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Pop-up probes are similar, but the electrodes rest behind a shield and are only moved the few millimeters necessary to bring them into the plasma near the wall. A Langmuir probe can be purchased off the shelf for on the order of 15,000 U.S. dollars, or they can be built by an experienced researcher or technician.
The langmuir (symbol: L) is a unit of exposure (or dosage) to a surface (e.g. of a crystal) and is used in ultra-high vacuum (UHV) surface physics to study the adsorption of gases. It is a practical unit, and is not dimensionally homogeneous, and so is used only in this field. It is named after American physicist Irving Langmuir.
From these basic hypotheses the mathematical formulation of the Langmuir adsorption isotherm can be derived in various independent and complementary ways: by the kinetics, the thermodynamics, and the statistical mechanics approaches respectively (see below for the different demonstrations). The Langmuir adsorption equation is
This is known as the single-probe method. (b) The surface areas are very small in comparison with the dimensions of the vessel containing the plasma and approximately equal to each other. This is the double-probe method. Conventional Langmuir probe theory assumes collisionless movement of charge carriers in the space charge sheath around the probe.
Schematic picture of a single ball-pen probe. Ions (in red) have a large gyromagnetic radius and can reach the collector more easily than electrons (in blue). A ball-pen probe [1] is a modified Langmuir probe used to measure the plasma potential [2] in magnetized plasmas. The ball-pen probe balances the electron and ion saturation currents, so ...
In this method, the plate is oriented perpendicular to the interface, and the force exerted on it is measured. Based on the work of Ludwig Wilhelmy, this method finds wide use in the preparation and monitoring of Langmuir films.
Dual Segmented Langmuir Probe (DSLP) is an instrument developed primarily by Czech researchers and engineers to study the magnetospheric background plasma flown on board the spacecraft of the European Space Agency Proba 2. [1] Data acquired by DSLP will be used to reach these specific scientific goals: [2]
The probe is spherical and has a diameter of 50 mm or so. Usually in probe diagnostics, one has to make the probe surface as small as possible, to keep the disturbance of the probe small. At the same time, the probe should still draw enough current to be measured precisely.