Compression mechanisms in the plasma focus pinch
The compression of the plasma focus pinch is a dynamic process, governed by the electrodynamics of pinch elongation and opposed by the negative rate of change of current dI/dt associated with the current dip. The compressibility of the plasma is influenced by the thermodynamics primarily the speci...
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Main Authors: | , , |
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Format: | Article |
Language: | English |
Published: |
AIP Publishing
2017
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Subjects: | |
Online Access: | http://eprints.intimal.edu.my/762/1/Compression%20mechanisms%20in%20the%20plasma%20focus%20pinch.pdf http://eprints.intimal.edu.my/762/ |
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Institution: | INTI International University |
Language: | English |
Summary: | The compression of the plasma focus pinch is a dynamic process, governed by the electrodynamics of pinch
elongation and opposed by the negative rate of change of current dI/dt associated with the current dip. The compressibility
of the plasma is influenced by the thermodynamics primarily the specific heat ratio; with greater compressibility as the
specific heat ratio γ reduces with increasing degree of freedom f of the plasma ensemble due to ionization energy for the
higher Z (atomic number) gases. The most drastic compression occurs when the emitted radiation of a high-Z plasma
dominates the dynamics leading in extreme cases to radiative collapse which is terminated only when the compressed
density is sufficiently high for the inevitable self-absorption of radiation to occur. We discuss the central pinch equation
which contains the basic electrodynamic terms with built-in thermodynamic factors and a dQ/dt term; with Q made up of
a Joule heat component and absorption-corrected radiative terms. Deuterium is considered as a thermodynamic reference
(fully ionized perfect gas with f = 3) as well as a zero-radiation reference (bremsstrahlung only; with radiation power
negligible compared with electrodynamic power). Higher Z gases are then considered and regimes of thermodynamic
enhancement of compression are systematically identified as are regimes of radiation-enhancement. The code which
incorporates all these effects is used to compute pinch radius ratios in various gases as a measure of compression.
Systematic numerical experiments reveal increasing severity in radiation-enhancement of compressions as atomic number
increases. The work progresses towards a scaling law for radiative collapse and a generalized specific heat ratio
incorporating radiation. |
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