Book contents
- Frontmatter
- Contents
- Preface to the first edition
- Preface to the second edition
- 1 Plasma diagnostics
- 2 Magnetic diagnostics
- 3 Plasma particle flux
- 4 Refractive-index measurements
- 5 Electromagnetic emission by free electrons
- 6 Electromagnetic radiation from bound electrons
- 7 Scattering of electromagnetic radiation
- 8 Neutral atom diagnostics
- 9 Fast ions and fusion products
- Appendix 1 Fourier analysis
- Appendix 2 Errors, fluctuations, and statistics
- Appendix 3 Survey of radiation technology
- Appendix 4 Definitions and identities of fundamental parameters
- Appendix 5 Atomic rates for beam diagnostics
- Glossary
- References
- Index
8 - Neutral atom diagnostics
Published online by Cambridge University Press: 23 November 2009
- Frontmatter
- Contents
- Preface to the first edition
- Preface to the second edition
- 1 Plasma diagnostics
- 2 Magnetic diagnostics
- 3 Plasma particle flux
- 4 Refractive-index measurements
- 5 Electromagnetic emission by free electrons
- 6 Electromagnetic radiation from bound electrons
- 7 Scattering of electromagnetic radiation
- 8 Neutral atom diagnostics
- 9 Fast ions and fusion products
- Appendix 1 Fourier analysis
- Appendix 2 Errors, fluctuations, and statistics
- Appendix 3 Survey of radiation technology
- Appendix 4 Definitions and identities of fundamental parameters
- Appendix 5 Atomic rates for beam diagnostics
- Glossary
- References
- Index
Summary
Diagnostics based on manipulating neutral atoms in the plasma are particularly important for magnetically confined plasmas because, unlike the charged ions, the atoms travel freely across the field. As a result, it is possible to use atoms that are emitted from the plasma to provide information about the plasma interior. It is also possible to send a beam of atoms into the plasma in a controlled way so as to produce a particular desired diagnostic configuration. This active probing often uses other phenomena, such as line radiation induced by the presence of the beam, to complete the diagnosis. However, because the beam propagation and related atomic processes are such a critical part of the diagnostic implementation, we gather together discussion of all these diagnostics within the present chapter.
Neutral particle analysis
Although most hot plasmas are almost completely ionized, there are, nevertheless, neutral atoms that are continually being formed within the plasma. Because these travel straight across any confining magnetic field, significant numbers can escape from the plasma without suffering a collision. These atoms then carry information out of the plasma about the state of the inner regions. They are called fast neutrals to distinguish them from the more numerous neutrals that tend to surround even a relatively hot plasma and that are edge particles, providing no information about the interior.
Collision processes
The proportion of fast neutrals that can reach the plasma edge (and hence be detected) without suffering a collision depends upon the collision cross sections for the various possible collisions.
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- Principles of Plasma Diagnostics , pp. 322 - 368Publisher: Cambridge University PressPrint publication year: 2002
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