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Microstability Of Tmx U During Initial Thermal Barrier Operation
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Book Synopsis Microstability of TMX-U During Initial Thermal Barrier Operation by :
Download or read book Microstability of TMX-U During Initial Thermal Barrier Operation written by and published by . This book was released on 1984 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: During the initial thermal barrier experiments on the Tandem Mirror Experiment-Upgrade (TMX-U), we successfully demonstrated the principle of improved axial tandem mirror confinement achieved by establishment of both the thermal barrier and the ion confining potential peak. During this operation, we created both hot (100-keV) mirror-confined electron and hot (8-keV) mirror-confined ion populations in the end cells. In certain parameter ranges, we observed these species to be weakly unstable to various microinstabilities, but we did not observe clear evidence for an absolute limit to confinement.
Book Synopsis Initial TMX-U Thermal-barrier Experiments by :
Download or read book Initial TMX-U Thermal-barrier Experiments written by and published by . This book was released on 1983 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper describes results from the initial thermal barrier experiments in the Tandem Mirror Experiment-Upgrade (TMX-U). Strong end plugging has been produced using a combination of ECRH gyrotrons with sloshing ion beam injection. Plugging has been achieved with a central cell higher than that of the end plugs. In these low-density central cell experiments (7 x 1011 cm−3) the axial losses (tau/sub parallel to/ = 20 to 80 ms) are smaller than the radial losses (tau/sub perpendicular to/ = 4 to 8 ms). Although no direct measurements are yet available to determine if a thermal barrier potential dip is generated, these experiments support many theoretical features of the thermal barrier concept.
Book Synopsis Recent Experimental Progress in the TMX-U Thermal Barrier Tandem Mirror Experiment by :
Download or read book Recent Experimental Progress in the TMX-U Thermal Barrier Tandem Mirror Experiment written by and published by . This book was released on 1984 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent experiments on the TMX-U thermal barrier device at LLNL have achieved the end plugging of axial ion losses up to a central cell density of n/sub c/ = 2 x 1012 cm. During these tests, the axial potential profile characteristic of a thermal barrier has been measured experimentally, indicating an ion-confining potential greater than 1.5 kV and a potential depression of 0.45 kV in the barrier region. The average beta of hot electrons in the thermal barrier has been increased to 15% and appears limited only by classical scattering and ECRH pulse duration. Furthermore, deuterium ions in the central cell have been heated with ICRF to an average energy of 1.5 keV, with a heating efficiency of 40%. During strong end plugging, the axial ion confinement time reached 50 to 100 ms while the nonambipolar radial ion confinement time was 5 to 15 ms - independent of end plugging. Radial ion confinement time exceeding 100 ms has been attained on shots without end plugging. Plates, floated electrically on the end walls, have increased the radial ion confinement time by a factor of 1.8. Further improvement in the central cell density during end plugging can be expected by increasing the ICRF, improving the central cell vacuum conditions and beam heating efficiency, and increasing the radial extent of the potential control plates on the end walls.
Book Synopsis Assessment of Hot-electron Microstability in the Initial TMX-U Experiments by :
Download or read book Assessment of Hot-electron Microstability in the Initial TMX-U Experiments written by and published by . This book was released on 1983 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: During the initial TMX-U experiments, we investigated the sloshing-ion and hot-electron distributions. We require these components to ultimately construct a thermal barrier for improved tandem mirror confinement. The plasma parameters we achieved approach values required for thermal barrier operation but have been limited by the power available. This report is concerned with the stability of the hot electron distribution formed. Nonthermal microwave emissions near the electron-cyclotron frequency f/sub ce/ of the minimum end-cell magnetic field indicate the presence of electron microinstabilities, which we have tentatively identified by their frequencies. We observed the upper-hybrid loss-cone mode (f/f/sub ce/ approx. 1.1) during high density operation with a relatively small fraction of hot electrons. At lower density operation with a higher hot electron fraction, we observed emissions consistent with the whistler instability. During emission bursts at 12.5 GHz (f/f/sub ce/ approx. 0.9) we observed a rapid rise in the high frequency thermal emissions, indicating a spreading of the distribution. Some of the more violent bursts are correlated with enhanced end loss currents.
Book Synopsis Thermal Barrier Confinement Experiments in the TMX-U Tandem Mirror by :
Download or read book Thermal Barrier Confinement Experiments in the TMX-U Tandem Mirror written by and published by . This book was released on 1984 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In our recent experiments on the TMX-U thermal-barrier device, we achieved the end plugging of axial ion losses up to a central cell density of n/sub c/ = 6 x 1012 cm−3. During lower density experiments, we measured the axial potential profile characteristic of a thermal barrier and found an ion-confining potential greater than 1.5 kV and a potential depression of 0.45 kV in the barrier region. The average beta of hot end plug electrons has reached 15% and of hot central cell ions has reached 6%. In addition, we heated deuterium ions in the central cell with ICRF to an average perpendicular energy of 2 keV. During strong end plugging at low density (7 x 1011 cm−3), the axial ion confinement time tau/sub parallel/ reached 50 to 100 ms while the nonambipolar radial ion confinement time tau/sub perpendicular/ was 14 ms - independent of end plugging. Electrically floating end walls increased the radial ion confinement time by a factor of 1.8. At higher densities and lower potentials, tau/sub parallel/ was 6 to 12 ms and tau/sub perpendicular/ exceeded 100 ms.
Book Synopsis TMX-U Tandem-Mirror Thermal-barrier Experiments by :
Download or read book TMX-U Tandem-Mirror Thermal-barrier Experiments written by and published by . This book was released on 1986 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Thermal-barrier experiments have been carried out in the Tandem Mirror Experiment-Upgrade (TMX-U). Measurements of nonambipolar and ambipolar radial transport show that these transport processes, as well as end losses, can be controlled at modest densities and durations. Central-cell heating methods using ion-cyclotron heating (ICH) and neutral-beam injection have been demonstrated. Potential measurements with recently developed methods indicate that deep thermal barriers can be established.
Book Synopsis Thermal Barrier Confinement Experiments in TMX-U Tandem Mirror. Revision 1 by :
Download or read book Thermal Barrier Confinement Experiments in TMX-U Tandem Mirror. Revision 1 written by and published by . This book was released on 1984 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In our recent experiments on the TMX-U thermal-barrier device, we achieved the end plugging of axial ion losses up to a central cell density of n/sub c/ = 6 x 1012 cm−3. During lower density experiments, we measured the axial potential profile characteristic of a thermal barrier and found an ion-confining potential greater than 1.5 kV and a potential depression of 0.45 kV in the barrier region. The average beta of hot end plug electrons has reached 15% and of hot central cell ions has reached 6%. In addition, we heated deuterium ions in the central cell with ICRF to an average perpendicular energy of 2 keV. During strong end plugging at low density (7 x 1011 cm−3), the axial ion confinement time tau/sub parallel to/ reached 50 to 100 ms while the nonambiopolar radial ion confinement time tau/sub perpendicular to/ was 14 ms - independent of end plugging. Electrically floating end walls doubled the radial ion confinement time. At higher densities and lower potentials, tau/sub parallel to/ was 6 to 12 ms and tau/sub perpendicular to/ exceeded 100 ms.
Book Synopsis TMX-Upgrade (TMX-U) Operation in the Sloshing-ion Mode by :
Download or read book TMX-Upgrade (TMX-U) Operation in the Sloshing-ion Mode written by and published by . This book was released on 1982 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This report summarizes initial results from TMX-U carried out from June through August 1982. In these successful experiments we operated TMX-U in the sloshing-ion mode. We generated sloshing ions, measured improved energy confinement, and observed improved microstability compared to TMX. The experiments operated about as we expected and we are pleased with the results. During this period many additional achievements were also recorded. The magnetically confined sloshing ions constitute one of the two ingredients needed to build a thermal barrier. The second ingredient consists of magnetically confined electrons, which will be studied in the next series of TMX-U experiments using microwave heating of the electrons. Later, the hot ions and electrons will be combined to form thermal barriers.
Book Synopsis TMX-U (Tandem Mirror Experiment-Upgrade) Tandem-mirror Thermal-barrier Experiments by :
Download or read book TMX-U (Tandem Mirror Experiment-Upgrade) Tandem-mirror Thermal-barrier Experiments written by and published by . This book was released on 1986 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Thermal-barrier experiments have been carried out in the Tandem Mirror Experiment-Upgrade (TMX-U). Measurements of nonambipolar and ambipolar radial transport show that these transport processes, as well as end losses, can be controlled at modest densities and durations. Central-cell heating methods using ion-cyclotron heating (ICH) and neutral-beam injection have been demonstrated. Potential mesurements with recently developed methods indicate that deep thermal barriers can be established.
Book Synopsis TMX Tandem-mirror Experiments and Thermal-barrier Theoretical Studies by :
Download or read book TMX Tandem-mirror Experiments and Thermal-barrier Theoretical Studies written by and published by . This book was released on 1982 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper describes recent analysis of energy confinement in the Tandem Mirror Experiment (TMX). TMX data also indicates that warm plasma limits the amplitude of the anisotropy driven Alfven ion cyclotron (AIC) mode. Theoretical calculations show strong AIC stabilization with off-normal beam injection as planned in TMX-U and MFTF-B. This paper reports results of theoretical analysis of hot electrons in thermal barriers including electron heating calculations by Monte Carlo and Fokker-Planck codes and analysis of hot electron MHD and microinstability. Initial results from the TMX-U experiment are presented which show the presence of sloshing ions.
Download or read book TMX-U Experimental Results written by and published by . This book was released on 1983 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper describes results from the Tandem Mirror Experiment-Upgrade (TMX-U). Mirror-confined electrons with 30 to 70 keV mean energy densities of 0.5 to 2.0 x 1012 cm−3 and average betas of 3 to 5% are produced using electron-cyclotron resonant heating (ECRH). These results are consistent with an electron Fokker-Planck code. Improved ion-cyclotron microstability is observed using neutral beam injection at 47° to the magnetic axis, rather than at 90° as in the previous experiment, TMX. Strong end plugging has been produced using a combination of ECRH gyrotrons with sloshing-ion beam injection. In these low-density central cell experiments (3 x 1011 cm−3) the axial losses (tau/sub parallel/ = 20 to 80 ms) are smaller than the nonambipolar radial losses (tau/sub perpendicular/ = 4 to 8 ms). Plugging has been achieved with a central cell density double that of the end plugs. Although no direct measurements are yet available to determine if a thermal barrier potential dip is generated, these experiments support many theoretical features of the thermal barrier concept.
Book Synopsis Microstability of the TMX Tandem Mirror Experiments by :
Download or read book Microstability of the TMX Tandem Mirror Experiments written by and published by . This book was released on 1987 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In the tandem mirror device, an efficient source of warm ions, the central cell, is available for stabilization of ion loss-cone instabilities. These instabilities previously limited ion confinement in single-cell mirror experiments. In the simple tandem mirror device, TMX, the drift cyclotron loss-cone (DCLC) mode was stabilized by plasma flow from the central cell into the end cell. However, to enhance the central-cell confinement and provide MHD stability, neutral beams were injected perpendicular to the magnetic field, which resulted in the excitation in the end cell of the Alfven ion-cyclotron (AIC) instability driven by plasma pressure and velocity distribution anisotropy. In the thermal-barrier experiment, TMX-U, the end-cell beams were injected at a 45° angle to the magnetic field to produce a sloshing-ion distribution, which is required to form the thermal barrier and the plugging potential. Ion distributions created by oblique injection were stable to the AIC mode and to the midplane (minimum magnetic field location) DCLC mode. However, an ion loss-cone instability remained at an axial location just outside the outboard peak of the sloshing-ion axial density profile, which is the density peak closest to the end wall. This mode can enhance the sloshing-ion loss rate, particularly at the lower levels of electron-cyclotron resonance heating (ECRH) used to form the thermal barrier. The stability to ion-cyclotron modes is critical to the performance of tandem mirrors and to designs for a mirror-based, high-fluence neutron source.
Book Synopsis Initial Assessment of the MHD Stability of TMX-U. by :
Download or read book Initial Assessment of the MHD Stability of TMX-U. written by and published by . This book was released on 1983 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In its operation to date TMX-U has reached values of beta which, for all except the hot electron beta, are close to the proposal values and has not encountered MHD stability problems. The hot electron beta values are presently limited by gyrotron output power and pulse length as well as ion confinement time. Further exploration of stability awaits full thermal barrier operation.
Book Synopsis Tandem Mirror Experiment Upgrade (TMX-U) Overview-recent Events by :
Download or read book Tandem Mirror Experiment Upgrade (TMX-U) Overview-recent Events written by and published by . This book was released on 1985 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Since its construction and commissioning was completed in the winter of 1981, the Tandem Mirror Experiment Upgrade (TMX-U) has been conducting tandem mirror thermal barrier experiments. The work, following the fall of 1983 when strong plugging with thermal barriers was achieved, has been directed toward controlling radial transport and forming thermal barriers with high density and Beta. This paper describes the overall engineering component of these efforts. Major changes to the machine have included vacuum improvements, changes to the Electron and Ion Cyclotron Resonance Heating systems (ECRH and ICRH), and the installation of a Plasma Potential Control system (PPC) for radial transport reduction. TMX-U operates an extensive diagnostics system that acquires data from 21 types of diagnostic instruments with more than 600 channels, in addition to 246 machine parameters. The changes and additions will be presented. The closing section of this paper will describe the initial study work for a proposed TMX-U octupole configured machine.
Book Synopsis Use of ICRH for Startup and Initial Heating of the TMX-U Central Cell by :
Download or read book Use of ICRH for Startup and Initial Heating of the TMX-U Central Cell written by and published by . This book was released on 1982 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Ion cyclotron resonance heating (ICRH) was evaluated and it was found to be satisfactory for use in establishing the conditions necessary to form a thermal barrier in TMX-upgrade (TMX-U). We discuss the constraints that must be satisfied in order to maintain a plasma, and outline a complete startup scenario that ends with the plasma at design parameters. The detailed discussions in this report concentrate on those parts of startup where ICRH is necessary. The ability of ICRH to couple power into a plasma at the fundamental ion cyclotron resonance, w/sub ci/, is determined from experiments with a half-turn loop antenna in the Phaedrus tandem mirror central cell. From these experiments, we get the empirical scaling that shows power deposited in the plasma is proportional to the plasma density.
Book Synopsis Microstability of the Sloshing Ions in TMX-U. by : Leon Val Berzins
Download or read book Microstability of the Sloshing Ions in TMX-U. written by Leon Val Berzins and published by . This book was released on 1988 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book TMX-U Diagnostic System written by and published by . This book was released on 1983 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Using data from the TMX-U diagnostic system, the production of sloshing ions has already been verified and the formation of electron thermal barriers is presently being investigated on the Tandem Mirror Experiment-Upgrade (TMX-U) at Lawrence Livermore National Laboratory. The TMX-U diagnostics are made up of the earlier TMX complement of diagnostics that determine confinement, microstability, and low-frequency stability, plus diagnostic instrumentation that measures electron parameters associated with mirror-confined electrons. This paper describes the three subsystems within the TMX-U diagnostic system: (1) the diagnostic facility (shot leader console, data cable system, and diagnostic timing system); (2) the individual diagnostic instruments that measure plasma and machine parameters; and (3) the data-acquisition and -analysis computer.
