requires no electrical power to operate. In this paper five permanent magnet designs in which the magnetic flux density can be altered are analyzed using numerical simulations, and compared based on the generated magnetic flux density in a sample volume and the amount of magnet material used. The designs are the concentric Halbach cylinder, the two half Halbach cylinders, the two linear Halbach arrays and the four and six rod mangle. The concentric Halbach cylinder design is found to be the best performing design, i.e. the design that provides the most magnetic flux density using the least amount of magnet material. A concentric Halbach cylinder has been constructed and the magnetic flux density, the homogeneity and the direction of the magnetic field are measured and compared with numerical simulation and a good agreement is found.

Explore related subjects

physics.ins-det

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

R. Bjørk, C. R. H. Bahl, A. Smith, N. Pryds. 2014-10-10. Comparison of adjustable permanent magnetic field sources. https://doi.org/10.1016/j.jmmm.2010.07.022

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Mortality of ultra-thin LGADs and PiN diodes from high energy deposition

Low Gain Avalanche Diodes are prime candidates for high-resolution timing applications in High Energy Physics, Nuclear science, and several other fields. Operating these devices in high-radiation environments presents various hazards, including the risk of their permanent degradation or destruction caused by effects such as Single Event Burnout. Studies using minimum ionizing particles found a greatly reduced Single Event Burnout risk by operating below a bias voltage corresponding to an average electric field of 12 V/$μ$m - however, as high energy particle colliders produce a wide energy spectrum of radiation, it is crucial to understand this phenomenon and other possible damage mechanisms at energy deposition levels greater than those of minimum ionizing particles. This was achieved by pre-irradiating LGADs and PiN diodes with active thicknesses of 20, 30, and 50 $μ$m up to 1.5 $\times$ 10$^{15}$ $\mathrm{n_{eq}/cm^2}$, and exposing them to beams of protons and heavy ions (C, O, Fe, Au) at the BNL Tandem van de Graaff accelerator. Several mortality categories were observed, defined by different electrical and mechanical damage signatures. This furthers our understanding of permanent radiation damage of silicon devices, crucial towards mitigating Single Event Burnout and other damage mechanisms to safely operate future detectors.

physics.ins-det↗
arXiv2026

Small but Tubby: A Magnetic Loop Antenna Made from 100 mm Copper Tubing

This paper presents the electrical model, key equations, and practical construction of a small transmitting magnetic loop antenna built from unusually large 100 mm diameter copper tubing. The large conductor surface area and wide-area transitions to the vacuum capacitors were designed to minimize resistive losses. The frequency range from 1.8 MHz to 31 MHz is unusually wide. Frequency, impedance matching, and azimuth are all adjusted automatically by servo motors. Indoor losses originate predominantly from near-field coupling to the environment rather than from the antenna itself. Temperature-rise measurements confirm that the bulk of the dissipated power is absorbed by the environment, not by the antenna components. The conducted H-field measurements demonstrate good agreement between the measured H-field and the theoretical free-space H-field calculated from the antenna geometry and an estimated loop current. The loop current was estimated from the measured antenna bandwidth and the applied transmit power. The antenna was developed for indoor operation where outdoor installation is not possible.

physics.ins-det↗
arXiv2026

Construction and characterisation of the DarkSide-20k veto silicon photo-multiplier tiles

Silicon photo-multipliers (SiPMs) are state-of-the-art sensors capable of detecting a single photoelectron under cryogenic conditions, with potentially lower radioactivity than widely used photomultiplier tubes. The DarkSide-20k experiment, designed to perform direct dark matter searches using liquid argon as the target material, employs SiPM technology to detect interactions in the active detector volumes, including the central dual-phase Time Projection Chamber and the Inner and Outer Veto volumes. The vetoes are designed to discriminate against radiogenic neutron and cosmic muon backgrounds associated with the dark matter search. This paper describes the completed production and test protocols for the "Veto Tiles" (called vTiles, arrays of 24 SiPMs integrated on a printed circuit board providing the power distribution and signal amplification); 16 vTiles are grouped into "Veto Photo-Detector Units" to instrument the Inner Veto volume. Each vTile underwent detailed testing at room and cryogenic temperatures, confirming stable operation, high signal-to-noise ratio, and low radioactive contamination, demonstrating the robustness of the proposed design for cryogenic conditions. The final production yield exceeded 87%, surpassing the 80% requirement and corresponding to 1920 Veto Tiles to populate 120 Veto Photo-Detector Units, plus an additional 6% as spares.

physics.ins-det↗