120372071
A NEW METHOD FOR ION CHARGE STATE ANALYSIS
We present results showing charge‐state separation of an ion beam in a purely cylindrical geometry, using the azimuthal magnetic field of a straight conductor. This geometry, which we refer to as a current coaxial lens, has advantages for the analysis of intense ion beams where it is important to minimize space‐charge blowup of the beam due to loss of space‐charge neutralization.
98482330
Formation of metal oxides by cathodic arc deposition
Abstract Cathodic arc deposition is an established and industrially applied technique for the formation of nitrides (e.g. TiN); it can also be used for metal oxide thin film formation. A cathodic arc plasma source with the desired cathode material is operated in an oxygen atmosphere of appropriate pressure, and metal oxides of various stoichiometric composition can be formed on different substrates. We report here on a series of experiments on metal oxide formation by cathodic arc deposition for different applications. Black copper oxide has been deposited on accelerator components to increase the radiative heat transfer between the parts. Various metal oxides such as tungsten oxide, niobium oxide, nickel oxide and vanadium oxide have been deposited on ITO glass to form electrochromic films for window applications. Optical waveguide structures can be formed by refractive index variation using oxide multilayers. We have synthesized multilayers of Al 2 O 3 -Y 2 O 3 -Al 2 O 3 -Si as possible basic structures for passive optoelectronic integrated circuits, and Al 2- x Er x O 3 thin films with a variable Er concentration which is a potential component layer for the production of active optoelectronic integrated devices such as amplifiers or lasers at a wavelength of 1.53 μm. Aluminum and chromium oxide films have been deposited on a number of substrates to impart improved corrosion resistance at high temperature. Titanium sub-oxides which are electrically conductive and corrosion resistant and stable in a number of aggressive environments have been deposited on various substrates. These sub-oxides are of great interest for use in electrochemical cells. Common features of all these depositions are the high deposition rate typical for cathodic arc deposition, the good adhesion of the films due to the high metal ion energy, and the advantage of an environmentally clean method in comparison to wet-chemical oxide formation techniques.
102339269
Surface resistivity tailoring of ceramic accelerator components
Metal plasma deposition and metal ion implantation techniques have been developed that could provide a good tool for the surface modification of insulating materials for accelerator applications such as ceramics and that could provide a method for tailoring the surface resistivity over a range of many orders of magnitude. The methods make use of the metal plasma that is produced by the cathodic arc discharge; the plasma itself can be deposited onto the surface at an energy of the order of 100 eV so as to form an adherent thin film, or an energetic metal ion beam can be formed for deep implantation of the metal species below the surface so as to incorporate a controllable amount of metal into the ceramic.<<ETX>>
121406807
Measurements of vacuum arc ion charge-state distributions
The charge-state distribution of ions generated in the metal vapor vacuum arc under a wide range of experimental conditions was measured. The experiments were carried out using an ion source in which the metal vapor vacuum arc is used as the method of plasma production and by which a high-quality, high-current beam of metal ions is produced. Charge-state spectra were measured using a time-of-flight diagnostic; arc voltages were also measured. Parameters that were varied include cathode material, arc current, axial magnetic field strength, neutral gas pressure, and arc geometry. >
121242075
High current metal ion beam transport in the UNILAC injector at GSI
Abstract Transport of high current beams of metal ions through the injector beam line of the heavy ion linear accelerator, UNILAC, has been demonstrated using the MEVVA high current metal ion source. Improved operation of the MEVVA source has been achieved in various ways, including shot-to-shot reproducibility of the beam pulse, beam noise, pulse shape, and absence of “missing” pulses. The source was first tested on a high current test stand beam line, and then moved over to regularly used UNILAC injector terminal. Flat and reproducible titanium ion beam pulses were efficiently transported through the system from the ion source to the Wideroe preaccelerator entrance. A beam current of 20 mA (pulse current) of titanium (all charge states, q = 1, 2, 3) was accelerated to an energy of 280 Q keV through the single-gap accelerating structure, and a current of over 5 mA of Ti 2+ was measured at the Wideroe entrance 13 m downstream.
119595199
Transport and acceleration of high current uranium ion beams
Abstract Measurements have been made of the transport of beams produced by the high current ion source, MEVVA, and of the injection of these beams into the GSI heavy ion RFQ linac. This configuration has provided initial tests of the MEVVA ion source in an injector environment, and of the RFQ with uranium as the accelerated species. Beam currents of 78 mA of titanium and 19 mA of uranium, at an extraction voltage of 40 kV, have been transported through a 4.7 m long beam transport channel, and up to 40 mA of uranium has been transported through a single-gap accelerating column at a voltage of about 150 kV. A current of up to 5 mA of U 3+ has been measured at the exit detector of the RFQ.
119047522
Cosmological backreaction from perturbations
We write the averaged Einstein equations in a form suitable for use with Newtonian gauge linear perturbation theory and track the size of the modifications to standard Robertson–Walker evolution on the largest scales as a function of redshift for both Einstein–de Sitter and ΛCDM cosmologies. In both cases the effective energy density arising from linear perturbations is of the order of 10−5 times the matter density, as would be expected, with an effective equation of state weff≈−1/19. Employing a modified Halofit code to extend our results to quasilinear scales, we find that, while larger, the deviations from Robertson–Walker behaviour remain of the order of 10−5.
119209860
The magnitude of the non-adiabatic pressure in the cosmic fluid
Understanding the non-adiabatic pressure, or relative entropy, perturbation is crucial for studies of early-Universe vorticity and cosmic microwave background observations. We calculate the evolution of the linear non-adiabatic pressure perturbation from radiation domination to late times, numerically solving the linear governing equations for a wide range of wavenumbers. Using adiabatic initial conditions consistent with Wilkinson Microwave Anisotropy Probe seven-year data, we find nevertheless that the non-adiabatic pressure perturbation is non-zero and grows at early times, peaking around the epoch of matter/radiation equality and decaying in matter domination. At early times or large redshifts (z= 10 000) its power spectrum peaks at a comoving wavenumber k≈ 0.2 h Mpc−1, while at late times (z= 500) it peaks at k≈ 0.02 h Mpc−1.
119227429
INTRINSIC BISPECTRA OF COSMIC MAGNETIC FIELDS
Forthcoming data sets from the Planck experiment and others are in a position to probe the cosmic microwave background (CMB) non-Gaussianity with higher accuracy than has yet been possible, and potentially open a new window into the physics of the very early universe. However, a signal need not necessarily be inflationary in origin, and possible contaminants should be examined in detail. One such is provided by early universe magnetic fields, which can be produced by a variety of models including during an inflationary phase, at phase transitions, or seeded by cosmic defects. Should such fields have been extant in the early universe, they would provide a natural source of CMB non-Gaussianity. Knowledge of the CMB angular bispectrum requires the complete Fourier-space (or "intrinsic") bispectrum. In this paper, I consider in detail the intrinsic bispectra of an early-universe magnetic field for a range of power-law magnetic spectra.
118824929
Accelerating the Universe with Gravitational Waves
Inflation generically produces primordial gravitational waves with a red spectral tilt. In this paper we calculate the backreaction produced by these gravitational waves on the expansion of the universe. We find that in radiation domination the backreaction acts as a relativistic fluid, while in matter domination a small dark energy emerges with an equation of state weff ? ?8/9.
118709501
Do Bound Structures Brake Cosmic Acceleration
In this paper we investigate the impact of the coupling between a quintessence field and clustered matter on the average equation of state of the scalar field. We take the NFW profile to be characteristic of bound structures on galactic and cluster scales, and the isothermal distribution to hold for objects on supercluster scales. Solving analytically for the scalar-field profile, we find that the greatest impact on the equation of state comes from the superclusters. Employing numerical case studies, we verify this effect and probe its dependence on the evolutionary state of the supercluster. An estimate across the Hubble volume yields corrections to the homogeneous equation of state of ~ 3%, increasing with coupling strength.