ITER plasma safety interface models and assessments

Physics models and requirements to be used as a basis for safety analysis studies are developed and physics results motivated by safety considerations are presented for the ITER design. Physics specifications are provided for enveloping plasma dynamic events for Category I (operational event), Category II (likely event), and Category III (unlikely event). A safety analysis code SAFALY has been developed to investigate plasma anomaly events. The plasma response to ex-vessel component failure and machine response to plasma transients are considered

Assessment of magnetic field asymmetries in ELMO Bumpy Square

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

Ignition and steady-state current drive capability of INTOR plasma

The confinement capability of the INTOR plasma for achieving ignition and noninductively driven, Q>5 steady-state operation has been assessed for various energy confinement scaling laws and current drive schemes by using a global power balance model. Plasma operation contours are used to illustrate the boundaries of the operating regimes in density-temperature (n-T) space. Results of the analysis indicate a very restricted capability (if any) for ignition and a limited flexibility in driven modes of operation in the INTOR (8-MA) design. Nearly a factor of two increase in plasma current (through stronger plasma shaping) could improve the feasibility of ignition in INTOR. 14 refs., 4 figs., 3 tabs

Microwave coupling in EBT reactor

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

Tokamak confinement projections and performance goals

One key quantity to be determined in the design of burning-plasma devices (CIT, ITER, reactors, etc.) is the level of plasma current (I) required to meet the desired plasma performance goals (ignition, high Q, etc.) and device objectives (fusion power, wall loading, current drive power, etc.). It is shown that these goals and objectives can be expressed in terms of the ''figure-of-merit'' parameter IA/sup alpha//R/sup x/(/approximately/f(LB/sup y/), where A is the aspect ratio, R is the major radius, L(= R, a) is the characteristic length, B is the toroidal magnetic field on axis, and the exponents ..cap alpha.. /approximately/ 1 +- 0.5 and x /approximately/ 0-0.5 (y /approximately/ 1-2) depend on the confinement assumptions and operational limits. To reach ignition or high Q, the main goal is to optimize IA/sup alpha//R/sup x/, subject to other engineering design constraints. In a CIT-like device (with R /approximately/ 2 m, kappa /approximately/ 2, q/sub psi/ greater than or equal to 3), the ignition requirements is I(A/3)/sup alpha/ /approximately/ 9-15 MA for ''enhanced'' L-mode (H-mode) confinement scaling expressions; an ITER-like device (with R /approximately/ 5-6 m, kappa /approximately/ 2, q/sub psi/ greater than or equal to 3) would require I(A/3)/sup alpha/ /approximately/ 15-25 MA. These requirements are embodied in the present CIT (with I /approximately/ 11 MA, A /approximately 3.25) and ITER (with I /approximately/ 18-22, A /approximately/ 3.1-2.6) designs. 12 refs., 1 fig., 3 tabs

Physics issues of an EBT reactor

The plasma physics areas that influence the operating characteristics of EBTs are the following: (1) particle orbits, equilibrium, and magnetic; (2) stability boundaries of both core and ring plasmas; (3) transport scaling; (4) heating; and (5) ring-core interaction and power balance. In addition to the conventional mode of EBT operation, innovative ideas that enhance the reactor performance include: (a) the use of supplementary (and/or trim) coils to improve confinement (and/or stability); (b) control of ambipolar potential (and its sign, i.e., positive electric field) to enhance confinement (and to be able to burn alternative fuels, i.e., D-D, etc., in a reasonably sized reactor); and (c) the possibility of fundamental ring mode heating to reduce microwave frequency requirements by a factor of 2. This paper reviews each of these areas briefly and discusses their projections to a reactor

Physics design options for compact ignition experiments

This paper considers the following topics: (1) physics assessments-design and engineering impact, (2) zero-dimensional confinement studies relating to physics requirements and options for ignited plasmas, classes of devices with equivalent performance, and sensitivity to variations in confinement models, and (3) one and one-half dimensional confinement studies relating to dynamic simulations, critical physics issues, startup analyses, and volt-second consumption. (MOW

ITER physics design guidelines at high aspect ratio

The physics requirements for ITER design are formulated in a set of physics design guidelines. These guidelines, established by the ITER Physics Group during the Conceptual Design Activity (CDA, 1988--90), were based on credible extrapolations of the tokamak physics database as assessed during the CDA, and defined a class of tokamak designs (with plasma current I {approximately}20 MA and aspect ratio A {approximately}2.5--3.5) that meet the ITER objectives. Recent US studies have indicated that there may be significant benefits if the ITER-CDA design point is moved from the low aspect ratio, high current baseline (A = 2.79, I = 22 MA) to a high aspect ratio machine at A {approximately}4, I {approximately}15 MA, especially regarding steady-state, technology-testing performance. To adequately assess the physics and technology testing capability of higher aspect ratio design options, several changes are proposed to the original ITER guidelines to reflect the latest (although limited) developments in physics understanding at higher aspect ratios. The critical issues for higher aspect ratio design options are the uncertainty in scaling of confinement with aspect ratio, the variation of vertical stability with elongation and aspect ratio, plasma shaping requirements, ability to control and maintain plasma current and q-profiles for MHD stability (and volt-second consumption), access for current drive, restrictions on field ripple and divertor plate incident angles, etc. 5 refs., 1 tab

EBT ring physics

This workshop attempted to evaluate the status of the current experimental and theoretical understanding of hot electron ring properties. The dominant physical processes that influence ring formation, scaling, and their optimal behavior are also studied. Separate abstracts were prepared for each of the 27 included papers. (MOW

EBT stability theory

Separate abstracts were prepared for each of the 13 included papers. (MOW