Search

Characterization of a hydrated uranyl fluoride (UO2F2·nH2O) deposit in a 17 ft long, 24 in OD process pipe at the former Oak Ridge Gaseous Diffusion Plant was successfully performed using 252Cf-source-correlated time-of-flight (TOF) transmission measurements. These measurements of neutrons and gamma rays through the pipe from an external 252Cf fission source were used to measure the deposit profile and its distribution along the pipe, the hydration (or H/U), and the total uranium mass. The measurements were performed with a source in an ionization chamber on one side of the pipe and detectors on the other. Scanning the pipe vertically and horizontally produced a spatial and time-dependent radiograph of the deposit in which transmitted gamma rays and neutrons were separated in time. The cross-correlation function between the source and the detector was measured with the Nuclear Weapons Identification System. After correcting for pipe effects, the deposit thickness was determined from the transmitted neutrons and H/U from the gamma rays. Results were consistent with a later intrusive observation of the shape and the color of the deposit; i.e., the deposit was annular and was on the top of the pipe at some locations, demonstrating the usefulness of this method for deposit characterization.

A novel method for measuring dead time in nuclear pulse processing circuitry has been developed using the autocorrelation measurement capability of the Nuclear Weapons Inspection System (NWIS). Initially developed for active neutron interrogation of nuclear weapons and other fissile assemblies, NWIS employs a custom gallium arsenide application specific integrated circuit and a new signature analysis software package to simultaneously acquire and display the autocorrelation and cross-correlation spectra of up to five detector/electronics systems. The system operates at clock frequencies up to 1 GHz, permitting the collection of timing pulses in bins as narrow as 1 ns. In normal operation NWIS uses well characterized detectors and constant fraction discriminators, but it may also be configured to accept pulses from any circuit and to use the autocorrelation spectrum to accurately determine dead-time. Unlike traditional dead-time assessment techniques that typically require multiple sources and an assumed dead-time model, NWIS provides single measurement assessment of circuit dead time and does not require an assumed dead-time model or a calibrated high count-rate source.

Edge equilibrium, turbulence and transport related plasma parameters from the Advanced Toroidal Facility (ATF) [Fusion Technol. 10, 179 (1986)] torsatron, the ZT-40M [Fusion Technol. 8, 1571 (1985)] reversed-field pinch, the Phaedrus-T [Nucl. Fusion 32, 2040 (1992)] tokamak, the Texas Experimental Tokamak (TEXT) [Nucl. Technol. Fusion 1, 479 (1981)], and the Tokamak Fusion Test Reactor (TFTR) [in Plasma Physics and Controlled Nuclear Fusion Research, 1990 (International Atomic Energy Agency, Vienna, 1991), Vol. 1, p. 9] have been obtained using a standardized Langmuir probe array and a consistent set of data analysis packages. Additional data from some other devices have also been furnished via private communications and incorporated from published results. Experimental results over a wide range of parameters are compared and the turbulence contribution to edge transport are assessed. Certain physical properties that are relevant to the modeling of edge turbulence are identified: namely, shear decorrelation of turbulence, the role of resistive dissipation and electron parallel thermal conduction, radial mode structure in sheared magnetic field, and electromagnetic contribution to the parallel Ohm’s law.

Electrostatic turbulence has been investigated in the edge region of the Advanced Toroidal Facility (ATF). A reversal in the poloidal phase velocity of the fluctuations has been observed (velocity shear) which determines a characteristic plasma radius. The location of this shear layer depends on the magnetic configuration, the limiter radius and the plasma conditions. Using the shear position as a reference point, the density fluctuation levels in ATF (currentless stellarator) are very similar to those previously reported in TEXT (ohmically heated tokamak), suggesting that the plasma current is not an important drive for the edge turbulence. The drives for the turbulence appear to be different inside and outside the shear location (ashear), with e/Te 1) and possibly larger e/Te in the plasma edge edge (r/ashear < 1). There is a spatial decorrelation in the fluctuations at the shear location; this suggests that the poloidal shear flow has an important influence on the edge turbulence. The poloidal correlation length depends on local plasma parameters (e.g. velocity and temperature). When neutral beam injection is added, the high frequency components of n increase.

An overview of recent AFT (Advanced Toroidal Facility) experimental results and program plans is presented, with emphasis on the role of magnetic configuration controls in transport studies. The ATF operating space is bounded by a density limit that effectively sets a limit on the energy confinement time tau /sub E/. Although this limit is not solely due to impurities, it has recently been raised by improved cleanliness following titanium gettering. This has led to collapse-free neutral beam injection discharges with global tau /sub E/ approximately=16 ms. Preliminary experiments show that stored energy and bootstrap current are sensitive to details of the magnetic configuration. >

The implementation plans and preparations for installation of the Fissile Mass Flow Monitor (FMFM) equipment at the ElectroChemical Plant (ECP), Zelenogorsk, Russia, are presented in this report. The FMFM, developed at Oak Ridge National Laboratory, is part of the Blend Down Monitoring System (BDMS), developed for the U.S. Department of Energy Highly Enriched Uranium (HEU) Transparency Implementation Program. The BDMS provides confidence to the United States that the Russian nuclear facilities supplying the lower-assay ({approx}4%) product low enriched uranium (P-LEU) to the United States from down-blended weapons-grade HEU are meeting the nonproliferation goals of the government-to-government HEU Purchase Agreement, signed between the Russian Federation and the United States in 1993. The first BDMS has been operational at Ural Electrochemical Integrated Plant, Novouralsk, since February 1999 and is successfully providing HEU transparency data to the United States. The second BDMS was installed at ECP in February 2003. The FMFM makes use of a set of thermalized californium-252 ({sup 252}Cf) spontaneous neutron sources for a modulated fission activation of the UF{sub 6} gas stream for measuring the {sup 235}U fissile mass flow rate. To do this, the FMFM measures the transport time of the fission fragments created from the fission activation processmore » under the modulated source to the downstream detectors by detecting the delayed gamma rays from the fission fragments. The FMFM provides unattended, nonintrusive measurements of the {sup 235}U mass flow in the HEU, LEU blend stock, and P-LEU process legs. The FMFM also provides the traceability of the HEU flow to the product process leg. This report documents the technical installation requirements and the expected operational characteristics of the ECP FMFM.« less

In this paper the implementation plans and preparations for installation of the Fissile Mass Flow Monitor (FMFM) equipment at the Siberian Chemical Enterprise (SChE), Seversk, Russia, will be presented. The FMFM, developed by Oak Ridge National Laboratory (ORNL), is part of the Blend Down Monitoring System (BDMS) for the U.S. Department of Energy (DOE) Highly Enriched Uranium (HEU) Transparency Implementation Program (TIP). The BDMS provides confidence to the United States that the Russian nuclear facilities supplying the lower assay (~4%) product low enriched uranium (P-LEU) to the United States from down-blended weapon-grade HEU are meeting the nonproliferation goals of the 1993 HEU Purchase Agreement signed between the Russian Federation and the United States. The first BDMS has been operational at Ural Electrochemical Integrated Plant (UEIP), Novouralsk, since February 1999. The second BDMS became operational at Electro Chemical Plant (ECP), Zelenogorsk, in March 2003. These systems are successfully providing HEU transparency data to the United States. The third BDMS was successfully installed on the HEU down-blending tee in the SChE Enrichment Plant in October 2004. The FMFM makes use of a set of thermalized californium-252 ( 252 Cf) spontaneous neutron sources for modulated fission activation of the uranium hexafluoride (UF6) gas stream for measuring the 235 U fissile mass flow rate. To do this, the FMFM measures the transport time of the fission fragments created from the fission activation process under the modulated source to the downstream detectors by detecting the delayed gamma rays from the fission fragments retained in the flow. The FMFM provides unattended nonintrusive measurements of the 235 U mass flow of the UF6 gas in the blending tee legs of HEU, the LEU blend stock, and the resulting P-LEU. The FMFM also confirms that HEUF6 gas identified in the HEU leg flows through the blending tee into the P-LEU leg. This paper will discuss details of the SChE FMFM equipment characteristics as well as the technical installation requirements.

In this paper, a detailed design description and the performance characteristics are presented for the gamma ray detector system developed for the fissile mass flow monitor (FMFM) to be used on 8-in.-diam process pipes. The FMFM continuously measures the 235 U fissile mass flow rate of a UF6 gas stream. It uses moderated and modulated 252 Cf neutron sources for fission activation of the UF6 gas. Four pairs of bismuth germinate (BGO) scintillation detectors are placed around the process pipe (on the top, bottom, front, and back) downstream of the neutron sources so that a high detection efficiency can be achieved for measuring the delayed gammas (> 0.3 MeV) emitted from the fission fragments in the stream for the flow measurements. The BGO crystal was selected because it is a novel scintillation material (a rugged, nonhygroscopic, neutroninsensitive, high-density, and high-Z material) with high absorption (stopping) power and because it has high peak photoefficiency for high-energy gammas. Each 4-in.-diam, 2-in.-thick BGO scintillation crystal is coupled to a 3-in.-diam photomultiplier tube (PMT). Both are shielded with lead to reduce the background signal. Each detector pair is housed in a metal enclosure that also contains an electronics board for signal shaping and counting. The front-end electronics boards independently amplify and shape the detector signals before they are summed. The combined signal is then fed into two single-channel analyzers (SCAs), which separate the pulses into low- and high-energy bands and subsequently determine the count rate in each band. A local area network node for providing secure data transmission to the FMFM computer and a local temperature sensor are also parts of each detector electronics board. The temperature response of the detector signal resulting from the intrinsic temperature coefficient of each BGOPMT assembly is used for real-time corrections of the system by monitoring the 186-keV spectrum line of 235 U obtained with the lower-energy SCA. The lower-energy SCA is also scanned during manual detector energy calibration to capture 186- or 96-keV spectral lines from the UF6, depending upon its enrichment. The higher-energy SCA output provides for the measurement of the 0.3- to 2-MeV delayed gamma ray signal from the fission fragments in the UF6 stream.

In stellarators, external coil currents rather than internal currents are used to produce the confinement fields. This allows for greater flexibility in the design and operation of a stellarator. This flexibility can be exploited in a series of experiments on one device, such as the ATF. MHD stability boundaries will be tested by varying the vertical field. Access to the second stability regime has been observed in initial experiments on ATF. In this regime, the relationship between stabilization of pressure-driven modes and transport improvement can be studied. The density profile peaking factor can be varied using pellet injection in order to understand the role of eta /sub j/ modes. As an example, the ATF-TEXT collaboration on edge fluctuations will compare the levels of resistive-gradient-driven fluctuations observed in the two devices. In addition, global confinement and local transport comparisons have been made to tokamaks and to other stellarators of roughly similar size and capabilities but with widely varying configuration properties. >

A computer controlled detector/electronics module has been designed and constructed for the Oak Ridge National Laboratory fissile mass flow (FMF) monitor. The FMF monitor employs a host computer, a modulated neutron source (Cf-252) and four of the gamma-ray detector/electronics modules described here to non-intrusively measure liquid or gas fissile-mass-flow rates in a pipe. The gamma-ray detector/electronics modules each consist of a bismuth germanate/photomultiplier-tube scintillation detector, an integrating preamplifier, a bipolar spectroscopy amplifier, two single channel analyzers, a temperature sensor and an on-board network communications node. The host computer automatically calibrates amplifier gain and single-channel analyzer thresholds via the network using a characteristic emission peak of the material flowing in the pipe and corrects for detector gain variations due to the temperature coefficients of the bismuth germanate. The single channel analyzer output pulses are counted by a microprocessor on board the network node and reported to the host computer. The key components of the detector/electronics module are described and initial data obtained with the FMF monitor are presented.

The feasibility of electron density profile measurements using a heavy ion beam probe in high‐temperature plasmas has been demonstrated earlier [J. Schwelberger et al., Bull. Am. Phys. Soc. 36, 2292 (1991); Yu. N. Dnestrovskij et al., Sov. J. Plasma Phys. 12, 130 (1986)]. Two algorithms were developed to obtain density profiles from the heavy ion beam probe on the Advanced Toroidal Facility (ATF). A comparison of the algorithms is presented with a detailed study of the errors involved in the measurements. The errors can be due to uncertainties in cross sections, electron temperature, the line average density measurement, and the ion trajectory calculations. The heavy ion beam probe density profile measurement is not very susceptible to errors as long as the electron temperature stays above 30 eV. If the electron temperature is below this value, a small uncertainty in the temperature introduces a large error in the density. Also, important for a good density profile measurement is the calculation of the co...

This paper presents a demonstration of fissile-mass-flow measurements using the Oak Ridge National Laboratory (ORNL) Fissile Mass Flow Monitor in the Paducah Gaseous Diffusion Plant (PGDP). This Flow Monitor is part of a Blend Down Monitoring System (BDMS) that will be installed in at least two Russian Federation (R.F.) blending facilities. The key objectives of the demonstration of the ORNL Flow Monitor are two: (a) demonstrate that the ORNL Flow Monitor equipment is capable of reliably monitoring the mass flow rate of {sup 235}UF{sub 6} gas, and (b) provide a demonstration of ORNL Flow Monitor system in operation with UF{sub 6} flow for a visiting R.F. delegation. These two objectives have been met by the PGDP demonstration, as presented in this paper.

A method was developed and successfully applied to characterize large uranyl fluoride (UO{sub 2}F{sub 2}) deposits at the former Oak Ridge Gaseous Diffusion Plant. These deposits were formed by a wet air in-leakage into the UF{sub 6} process gas lines over a period of years. The resulting UO{sub 2}F{sub 2} is hygroscopic, readily absorbing moisture from the air to form hydrates as UO{sub 2}F{sub 2}-nH{sub 2}O. The ratio of hydrogen to uranium can vary from 0--16, and has significant nuclear criticality safety impacts for large deposits. In order to properly formulate the required course of action, a non-intrusive characterization of the distribution of the fissile material within the pipe, its total mass, and amount of hydration was necessary. The Nuclear Weapons Identification System (NWIS) previously developed at the Oak Ridge Y-12 Plant for identification of uranium weapons components in storage containers was used to successfully characterize these deposits.

We describe a high‐gain (∼107) amplifier for use with large‐area silicon photodiodes for monitoring the intensity of plasma light from fusion experiments. To achieve the necessary gain without saturating the output signal, the amplifier design incorporates a bootstrap technique and capacitive coupling between amplifier stages. This design eliminates voltage offset at the amplifier output due to detector leakage, while retaining desirable low‐frequency response characteristics.

An experimental scheme to extend the investigation of plasma turbulence has been implemented. It involves driving waves into the plasma to modify the statistical properties of the fluctuations; the dynamical balance of the turbulence is perturbed via the injection of waves at selected spectral regions. New analysis techniques based on conditional sampling and high order correlation are developed for studying the wave launching and the wave‐wave coupling processes. Experimental results from TEXT‐U tokamak show that the launched waves interact with the intrinsic fluctuations both linearly and nonlinearly. The attainment of driven nonlinearity is necessary for this diagnostic scheme to work. It is also the key to an active modification and control of edge turbulence in tokamaks.

There exist two separate and independent magnetic field asymmetries in the ELMO Bumpy Square (EBS). One is associated with the small perturbations in the magnetic field, known as the field errors, caused by coil misalignments during installation, imperfection in coil winding, etc. The second source of asymmetry is the magnetic field ripple in the high-field toroidal solenoids (corners) produced by the finiteness of the number of coils. In general, these two sources of asymmetry introduce enhanced transport losses (in addition to other effects) to the system, although they affect different classes of particles. Toroidally passing (circulating) particles (v/sub parallel//v approx. 1) are influenced by the field errors, whereas trapped particles (v/sub parallel//v approx. 0) in the corners are influenced by the field ripple. In this paper we discuss these two effects separately and calculate the allowable magnitudes of the field error and field ripple in EBS, both for an experimental-size device and for a reactor.

Transport simulation and modeling studies for the ELMO bumpy Torus (EBT) reactor are carried out by using 0-D and 1-1/2-D transport calculations. The time-dependent 0-D model is used for global analysis whereas the 1-1/2-D radial transport code is used for accurate determination of density, temperature, and ambipolar potential profiles and of the role of these profiles in reactor plasma performance. Analysis with the 1-1/2-D transport code shows that profile effects near the outer edge of the hot electron ring lead to enhanced confinement by a least a factor of 2 to 5 beyond the simple scaling that is obtained from the global analysis. The radial profiles of core plasma density and temperatures (or core pressure) obtained from 1-1/2-D transport calculations are found to be similar to those theoretically required for stability.

Experiments were conducted in the ELMO Bumpy Torus (EBT) from 1973 until 1984. A number of papers have been published concerning various aspects of experiments during the final two years of operation. The paper summarizes the final experimental conclusions and discusses those issues which remain unresolved. The main conclusions are as follows: (1) measurements of the width of the hot electron rings showed them to be wider than previously suspected, diluting their diamagnetism and negating their ability to locally reverse the magnetic field gradient; (2) two-dimensional plots of the plasma potential revealed open potential contours in the C-mode and closed potential contours near the plasma centre in the T-mode; (3) an in–out asymmetry in the plasma potential was always observed, giving rise to electric fields which drove convective plasma loss.

A simple and inexpensive 4-mm direct reading fast (rise time approx. 100 ..mu..s) microwave interferometer is described. The system is particularly useful for density measurements on the ELMO Bumpy Torus (EBT) during pulsed operation.

The energy spectrum of the synchrotron radiation emitted by the relativistic ring electrons in ELMP bumpy Torus (EBT) has been calculated for various classes of isotropic and anisotropic ring electron distribution functions. Calculations have been carried out for present (EBT-I/S) and planned (EBT-P) experiments. The ring temperatures in EBT-I and EBT-S are approx. 200 and approx. 500 keV, respectively. The projected ring temperature in EBT-P is approx. 1000 to 1500 keV. The calculations indicate that the radiation is predominantly in higher harmonics (l greater than or equal to ..gamma../sup 2//2) and the radiation spectrum monotonically decreases and becomes almost flat at high frequencies, as observed in the experiments. With increasing temperature and anisotropy, the total emission increases, the slope of the spectrum decreases, and the peak of the spectrum moves to higher frequency. Correlations of calculated intensity variations with temperature, density, beta, anisotropy, etc., are given that can be used as a useful tool for comparison of theory and experiment, as well as in the determination of ring properties and scaling of the radiation with ring parameters.

Reported here are the results of two nonstandard heating experiments. In one, the fundamental ECH resonance at either 10.6 or 18 GHz was placed at the usual ring position in an attempt to generate rings solely with fundamental heating; this is the fundamental resonance configuration (FR). In a second experiment, an attempt was made to heat the ring and core separately by forming the ring as above with 10.6 GHz and then heating the core with the fundamental and second harmonic of 28 GHz; this is the separately coupled ring and toroidal core heating configuration (SCRATCH). In both cases, the hot electron annuli were formed and stabilized the core plasma as in the SR experiments. In FR, the rings form at the second harmonic and no significant potential structures were found. In SCRATCH, either a potential well or a potential hill could be formed. In both heating regimes, significant ion heating above that found in standard heating experiments was found.

A computer model (RIPPLE) was developed to examine the magnetic field ripple effects on plasma transport and on scaling in circular and noncircular tokamaks. Calculations include the radial and poloidal variation in the magnitude of the field ripple. Two main magnetic field computer programs were used to calculate the magnetic field due to current flowing in a coil of finite rectangular cross section: BFULT for tori of circular coils, and BOVAL for tori of noncircular coils. This paper presents the relevant results and discusses the criteria for the choice of the number of toroidal field coils for a given tokamak configuration.

This report summarizes the results of a recent ELMO Bumpy Torus (EBT) reactor study that includes ring and core plasma properties with consistent treatment of coupled ring-core stability criteria and power balance requirements. The principal finding is that constraints imposed by these coupling and other physics and technology considerations permit a broad operating window for reactor design optimization. Within this operating window, physics and engineering systems analysis and cost sensitivity studies indicate that reactors with approx. 6 to 10%, P approx. 1200 to 1700 MW(e), wall loading approx. 1.0 to 2.5 MW/m/sup 2/, and recirculating power fraction (including ring-sustaining power and all other reactors auxiliaries) approx. 10 to 15% are possible. A number of concept improvements are also proposed that are found to offer the potential for further improvement of the reactor size and parameters. These include, but are not limited to, the use of: (1) supplementary coils or noncircular mirror coils to improve magnetic geometry and reduce size, (2) energetic ion rings to improve ring power requirements, (3) positive potential to enhance confinement and reduce size, and (4) profile control to improve stability and overall fusion power density.

The perpendicular energy gain ..delta..W/sub perpendicular to/ of electrons from the applied extraordinary microwave field in ELMO Bumpy Torus (EBT) is calculated by means of the stochastic model for the field-plasma cyclotron resonance interactions. In these calculations an inhomogeneous bumpy magnetic field is chosen in order to simulate the field strength of the EBT as well as to include the effects of mirror trapping. The effects of the initial energy of the electrons and the value of the mirror ratio on the trapping are discussed, and the heating rate ..delta..W/sub perpendicular to//..delta..t (where ..delta..t is the reflection time from the mirror) is estimated. The loaded cavity quality factor Q/sub L/ is then expressed from the heating rate, the result is applied to the EBT-I plasma, and a value of Q/sub L/ approx. = 15 is found.

In the ELMO Bumpy Torus (EBT), the plasma parmeters depend on the microwave heating power P/sub ..mu../ and on the neutral gas pressure p/sub o/, both of which define the operating regime (mode) of the device. In order to assess interrelationships between various confinement parameters, we have studied radial transport by incorporating experimental observations into model calculations. Experimentally, the ambipolar potential well phi is measured and is one of the important parameters that strongly affect the confinement properties. In this study, we make use of P/sub ..mu../, p/sub o/, and phi in transport modeling to predict the scaling of the density (n) and temperatures (T/sub e/, T/sub i/) with these quantities. The scaling calculations are based on neoclassical theory of transport coefficients and experimental observations. A quadratic potential profile and almost flat n and T/sub e/ profiles are assumed.

The absorption of electron cyclotron waves propagating along an externally applied magnetic field in a uniform plasma surrounded by a cylindrical metallic cavity wall is studied. In the model, the cavity wall, the vacuum-plasma interface, and the effects of finite electron temperature are considered, and the dispersion relation for the wave propagation is derived. The results are then applied to the ELMO Bumpy Torus (EBT-I) plasma, and the propagation characteristics are computed. The wave absorption in the ordinary mode is found to be a result of the wall effects, which cannot be predicted with the infinite plasma theory. The loaded quality factor, Q/sub L/, is also estimated from the model to be about 12, which is in good agreement with the experimentally observed value.

The transport problem for an ohmically heated tokamak plasma is investigated analytically with the separation of the variables time, t, and rho = r/sup 2/h(t), where r is the space coordinate and h(t) is only a function of time. This investigation examines the circumstances under which these analytical solutions are possible. The time evolution of the current density and temperature profiles is then obtained for a simple plasma model which includes the electric field diffusion and heat conduction losses. Expressions are also given for plasma discharge parameters such as the time evolution of the safety factor, the plasma current, the poloidal flux function, the skin time, the poloidal beta, the transformer flux, and the electron energy lifetime. The results are then applied to a typical size tokamak device.

Neoclassical equilibrium and transport have been calculated with analytic solutions of a drift-kinetic equation in which the effect of collisions is included. The necessary introduction of approximations precluded the full description of the distribution function in all regimes and over all particle energies. C. O. Beasley, H. K. Meier, W. I. van Rij, and J. E. McCune have used the techniques inherent to the collisional plasma model (CPM) to develop a computer simulation for the dynamics of toroidally confined plasmas in the drift-kinetic, Fokker-Planck description. The CPM permits study of the neoclassical equilibrium without approximation in the drift-kinetic ordering. The neoclassical electron distribution function derived by M. N. Rosenbluth, R. D. Hazeltine, and F. L. Hinton is compared with the CPM for the banana regime. Good general agreement is obtained; discrepancies are attributed to a poor modeling of the collisional (low energy) particles in the model of Rosenbluth et al. The CPM is also compared with calculations by K. T. Tsang and J. D. Callen in the Pfirsch-Schlueter regime. When approximations made in these calculations are taken into consideration, good agreement is observed.

The spectrum of the synchrotron radiation emitted by the relativistic electron rings in the ELMO Bumpy Torus (EBT) has been formulated. A computer code (CYCLO has been developed for the numerical calculations for the range of frequencies (especially higher harmonics) and temperatures (approx. 0.1 to 2 MeV) of interest. The analysis has been carried out for various classes of isotropic (not necessarily Maxwellian) and anisotropic ring electron distribution functions. Calculations include the radial profiles of the ring electron density and temperature (approximated from fits to the experimental data) and include consistent magnetic field modifications (magnetic well due to high-beta ring) deduced from the pressure balance. The calculated spectra and emission levels for the Maxwellian distribution are in reasonable agreement with those measured, though detailed comparisons of theory and experiment have not been made. Because of the relativistic temperatures, the radiation is predominantly in higher harmonics. The spectrum of emission for each harmonic indicates broadening of individual lines with large frequency widths that causes pronounced overlapping of harmonics and results in a monotonically decreasing spectrum as observed in the experiments.

For a typical size ELMO Bumpy Torus (EBT) reactor (approx. 1000 MWe), microwave frequencies required lie in the range of 60 to 110 GHz at power levels of 50 to 75 MW. As the frequency rises, the unloaded cavity (i.e., without plasma) quality factor Q decreases. Because of the short wavelengths of microwave heating power and the large cavity dimensions of a reactor, it is possible to apply quasi-optical principles in the efficient coupling of power to the plasma. The use of a confocal Fabry-Perot resonator with spherical mirrors is discussed; these serve to confine the microwave power to the region occupied by the plasma. The potential advantages of these resonators include high efficiency utilization of microwave power, minimal thermal burden on the cryopumping system, and significant benefit in preventing microwave leakage from the device. An estimation of the unloaded cavity quality factor Q and the design considerations of Fabry-Perot resonator are given.

Transport simulation and modeling studies for the ELMO Bumpy Torus (EBT) reactor are carried out by using zero-dimensional (0-D) and one-and-one-half-dimensional (1 1/2-D) transport calculations. The time-dependent 0-D model is used for global analysis, whereas the 1 1/2-D radial transport code is used for accurate determination of density, temperature, and ambipolar potential profiles and of the role of these profiles in reactor plasma performance. Analysis with the 1 1/2-D transport code shows that profile effects near the outer edge of the hot electron ring lead to enhanced confinement by at least a factor of 2 to 5 beyond the simple scaling that is obtained from the global analysis. The radial profiles of core plasma density and temperatures (or core pressure) obtained from 1 1/2-D transport calculations are found to be similar to those theoretically required for stability.

A simple and inexpensive 4‐mm direct reading fast (rise time∼100 μs) microwave interferometer is described. The system is particularly useful for density measurements on the ELMO Bumpy Torus (EBT) during pulsed operation.