An analysis of VUV C (IV) emission from the JET divertor giving measurements of electron temperatures

K. D. Lawson, K. M. Aggarwal, I. H. Coffey, F. P. Keenan, M. G. O'Mullane, L. Ryc, J. Zacks, JET-EFDA Contributors

Research output: Contribution to journalArticle

11 Citations (Scopus)

Abstract

A description of the radiation emitted by impurities from within a plasma is crucial if spectral line intensities are to be used in detailed studies, such as the analysis of impurity transport. The simplest and most direct check that can be made on measurements of line intensities is to analyse their ratios with other lines from the same ion. This avoids uncertainties in determining the volume of the emitting plasma and the absolute sensitivity calibration of the spectrometer and, in some cases, the need even for accurate measurements of parameters such as electron density. Consistency is required between the measured line intensity ratios and the theoretical values. The expected consistency has not been found for radiation emitted from the JET scrape-off layer (e.g. Lawson et al 2009a JINST 4 P04013), meaning that the description of the spectral line intensities of impurity emission from the plasma edge is incomplete. In order to gain further understanding of the discrepancies, an analysis has been carried out for emission from the JET divertor plasma and this is reported in this paper. Carbon was the main low Z intrinsic impurity in JET and an analysis of spectral line intensity ratios has been made for the C (IV) radiation emitted from the JET divertor. In this case, agreement is found between the measured and theoretical ratios to a very high accuracy, namely to within the experimental uncertainty of similar to +/- 10 This confirms that the description of the line intensities for the present observations is complete. For some elements and ionization stages, an analysis of line intensity ratios can lead to the determination of parameters such as the electron temperature of the emitting plasma region and estimates of the contribution of recombination to the electron energy level populations. This applies to C (IV) and, to show the value and possibilities of the spectral measurements, these parameters have been calculated for a database of Ohmic and additionally heated phases of a large number of pulses. The importance of dielectronic, radiative and charge-exchange recombination as well as ionization has been investigated. In addition, the development of T-e throughout two example discharges is illustrated. The presented results indicate a number of areas for further investigation.
LanguageEnglish
JournalPlasma Physics and Controlled Fusion
Volume53
Issue number1. Special Issue SI
DOIs
Publication statusPublished - Jan 2011

Fingerprint

Electron temperature
electron energy
Plasmas
Impurities
Radiation
line spectra
Ionization
impurities
radiation
Electron energy levels
ionization
Carrier concentration
Spectrometers
Ion exchange
Calibration
charge exchange
Carbon
Ions
energy levels
spectrometers

Keywords

  • oscillator-strengths
  • ions
  • excitation
  • spectrometer
  • wave collision strengths

Cite this

Lawson, K. D., Aggarwal, K. M., Coffey, I. H., Keenan, F. P., O'Mullane, M. G., Ryc, L., ... Contributors, JET-EFDA. (2011). An analysis of VUV C (IV) emission from the JET divertor giving measurements of electron temperatures. Plasma Physics and Controlled Fusion, 53(1. Special Issue SI). https://doi.org/10.1088/0741-3335/53/1/015002
Lawson, K. D. ; Aggarwal, K. M. ; Coffey, I. H. ; Keenan, F. P. ; O'Mullane, M. G. ; Ryc, L. ; Zacks, J. ; Contributors, JET-EFDA. / An analysis of VUV C (IV) emission from the JET divertor giving measurements of electron temperatures. In: Plasma Physics and Controlled Fusion. 2011 ; Vol. 53, No. 1. Special Issue SI.
@article{74e8f38e5e3647209280e8dd763dbbf3,
title = "An analysis of VUV C (IV) emission from the JET divertor giving measurements of electron temperatures",
abstract = "A description of the radiation emitted by impurities from within a plasma is crucial if spectral line intensities are to be used in detailed studies, such as the analysis of impurity transport. The simplest and most direct check that can be made on measurements of line intensities is to analyse their ratios with other lines from the same ion. This avoids uncertainties in determining the volume of the emitting plasma and the absolute sensitivity calibration of the spectrometer and, in some cases, the need even for accurate measurements of parameters such as electron density. Consistency is required between the measured line intensity ratios and the theoretical values. The expected consistency has not been found for radiation emitted from the JET scrape-off layer (e.g. Lawson et al 2009a JINST 4 P04013), meaning that the description of the spectral line intensities of impurity emission from the plasma edge is incomplete. In order to gain further understanding of the discrepancies, an analysis has been carried out for emission from the JET divertor plasma and this is reported in this paper. Carbon was the main low Z intrinsic impurity in JET and an analysis of spectral line intensity ratios has been made for the C (IV) radiation emitted from the JET divertor. In this case, agreement is found between the measured and theoretical ratios to a very high accuracy, namely to within the experimental uncertainty of similar to +/- 10 This confirms that the description of the line intensities for the present observations is complete. For some elements and ionization stages, an analysis of line intensity ratios can lead to the determination of parameters such as the electron temperature of the emitting plasma region and estimates of the contribution of recombination to the electron energy level populations. This applies to C (IV) and, to show the value and possibilities of the spectral measurements, these parameters have been calculated for a database of Ohmic and additionally heated phases of a large number of pulses. The importance of dielectronic, radiative and charge-exchange recombination as well as ionization has been investigated. In addition, the development of T-e throughout two example discharges is illustrated. The presented results indicate a number of areas for further investigation.",
keywords = "oscillator-strengths, ions , excitation, spectrometer, wave collision strengths",
author = "Lawson, {K. D.} and Aggarwal, {K. M.} and Coffey, {I. H.} and Keenan, {F. P.} and O'Mullane, {M. G.} and L. Ryc and J. Zacks and JET-EFDA Contributors",
year = "2011",
month = "1",
doi = "10.1088/0741-3335/53/1/015002",
language = "English",
volume = "53",
journal = "Plasma Physics and Controlled Fusion",
issn = "0741-3335",
number = "1. Special Issue SI",

}

Lawson, KD, Aggarwal, KM, Coffey, IH, Keenan, FP, O'Mullane, MG, Ryc, L, Zacks, J & Contributors, JET-EFDA 2011, 'An analysis of VUV C (IV) emission from the JET divertor giving measurements of electron temperatures' Plasma Physics and Controlled Fusion, vol. 53, no. 1. Special Issue SI. https://doi.org/10.1088/0741-3335/53/1/015002

An analysis of VUV C (IV) emission from the JET divertor giving measurements of electron temperatures. / Lawson, K. D.; Aggarwal, K. M.; Coffey, I. H.; Keenan, F. P.; O'Mullane, M. G.; Ryc, L.; Zacks, J.; Contributors, JET-EFDA.

In: Plasma Physics and Controlled Fusion, Vol. 53, No. 1. Special Issue SI, 01.2011.

Research output: Contribution to journalArticle

TY - JOUR

T1 - An analysis of VUV C (IV) emission from the JET divertor giving measurements of electron temperatures

AU - Lawson, K. D.

AU - Aggarwal, K. M.

AU - Coffey, I. H.

AU - Keenan, F. P.

AU - O'Mullane, M. G.

AU - Ryc, L.

AU - Zacks, J.

AU - Contributors, JET-EFDA

PY - 2011/1

Y1 - 2011/1

N2 - A description of the radiation emitted by impurities from within a plasma is crucial if spectral line intensities are to be used in detailed studies, such as the analysis of impurity transport. The simplest and most direct check that can be made on measurements of line intensities is to analyse their ratios with other lines from the same ion. This avoids uncertainties in determining the volume of the emitting plasma and the absolute sensitivity calibration of the spectrometer and, in some cases, the need even for accurate measurements of parameters such as electron density. Consistency is required between the measured line intensity ratios and the theoretical values. The expected consistency has not been found for radiation emitted from the JET scrape-off layer (e.g. Lawson et al 2009a JINST 4 P04013), meaning that the description of the spectral line intensities of impurity emission from the plasma edge is incomplete. In order to gain further understanding of the discrepancies, an analysis has been carried out for emission from the JET divertor plasma and this is reported in this paper. Carbon was the main low Z intrinsic impurity in JET and an analysis of spectral line intensity ratios has been made for the C (IV) radiation emitted from the JET divertor. In this case, agreement is found between the measured and theoretical ratios to a very high accuracy, namely to within the experimental uncertainty of similar to +/- 10 This confirms that the description of the line intensities for the present observations is complete. For some elements and ionization stages, an analysis of line intensity ratios can lead to the determination of parameters such as the electron temperature of the emitting plasma region and estimates of the contribution of recombination to the electron energy level populations. This applies to C (IV) and, to show the value and possibilities of the spectral measurements, these parameters have been calculated for a database of Ohmic and additionally heated phases of a large number of pulses. The importance of dielectronic, radiative and charge-exchange recombination as well as ionization has been investigated. In addition, the development of T-e throughout two example discharges is illustrated. The presented results indicate a number of areas for further investigation.

AB - A description of the radiation emitted by impurities from within a plasma is crucial if spectral line intensities are to be used in detailed studies, such as the analysis of impurity transport. The simplest and most direct check that can be made on measurements of line intensities is to analyse their ratios with other lines from the same ion. This avoids uncertainties in determining the volume of the emitting plasma and the absolute sensitivity calibration of the spectrometer and, in some cases, the need even for accurate measurements of parameters such as electron density. Consistency is required between the measured line intensity ratios and the theoretical values. The expected consistency has not been found for radiation emitted from the JET scrape-off layer (e.g. Lawson et al 2009a JINST 4 P04013), meaning that the description of the spectral line intensities of impurity emission from the plasma edge is incomplete. In order to gain further understanding of the discrepancies, an analysis has been carried out for emission from the JET divertor plasma and this is reported in this paper. Carbon was the main low Z intrinsic impurity in JET and an analysis of spectral line intensity ratios has been made for the C (IV) radiation emitted from the JET divertor. In this case, agreement is found between the measured and theoretical ratios to a very high accuracy, namely to within the experimental uncertainty of similar to +/- 10 This confirms that the description of the line intensities for the present observations is complete. For some elements and ionization stages, an analysis of line intensity ratios can lead to the determination of parameters such as the electron temperature of the emitting plasma region and estimates of the contribution of recombination to the electron energy level populations. This applies to C (IV) and, to show the value and possibilities of the spectral measurements, these parameters have been calculated for a database of Ohmic and additionally heated phases of a large number of pulses. The importance of dielectronic, radiative and charge-exchange recombination as well as ionization has been investigated. In addition, the development of T-e throughout two example discharges is illustrated. The presented results indicate a number of areas for further investigation.

KW - oscillator-strengths

KW - ions

KW - excitation

KW - spectrometer

KW - wave collision strengths

UR - http://www.scopus.com/inward/record.url?scp=79551620052&partnerID=8YFLogxK

U2 - 10.1088/0741-3335/53/1/015002

DO - 10.1088/0741-3335/53/1/015002

M3 - Article

VL - 53

JO - Plasma Physics and Controlled Fusion

T2 - Plasma Physics and Controlled Fusion

JF - Plasma Physics and Controlled Fusion

SN - 0741-3335

IS - 1. Special Issue SI

ER -