10,726 research outputs found
Portrait of Dymphna Cusack, author [picture]
No full textCondition: Good.; Part of collection: Ion Idriess glass plate negative collection.; Title from signature on image.; Also available in an electronic version via the Internet at: http://nla.gov.au/nla.pic-vn3299415. "My love, Dymphna Cusack 1954"--signature on image
Measurement of MAST edge ion temperatures and velocities
No full textA novel experimental method using gas puffing of neutrals to stimulate charge exchange emission has been developed to measure ion temperatures and toroidal rotation velocities in the edge of MAST. This uses cold deuterium gas puffing as the source of neutrals in place of the more usual method of donation from neutral beams. A pre-existing spectroscopy system with 60 toroidal chords with spatial resolution of 1.5 mm and temporal resolution of 10 ms was adopted for this purpose. The C6+(n = 8 → 7) transition at 5290.5 A was identified as the optimal emission line, while a resonance in the cross section between the D0(n = 2) and C6+(n = 8) energy levels makes the measurement feasible.
In order to assess the potential of this measurement method a model of the expected performance of the system was created. All important processes in the edge regime were identified and density profiles of electrons, carbon ions and deuterium neutrals were modelled. These were combined to produce a prediction of performance.
The spectrum observed was complicated by molecular deuterium emission and a fitting routine to this complex data was developed and benchmarked. Correction factors were also
identified and calculated for the emission line. System improvements were made including a new bandpass filter, gas valve and camera.
Analysis of the measured intensity profiles showed a good response to gas puffing and toroidal velocity and ion temperature results are presented. A large reverse shear in the toroidal rotation is observed close to the separatrix in normal operation, but not in counter-rotation experiments. This is attributed to parallel Pfirsch-Schluter flow. The ion temperature results display a large difference between ion and electron temperature in the pedestal region in many H-mode discharges. This is linked to the collisionality of the ions such that flux surface coupling in the banana regime leads to small ion gradients
Ion Idriess, author, 1953
No full textIon Idriess, author, sitting at a desk reading his book "Lightning Ridge
MIAMI: Microscope and ion accelerator for materials investigations
No full textA transmission electron microscope (TEM) with in situ ion irradiation has been built at the University of Salford, U.K. The system consists of a Colutron G-2 ion source connected to a JEOL JEM-2000FX TEM via an in-house designed and constructed ion beam transport system. The ion source can deliver ion energies from 0.5 to 10 keV for singly charged ions and can be floated up to 100 kV to allow acceleration to higher energies. Ion species from H to Xe can be produced for the full range of energies allowing the investigation of implantation with light ions such as helium as well as the effects of displacing irradiation with heavy inert or self-ions. The ability to implant light ions at energies low enough such that they come to rest within the thickness of a TEM sample and to also irradiate with heavier species at energies sufficient to cause large numbers of atomic displacements makes this facility ideally suited to the study of materials for use in nuclear environments. TEM allows the internal microstructure of a sample to be imaged at the nanoscale. By irradiating in situ it is possible to observe the dynamic evolution of radiation damage which can occur during irradiation as a result of competing processes within the system being studied. Furthermore, experimental variables such as temperature can be controlled and maintained throughout both irradiation and observation. This combination of capabilities enables an understanding of the underlying atomistic processes to be gained and thus gives invaluable insights into the fundamental physics governing the response of materials to irradiation. Details of the design and specifications of the MIAMI facility are given along with examples of initial experimental results in silicon and silicon carbide
Small microwave ion source for an ion implanter
No full textThree kinds of small 24.5 GHz microwave ion sources have been developed for a middle current implanter. The magnetic fields of the sources are produced by an electromagnetic coil, electromagnetic coil added permanent magnet ring, and permanent magnet rings, respectively. Adopting single-hole accel-decel extraction electrodes with about 5 mA of nitrogen and oxygen, ion current can be extracted from them. The microwave power consumption is about 100-200 W. (C) 1996 American Institute of Physics.Instruments & InstrumentationPhysics, AppliedSCI(E)
Recent ion source development in China
No full textThe recent development of various types of ion sources and their application in China is reviewed. Emphasis is given to new improvements of the electron cyclotron resonance ion source; MEVVA ion source, electron beam evaporation metal ion source, compact multicusp ion source, as well as compact negative ion sources with permanent magnets. Some of the new proposals are also presented. (C) 1996 American Institute of Physics.Instruments & InstrumentationPhysics, AppliedSCI(E)
Doubly-charged Negative Ion of C60 Molecule
No full textWithin the Dirac- and Lorentz-bubble potential models an electronic structure of the doubly-charged negative ion -2 C has been studied by a variational method. It is s 60 hown that even in the first approximation of this method when a trial wave function of the two electrons is represented as a product of one-electron functions the total energy of the system is negative, a manifestation of the existence of a stable state of the doubly-charged negative ion in these models. The second electron affinity of C60 according to estimation is about ?2 ? 1 eV. The photodetachment cross sections ?(?) of this ion have been calculated as well. Near threshold ?(?) is found to exhibit peculiar and interesting behavior. The first cross section accompanied by the transformation of the doubly-charged negative ion into a singly-charged one is exponentially small near the process threshold. The second cross section corresponds to the photodetachment of a singly-charged ion; it increases at the threshold as a power function of the kinetic energy of the photoelectron. These cross sections are of the same order as the photodetachment cross sections of atomic ions with the same electron affinity
Studying individual magnetic nanoparticles with X-ray PEEM
No full textThe thesis addresses a subject with broad implications in various scientific and technical areas. It presents unique direct observations of the magnetic state of single particles of iron (Fe), cobalt (Co) and nickel (Ni) with nanoscopic dimensions by means of spatially-resolved X-ray magnetic circular dichroism (XMCD). The X-ray photoemission electron microscopy (PEEM) data are complemented with in situ reflection high energy electron diffraction (RHEED) investigations, ex situ scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements. This approach enabled to correlate the magnetic character of the particles with their individual size. The experimental findings are compared with calculated magnetic anisotropy contributions of the three different types of deposited nanoparticles (NPs). It was found that despite their different atomic structure, the body-centered cubic (bcc) iron and face-centered cubic (fcc) cobalt nanoparticles have a similar behavior and can exist in a state which demonstrates an unexpected ferromagnetic (FM) behavior with sizes down to 8 nm at room temperature (RT), while nickel particles only exhibit the expected superparamagnetic (SPM) behavior. This ferromagnetic state is assigned to an energetically excited, metastable structure which has a remarkably long life time before it decays into the expected superparamagnetic state. Combining PEEM with XMCD measurements allowed for the first time to follow the spontaneous transition from ferromagnetic to superparamagnetic behavior in single nanoparticles.
Detailed calculations of all magnetic anisotropy contributions for different sizes and types of particles indicate that the reported high anisotropy state can be associated with a meta-stable structural state due to the presence of local defects within the NPs, independent of the particle atomic structure and size.
These observations shed new light on the mechanisms which establish the size-dependent evolution of magnetic properties at the nanoscale
Development of ion sources for materials processing in China
No full textThis article reviews the development of ion sources for materials processing and the progress of commercial product of ion sources in China. The various ion-beam processing and the relative needs to ion sources are mentioned and discussed, such as ion sources with ion implantation, plasma immersion ion implantation, ion-beam-assisted deposition, ion-beam deposition, and so on. The states of progress for different kinds of ion sources specially for electron cyclotron resonance/ microwave, metal vapor vacuum arc, radio frequency (rf) ion source, end-Hall ion source, and cluster ion source, are given and discussed. (c) 2006 American Institute of Physics.Instruments & InstrumentationPhysics, AppliedSCI(E)CPCI-S(ISTP)
A side extraction PIG negative ion source with a permanent magnet
No full textA side extraction PIG ion source with a permanent magnet is introduced, which can be used not only for producing miliampere positive ion beams, but also for direct extraction of negative ions of some elements with larger electron affinity. So far H, O, and F negative ions have been extracted from the source. At -15 kV extraction voltage, O- ion beams of 130 mu A and a F- ion beam of 75 mu A are extracted, and the discharge power consumption is 110 and 280 W, respectively. (C) 1996 American Institute of Physics.Instruments & InstrumentationPhysics, AppliedSCI(E)
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