No abstract available

[en] The interference of Coulomb and Nuclear Excitation is studied by the scattering of 70.4 MeV ¹²C Ions from the even Nd nuclei (¹⁴²Nd, ¹⁴⁴Nd, ¹⁴⁶Nd, ¹⁴⁸Nd, and ¹⁵⁰Nd). These isotopes span the region from the almost spherical nucleus ¹⁴²Nd (β₂ approximately equals 0.1) to the quite deformed nucleus ¹⁵⁰Nd (β₂ approximately equals 0.3). The differential cross sections for elastic scattering and inelastic scattering from the low lying 2⁺, 4⁺, 3^-, and 2₂⁺ states of these isotopes were obtained. In addition, the cross sections of the 2⁺(4.4 MeV) state of the projectile ¹²C and the 6⁺ state in ¹⁵⁰Nd were also obtained

[en] The interference of Coulomb and nuclear excitation is studied by the scattering of 70.4 MeV ¹²C ions from the even Nd nuclei (¹⁴²Nd, ¹⁴⁴Nd, ¹⁴⁶Nd, ¹⁴⁸Nd, and ¹⁵⁰Nd). These isotopes span the region from the almost spherical nucleus ¹⁴²Nd (β₂ approximately equals 0.1) to the quite deformed nucleus ¹⁵⁰Nd (β₂ approximately equals 0.3). The differential cross sections for elastic scattering and inelastic scattering from the low lying 2⁺, 4⁺, 3^-, and 2₂⁺ states of these isotopes were obtained. In addition, the cross sections of the 2⁺ (4.4 MeV) state of the projectile ¹²C and the 6⁺ state in ¹⁵⁰Nd were also obtained. Coulomb and nuclear excitation of the 2⁺ states in these targets produce rather smooth angular distributions, but for the 3^- and 4⁺ states rather pronounced interference minima are present. The interference structure of the 3^- states shift systematically toward smaller angles with increasing mass. A total angular shift of approximately 5⁰ occurs in going from ¹⁴²Nd to ¹⁵⁰Nd. The Coulomb-nuclear interference minimum for the 2⁺ state in ¹²C is shifted toward larger angles (approximately equals 3⁰) relative to the 3^- minimum in ¹⁴⁴Nd. The angular distributions are analyzed first within the framework of the optical model and the distorted wave Born approximation (DWBA) using the collective model formalism. The DWBA calculations reproduce the 2⁺ and 3^- angular distributions quite well provided nuclear deformation lengths are allowed to take on values which differ by 20% to 50% from their corresponding Coulomb deformation lengths. The 4⁺ angular distributions cannot be described by a single-step DWBA calculation

[en] A thorough understanding of the hot electron rings in ELMO Bumpy Torus-Scale (EBT-S) is essential to the bumpy torus concept of plasma production, since the rings provide bulk plasma stability. The hot electrons are produced via electron cyclotron resonant heating using a 28-GHz cw gyrotron, which has operated up to power levels of 200 kW. The parameters of the energetic electron rings are studied via hard x-ray measurement techniques and with diamagnetic pickup coils. The hard x-ray measurements have used collimated NaI(Tl) detectors to determine the electron temperature T_e and electron density n_e for the hot electron annulus. Typical values of T_e are 400 to 500 keV and of n_e 2 to 5 x 10¹¹ cm^-3. The total stored energy of a single energetic electron ring as measured by diamagnetic pickup loops approaches approx. 40 J and is in good agreement with that deduced from hard x-ray measurements. By combining the experimental measurements from hard x-rays and the diamagnetic loops, an estimate can be obtained for the volume of a single hot electron ring. The ring volume is determined to be approx. 2.2 litres, and this volume remains approximately constant over the T-mode operating regime. Finally, the power in the electrons scattered out of the ring is measured indirectly by measuring the x-ray radiation produced when those electrons strike the chamber walls. The variation of this radiation with increasing microwave power levels is found to be consistent with classical scattering estimates

No abstract available

[en] A workshop on helium transport and exhaust in tokamaks was held in Gatlinburg, Tennessee, April 6--18, 1991. The chief purpose of the workshop was to foster discussion of plans for future experiments in the study of adequate helium removal from advanced fusion devices such as the International Thermonuclear Engineering Reactor (ITER). The areas covered at the workshop are outlined, and the results presented are discussed in detail

[en] One of 12 beryllium tiles on a top rail limiter in the Impurity Study Experiment (ISX-B) tokamak was intentionally made radioactive. The migration of the radioactivity due to melting, ablation, and general excoriation of the radioactive tile was studied. Several hundred milligrams of material from the radioactive tile were spread to the other tiles over the course of the experiment, which consisted of more than 3000 tokamak shots. A small amount of activity was found on the bottom of the tokamak vacuum vessel. The distribution of activity on the other limiter tiles showed a marked radially inward directivity, although all of the tiles received some activity. The possibility that some of the activity was the result of photo- and electro-excitation by runaway electrons cannot be ruled out but probably cannot account for the bulk of the effect

No abstract available

[en] Soft x-ray bremsstrahlung measurements have been performed on the ELMO Bumpy Torus (EBT-S) plasma to determine the electron temperature T_e and electron density n_e using a calibrated Si(Li) detector over a wide range of operating conditions. The purpose of this paper is to outline the necessary assumptions and essential x-ray techniques that are inherent in soft x-ray measurements in order to investigate the electron heating and confinement properties of EBT-S. In addition, by utilizing the electron density as determined by the soft x-ray measurements, the previous EBT-S confinement analyses have been extended. The steady-state plasma of EBT-S is heated by microwaves using a cw gyrotron that can operate up to power levels of 200 kW. From the soft x-ray measurements, both the electron temperature and density are found to increase at higher microwave power levels. For operation at microwave power levels of 200 kW, T_e approaches 1 keV while n_e approaches 1.2 x 10¹² cm^-3. In general, confinement properties are found to improve with increased microwave power. The data are compared with neoclassical transport scaling and the electron transport is found to be collisionless (nu/Ω < 1) as well as neoclassical

[en] A thorough understanding of the hot electron rings in ELMO Bumpy Torus-Scale (EBT-S) is essential to the bumpy torus concept of plasma production, since the rings provide bulk plasma stability. The hot electrons are produced via electron cyclotron resonant heating using a 28-GHz cw gyrotron, which has operated up to power levels of 200 kW. The parameters of the energetic electron rings are studied via hard x-ray measurement techniques and with diamagnetic pickup coils. The hard x-ray measurements have used collimated NaI(T1) detectors to determine the electron temperature T_e and electron density n_e for the hot electron annulus. Typical values of T_e are 400 to 500 keV and of n_e 2-5 x 10¹¹ cm^-3. The total stored energy of a single energetic electron ring as measured by diamagnetic pickup loops approaches approx. 40 J and is in good agreement with that deduced from hard x-ray measurements. By combining the experimental measurements from hard x-rays and the diamagnetic loops, an estimate can be obtained for the volume of a single hot electron ring. The ring volume is determined to be approx. 2.2 litres, and this volume remains approximately constant over the T-mode operating regime. Finally, the power in the electrons scattered out of the ring is measured indirectly by measuringthe x-ray radiation produced when those electrons strike the chamber walls. The variation of this radiation with increasing microwave power levels is found to be consistent with classical scattering estimates