Top-hat Analyzer Research Articles

New Spectrometer ULTIMAN for Space Plasma Research

Measurements of ion velocity distributions are one of basic goals of space plasma studies. There is variety of ion and electron spectrometers (see, for example, Wüest et al., 2007; Young et al., 2007; Zurbuchen and Gershman, 2016; Vaisberg et al., 2016). The most commonly used ion spectrometer is the top-hat analyzer (Carlson et al., 1983) consisting of a toroidal electrostatic analyzer, an electrostatic scanner, and a timeof-flight section with thin foil as a start element and ion preacceleration. We describe a new energy-mass analyzer with an electrostatic scanner providing a hemispheric field of view with small aberration, a toroidal electrostatic analyzer, and a time-of-flight synchronizer with a simple gate. It provides desirable hemisphere scanning, wide energy range, and reasonable mass resolution to meet most space exploration challenges. It can provide detailed measurements of the ion velocity distribution of ion species without significant gaps to obtain the structure of the hot plasma flow. With simple electrooptics elements this analyzer can be easily modified for many plasma research purposes.

The All-sky Spectrometer of Hot Cosmic Plasma

The main instruments for analyzing the processes occurring in cosmic plasma are energy and mass analyzers of charged particle beams. The analyzers’ operation is based on the separation of charged particles according to the energies of their motion or their masses in electric or magnetic fields. Currently, the top-hat analyzer is considered the main instrument for obtaining information about the state of cosmic plasma. However, it has a number of disadvantages: a significant time cycle for registering angular dependences in a total solid angle of 4π sr and low accuracy of determining the polar angles, which are associated with the need to rotate the analyzer during measurements. Over the past 20 years, plasma analyzers with a large viewing angle have been developed as an alternative to the top-hat analyzer. The design of the analyzer proposed in this work is capable of measuring plasma characteristics in a solid angle of 2π sr in one act of data registration. The all-sky spectrometer of hot cosmic plasma consists of two stages: the first stage is a conical lens of an original design, which serves to transform an extremely wide entrance flow of particles into a narrow cone-shaped beam; the second hexapole-cylindrical stage plays the role of an energy analyzer of a narrow cone-shaped flow. The paper describes the calculations and modeling of the proposed analyzer on the basis of original numerical and approximate analytical methods for designing systems of electron and ion optics. The main parameters of the device are calculated.

A hybrid electrostatic retarding potential analyzer for the measurement of plasmas at extremely high energy resolution.

Many space plasmas (especially electrons generated in planetary ionospheres) exhibit fine-detailed structures that are challenging to fully resolve with the energy resolution of typical space plasma analyzers (10% → 20%). While analyzers with higher resolution have flown, generally this comes at the expense of sensitivity and temporal resolution. We present a new technique for measuring plasmas with extremely high energy resolution through the combination of a top-hat Electrostatic Analyzer (ESA) followed by an internally mounted Retarding Potential Analyzer (RPA). When high resolutions are not required, the RPA is grounded, and the instrument may operate as a typical general-purpose plasma analyzer using its ESA alone. We also describe how such an instrument may use its RPA to remotely vary the geometric factor (sensitivity) of a top hat analyzer, as was performed on the New Horizons Solar Wind at Pluto and MAVEN SupraThermal and Thermal Ion Composition instruments. Finally, we present results from laboratory testing of our prototype, showing that this technique may be used to construct an instrument with 1.6% energy resolution, constant over all energies and angles.

The Solar Wind Around Pluto (SWAP) Instrument Aboard New Horizons

The Solar Wind Around Pluto (SWAP) instrument on New Horizons will measure the interaction between the solar wind and ions created by atmospheric loss from Pluto. These measurements provide a characterization of the total loss rate and allow us to examine the complex plasma interactions at Pluto for the first time. Constrained to fit within minimal resources, SWAP is optimized to make plasma-ion measurements at all rotation angles as the New Horizons spacecraft scans to image Pluto and Charon during the flyby. To meet these unique requirements, we combined a cylindrically symmetric retarding potential analyzer with small deflectors, a top-hat analyzer, and a redundant/coincidence detection scheme. This configuration allows for highly sensitive measurements and a controllable energy passband at all scan angles of the spacecraft.

A Panoramic Plasma Spectrometer: An All-Sky Camera for Charged Particles

The necessity of the high temporal resolution measurements of the complete velocity distribution function of charged particles in space leads to the invention of analyzers of new types including top-hat analyzers [2] for operation onboard rotating spacecraft and instruments with electrostatic scanning [3] for operation onboard slowly rotating spacecraft or onboard spacecraft with tri-axial stabilization. The instrument SKA-1 with electrostatic scanning [3] mounted on the Interball Tail Probe satellite had a temporal resolution of 10 s. There were two electrostatic mirrors and 36 Thomson parabola analyzers in the mass-spectrometer FONEMA for the Mars-96 mission [4], which guaranteed full coverage of 4 π angle and a temporal resolution of ~0.2 s. However, the failure of launching the Mars96 project did not allow one to use this unique instrument. The highest temporal resolution in measurements of the three-dimensional velocity distribution function of charged particles ( ~3 s) is achieved by employing a tophat analyzer on a rotating spacecraft. In this case, the temporal resolution is determined by the velocity of rotation of a spacecraft around its axis. Further improvement of the temporal resolution requires either arrangement of many detectors (which in turn causes many technical problems) or employment of new approaches. Earlier [1] we proposed a miniature electro-optic system that guarantees complete 2 π field of view ( 4 π with two analyzers) with a single coordinate-sensitive detector: an all-sky camera for charged particles. The feed optics can be modified for specific conditions of experiments and for different analyzers of the second stage. The suggested concept can guarantee very fast, flexible, and complete three-dimensional measurements of charged particles (ions or electrons).

A tophat ring current sensor

Observational knowledge of ring current particle pitch angle distributions and the theoretical understanding of such distributions in terms of particle transport and loss mechanisms are still incomplete. The recovery phase of major storms is associated with the loss of ring current ions through charge exchange with exospheric neutrals, wave particle scattering such as the ion cyclotron waves or Pc5 waves, or through E× B convection to the front side magnetosphere. Modelers often need to postulate additional pitch angle diffusion in order to fit the observed anisotropies. We describe here a ring current sensor based on existing technologies and concepts. The proposed instrument is a tophat analyzer with a time-of-flight section. The instrument is designed to detect with high pitch angle resolution ions that form the Earth's ring current within the energy range of 10 to 300 keV. High pitch angle resolution allows distinguishing between different ring current decay mechanisms.

TFAS (a tophat for all species): design and computer optimization of a new electrostatic analyzer

TFAS (tophat for all species) is discussed. It is a 360 degrees field-of-view electrostatic analyzer that can process particles of either charge simultaneously. The TFAS analyzer resembles two tophat analyzers placed hat to hat, but with the tophat plates removed and the tophat region shared in common by both analyzers. In the tophat region, deflection is by parallel plates, one with potential +V and the other with potential -V. A collimator allows particles to enter this parallel plate region and the particles are then deflected into the spherical deflection region of the analyzer. The TFAS has characteristics comparable to the spherical tophat analyzer. A mathematical analysis is presented showing the optimal dimensions selection for the TFAS analyzer, given a particular tophat angle. Raytracing simulations have been performed. Design curves showing various analyzer characteristics as a function of tophat angle are presented. The design curves are compared to similar curves already in the literature for the spherical tophat analyzer. Differences between the TFAS analyzer and the spherical tophat analyzer are summarized.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>