119438526
Microquasar Observations with MERLIN
A series of observations of microquasar GRS1915+105 were made by the MERLIN telescope array in the spring of 2003 at 18 cm. The images show polarization in the jet components, with two epochs displaying Faraday rotation of about 2500 rad/m2. This effect is a demonstration of the similarities between microquasars and extragalactic jets.
2295410
Keck spectroscopy of CLASS gravitational lenses
We present the optical spectra of four newly discovered gravitational lenses from the Cosmic Lens All-Sky Survey (CLASS). These observations were carried out using the Low Resolution Imaging Spectrograph on the W. M. Keck-I Telescope as part of a program to study galaxy-scale gravitational lenses. From our spectra we found the redshift of the background source in CLASS B0128+437 (zs = 3.1240 ± 0.0042) and the lensing galaxy redshifts in CLASS B0445+123 (zl = 0.5583 ± 0.0003) and CLASS B0850+054 (zl = 0.5883±0.0006). Intriguingly, we also discovered that CLASS B0631+519 may have two lensing galaxies (zl,1 = 0.0896 ± 0.0001, zl,2 = 0.6196 ± 0.0004). We also found a single unidentified emission line from the lensing galaxy in CLASS B0128+437 and the lensed source in CLASS B0850+054. We find the lensing galaxies in CLASS B0445+123 and CLASS B0631+519 (l, 2) to be early-type galaxies with Einstein Radii of 2.8 − 3.0 h kpc. The deflector in CLASS B0850+054 is a late-type galaxy with an Einstein Radius of 1.6 h kpc.
15014169
Multi-wavelength INTEGRAL network (MINE) observations of the microquasar GRS 1915+105
We present the international collaboration MINE (Multi-lambda Integral NEtwork) aimed at conducting multi-wavelength observations of X-ray binaries and microquasars simultaneously with the INTEGRAL gamma-ray satellite. We will focus on the 2003 March-April campaign of observations of the peculiar microquasar GRS 1915+105 gathering radio, IR and X-ray data. The source was observed 3 times in the plateau state, before and after a major radio and X-ray flare. It showed strong steady optically thick radio emission corresponding to powerful compact jets resolved in the radio images, bright near-infrared emission, a strong QPO at 2.5 Hz in the X-rays and a power law dominated spectrum without cutoff in the 3-300 keV range. We compare the different observations, their multi-wavelength light curves, including JEM-X, ISGRI and SPI, and the parameters deduced from fitting the spectra obtained with these instruments on board INTEGRAL.
9431894
ARCS, the Arcminute Radio Cluster‐lens Search – I. Selection criteria and initial results
We present the results of an unbiased radio search for gravitational lensing events with image separations between 15 and 60 arcsec, which would be associated with clusters of galaxies with masses >1013–14 M⊙. A parent population of 1023 extended radio sources stronger than 35 mJy with stellar optical identifications was selected using the FIRST radio catalogue at 1.4 GHz and the APM optical catalogue. The FIRST catalogue was then searched for companions to the parent sources stronger than 7 mJy and with separation in the range 15 to 60 arcsec. Higher-resolution observations of the resulting 38 lens candidates were made with the VLA at 1.4 and 5 GHz, and with MERLIN at 5 GHz in order to test the lens hypothesis in each case. None of our targets was found to be a gravitational lens system. These results provide the best current constraint on the lensing rate for this angular scale, but improved calculations of lensing rates from realistic simulations of the clustering of matter on the relevant scales are required before cosmologically significant constraints can be derived from this null result. We now have an efficient, tested observational strategy with which it will be possible to make an order-of-magnitude larger unbiased search in the near future.
7400310
A survey of polarization in the JVAS/CLASS flat-spectrum radio source surveys – I. The data and catalogue production
We have used the very large JVAS/CLASS 8.4-GHz surveys of flat-spectrum radio sources to obtain a large, uniformly observed and calibrated, sample of radio source polarizations. These are useful for many investigations of the properties of radio sources and the interstellar medium. We discuss comparisons with polarization measurements from this survey and from other large-scale surveys of polarization in flat-spectrum sources.
1137585
Global 8.4-GHz VLBI observations of JVAS B0218+357
In this paper we present new observations of the gravitational lens system JVAS B0218+357 made with a global very long baseline interferometry (VLBI) network at a frequency of 8.4 GHz. Our maps have an rms noise of 30 μJy beam - 1 and with these we have been able to image much of the extended structure of the radio jet in both the A and B images at high resolution (∼1 mas). The main use of these maps will be to enable us to further constrain the lens model for the purposes of H 0 determination. We are able to identify several subcomponents common to both images with the expected parity reversal, including one which we identify as a counter-jet. We have not been successful in detecting either the core of the lensing galaxy or a third image. Using a model of the lensing galaxy we have back-projected both of the images to the source plane and find that they agree well. However, there are small, but significant, differences which we suggest may arise from multi-path scattering in the interstellar medium (ISM) of the lensing galaxy. We also find an exponent of the radial mass distribution of β 1.04, in agreement with lens modelling of published 15-GHz VLBI data. Polarization maps of each image are presented which show that the distributions of polarization across images A and B are different. We suggest that this results from Faraday rotation and associated depolarization in the lensing galaxy.
101266125
Recent advances in vacuum arc ion sources
Intense beams of metal ions can be formed from a vacuum arc ion source. Broadbeam extraction is convenient, and the time-averaged ion beam current delivered downstream can readily be in the tens of milliamperes range. The vacuum arc ion source has for these reasons found good application for metallurgical surface modification--it provides relatively simple and inexpensive access to high dose metal ion implantation. Several important source developments have been demonstrated recently, including very broad beam operation, macroparticle removal, charge state enhancement, and formation of gaseous beams. The authors have made a very broad beam source embodiment with beam formation electrodes 50 cm in diameter, producing a beam of width {approximately}35 cm for a nominal beam area of {approximately}1,000 cm{sup 2}, and a pulsed Ti beam current of about 7 A was formed at a mean ion energy of {approximately}100 keV. Separately, they`ve developed high efficiency macroparticle-removing magnetic filters and incorporated such a filter into a vacuum arc ion source so as to form macroparticle-free ion beams. Jointly with researchers at the High Current Electronics Institute at Tomsk, Russia, and the Gesellschaft fuer Schwerionenforschung at Darmstadt, Germany, they`ve developed a compact technique for increasing the charge states of ions produced in the vacuum arc plasma and thus providing a simple means of increasing the ion energy at fixed extractor voltage. Finally, operation with mixed metal and gaseous ion species has been demonstrated. Here, they briefly review the operation of vacuum marc ion sources and the typical beam and implantation parameters that can be obtained, and describe these source advances and their bearing on metal ion implantation applications.
119423648
Operational characteristics of a metal vapor vacuum arc ion source
The MEVVA ion source can produce high current pulsed beams of metallic ions using a metal vapor vacuum arc discharge as the plasma medium from which the ions are extracted. In this study, the operational characteristics of the MEVVA IV ion sources are summarized. Results are presented of measurements of the ion beam current as a function of arc current over a range of extraction voltage. Ti, Ta, and Pb were examined as the cathode materials. The arc current ranged from 50 to 250 A and the extraction voltage from 10 to 80 kV. The ion beam current was measured at two different distances from the ion source using Faraday cups, so as to investigate the beam divergence. Additionally, the cathode erosion rates were measured. Optimum operating conditions of the MEVVA ion source were determined.
101079593
Vacuum arc ion sources - micro to macro
Vacuum arc ion sources provide a convenient tool for the production of intense beams of metal ions. The sources are relatively easy to construct and they can produce beams from all of the solid metals as well as of compounds, alloys and mixtures. We have made a number of different kinds of such sources over the course of our development work at LBL in the past decade, from very small {open_quote}thumb-size{close_quote} versions to a very large one with 50-cm diameter extractor. Beam current ranges from a few milliamperes up to almost 10 amperes and extraction voltage from about 1 kV to 100 kV. Multicathode versions have been made so that one can switch between metal ion species simply and quickly. Most of the sources have been operated in a repetitively pulsed mode, and we`ve tested a dc version also. Here we outline some construction features of the array of vacuum arc ion sources that we`ve developed and used, and describe their performance and limitations.
122299704
Transport of vacuum arc plasma through straight and curved magnetic ducts
We report on an experimental investigation of the transport of a metal vapor vacuum arc plasma through straight and curved magnetic solenoids for the case of an iron plasma and for magnetic field strength up to 650 G. We find that the fraction of plasma transported increases with magnetic field strength and saturates at a field at which the ion gyroradius equals the radius of the plasma channel. The magnetic field strength at the cathode location, where the plasma is injected into the solenoid, was found to be important, and for the present work the injection efficiency optimizes at a field of about 150 G.
139645374
HIGH TECH METAL SURFACES USING ION IMPLANTATION