The magnet system is one of the key elements of a watt balance. For the new watt balance currently under construction at the National Institute of Standards and Technology, a permanent magnet system was chosen. We describe the detailed construction of the magnet system, first measurements of the field profile, and shimming techniques that were used to achieve a flat field profile. The relative change of the radial magnetic flux density is less than 10 −4 over a range of 5 cm. We further characterize the most important aspects of the magnet and give order of magnitude estimates for several systematic effects that originate from the magnet system.

Cycloidal mass analyzers are unique sector mass analyzers as they exhibit perfect double focusing, making them ideal for incorporating spatial aperture coding, which can increase the throughput of a mass analyzer without affecting the resolving power. However, the focusing properties of the cycloidal mass analyzer depend on the uniformity of the electric and magnetic fields. In this paper, finite element simulation and charged particle tracing were used to investigate the effect of field uniformity on imaging performance of a cycloidal mass analyzer. For the magnetic field, we evaluate a new permanent magnet geometry by comparing it to a traditional geometry. Results indicate that creating an aperture image in a cycloidal mass spectrometer with the same FWHM as the slit requires less than 1% variation in magnetic field strength along the ion trajectories. The new magnet design, called the opposed dipole magnet, has less than 1% field variation over an area approximately 62 × 65 mm; nearly twice the area available in a traditional design of similar size and weight. This allows ion imaging across larger detector arrays without loss of resolving power. In addition, we compare the aperture imaging quality of a traditionally used cycloidal mass spectrometer electric design with a new optimized design with improved field uniformity. Graphical abstract ᅟ.

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Transport Canada (TC) and the Federal Aviation Administration (FAA) have been active players in the research and development of trace explosive detection systems (TEDS). Under the direction of TC, private industry has been asked to develop devices meeting more and more stringent criteria. The recent development of a specification for TEDS by TC will provide industry with a clear blueprint for developing devices which will serve the traveling public today and into the foreseeable future. One of the ongoing projects involves the use of laser-based explosives detection. This technique involves the use of laser-generated infrared radiation to scan the surface of objects. The interaction of the laser radiation with any residual explosive on the surface of the object will initiate 'micro' bursts. The resulting light generated by these bursts can be detected and is characteristic of the explosive involved. Temporal and spectral analyses of the emitted light reveal unique signal pattems that are used to differentiate the 'micro' bursts. The results are preliminary, however, the technique offers the potential for detecting explosives on objects in near-real time. Thus, the technique could be used to scan carry-on baggage as the individual pieces of luggage travel on the x-ray system's conveyer belt.

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