An electrostatic analyzer or ESA is an instrument used in
ion optics that employs an
electric field
An electric field (sometimes called E-field) is a field (physics), physical field that surrounds electrically charged particles such as electrons. In classical electromagnetism, the electric field of a single charge (or group of charges) descri ...
to allow the passage of only those
ions
An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
or
electrons
The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...
that have a given specific
energy
Energy () is the physical quantity, quantitative physical property, property that is transferred to a physical body, body or to a physical system, recognizable in the performance of Work (thermodynamics), work and in the form of heat and l ...
. It usually also focuses these particles (concentrates them) into a smaller area. ESAs are typically used as components of space instrumentation, to limit the scanning (sensing) energy range and, thereby also, the range of particles targeted for detection and scientific measurement. The closest analogue in
photon optics is a
filter.
Radial cylindrical analyzer
Electrostatic analyzers are designed in different configurations. A simple version is a radial cylindrical analyzer, which consists of two curved parallel plates at different potentials. Ions or electrons enter the analyzer at one end and either pass through the other end or collide with the walls of the analyzer, depending on their initial energy. In these types of analyzers, only the
radial
Radial is a geometric term of location which may refer to:
Mathematics and Direction
* Vector (geometric), a line
* Radius, adjective form of
* Radial distance (geometry), a directional coordinate in a polar coordinate system
* Radial set
* A ...
component of the velocity of a charged particle is changed by an ESA since the potential on the plates only varies in the radial direction if one considers the geometry in cylindrical coordinates.
Poisson's Equation
Poisson's equation is an elliptic partial differential equation of broad utility in theoretical physics. For example, the solution to Poisson's equation is the potential field caused by a given electric charge or mass density distribution; with t ...
can be then used to calculate the magnitude of the electric field pointing radially inwards. The resultant inward-pointing force generated by this electric field will cause the particles' trajectories to curve in a uniform circular motion. Depending on initial energy (velocity), only certain particles will therefore have the "correct" motion to exit the analyzer by tracing its physical structure, while others will collide into the walls of the instrument. In addition to the energy, the angle of entry will also affect the particles' time-of-flight through the analyzer as well as exit angle. In practice, the plates are usually oppositely charged and at very high potentials. Also, the inner surface of the analyzer, usually made of aluminum for space missions, is sometimes
plated
Plating is a finishing process in which a metal is deposited on a surface. Plating has been done for hundreds of years; it is also critical for modern technology. Plating is used to decorate objects, for corrosion inhibition, to improve solderab ...
with black chrome or even
Ebonol C to absorb stray light, instead of allowing it to bounce its way through.
Face-field cylindrical and conical electrostatic energy analyzers
The well-known class of cylindrical face-field energy analyzers and a more recently developed type of face-field conical electrostatic energy analyzers are very useful instruments with very wide area of applications. These instruments can achieve very high energy resolution combined with large acceptance aperture, what is very important for measurements of in-space plasma flows. This new class of analyzers can be used in a variety of applications for studying objects with different forms and sizes, and for analysis of remote objects in the exploration of nanomaterials within a set of different methods.
ESAs are usually designed and analyzed using an off-the-shelf ion-optics simulation-software package which includes the capability of performing
Monte Carlo
Monte Carlo ( ; ; or colloquially ; , ; ) is an official administrative area of Monaco, specifically the Ward (country subdivision), ward of Monte Carlo/Spélugues, where the Monte Carlo Casino is located. Informally, the name also refers to ...
simulations on known test particles, thus providing the designer a better understanding of the response characteristics of the analyzer itself.
Use in space instrumentation
Examples of space instruments or missions using Electrostatic Analyzers:
* The CAPS (Cassini Plasma Spectrometer) instrument on the
Cassini-Huygens spacecraft
* IBEX-Hi and IBEX-Lo instruments on the
Interstellar Boundary Explorer
Interstellar Boundary Explorer (IBEX or Explorer 91 or SMEX-10) is a NASA satellite in Earth orbit that uses energetic neutral atoms (ENAs) to image the interaction region between the Solar System and Outer space, interstellar space. The missi ...
spacecraft
*
Mariner 10
''Mariner 10'' was an American Robotic spacecraft, robotic space probe launched by NASA on 3 November 1973, to fly by the planets Mercury (planet), Mercury and Venus. It was the first spacecraft to perform flybys of multiple planets.
''Marin ...
* The
SWAP (Solar Wind Analyser around Pluto) instrument on the
New Horizons
''New Horizons'' is an Interplanetary spaceflight, interplanetary space probe launched as a part of NASA's New Frontiers program. Engineered by the Johns Hopkins University Applied Physics Laboratory (APL) and the Southwest Research Institut ...
spacecraft
*
Pioneer 6, 7, and 8 missions
*
Ranger 1
*
THEMIS
In Greek mythology and religion, Themis (; ) is the goddess and personification of justice, divine order, law, and custom. She is one of the twelve Titan children of Gaia and Uranus, and the second wife of Zeus. She is associated with oracles a ...
mission
* The ASPERA-3 and ASPERA-4 IMA instruments onboard
Mars Express
''Mars Express'' is a space exploration mission by the European Space Agency, European Space Agency (ESA) exploring the planet Mars and its moons since 2003, and the first planetary mission attempted by ESA.
''Mars Express'' consisted of two ...
and
Venus Express
* The ICA and IES ion and electron instruments on board the ESA/
Rosetta
Rosetta ( ) or Rashid (, ; ) is a port city of the Nile Delta, east of Alexandria, in Egypt's Beheira governorate. The Rosetta Stone was discovered there in 1799.
Founded around the 9th century on the site of the ancient town of Bolbitine, R ...
mission
* The SWIA, SWEA and STATIC instruments on
MAVEN
MAVEN is a NASA spacecraft orbiting Mars to study the loss of that planet's atmospheric gases to space, providing insight into the history of the planet's climate and water. The name is an acronym for "Mars Atmosphere and Volatile Evolution" w ...
. STATIC includes a time-of-flight measurement to obtain the mass/charge ratio in addition to its electrostatic analyzer.
*
Jovian Auroral Distributions Experiment (JADE) on the
Juno (spacecraft)
''Juno'' is a NASA space probe orbiting the planet Jupiter. Built by Lockheed Martin Space Systems, Lockheed Martin and operated by NASA Jet Propulsion Laboratory, the spacecraft was launched from Cape Canaveral Air Force Station on August 5 ...
Jupiter orbiter
* Solar Probe ANalyzer (SPAN) on board the Parker Solar Probe Mission
Solar Wind and Pickup Ions (SWAPI)instrument aboard th
Interstellar Mapping & Acceleration Probe (IMAP)spacecraft scheduled for launch in 2025.
See also
*
Ion Optics
References
{{Reflist
Electrostatics