Line-coincidence photopumping in a co-mixed KCL plasma
File(s)
Author(s)
Burridge, Daniel
Type
Thesis
Abstract
High Energy Density laboratory facilities allow for the production of plasmas
with a wide range of conditions, enabling the experimental investigation of
a variety of physical phenomena. One such interaction is line-coincidence
photopumping, whereby line radiation from one ion species is used to excite
a different ion species. This allows for ion species to depart from Local Thermodynamic
Equilibrium (LTE), potentially resulting in enhanced emission
on some spectral lines or even gain, under the appropriate plasma conditions;
a mechanism first proposed to account for the enhanced emission of several
lines in astrophysical plasma.
This thesis considers line-coincidence photopumping, beginning with a systemic
search of potential coincidence schemes prior to conducting initial modelling
of the plasma conditions required for a range of potential coincidence
schemes. Subsequent detailed investigation of the co-mixed K-Cl scheme is
conducted, followed by the identification of a spectroscopic analysis method
which can be applied to experimental and calculated data.
The K-Cl scheme was investigated experimentally on the ORION platform,
with laser drive imposed onto microdot targets to produce plasma conditions
predicted to be required for line-coincidence photopumping. Statistical
analysis of the data indicated that enhancement was observed; the first laboratory
demonstration of enhancement within a co-mixed plasma.
A modelling approach was developed to couple the output from non-LTE
radiation hydrodynamic calculations to subsequent non-LTE atomic kinetics
and line transport calculations. Modelling predictions of the ORION experimental
configuration are within an order of magnitude of experimental
data. Contaminants present in the targets, 2D approximations of the laser
spot geometry and limited knowledge of the laser beam temporal profile are
identified as potential contributors to the modelling discrepancy.
with a wide range of conditions, enabling the experimental investigation of
a variety of physical phenomena. One such interaction is line-coincidence
photopumping, whereby line radiation from one ion species is used to excite
a different ion species. This allows for ion species to depart from Local Thermodynamic
Equilibrium (LTE), potentially resulting in enhanced emission
on some spectral lines or even gain, under the appropriate plasma conditions;
a mechanism first proposed to account for the enhanced emission of several
lines in astrophysical plasma.
This thesis considers line-coincidence photopumping, beginning with a systemic
search of potential coincidence schemes prior to conducting initial modelling
of the plasma conditions required for a range of potential coincidence
schemes. Subsequent detailed investigation of the co-mixed K-Cl scheme is
conducted, followed by the identification of a spectroscopic analysis method
which can be applied to experimental and calculated data.
The K-Cl scheme was investigated experimentally on the ORION platform,
with laser drive imposed onto microdot targets to produce plasma conditions
predicted to be required for line-coincidence photopumping. Statistical
analysis of the data indicated that enhancement was observed; the first laboratory
demonstration of enhancement within a co-mixed plasma.
A modelling approach was developed to couple the output from non-LTE
radiation hydrodynamic calculations to subsequent non-LTE atomic kinetics
and line transport calculations. Modelling predictions of the ORION experimental
configuration are within an order of magnitude of experimental
data. Contaminants present in the targets, 2D approximations of the laser
spot geometry and limited knowledge of the laser beam temporal profile are
identified as potential contributors to the modelling discrepancy.
Version
Open Access
Date Issued
2022-12-13
Date Awarded
01/10/2023
License URL
Advisor
Rose, Steven
Publisher Department
Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)