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Brantov A.V.,Russian Academy of Sciences | Bychenkov V.Yu.,Russian Academy of Sciences | Popov K.I.,University of Ottawa | Fedosejevs R.,University of Alberta | And 2 more authors.
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2011

Based on 3D particle-in-cell (PIC) simulations a comparative analysis of laser-triggered proton generation from the interaction of short high-intensity laser pulses with ultrathin foils and dense gas jets has been performed. It has been shown that for ultra-relativistic laser intensities the use of low-density targets with near critical density (aerogel or dense gas jet) has no advantage in comparison with ultrathin foils in terms of maximum proton energy and spectrum quality. Utilization of mass-limited foils with submicron thickness demonstrates even greater superiority for overdense targets and allows one to produce monoenergetic proton beams with energies of hundreds of mega-electron-volts by using high-contrast laser pulses with energies of the order of tens of Joules. © 2011 Elsevier B.V.

Krauser J.,Hochschule Harz University of Applied Sciences | Nix A.-K.,University of Gottingen | Gehrke H.-G.,University of Gottingen | Hofsass H.,University of Gottingen | And 2 more authors.
Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms | Year: 2012

Conducting ion tracks are formed when high-energy heavy ions (e.g. 1 GeV Au) pass through tetrahedral amorphous carbon (ta-C). These nanowires with a diameter of about 8 nm are embedded in the insulating ta-C matrix and of interest for various nanotechnological applications. Usually the overall conductivity of the tracks and the current/voltage characteristics (Ohmic or non-Ohmic) vary strongly from track to track, even when measured on the same sample, indicating that the track formation is neither complete nor homogeneous. To improve the track conductivity, doping of ta-C with N, B, Cu, or Fe is investigated. Beneficial changes in track conductivity after doping compete with a conductivity increase of the surrounding matrix material. Best results are achieved by incorporation of 1 at.% Cu, while for different reasons, the improvement of the tracks remains moderate for N, B, and Fe doping. Conductivity enhancement of the tracks is assumed to develop during the ion track formation process by an increased number of localized states which contribute to the current transport. © 2011 Elsevier B.V. All rights reserved.

Ogul R.,Selcuk University | Imal H.,Selcuk University | Ergun A.,Selcuk University | Buyukcizmeci N.,Selcuk University | And 2 more authors.
EPJ Web of Conferences | Year: 2015

We have investigated and interpreted the production cross sections and isotopic distributions of projectile-like residues in the reactions 124Sn + 124Sn and 112Sn + 112Sn at an incident beam energy of 1 GeV/nucleon measured with the FRS fragment separator at the GSI laboratory. For the interpretation of the data, calculations within the statistical multifragmentation model (SMM) for an ensemble of excited sources were performed with ensemble parameters. The possible modification of symmetry energy parameter, in the multifragmentation region at the low density and hot freeze-out environment, is studied. It is reconfirmed that a significant reduction of the symmetry energy term is found necessary to reproduce experimental results at these conditions. We have also found a decreasing trend of the symmetry energy for large neutron-rich fragments of low excitation energy which is interpreted as a nuclear-structure effect.

Celona L.,National Institute of Nuclear Physics, Italy | Gammino S.,National Institute of Nuclear Physics, Italy | Ciavola G.,National Institute of Nuclear Physics, Italy | Maimone F.,Helmholtzzentrum fur Schwerionenforschung GmbH | Mascali D.,National Institute of Nuclear Physics, Italy
Review of Scientific Instruments | Year: 2010

Coupling improvements between microwaves and plasmas are a key factor to design more powerful electron cyclotron resonance and microwave ion sources. On this purpose different activities have been undertaken by the INFN-LNS ion source team and a new approach was developed. Recent experiments confirmed the simulations, demonstrating that even in presence of a dense plasma, resonant modes are excited inside the cavity and the plasma dynamics depends on their structure. An overview of the coupling issues on microwave ion sources is also given along with a discussion on alternative coupling techniques. © 2010 American Institute of Physics.

Krauser J.,Hochschule Harz University of Applied Sciences | Gehrke H.-G.,University of Gottingen | Hofsass H.,University of Gottingen | Trautmann C.,Helmholtzzentrum fur Schwerionenforschung GmbH | Weidinger A.,Helmholtz Center Berlin
Proceedings of the IEEE Conference on Nanotechnology | Year: 2011

In this work we combine ion track techniques to construct self-aligned vertical structures with nanometer dimensions. The main idea is to use multilayer targets and apply various etching techniques to create openings along the ion path. By irradiating such a multilayered sample including a tetrahedral amorphous carbon (ta-C) layer and a polymer film on top of the stack with swift heavy ions, the track in the polymer and the electrically conducting track in the ta-C layer are self-aligned and need no extra adjustment. Additional layers, e.g., metals or insulators which are little or not affected by the passage of the ions, can be inserted between the polymer resist and the ta-C film. Two appropriate device applications are proposed: a nano-sized field emission cathode and a two terminal quantum dot structure which might be completed to a transistor by adding a gate terminal. © 2011 IEEE.

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