Thus, the electron temperature can be obtained directly with high temporal resolution without additional power supply.
The conventional Faraday cup is applied for measurements of ion (or electron) flows from plasma boundaries and for mass spectrometry.
Langmuir probe measurements are based on the estimation of current versus voltage characteristics of a circuit consisting of two metallic electrodes that are both immersed in the plasma under study.
(b) The surface areas are very small in comparison with the dimensions of the vessel containing the plasma and approximately equal to each other.
In contrast, energy analyzers that employ the use of a magnetic field as a discriminator are very similar to mass spectrometers.
Particles travel through a magnetic field in the probe and require a specific velocity in order to reach the detector.
Nonlinear effects like the I-V characteristic of the boundary sheath are utilized for Langmuir probe measurements but they are usually neglected for modelling of RF discharges due to their very inconvenient mathematical treatment.
[8] The splitting of some emission lines due to the Stark effect can be used to determine the local electric field.
If a sufficiently complete collisional radiative model is used, the temperature (and, to a lesser degree, density) of plasmas can often be inferred by taking ratios of the emission intensities of various atomic spectral lines.
[10][11] The presence of a magnetic field splits the atomic energy levels due to the Zeeman effect.
In extremely high-temperature plasmas, such as those found in magnetic fusion experiments, light elements become fully ionized and do not emit line radiation.
However, when a beam of neutral atoms is fired into the plasma, a process known as charge exchange occurs.
[12][13] In this technique, charge exchange occurs between the neutral beam atoms and the fast deuterium ions present in the plasma.
This method exploits the substantial Doppler shift exhibited by Balmer-alpha light emitted by the energetic atoms in order to determine the density of the fast ions.
TALIF is capable of providing precise measurements of absolute ground state atomic densities, such as those of hydrogen, oxygen, and nitrogen.
However, achieving such precision necessitates appropriate calibration methods, which can be accomplished through titration or a more modern approach involving a comparison with a noble gases.
The incident laser beam is optimised, spatially, spectrally, and pulse energy, to detach an electron bound to a negative ion.
With an appropriate choice of beam species and velocity and of geometry, this effect can be used to determine the magnetic field in the plasma.
In a sufficiently thick and dense plasma, the intensity of the emission will follow Planck's law, and only depend on the electron temperature.
The electron density can be determined from the intensity of the scattered light, but a careful absolute calibration is required.
By measuring the neutron flux, plasma properties such as ion temperature and fusion power can be determined.