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ECH mirror interface tank for 110 GHz, 1 MW gyrotron

Description: A 1 MW, 110 GHz gyrotron is to be installed at General Optical Atomics in 1995. A Mirror Optics Unit (MOU) has been Unit designed and built to connect to the existing 110 GHz transmission line system. The unit reduces and directs a 145 mm diameter beam from the gyrotron to a 19 mm diameter beam which is then injected into a 31.8 mm diameter corrugated waveguide of the transmission line system. The unit operates under vacuum and is able to absorb beam spray from the gyrotron. The tank also contains various diagnostics equipment to protect the gyrotron and to determine the amount of energy loss in the tank, and at the window of the gyrotron output. This paper discusses further the design parameters, assembly and installation of the unit in the transmission line system.
Date: October 1, 1995
Creator: O`Neil, R.C.; Callis, R.W.; Cary, W.P.; Doane, J.L.; Gallix, R.; Hodapp, T.R. et al.
Partner: UNT Libraries Government Documents Department

Engineering design of the ITER RF systems

Description: Parallel conceptual design efforts for auxiliary heating systems on ITER are being carried out in both the electron cyclotron range of frequencies (ECRF) and ion cyclotron range of frequencies (ICRF). These systems are required to deliver a minimum of 50 MW of CW power to the plasma for the primary purpose of heating and the secondary purpose of current drive. Current designs of the two systems are presented and the primary design issues are discussed.
Date: December 31, 1994
Creator: Makowski, M.; Bosia, G.; Nagashima, T. & Remsen, D.
Partner: UNT Libraries Government Documents Department

Electron cyclotron heating and current drive approach for low-temperature startup plasmas using O-X-EBW mode conversion

Description: A mechanism for heating and driving currents in very overdense plasmas is considered based on a double-mode conversion: Ordinary mode to Extraordinary mode to electron Bernstein wave. The possibility of using this mechanism for plasma buildup and current ramp in the National Spherical Torus Experiment is investigated.
Date: June 1, 1997
Creator: Batchelor, D.B. & Bigelow, T.S.
Partner: UNT Libraries Government Documents Department

The 110 GHz ECH installation on DII-D: Status and initial experimental results

Description: Two 110 GHz gyrotrons with nominal output power of 1 MW each have been installed on the DIII-D tokamak. The gyrotrons, produced by Gycom and Communications and Power Industries, are connected to the tokamak by windowless evacuated transmission lines using circular corrugated waveguide carrying the HE{sub 11} mode. Initial experiments with the Gycom gyrotron showed good central heating efficiency at the second harmonic resonance with record central electron temperatures for DIII-D in excess of 10 keV achieved. The beam spot in the DIII-D vacuum vessel was well focused, with a diameter of approximately 8 cm, and it could be steered poloidally by a remotely adjustable mirror. The injection was at 19 deg off-perpendicular for current drive and the beams could be modulated for studies of energy transport and power deposition. The system will be described and the initial physics results will be presented. A third gyrotron, also at 110 GHz, will be installed later this year. Progress with this CPI tube will be discussed and future plans for the ECH installation and physics experiments using it will be presented.
Date: May 1997
Creator: Lohr, J.; Callis, R.W. & O`Neill, R.C.
Partner: UNT Libraries Government Documents Department

Initial results from the multi-megawatt 110 GHz ECH system for the DIII-D tokamak

Description: The first of three MW-level 110 GHz gyrotrons was operated into the DIII-D tokamak in late 1996. Two additional units will be commissioned during 1997. Each gyrotron is connected to the tokamak by a low loss, windowless, evacuated transmission line using circular corrugated waveguide carrying the HE{sub 11} mode. The microwave beam spot is well focused with a spot size of approximately 6 cm and can be steered poloidally from the center to the outer edge of the plasma. The initial operation with about 0.5 MW delivered to a low density plasma for 0.5 s showed good central electron heating, with peak temperature in excess of 10 keV. The injection was 19{degree} off perpendicular for current drive.
Date: April 1, 1997
Creator: Callis, R.W.; Lohr, J.; O`Neill, R.C.; Ponce, D.; Luce, T.C.; Prater, R. et al.
Partner: UNT Libraries Government Documents Department

Dynamics of electronegative plasmas for materials processing. Final report

Description: The purpose of this project is to study the equilibrium particle and energy balance and the heating mechanisms in electronegative r.f. discharges. Particular attention is given to the formation of non-Maxwellian electron distributions and their effect on the macroscopic parameters. The research includes theory, particle-in-cell simulation, and experimental investigations. The sheath heating theory and the simulation results developed for electropositive plasmas are used to guide the investigations. The investigation was centered on, but is not limited to, the study of oxygen feedstock gas in capacitively and inductively coupled r.f. discharges. 15 refs.
Date: December 31, 1996
Creator: Lichtenberg, A.J. & Lieberman, M.A.
Partner: UNT Libraries Government Documents Department

Progress on radio frequency auxiliary heating system designs in ITER

Description: ITER will require over 100 MW of auxiliary power for heating, on- and off-axis current drive, accessing the H-mode, and plasma shut-down. The Electron Cyclotron Range of Frequencies (ECRF) and Ion Cyclotron Range of Frequencies (ICRF) are two forms of Radio Frequency (RF) auxiliary power being developed for these applications. Design concepts for both the ECRF and ICRF systems are presented, key features and critical design issues are discussed, and projected performances outlined.
Date: September 1, 1996
Creator: Makowski, M.; Bosia, G. & Elio, F.
Partner: UNT Libraries Government Documents Department

The DIII-D ECH multiple gyrotron control system

Description: DIII-D`s ECH upgrade with 1 MW, 110 GHz gyrotrons is ongoing, and with it, an upgrade of the control system. The ECH Multiple Gyrotron Control System uses software distributed among networked computers, interfaced to a programmable logic controller (PLC), the timing and pulse system, power supplies, vacuum and wave guide controls, and instrumentation. During DIII-D operations, the system will allow a chief and a co-operator to control and monitor a number of gyrotrons from different manufacturers. The software, written using LabVIEW, allows for remote and multiple operator control. Thus any supported computer can become a control station and multiple projects can be simultaneously accommodated. Each operator can be given access to the controls of all gyrotrons or to a subset of controls. Status information is also remotely available. The use of a PLC simplifies the hardware and software design. It reduces interlock and control circuitry, includes monitoring for slow analog signals, and allows one software driver to efficiently interface to a number of systems. In addition, the interlock logic can be easily changed and control points can be forced as needed. The pulse system is designed around arbitrary function generators. Various modulation schemes can be accommodated, including real-time control of the modulation. This discussion will include the hardware and software design of the control system and its current implementation.
Date: November 1, 1997
Creator: Ponce, D.; Lohr, J.; Tooker, J.F.; Cary, W.P. & Harris, T.E.
Partner: UNT Libraries Government Documents Department

A design study for the ECH launcher for ITER

Description: The Design Description Document for ITER calls for 50 MW of electron cyclotron power at a frequency of 170 GHz, upgradeable to 100 MW. This power is intended to heat the plasma from Ohmic temperatures to ignition, in concert with power from some combination of neutral injection and/or ICRF heating. The second major application of ECH power is current drive. In the advanced steady-state scenarios, the total current is 12 to 16 MA, of which 75% is driven by bootstrap effects. The current drive requirement is 2 to 3 MA at a relative minor radius of 0.7, plus a small current near the center of the discharge. ECH power is also used for plasma initiation and startup, using a separate ECH system of two fixed frequencies between 90 to 140 GHz and total power to 6 MW. Suppression or control of MHD instabilities like neoclassical tearing modes, sawteeth, ELMs, and locked modes are also important objectives for the ECH systems. However, the launching and power characteristics of the ECH for these applications is highly specialized. The ability to modulate at high frequency (at least several tens of kHz), the ability to redirect the beams with precision at relatively high speed, and the requirement that the stabilization be carried out at the same time as the bulk heating and current drive imply that separate and specialized ECH systems are needed for the stabilization activities. For example, for stabilization of neoclassical tearing modes current must be driven inside the islands near the q = 2 surface. If this is done near the outboard mid plane, a system with optimized frequency might be much more effective than what could be done with the main 170 GHz system. This paper does not treat the launchers for the stabilization systems.
Date: April 1, 1997
Creator: Prater, R.; Grunloh, H.J.; Moeller, C.P.; Doane, J.L.; Olstad, R.A.; Makowski, M.A. et al.
Partner: UNT Libraries Government Documents Department

Polarization Measurements During Electron Cyclotron Heating Experiments in the DIII-D Tokamak

Description: The polarization of the launched electron cyclotron wave has been optimized for coupling to the X-mode by adjusting the inclination of grooved mirrors located in two consecutive mitre bends of the waveguide. The unwanted O-mode component of the launched beam can be positively identified by the difference in the power deposition profiles between X-mode and O-mode. The optimal polarization for X-mode launch is in good agreement with theoretical expectations.
Date: July 1, 1999
Creator: Petty, C.C.; Luce, T.C.; Austin, M.E.; Ikezi, H.; Lohr, J. & Prater, R.
Partner: UNT Libraries Government Documents Department

The 8.4 MW Modulator/Regulator Power Systems for the Electron Cyclotron Heating Facility Upgrade at DIII-D

Description: Over the next three years the DIII-D National Fusion Facility at General Atomics will upgrade its electron cyclotron heating (ECH) capability from the present 3 MW at 110 GHz to 10 MW of injected microwave power. There will be ten gyrotron tubes supplied by five 8.4 MW modulator/regulator (M/R) power systems. The project has gained considerable leverage from the acquisition of surplus hardware from the MFTF program that was conducted at LLNL in the early 1980s. One of these systems had been refurbished and converted for use as an ECH power supply earlier. The experience gained and the lessons learned from operating that system have proved valuable in guiding the engineering of the new systems. This paper provides an overview of the power system design and a report on the present status of the project.
Date: December 1999
Creator: Pronko, S. G. E. & Baggest, D. S.
Partner: UNT Libraries Government Documents Department

Summary of the experimental session EC-10 workshop

Description: This review summarizes a subset of the EC-10 presentations which had been assigned by the organizing committee identification tags beginning with EX. There were fourteen presentations in this group, seven oral and seven posters. Included among the oral presentations were two invited talks. With the exception of the review of plans for electron cyclotron waves in ITER, there were all reports of physics experiments or operational experience as opposed to accounts of hardware development.
Date: June 1, 1997
Creator: Lohr, J.
Partner: UNT Libraries Government Documents Department

T25 ITER ECH window development 110 GHz ECH distributed window development. Final report, May 1, 1994--December 31, 1995

Description: Electron Cyclotron Heating (ECH) is one of the major candidates for Heating and Current Drive on ITER. ECH is extremely attractive from a reactor engineering point of view, offering compact launch structures, high injected power density, and a simple interface with the shield/blanket. Economic deployment of ECH for ITER requires MW unit microwave sources (gyrotrons). The present technology limitation is the availability of suitable low loss output windows. These are needed for the torus as well as the tube. The torus window, in particular, is a demanding application as it also serves as a tritium barrier. Several distinct window concepts are under development by the various Parties. This report summarizes the efforts to make and test a {open_quotes}distributed{close_quotes} window suitable for 1 MW cw operation at 110 GHz. A companion report (Final Report on Task 245+) describes the efforts to make a distributed window suitable for 1 MW cw operation at 170 GHz, the main frequency of interest to ITER. General Atomics (GA) fabricated a 4 in. x 4 in. 110 GHz distributed window which was delivered in September 1995 to Communications and Power Industries (CPI). Hot tests at CPI confirmed the power handling capability of the window. Tests were conducted with a reduced beam size at 200 kW with 0.7 s pulses without any arcing or excessive window temperatures. The power density and pulse length were equivalent to that in a full size 1.2 MW CW beam with a peak-to-average power ratio of 2.7. This window was assembled using a gold braze material to bond the sapphire strips to the niobium frame. The braze was successful except for small leaks at two locations, and re-braze efforts were unsuccessful.
Date: January 1, 1998
Creator: Olstad, R.A.; Moeller, C.P. & Grunloh, H.J.
Partner: UNT Libraries Government Documents Department

Detailed Measurements of ECCD Efficiency on DIII-D for Comparison with Theory

Description: Recent experiments on the DIII-D tokamak have focused on determining the effect of trapped particles on the electron cyclotron current drive (ECCD) efficiency. Localized power deposition and current drive were observed for both L-mode and ELMing H-mode plasmas. The ECCD efficiency was measured for both co and counter injection. Overall, the experimental ECCD efficiency was in good agreement with the CQL3D Fokker-Planck model over a wide range of injection angles and plasma parameters.
Date: May 1, 2002
Creator: Petty, C.C.; Prater, R.; Lohr, J.; Luce, T.C.; Ellis,III, R.A., Harvey, R.W.; Kinsey, J.E. et al.
Partner: UNT Libraries Government Documents Department

Extrapolation of the Dutch 1 MW tunable free electron maser to a 5 MW ECRH source

Description: A Free Electron Maser (FEM) is now under construction at the FOM Institute (Rijnhuizen) Netherlands with the goal of producing 1 MW long pulse to CW microwave output in the range 130 GHz to 250 GHz with wall plug efficiencies of 50% (Verhoeven, et al EC-9 Conference). An extrapolated version of this device is proposed which by scaling up the beam current, would produce microwave power levels of up to 5 MW CW in order to reduce the cost per watt and increase the power per module, thus providing the fusion community with a practical ECRH source.
Date: April 1, 1995
Creator: Caplan, M.; Nelson, S.; Kamin, G.; Antonsen, T. Levush, B.; Urbanus, W. & Tulupov, A.
Partner: UNT Libraries Government Documents Department

Recent developments on the high power ECH installation at the DIII-D tokamak

Description: The 110 GHz gyrotron installation on the DIII-D tokamak has been upgraded to three tubes in the megawatt class with plans for further upgrades. The latest addition uses a diamond output window. The report describes the installation, plans, and experimental results to date.
Date: September 1, 1998
Creator: Lohr, J.; Ponce, D.; Callis, R.W.; Doane, J.L.; Ikezi, H. & Moeller, C.P.
Partner: UNT Libraries Government Documents Department

Evaluation of wave dispersion, mode-conversion, and damping for ECRH with exact relativistic corrections

Description: The complex dispersion functions of Eq. (3) in Ref. 1 have recently been computed accurately and reliably over their entire range of parameters, without recourse to the usual slightly-relativistic approximation, which may have difficulty for oblique incidence. In the future, the local dispersion properties of ECRF waves will be reevaluated for parameters of interest to ECRF conditions in several existing and proposed fusion experiments, with particular emphasis on the damping and mode-conversion of both ordinary and extraordinary waves to electrostatic waves near the upper hybrid and cyclotron frequencies.
Date: December 31, 1991
Creator: Smithe, D.N. & Colestock, P.L.
Partner: UNT Libraries Government Documents Department

NRL quasioptical gyrotron program. Final report, November 1, 1991--October 31, 1993

Description: The quasioptical gyrotron (QOG) has been under development as a high power, tunable source for tokamak plasma heating applications. Given the critical importance of source efficiency for large-scale ESCH applications, understanding the causes of the low QOG efficiency and finding ways of improving it became a top priority for the current NRL program. The importance of the present work is that is represents new insight into the factors controlling the efficiency of quasioptical gyrotrons. The author has demonstrated that the technique of mode priming provides a method for improving efficiency via enhanced mode detuning and leads to more stable single-mode operation of highly over-moded resonators. The latter feature is an important consideration for output coupler and rf transmission system optimization and can make the QOG less sensitive to external influences such as window reflections. He has shown that a prebunching resonator is readily implemented in the quasioptical configuration. It is relatively free of the problems of spurious modes and cross-talk which plague over-moded prebunching cavities in conventional gyrotrons. The observation of almost 18% efficiency represents a doubling of the previous best single-mode results. Further improvements are expected from the optimization of start-up conditions and the study of the effects of the second harmonic interaction.
Date: June 1, 1997
Creator: Fliflet, A.
Partner: UNT Libraries Government Documents Department

Upgrade of the DIII-D RF systems

Description: The DIII-D Advanced Tokamak Program requires the ability to modify the current density profile for extended time periods in order to achieve the improved plasma conditions now achieved with transient means. To support this requirement DIII-D has just completed a major addition to its ion cyclotron range of frequency (ICRF) systems. This upgrade project added two new fast wave current drive (FWCD) systems, with each system consisting of a 2 MW, 30 to 120 MHz transmitter, an all ceramic insulated transmission line, and water-cooled four-strap antenna. With this addition of 4 MW of FWCD power to the original 2 MW, 30 to 60 MHz capability, experiments can be performed with centrally localized current drive enhancement. For off-axis current modification, plans are in place to add 110 GHz electron cyclotron heating (ECH) power to DIII-D. Initially, 3 MW of power will be available with plans to increase the power to 6 MW and to 10 MW.
Date: October 1, 1995
Creator: Callis, R. W.; Cary, W. P. & O`Neill, R. C.
Partner: UNT Libraries Government Documents Department

Experimental tests of transport models using modulated ECH

Description: Both the dynamic and equilibrium thermal responses of an L-mode plasma to repetitive ECH heat pulses were measured and compared to predictions from several thermal transport models. While no model consistently agreed with all observations, the GLF23 model was most consistent with the perturbated electron and ion temperature responses for one of the cases studied which may indicate a key role played by electron modes in the core of these discharges. Generally, the IIF and MM models performed well for the perturbed electron response while the GLF23 and IFS/PPPL models agreed with the perturbed ion response for all three cases studied. No single model agreed well with the equilibrium temperature profiles measured.
Date: December 1998
Creator: DeBoo, J. C.; Kinsey, J. E. & Bravenec, R.
Partner: UNT Libraries Government Documents Department

Modeling of electron cyclotron current drive experiments on DIII-D

Description: Electron Cyclotron Current Drive (ECCD) is considered a leading candidate for current profile control in Advanced Tokamak (AT) operation. Localized ECCD has been clearly demonstrated in recent proof-of-principle experiments on DIII-D. The measured ECCD efficiency near the magnetic axis agrees well with standard theoretical predictions. However, for off-axis current drive the normalized experimental efficiency does not decrease with minor radius as expected from the standard theory; the observed reduction of ECCD efficiency due to trapped electron effects in the off-axis cases is smaller than theoretical predictions. The standard approach of modeling ECCD in tokamaks has been based on the bounce-average calculations, which assume the bounce frequency is much larger than the effective collision frequency for trapped electrons at all energies. The assumption is clearly invalid at low energies. Finite collisionality will effectively reduce the trapped electron fraction, hence, increase current drive efficiency. Here, a velocity-space connection formula is proposed to estimate the collisionality effect on electron cyclotron current drive efficiency. The collisionality correction gives modest improvement in agreement between theoretical and recent DIII-D experimental results.
Date: May 1, 1999
Creator: Lin-Liu, Y.R.; Chan, V.S.; Luce, T.C.; Prater, R.; Sauter, O. & Harvey, R.W.
Partner: UNT Libraries Government Documents Department

Distinguishing Gyro-Bohm and Bohm scaling in stellarators

Description: With statistical analysis of global data from one, two and four stellarators, it is possible to draw limited conclusions whether Gyro- Bohm or Bohm scaling prevails. Either scaling may be favored, depending on whether corrections are included for possible {Beta} and v{sub *} corrections and whether all data are taken, or selected cases with low collisionality, or low net toroidal current, or with ECH heating applied, and so on. Monte Carlo-like simulations are used to test reliability of inferences about power-law scaling exponents made from data having substantial statistical variance and collinearity of control parameters. These show that for reliable conclusions, statistical studies should be augmented; more directed experimental studies are needed, with well controlled discharges and radially resolved data - such as those already begun on ATF and W7-AS.
Date: May 5, 1993
Creator: Dory, R.A.; Murakami, M. & Stroth, U.
Partner: UNT Libraries Government Documents Department