John Coonrod | PPPL - Academia.edu (original) (raw)

Papers by John Coonrod

Nuclear Fusion, 1989

New and more accurate techniques for finding poloidal and toroidal mode numbers of MHD oscillatio... more New and more accurate techniques for finding poloidal and toroidal mode numbers of MHD oscillations from Mirnov coils are presented. It is found that the data for the MHD mode structure are best fit by a model which can accommodate toroidal effects on the mode geometry. The experimentally observed toroidal effects are compared with theoretical expectations. Examples of other physical MHD phenomena occurring during startup on TFTR are also illustrated. An example of toroidally coupled 4,1 and 3,1 modes is presented. An efficient algorithm is described that computes the best fit to Mirnov coil phase data by determining both the m, n numbers and a free toroidal correction parameter (λ', where λ' = 0 → cylindrical). The possibility of the mode being poloidally asymmetric owing to toroidal effects and an off-centre location of the mode justify leaving the λ' parameter free. Since the optimal value of λ' can be obtained automatically with a computer, the need for 'gues...

An onl~ne computer system has been developed as a replacement for oscilloscopes and cameras on th... more An onl~ne computer system has been developed as a replacement for oscilloscopes and cameras on the Tormac project. Up to 32 simultaneous waveforms are recorded at up to 2•MHz in analog shift registers, then digitized sequentially after the event into a small PDP-11 computer. Data and functions of data may be displayed or plotted locally, and then forwarded for storage at a larger, remote computer via a network arrangement. Advantages over scopes have been lower incremental cost c~ $200/channel), less noise pickup, better resolution(< 1%), and immediate presentation of data.

The methods for finding poloidal and toroidal numbers of MHD oscil lation; from Mimov coils are r... more The methods for finding poloidal and toroidal numbers of MHD oscil lation; from Mimov coils are reviewed and modified. Examples of various MHD phenom ena occurring during start-up on TFTR are illustrated. It is found that the MHD mode structure best fits a mode! with the toroidal correction ] ' 2 included. A new algorithm which finds m, n numbers can accommodate toroidal effects which are manifested in the phase data. The algorithm can find rn.n numbers with a given toroidal correction parameter A', (A' = 0 => cylindrical). This algorithm is also used to find the optimal value of A' automatically, eliminating the need for "guesswork." The algorithm finds the best parameters to the fit much faster than more conventional computational techniques.

Development, 2016

According to a recent study funded by the UN Democracy Fund (UNDEF), countries are decentralizing... more According to a recent study funded by the UN Democracy Fund (UNDEF), countries are decentralizing governance, moving resources and decision-making closer to citizens, and establishing public forums where people hold government accountable for public services. These steps accelerate economic and social progress, yet are largely ignored at the global policy level.

It has been reproduced from the best available copy to permit the broadest possible availability.

A novel 50 cm long position sensing proportional chamber has been constructed for use in transver... more A novel 50 cm long position sensing proportional chamber has been constructed for use in transverse section reconstruction measurements. Characteristics of this detector are: position resolution 1 mm, energy resolution 20%, efficiency at 60 keV 31%, and deadtime 2 ¿sec. Fan beam x-ray transmission measurements at many angles are stored in a PDP 11/45 minicomputer which performs and displays the

Tormac is a concept for magnetically confining a highS fusion plasma in a toroidal, stuffed line ... more Tormac is a concept for magnetically confining a highS fusion plasma in a toroidal, stuffed line cusp. A Tormac plasma has two regions: an interior confined on the closed toroidal field lines of the stuffing field, and an exterior sheath on open, cusped field lines. The interior plasma gives the device a longer confinement time than a standard mirror, while the favorable curvature of the cusp fields allow the plasma to be stable' at higher values of B (the ratio of plasma pressure to magnetic pressure) than a totally closed configuration like Tokamak. Tormac IV-c is an attempt to create and study a Tormac plasma with two cusp lines, a bi-cusp. It is a pulsed ex periment. 10-50 mTorr of gas is preionized in a .5 meter diameter glass vessel in the presence of a 300 Gauss bias field. A 3-4 kG compression field then rises in 8.3 usee, sweeping up the plasma, and decays with T = 80 usee. During that time, data are taken by Thomson scattering, laser interferometry, magnetic probes, and spectroscopy, and stored by an online computer.-viii-The results indicate that the plasma is incompletely ionized, cold (Te < 5 eV) and in contact with the wall at small major radius. The bicusp configuration depends on a combination of toroidal and poloidal fields forming the magnetic piston which compresses the plasma. This occurs at the outer radius where the field is primarily poloidal, but fails at the inner wall as the toroidal field pene trates rapidly throughout the plasma. This thesis describes the design, construction and operation of Tormac IV-c, and reports on the results, with emphasis on describing the behavior of the density compres sion and field penetration.-ix-PREFACE This thesis describes the construction, operation, and results of Tormac IV-c, a plasma confinement device built by Hartin J. Greenwald and myself at the Lawrence Berkeley Laboratory. His thesis, "Temperature Measurements in the Tormac IV-c plasma" (LBL-8166), and this foru complementary volumes in emphasis, although each is an independently complete description of the apparatus and data. I have organized this paper in five chapters, each of which could be read separately. The introduction and the summary section of the data chapter describe the results, and the rest contains details. The work on data acquisition in Chapter 5 is useful to any experiment using computers, and is not restricted to plasma experiments per se. This experiment is an integral part of the Toraiac Project led by Morton A. Levine, which resides in the Magnetic Fusion Energy Program at LBL led by Hulf Kunkel. It was done with the collaboration and support of a large number of physicists and technicians. Participants over the last four years include (in approximate seniority):

The purpose of this paper is explore effective methodologies for addressing the interlinked objec... more The purpose of this paper is explore effective methodologies for addressing the interlinked objectives of the UN 2030 Sustainable Development Goals (SDGs) in impoverished rural areas across Africa, South Asia and indigenous Latin America, with a special focus on governance and gender. The paper cites examples from the programs of one NGO, The Hunger Project.

Plasma Physics, 1980

Gaussian He II 4686-A spectral lines having full widths at half maximum of over 2 A have been obs... more Gaussian He II 4686-A spectral lines having full widths at half maximum of over 2 A have been observed in the Tormac plasmas. Interpretation of these widths as due to Doppler broadening would give ion temperatures of more than 100 eV, in contradiction with other diagnostics. Indications are that these widths are not simply explained by either Doppler broadening or Stark broadening due to interparticle fields. Some evidence exists of nonthermal turbulent conditions, which could broaden the lines by the Stark effect, if there exist large enough electric fields, or by the Doppler effect, if there is appreciable mass motion.

Plasma Physics, 1980

ABSTRACT

Review of Scientific Instruments, 1985

The various operating modes of TFTR require the use of a sophisticated system of magnetic diagnos... more The various operating modes of TFTR require the use of a sophisticated system of magnetic diagnostics integrated with a feedback control system. This system has successfully controlled the plasma current and position over a range of major and minor radii, during strong compression, and will soon be used during intense neutral beam heating. Current and position values are held constant to within 2 kA and 1 cm. A wide variety of preoperational field measurements were required to determine proper compensation for dynamic stray fields due to eddy currents. Data from plasma profile diagnostics, such as bolometer arrays, Thomson scattering, soft x-ray diode array, and the scanning radiometer, have been compared to the absolute position deduced from magnetics. In addition to control functions, magnetic diagnostics on TFTR provide data on plasma current asymmetry, βθ, MHD fluctuations, loop voltage, and flux consumption. This paper will discuss the mechanical and electronic design constraints, as well as the analytic and calibration techniques required.

Nuclear Fusion, 1989

New and more accurate techniques for finding poloidal and toroidal mode numbers of MHD oscillatio... more New and more accurate techniques for finding poloidal and toroidal mode numbers of MHD oscillations from Mirnov coils are presented. It is found that the data for the MHD mode structure are best fit by a model which can accommodate toroidal effects on the mode geometry. The experimentally observed toroidal effects are compared with theoretical expectations. Examples of other physical MHD phenomena occurring during startup on TFTR are also illustrated. An example of toroidally coupled 4,1 and 3,1 modes is presented. An efficient algorithm is described that computes the best fit to Mirnov coil phase data by determining both the m, n numbers and a free toroidal correction parameter (λ', where λ' = 0 → cylindrical). The possibility of the mode being poloidally asymmetric owing to toroidal effects and an off-centre location of the mode justify leaving the λ' parameter free. Since the optimal value of λ' can be obtained automatically with a computer, the need for 'gues...

An onl~ne computer system has been developed as a replacement for oscilloscopes and cameras on th... more An onl~ne computer system has been developed as a replacement for oscilloscopes and cameras on the Tormac project. Up to 32 simultaneous waveforms are recorded at up to 2•MHz in analog shift registers, then digitized sequentially after the event into a small PDP-11 computer. Data and functions of data may be displayed or plotted locally, and then forwarded for storage at a larger, remote computer via a network arrangement. Advantages over scopes have been lower incremental cost c~ $200/channel), less noise pickup, better resolution(< 1%), and immediate presentation of data.

The methods for finding poloidal and toroidal numbers of MHD oscil lation; from Mimov coils are r... more The methods for finding poloidal and toroidal numbers of MHD oscil lation; from Mimov coils are reviewed and modified. Examples of various MHD phenom ena occurring during start-up on TFTR are illustrated. It is found that the MHD mode structure best fits a mode! with the toroidal correction ] ' 2 included. A new algorithm which finds m, n numbers can accommodate toroidal effects which are manifested in the phase data. The algorithm can find rn.n numbers with a given toroidal correction parameter A', (A' = 0 => cylindrical). This algorithm is also used to find the optimal value of A' automatically, eliminating the need for "guesswork." The algorithm finds the best parameters to the fit much faster than more conventional computational techniques.

Development, 2016

According to a recent study funded by the UN Democracy Fund (UNDEF), countries are decentralizing... more According to a recent study funded by the UN Democracy Fund (UNDEF), countries are decentralizing governance, moving resources and decision-making closer to citizens, and establishing public forums where people hold government accountable for public services. These steps accelerate economic and social progress, yet are largely ignored at the global policy level.

It has been reproduced from the best available copy to permit the broadest possible availability.

A novel 50 cm long position sensing proportional chamber has been constructed for use in transver... more A novel 50 cm long position sensing proportional chamber has been constructed for use in transverse section reconstruction measurements. Characteristics of this detector are: position resolution 1 mm, energy resolution 20%, efficiency at 60 keV 31%, and deadtime 2 ¿sec. Fan beam x-ray transmission measurements at many angles are stored in a PDP 11/45 minicomputer which performs and displays the

Tormac is a concept for magnetically confining a highS fusion plasma in a toroidal, stuffed line ... more Tormac is a concept for magnetically confining a highS fusion plasma in a toroidal, stuffed line cusp. A Tormac plasma has two regions: an interior confined on the closed toroidal field lines of the stuffing field, and an exterior sheath on open, cusped field lines. The interior plasma gives the device a longer confinement time than a standard mirror, while the favorable curvature of the cusp fields allow the plasma to be stable' at higher values of B (the ratio of plasma pressure to magnetic pressure) than a totally closed configuration like Tokamak. Tormac IV-c is an attempt to create and study a Tormac plasma with two cusp lines, a bi-cusp. It is a pulsed ex periment. 10-50 mTorr of gas is preionized in a .5 meter diameter glass vessel in the presence of a 300 Gauss bias field. A 3-4 kG compression field then rises in 8.3 usee, sweeping up the plasma, and decays with T = 80 usee. During that time, data are taken by Thomson scattering, laser interferometry, magnetic probes, and spectroscopy, and stored by an online computer.-viii-The results indicate that the plasma is incompletely ionized, cold (Te < 5 eV) and in contact with the wall at small major radius. The bicusp configuration depends on a combination of toroidal and poloidal fields forming the magnetic piston which compresses the plasma. This occurs at the outer radius where the field is primarily poloidal, but fails at the inner wall as the toroidal field pene trates rapidly throughout the plasma. This thesis describes the design, construction and operation of Tormac IV-c, and reports on the results, with emphasis on describing the behavior of the density compres sion and field penetration.-ix-PREFACE This thesis describes the construction, operation, and results of Tormac IV-c, a plasma confinement device built by Hartin J. Greenwald and myself at the Lawrence Berkeley Laboratory. His thesis, "Temperature Measurements in the Tormac IV-c plasma" (LBL-8166), and this foru complementary volumes in emphasis, although each is an independently complete description of the apparatus and data. I have organized this paper in five chapters, each of which could be read separately. The introduction and the summary section of the data chapter describe the results, and the rest contains details. The work on data acquisition in Chapter 5 is useful to any experiment using computers, and is not restricted to plasma experiments per se. This experiment is an integral part of the Toraiac Project led by Morton A. Levine, which resides in the Magnetic Fusion Energy Program at LBL led by Hulf Kunkel. It was done with the collaboration and support of a large number of physicists and technicians. Participants over the last four years include (in approximate seniority):

The purpose of this paper is explore effective methodologies for addressing the interlinked objec... more The purpose of this paper is explore effective methodologies for addressing the interlinked objectives of the UN 2030 Sustainable Development Goals (SDGs) in impoverished rural areas across Africa, South Asia and indigenous Latin America, with a special focus on governance and gender. The paper cites examples from the programs of one NGO, The Hunger Project.

Plasma Physics, 1980

Gaussian He II 4686-A spectral lines having full widths at half maximum of over 2 A have been obs... more Gaussian He II 4686-A spectral lines having full widths at half maximum of over 2 A have been observed in the Tormac plasmas. Interpretation of these widths as due to Doppler broadening would give ion temperatures of more than 100 eV, in contradiction with other diagnostics. Indications are that these widths are not simply explained by either Doppler broadening or Stark broadening due to interparticle fields. Some evidence exists of nonthermal turbulent conditions, which could broaden the lines by the Stark effect, if there exist large enough electric fields, or by the Doppler effect, if there is appreciable mass motion.

Plasma Physics, 1980

ABSTRACT

Review of Scientific Instruments, 1985

The various operating modes of TFTR require the use of a sophisticated system of magnetic diagnos... more The various operating modes of TFTR require the use of a sophisticated system of magnetic diagnostics integrated with a feedback control system. This system has successfully controlled the plasma current and position over a range of major and minor radii, during strong compression, and will soon be used during intense neutral beam heating. Current and position values are held constant to within 2 kA and 1 cm. A wide variety of preoperational field measurements were required to determine proper compensation for dynamic stray fields due to eddy currents. Data from plasma profile diagnostics, such as bolometer arrays, Thomson scattering, soft x-ray diode array, and the scanning radiometer, have been compared to the absolute position deduced from magnetics. In addition to control functions, magnetic diagnostics on TFTR provide data on plasma current asymmetry, βθ, MHD fluctuations, loop voltage, and flux consumption. This paper will discuss the mechanical and electronic design constraints, as well as the analytic and calibration techniques required.