Basic Physics Research Research Articles

Some Basic Physics Results for Plasma Spectroscopy and Modelling

Spectroscopic diagnostics and modelling of technical or divertor plasmas require many results from basic physics research. Reasonable simplifications must be introduced and information is necessary about atomic and molecular processes in the plasma volume and at the walls. As a first approximation, the corona model is presented, which is applicable for excitation and ionisation at low densities. This model requires cross sections and rate coefficients for electron impact. Many of these can be found in the literature, but it is also shown, how they can be estimated from the optical f-values. Consideration of competing processes is often required, as e.g. dissociative excitation, excitation transfer, charge exchange or quenching. Some examples are reported. At higher electron densities, collisional-radiative models must be used, which are available for electron impact collisions. Redistribution by neutral particles can present a major problem in low density discharges and many questions are still open. Heavy particle reaction rates are published in the literature, but must sometimes be taken with caution. The optical thickness of resonance lines is discussed, which may considerably affect line emission also in the visible spectral range. Models and programs are described for taking into account opacity and the results are shown. In addition to reaction cross sections, the electron energy distribution function must be known, which is often non-Maxwellian. It is demonstrated, how deviations can be recognised in spectroscopic criteria with different energy thresholds and how the high-energy tail may be reconstructed for further use in diagnostics or modelling. Eventually, a self-consistent model of these plasmas is highly desirable calculating electrical and magnetic fields, all chemical reaction rates and the consequent distribution functions.

An Unattended Cloud-Profiling Radar for Use in Climate Research

A new millimeter-wave cloud radar (MMCR) has been designed to provide detailed, long-term observations of nonprecipitating and weakly precipitating clouds at Cloud and Radiation Testbed (CART) sites of the Department of Energy's Atmospheric Radiation Measurement (ARM) program. Scientific requirements included excellent sensitivity and vertical resolution to detect weak and thin multiple layers of ice and liquid water clouds over the sites and long-term, unattended operations in remote locales. In response to these requirements, the innovative radar design features a vertically pointing, single-polarization, Doppler system operating at 35 GHz (Ka band). It uses a low-peak-power transmitter for long-term reliability and high-gain antenna and pulse-compressed waveforms to maximize sensitivity and resolution. The radar uses the same kind of signal processor as that used in commercial wind profilers. The first MMCR began operations at the CART in northern Oklahoma in late 1996 and has operated continuously there for thousands of hours. It routinely provides remarkably detailed images of the ever-changing cloud structure and kinematics over this densely instrumented site. Examples of the data are presented. The radar measurements will greatly improve quantitative documentation of cloud conditions over the CART sites and will bolster ARM research to understand how clouds impact climate through their effects on radiative transfer. Millimeter-wave radars such as the MMCR also have potential applications in the fields of aviation weather, weather modification, and basic cloud physics research.

Out of particles: Impact of CERN, DESY and SLAC research to fields other than physics

Abstract This paper presents the results of an exploratory bibliometric study aiming at an analysis of basic high energy physics (HEP) research impact on fields other than physics, and particularly on application-oriented R&D. After a general discussion of an extensive citation analysis of basic research publications from three HEP institutes—CERN, DESY, and SLAC—the paper focuses on the ‘knowledge flow’ from physics to non-physics, and more specifically the flow from basic physics research to the ‘applied world’. At this level, we report journal- as well as research field characteristics, and we identify the most frequently citing R&D groups. We conclude that DESY is most cited by the ‘applied world’, followed by SLAC and CERN. If the number of journals that institutes have in common—whether based on the source or the citing publication—is taken as an indicator of the resemblance of their research interests, we found that CERN and SLAC have the closest resemblance, followed by SLAC and DESY, with CERN a...

Low-voltage high-resolution SEM: A valuable resource for the polymer morphologist

The elucidation of polymer morphology has historically been accomplished using optical microscopy (OM), conventional transmission electron microscopy (TEM), X-ray scattering and more recently for crystalline polymers, high resolution TEM (HRTEM). Significant work using scanning electron microscopy (SEM) to study synthetic polymers began in the late 1960's, but for twenty years after these first studies, the smallest features imaged by SEM in polymer samples have typically been 1-10 μm. The evolution of the low voltage high resolution SEM (LVHRSEM) now provides polymer scientists with the opportunity to image structures topographically on the order of 50-100 Å, a level of microstructure important in basic polymer physics research. The potential for improved understanding of polymer morphology is significant, especially when HRSEM data is combined with information from other complementary techniques such as TEM, X-ray scattering, and the scanning probe microscopies (SPM, AFM, STM).The advantages of LVHRSEM over conventional thermionic source SEM as a polymer characterization technique include: i) low keV operation reduces or eliminates charging in uncoated insulating polymers, ii) the high brightness, low energy spread, small spot size field emission gun allows for operation at low keV without significant loss of resolution (practically, resolution on the order of 50 Å at 1.0 keV in a polymer sample is attainable), iii) imaging of surface topography is improved at low keV as the beam/sample interaction volume is smaller and closer to the surface, resulting in more secondary electrons being generated within the secondary electron escape depth, and iv) the immersion lens system improves the signal to noise ratio by decreasing the noise component in the secondary electron signal.

Serving Students, Science, or Society? The Secondary School Physics Curriculum in the United States, 1930-65

On 4 October 1957, the Soviet Union launched Sputnik, the world's first satellite, into orbit. In the weeks that followed, Americans questioned why the Soviet Union, a country with only a fraction of the material prosperity of the United States, was able to surpass the world's wealthiest and most powerful nation in the race to outer space. In the minds of many university scholars and members of the public alike, the fault seemed to lie with a flabby American high school curriculum that was no match for the Soviet Union's merciless regimen of math and science for its brightest students. Quickly, the race to beat the Soviets in space became a race to outdo them in the classroom as well, with many educators and university scientists seeing physics as needing the most sweeping overhaul among all subjects within the high school curriculum, in order for America to produce the scientists and engineers needed to compete with the Soviets. After Sputnik's launch, the American high school physics curriculum underwent major reforms, yet it already had undergone what seemed an equally extensive change just after World War II. Starting in the 1940s and continuing into the early 1950s, progessive educators created a physics curriculum that related science to the everyday concerns, problems, and interests of teenagers as a way to meet the needs of non-collegebound students whose numbers in high schools had swelled during the previous two decades. After Sputnik, reformers advocated replacing the progressive curriculum with a discipline-based curriculum, as, for example, the one that the Physical Science Study Committee (PSSC) created in the late 1950s to promote basic research in physics and to develop the manpower required to compete with the Soviet Union in space and military technology. Both of these reform efforts influenced the high school physics curriculum over the long term, though at times in ways that the

Analysing The Economic Payoffs From Basic Research

Cost benefit approaches for evaluating the contribution of basic research investment have severe limitations and a number of undesirable consequences. We propose an alternative, information-theoretic, approach for identifying the economic benefits engendered by basic research. We emphasize the role of information linkages, the economic value of both findings and non-findings, and the consequences of disclosure incentives for realizing the economic benefits from basic research investments. We introduce the concepts of homotopic mappings and analogic links as relevant for differentiating among the prospective contributions of competing basic research projects, and we examine how the lumpiness or indivisibility of basic research investments may influence the conduct of basic research. The methodology and reasoning of our approach is illustrated by an examination of the case of basic research in high energy physics.

Structural traits of destruction of tungsten base cathode materials

STRUCTURAL TRAITS OF DESTRUCTION OF TUNGSTEN BASE CATHODE MATERIALS P. Ya. Radchenko, V. V. Panichkina, A. V. Krainikov, and A. V. Perepelkin UDC 621.762.5001 Beams of heavy ions are widely used in basic physical research as well as in the solu- tion of a number of technical and applied problems [i]. This became possible thanks to ac- celeration techniques and the use of sources of multiply charged ions (MCI). One of the most efficient sources is the arc source with heated cathode [2]. The rate of destruction of the cathode on the side of the discharge in ion bombardment determines the length of continuous operation of such a source. A change of the geometry of the discharge and also atoms of the deteriorating cathode affect the intensity of the flux of MCI. The operating conditions of the source of MCI (voltage 500-1000 V, current 5-20 A) dic- tate the basic demands on the material of the cathode: high melting point, low coefficient of sputtering, good thermal conductivity, and large work function [2]. These requirements are most fully met by tungsten, and cathodes are therefore usually made by machining forged tungsten rods. The complex shape of the cathode and the brittleness of tungsten at medium and low temperatures make such machining difficult. Sintering would greatly simplify the production technology of tungsten cathodes [3]. Unless sintering materials are subjected to forming, they always contain residual pores. We therefore studied the effect of residual porosity on the serviceability of sintered cath- odes in comparison with forged ones. The cathodes were made from tungsten powder with particle size 0.5-i Dm. To enhance the density of the products and to reduce the sintering temperature, an activator (nickel) was added to the powder. After pressing in molds and one sintering of the compacts in hy- drogen at different temperatures the cathodes had density of 16.51 to 18.68 g/cm 3, i.e., they contained between 2.7 and 14.1% pores (Fig. i). They were tested on a stand of ion sources and in the cyclotron U-300 of the Laboratory of Nuclear Reactions of the Joint In- stitute of Nuclear Research, and also on the stand and in the cyclotron U-240 of the Insti- tute of Nuclear Research of the Academy of Sciences of the UkrSSR [3]. The parameters of discharge of the ion source were determined from the maximal detachment of MCI of argon (At +6, Ar+7). The cathode sputtering was estimated by the loss of weight of the cathodes during the testing time. The sources operated with 100 Hz frequency and arc current pulse width of approximately 1.7"10 -s sec. The current of sextuply and heptuply charged argon ions depends on the density of the sintered cathodes: it is the higher, the denser the material is (Table i). However, when porosity is lower than 5%, the characteristics of sintered cathodes become comparable with the characteristics of forged cathodes because the tungsten rods also have some porosity. Analogously the weight loss of the cathode also depends on the porosity. Sintered tungsten with porosity of less than 5% is therefore suitable as cathode material for sources of MCI. And since the technology of powder metallurgy provides parts with the required configura- tion with dimensional fluctuations of 0.1 mm, sintered cathodes do not require additional machining. During the tests it was found that the durability of cathodes also depends on their microstructure, and not only on their density. In some cases cathodes with equal density had different durability. Cathodes with coarse-grained structure had the smallest weight loss. The photomicrographs of the working surfaces of cathodes show distinctly (Fig. 2) that destruction occurs along the weakest link of the structure, viz., the grain boundary (GB). In coarse-grained material, where the grain size is comparable with or larger than institute of Materials Science, Academy of Sciences of the Ukraine. Translated from Poroshkovaya Metallurgiya, No. ii (347), pp. 59-65, November, 1991. Original article sub- mitted November i0, 1989. 952 0038-5735/91/3011-0952512.50 9 1992 Plenum Publishing Corporation

Laser-induced fluorescence characterization of a multidipole filament plasma

A multidipole filament discharge was characterized using sub-Doppler laser-induced fluorescence (LIF). The ion temperature was found to be Ti=0.028±0.007 eV, measured in the center of an argon discharge. This stands in contrast to the much higher ion temperatures, 0.2<Ti<0.5 eV, reported by researchers using gridded electrostatic energy analyzers. The discrepancy is attributed to the energy resolution of the detectors, with the LIF providing more accurate measurements. In another result, the metastable excited-state ion density was found to scale linearly with the electron density and the discharge current under most conditions. This experiment also demonstrates that LIF can be used for basic plasma physics research in multidipole discharges.

Putting Eastern Philosophies into Western Psychotherapies

This paper examined the multidisciplinary trends in modern society that have given rise to the notion of the interconnectedness of the universe. This idea constitutes a radical departure from the spirit of basic research in physics, which had always been bent on finding the fundamental constituents of nature. The new physics abandons not only the idea of fundamental building blocks of matter, but accepts no fundamental entities whatsoever--no fundamental laws, equations, or principles. The universe is seen as a dynamic web of interrelated events, all following from the properties of other parts. The overall consistency of their mutual interrelations determines the structure of the entire web. It is evident that this idea is very much in the spirit of Eastern thought. The requirement of self-consistency that forms the basis of the new physics and the unity and interrelation of all phenomena, so strongly emphasized in Eastern mysticism, are just different aspects of the same idea, also exemplified by systems theory in psychology. The properties of any part are determined, not by some fundamental law but by the properties of all the other parts. Society as a whole is at a crossroads--at the dawn of delivery or at the dawn of destruction. What is needed for survival is a higher form of consciousness, a new stage of psychological development--one that takes into account new forms of reality. This reality has always been explored by the Eastern philosophers. It is time for this trend to expand into Western forms of psychotherapy by acknowledging the existence of a final integrative stage of development--that of global awareness.(ABSTRACT TRUNCATED AT 250 WORDS)

Silicon layers grown over SiO2 by liquid phase epitaxy: Electron Microscopical study

Defect-free silicon layers grown on insulators (SOI) are an essential component for future three-dimensional integration of semiconductor devices. Liquid phase epitaxy (LPE) has proved to be a powerful technique to grow high quality SOI structures for devices and for basic physical research. Electron microscopy is indispensable for the development of the growth technique and reveals many interesting structural properties of these materials. Transmission and scanning electron microscopy can be applied to study growth mechanisms, structural defects, and the morphology of Si and SOI layers grown from metallic solutions of various compositions.The treatment of the Si substrates prior to the epitaxial growth described here is wet chemical etching and plasma etching with NF3 ions. At a sample temperature of 20°C the ion etched surface appeared rough (Fig. 1). Plasma etching at a sample temperature of −125°C, however, yields smooth and clean Si surfaces, and, in addition, high anisotropy (small side etching) and selectivity (low etch rate of SiO2) as shown in Fig. 2.

Muon catalyzed fusion

Muon catalyzed fusion (μCF) has proved to be a fruitful subject for basic physics research as well as an unusual source of cold nuclear fusion. Recent experiments have demonstrated that over 100 fusions per muon can be catalyzed by formation of the dt¬ molecule in mixtures of deuterium and tritium. After a brief review of the subject's history, the dtμ catalysis cycle and the principal relations used in its analysis are described. Some of the more important atomic and molecular processes and cross sections needed for understanding the μCF cycle are then discussed. Finally, the status of current research is appraised.

R.S. Pease: the pre-fusion days

The author describes the early years of R.S. Pease's career with the UKAEA. The development of materials, chemical technology and basic physics research related to the science and technology of nuclear weapons and civil nuclear energy is outlined, with particular reference to Dr Pease's contributions.

Basic plasma physics research in pulsed-power technology at Ecole Polytechnique

Various aspects of the pulsed power research program at Ecole Polytechnique are reviewed. Topics include a surface and a flashboard switch, the development of plasma guns for both switching and z-pinch diodes, and studies of beam control and synchronization.

Development of an Electron-Beam-Pumped High-Power KrF Laser as a Short-Pulse Amplifier

Two modules of a low impedance electron-beam (e-beam) machine were developed to pump a 200-J, 70-ns KrF laser from both sides. The laser was designed as the power amplifier of a picosecond, terawatt excimer laser system, which will be applied to a basic physical research on extreme ultraviolet lasers. Each driving circuit of the e-beam diode was a 2.8 double parallel plate Blumlein with a 500-kV rail gap as the main switch. The energy deposited in the 42-iota laser gain region was measured by several diagnostics energy transfer efficiency and the spatial uniformity of energy deposition with the guide magnetic field of 1 kG. The triggered operation of 500-kV rail gaps, which is essential for amplifier system synchronization, was realized by the ultraviolet laser irradiation along the rail-gap axis with reduced switching time and jitter of 20 and 1.9 ns, respectively.

Applications of the MEVVA high current metal ion source

A new kind of ion source has been developed in which a MEtal Vapor Vacuum Arc (MEVVA) is used to produce the plasma from which the ion beam is extracted. The novel and exciting feture of this source is the very high metal ion beam current attainable. A total ion beam current of over 1 Ae has been extracted from the embodiment of the concept that we are presently using, and this is not a limit of the method. The source was developed to upgrade the uranium ion beam intensity of the Bevatron, LBL's heavy ion synchrotron, for basic nuclear physics research. Other important applications include its use within the Heavy Ion Fusion research effort; for ion implantation; and for other basic research uses. In this paper the source is described briefly, its performance outlined, and its potential and limitations for a variety of applications is discussed.

CEBAF: A microscope for nucleI

The newest major construction project planned by the Energy Research Office of the US Department of Energy is CEBAF, the 4 GeV continuous electron beam accelerator facility dedicated to basic nuclear physics research. The status of the project, its physics program, and present plans for the initial complement of experimental equipment are briefly reviewed.

RACETRACK: Novel device for basic research on magnetized plasmas

The construction and operation of a novel magnetized plasma device are described. The device combines characteristics of both linear mirror and toroidal confinement. It opens up new areas of basic plasma physics research. Examples of experiments on potential formation are presented.

PURPOSEFUL AND ACCIDENTAL WEATHER MODIFICATION: OUR CURRENT UNDERSTANDING

The fields of planned and inadvertent weather are reviewed. The history, major problems, current scientific status, and research needs are assessed. Planned weather modification has been plagued by groups with conflicting interests and views, and most of the major U.S. experiments have failed owing to various problems. Basic research in cloud physics and dynamics is needed but the field now has the expertise and instrumentation to make major advances. Inadvertent weather modification studies have defined many of the urban influences but studies of regional-scale effects from irrigation and aircraft contrails need to be pursued. Studies are recommended to define better the social and environmental impacts from altered weather.

ACT-I: A steady-state torus for basic plasma physics research

ACT-I: A steady-state torus for basic plasma physics research

Anodic oxidation — an improved technique in the chemical recovery and refinement of isotopic thallium

The Electromagnetic Isotope Separations Program of the Oak Ridge National Laboratory has been involved in the seperation, chemical recovery and refinement of the stable isotopes of thallium since 1947. The initial interest was in obtaining chemically pure, isotopically enriched samples of each of the stable isotopes of thallium for basic physical research. Recently, the major emphasis has shifted to 203Tl which is used to produce the radiopharmaceutical isotope 201Tl. Two persistent problems in the chemistry of isotopic thallium have been the production of unoxidized, homogeneous ingots of thallium metal and the elimination of sulfur contamination in thallic oxide. The application of anodic oxidation in the chemistry has resulted in a significant reduction of the problems previously encountered as well as considerable improvement in the chemical purity of the product. The details of this procedure and a general description of all of the appropriate thallium chemistry will be presented. In addition, the generalization of the technique to the refinement of other elements will be discussed.