Acknowledgement.- Note on Transliteration.- Chapter 1. Purpose and Background of Study.- Chapter ... more Acknowledgement.- Note on Transliteration.- Chapter 1. Purpose and Background of Study.- Chapter 2. The Mongols in Iran.- Chapter 3. Shirazi's Life.- Chapter 4. The Principal Astronomical Sources.- Chapter 5. Persian vs. Arabic: Language as a Determinant of Content.- Chapter 6. Conclusion.- Figures- Bibliography.- Appendix A.- Appendix B.- Appendix C.- Appendix D.- Appendix E.- Index.
ABSTRACT A helical resonator plasma source is a resonant, slow-wave, plasma-loaded structure. It ... more ABSTRACT A helical resonator plasma source is a resonant, slow-wave, plasma-loaded structure. It consists of a cylindrical plasma generated by a surrounding helical coil, which, in turn, is surrounded by an earthed coaxial cylinder. Such sources can be efficiently matched to an external power source and can operate at low gas pressures. A quasi-static approximation is used to obtain the fields, which are then employed to calculate the electron heating. The equations of particle and energy balance are used to obtain plasma density and temperature. To solve these equations simultaneously, an iterative procedure is used. Experimental measurements of density and coil voltage as a function of input power are obtained for argon and nitrogen, at 20 mTorr and 2 mTorr. Comparison with theory indicates qualitative agreement. Observed differences between theory and experiment are discussed.
The electromagnetic modes for the helical resonator are derived in the sheath helix approximation... more The electromagnetic modes for the helical resonator are derived in the sheath helix approximation, assuming a nonlossy, cold plasma. The modes fall into two groups --one of which appears only when the plasma frequency is greater than the driving frequency. This is the mode of interest under normal operating conditions. The nature of the power coupling to the resonator is examined by observing the matching behavior of the plasma device as a function of driving frequency and tap position. A transmission line model for the resonator indicates that the wave-forms can be thought of as quarter wave sinusoids only when the losses due to the plasma are small. Optimal tap positions and driving frequencies are obtained as a function of the plasma losses for this model. To examine the plasma equilibrium a global model, similar to previously derived models for the rectangular geometry of parallel-plate discharges, is developed. Measurements of absorbed power, plasma density, and coil voltage give good agreement, indicating that the global model captures the essential characteristics of the discharge. This is particularly true at pressures >=20 mTorr, where ohmic heating comprises a considerable fraction of the electron heating. At lower pressures, where stochastic electron heating dominates, the densities and coil voltages are in rough agreement with the measurements.
ABSTRACT A helical resonator plasma source is a resonant, slow-wave, plasma-loaded structure. It ... more ABSTRACT A helical resonator plasma source is a resonant, slow-wave, plasma-loaded structure. It consists of a cylindrical plasma generated by a surrounding helical coil, which, in turn, is surrounded by an earthed coaxial cylinder. Such sources can be efficiently matched to an external power source and can operate at low gas pressures. A quasi-static approximation is used to obtain the fields, which are then employed to calculate the electron heating. The equations of particle and energy balance are used to obtain plasma density and temperature. To solve these equations simultaneously, an iterative procedure is used. Experimental measurements of density and coil voltage as a function of input power are obtained for argon and nitrogen, at 20 mTorr and 2 mTorr. Comparison with theory indicates qualitative agreement. Observed differences between theory and experiment are discussed.
Acknowledgement.- Note on Transliteration.- Chapter 1. Purpose and Background of Study.- Chapter ... more Acknowledgement.- Note on Transliteration.- Chapter 1. Purpose and Background of Study.- Chapter 2. The Mongols in Iran.- Chapter 3. Shirazi's Life.- Chapter 4. The Principal Astronomical Sources.- Chapter 5. Persian vs. Arabic: Language as a Determinant of Content.- Chapter 6. Conclusion.- Figures- Bibliography.- Appendix A.- Appendix B.- Appendix C.- Appendix D.- Appendix E.- Index.
ABSTRACT A helical resonator plasma source is a resonant, slow-wave, plasma-loaded structure. It ... more ABSTRACT A helical resonator plasma source is a resonant, slow-wave, plasma-loaded structure. It consists of a cylindrical plasma generated by a surrounding helical coil, which, in turn, is surrounded by an earthed coaxial cylinder. Such sources can be efficiently matched to an external power source and can operate at low gas pressures. A quasi-static approximation is used to obtain the fields, which are then employed to calculate the electron heating. The equations of particle and energy balance are used to obtain plasma density and temperature. To solve these equations simultaneously, an iterative procedure is used. Experimental measurements of density and coil voltage as a function of input power are obtained for argon and nitrogen, at 20 mTorr and 2 mTorr. Comparison with theory indicates qualitative agreement. Observed differences between theory and experiment are discussed.
The electromagnetic modes for the helical resonator are derived in the sheath helix approximation... more The electromagnetic modes for the helical resonator are derived in the sheath helix approximation, assuming a nonlossy, cold plasma. The modes fall into two groups --one of which appears only when the plasma frequency is greater than the driving frequency. This is the mode of interest under normal operating conditions. The nature of the power coupling to the resonator is examined by observing the matching behavior of the plasma device as a function of driving frequency and tap position. A transmission line model for the resonator indicates that the wave-forms can be thought of as quarter wave sinusoids only when the losses due to the plasma are small. Optimal tap positions and driving frequencies are obtained as a function of the plasma losses for this model. To examine the plasma equilibrium a global model, similar to previously derived models for the rectangular geometry of parallel-plate discharges, is developed. Measurements of absorbed power, plasma density, and coil voltage give good agreement, indicating that the global model captures the essential characteristics of the discharge. This is particularly true at pressures >=20 mTorr, where ohmic heating comprises a considerable fraction of the electron heating. At lower pressures, where stochastic electron heating dominates, the densities and coil voltages are in rough agreement with the measurements.
ABSTRACT A helical resonator plasma source is a resonant, slow-wave, plasma-loaded structure. It ... more ABSTRACT A helical resonator plasma source is a resonant, slow-wave, plasma-loaded structure. It consists of a cylindrical plasma generated by a surrounding helical coil, which, in turn, is surrounded by an earthed coaxial cylinder. Such sources can be efficiently matched to an external power source and can operate at low gas pressures. A quasi-static approximation is used to obtain the fields, which are then employed to calculate the electron heating. The equations of particle and energy balance are used to obtain plasma density and temperature. To solve these equations simultaneously, an iterative procedure is used. Experimental measurements of density and coil voltage as a function of input power are obtained for argon and nitrogen, at 20 mTorr and 2 mTorr. Comparison with theory indicates qualitative agreement. Observed differences between theory and experiment are discussed.
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