9 research outputs found
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Robust rf control of accelerators
The problem of controlling the variations in the rf power systems can be effectively cast as an application of modern control theory. Two components of this theory are obtaining a model and a feedback structure. The model inaccuracies influence the choice of a particular controller structure. One can design wither a variable, adaptive controller or a fixed, robust controller to achieve the desired objective. The adaptive control scheme usually results in very complex hardware; and therefore, shall not be pursued. In contrast, the robust control method leads to simplified hardware. However, robust control requires a more accurate mathematical model of the physical process than is required by adaptive control. Our research at the Los Alamos National Laboratory (LANL) and the University of New Mexico has led to the development and implementation of a new rf power feedback system. In this paper, we report on our research progress. In section one, the robust control problem for the rf power system and the philosophy adopted for the beginning phase of our research is presented. In section two, results of our proof-of-principle experiments are presented. In section three, we describe the actual controller configuration that is used in LANL FEL physics experiments. The novelty of our approach is that the control hardware is implemented directly in rf without demodulating, compensating, and then remodulating
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Static load cycle testing of a low-aspect-ratio four-inch wall, TRG-type structure, TRG-5-4 (1. 0, 0. 56)
This report is the second in a series of test reports that details the quasi-static cyclic testing of low height-to-length aspect ratio reinforced concrete structures. The test structures were designed according to the recommendations of a technical review group for the US Nuclear Regulatory Commission sponsored Seismic Category I Structures Program. The structure tested and reported here had 4-in.-thick shear and end walls, and the elastic deformation was dominated by shear. The background of the program and previous results are given for completeness. Details of the geometry, material property tests, construction history, ultrasonic testing, and modal testing to find the undamaged dynamic characteristics of the structures are given. Next, the static test procedure and results in terms of stiffness and load deformation behavior are given. Finally, results are shown relative to other known results, and conclusions are presented. 33 refs., 140 figs., 13 tabs
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An in situ moisture monitoring system for a solid low-level radioactive disposal pit at Los Alamos National Laboratory, Technical Area 54, Area G
At the end of the 1950's, Los Alamos National Laboratory began to develop a Laboratory-wide, shallow-land, solid low-level radioactive waste disposal area on top of Mesita del Buey at TA-54, Area G. An in situ hydrologic monitoring system in the zone of aeration was developed in early 1990 to detect the presence of the infiltration of meteoric water into Pit 37 at Area G. Monitoring the water movement through the pit cap into the waste with leaching and transport the containment rock and possible contamination of the main aquifer is of primary concern. 2 refs., 1 fig
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Microwave enhanced diffusion
The observation of more rapid reaction and/or sintering during microwave processing of ceramics has lead to speculation that microwave processing results in enhanced diffusion.'' The loss mechanisms by which microwaves interact with a crystal lattice have been reviewed. These mechanisms were evaluated with regard to the atomic theory of diffusion. The potential for these loss mechanisms to influence atomic diffusion, and thus produce enhancement will be discussed. Existing evidence, both direct and indirect, regarding microwave enhanced diffusion has been reviewed and will be discussed along with recent experimental data. 15 refs., 5 figs
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In-situ derivative cyclic voltabsorptometric studies on poly-3-methylthiophene
Spectroscopic behavior of poly-3-methylthiophene (P3MT) has been studied employing derivative cyclic volt-absorptometric (DCVA) techniques. In the DCVA technique, the derivative absorption signal (dA/dt) is recorded as a function of the applied potential. The dA/dt signals, the spectroscopic analog of electrochemical currents in cyclic voltammetry, are capable of monitoring the potential dependency for the absorption band effectively discriminating against nonfaradaic signals. The DCVA studies on the P3MT system show that the neutral form of P3MT, absorbing at 490 nm (at less than 0.3 V vs. Ag), changes to the radical cation from, which absorbs at 760 nm. Initially, the formation of the radical cation goes through an isosbestic point, indicating that the conversion of the neutral to radical (polaron) form is chemically reversible. However, upon increasing the electrode potential, the rate of the radical formation at 760 nm starts to decrease, with the formation of another band at about 1250 nm, attributable to a quinoid (bipolaron) form. This trend begins above 0.6 V, shifting to a more positive voltage as the thickness of the film grows. This observation indicates that the electrochemical conversion of the neutral to radical form, followed by the quinoid form, is a slow process controlled by the diffusion of counter ions through the film. In-situ conductivity measurements as a function of applied potentials and chronoamperometric results support the observed spectroscopic behavior. 20 refs., 6 figs
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Genetic algorithms and the immune system
Using genetic algorithm techniques we introduce a model to examine the hypothesis that antibody and T cell receptor genes evolved so as to encode the information needed to recognize schemas that characterize common pathogens. We have implemented the algorithm on the Connection Machine for 16,384 64-bit antigens and 512 64-bit antibodies. 8 refs
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Shell model calculations for exotic nuclei
In this paper we review the progress of the shell-model approach to understanding the properties of light exotic nuclei (A < 40). By shell-model'' we mean the consistent and large-scale application of the classic methods discussed, for example, in the book of de-Shalit and Talmi. Modern calculations incorporate as many of the important configurations as possible and make use of realistic effective interactions for the valence nucleons. Properties such as the nuclear densities depend on the mean-field potential, which is usually separately from the valence interaction. We will discuss results for radii which are based on a standard Hartree-Fock approach with Skyrme-type interactions
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Model-reference adaptive control applied to load-following of a space-nuclear power system
Nuclear power systems are presently being investigated as an alternative for both commercial and military space power systems because of their projected longevity of 7 to 10 years, their mass advantage over other space power sources at powers above approximately 25 kW{sub e}, and their ability to operate without direct illumination from the sun. These space-nuclear power systems are being designed to supply from tens of kilowatts to multimegawatts of power for continuous operation of seven years and more. Space-nuclear power systems designs that meet these requirements will not be available for refueling or maintenance during their lifetime. To ensure that the space-nuclear power system will operate safely and will respond in a predictable and desired manner, the design of the system's controller must account for changes in the system parameters over its lifetime. This paper applies model-reference adaptive control to an increase in the power demand by the load. A model-reference adaptive controller will force the actual space-nuclear power system to follow the predictable and desired response of a reference model, despite changes in the actual system's operating parameters. Included in this paper are the model-reference adaptive control algorithm, the description of the computer simulation of a space-nuclear power system and the reference model, and results that demonstrate the application of model-reference adaptive control to a change in the load power demand. The results demonstrate that model-reference adaptive control can ensure the transient response of the system despite differences between the design of the system and the as-built system as well as for variations in the systems parameters. 5 refs., 3 figs