oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2020 ( 5 )

2019 ( 362 )

2018 ( 432 )

2017 ( 454 )

Custom range...

Search Results: 1 - 10 of 374476 matches for " C. P. Welsch "
All listed articles are free for downloading (OA Articles)
Page 1 /374476
Display every page Item
Development of Rebunching Cavities at IAP
C. P. Welsch,K. -U. Kuehnel,A. Schempp
Physics , 2000,
Abstract: A focus of work at IAP has been the development and optimization of spiral loaded cavities since the 1970s [A. Schempp et al, NIM 135, 409 (1976)]. These cavities feature a high efficiency, a compact design and a big variety of possible fields of application. They find use both as bunchers and post accelerators to vary the final energy of the beam. In comparison to other available designs, the advantage of these structures lies in their small size. Furthermore they can easily be tuned to the required resonance frequency by varying the length of the spiral. Due to the small size of the cavities the required budget can also be kept low. Here, two slightly different types of spiral loaded cavities, which were built for the REX-ISOLDE project at CERN and the intensity upgrade program at GSI are being discussed.
Development of rebunching cavities at IAP
C. P. Welsch,K. U. Kuehnel,A. Schempp
Physics , 2000,
Abstract: A focus of work at IAP has been the development and optimization of spiral loaded cavities since the 1970s [A. Schempp et al, NIM 135, 409 (1976)]. These cavities feature a high efficiency, a compact design and a big variety of possible fields of application. They find use both as bunchers and post accelerators to vary the final energy of the beam. In comparison to other available designs, the advantage of these structures lies in their small size. Furthermore they can easily be tuned to the required resonance frequency by varying the length of the spiral. Due to the small size of the cavities the required budget can also be kept low. Here, two slightly different types of spiral loaded cavities, which were built for the REX-ISOLDE project at CERN and the intensity upgrade program at GSI are being discussed.
Design of a novel electrostatic ion storage ring at KACST
M. O. A. El Ghazaly,S. M. Alshammari,C. P. Welsch,H. H. Alharbi
Physics , 2013, DOI: 10.1016/j.nima.2013.01.026
Abstract: A new electrostatic storage ring for beams at energies up to 30keV.q is currently under development at the National Centre for Mathematics and Physics (NCMP), King Abdulaziz City for Science and Technology (KACST). The ring design is based on the existing electrostatic storage rings, but stretches significantly beyond them in that it shall form the core of a unique flexible experimental facility at KACST. The lattice of this ring has been designed in a way that enables the use of state-of-the-art experimental methods to study electron-ion, laser-ion, and ion-neutral beams interactions. The lattice design also allows for a future upgrade of the ring to a double storage ring structure that would enable ion-ion beam interactions to be performed. In this paper, we present the design of this ring with a focus on beam dynamics calculations for the 7o single-bend racetrack layout. The study is principally based on the SIMION8 program. We complemented this study further by using purpose-written routine and MAD-X simulation code. An in-depth investigation into beam stability under consideration of non-linear field components in the electrostatic optical elements, is presented. Finally, different working points and stability regions are discussed.
Beam Halo Imaging with a Digital Optical Mask
H. D. Zhang,R. B. Fiorito,A. G. Shkvarunets,R. A. Kishek,C. P. Welsch
Physics , 2012, DOI: 10.1103/PhysRevSTAB.15.072803
Abstract: Beam halo is an important factor in any high intensity accelerator. It can cause difficulties in the control of the beam, emittance growth, particle loss and even damage to the accelerator. It is therefore essential to understand the mechanisms of halo formation and its dynamics in order to control and minimize its effects. Experimental measurement of the halo distribution is an important tool for such studies. In this paper, we present a new adaptive masking method that we have developed to image beam halo, which uses a digital micro-mirror-array device (DMD). This method has been thoroughly investigated in the laboratory using laser and white light sources, and with real beams produced by the University of Maryland Electron Ring (UMER). A high dynamic range ~10(5) has been demonstrated with this new method and recent studies indicate that this number can be exceeded for more intense beams by at least an order of magnitude. The method is flexible, easy to setup and can be used at any accelerator or light source. We present the results of our measurements of the performance of the method and images of beam halos produced under various experimental conditions.
Global Energetics of Thirty-Eight Large Solar Eruptive Events
A. G. Emslie,B. R. Dennis,A. Y. Shih,P. C. Chamberlin,R. A. Mewaldt,C. S. Moore,G. H. Share,A. Vourlidas,B. T. Welsch
Physics , 2012, DOI: 10.1088/0004-637X/759/1/71
Abstract: We have evaluated the energetics of 38 solar eruptive events observed by a variety of spacecraft instruments between February 2002 and December 2006, as accurately as the observations allow. The measured energetic components include: (1) the radiated energy in the GOES 1 - 8 A band; (2) the total energy radiated from the soft X-ray (SXR) emitting plasma; (3) the peak energy in the SXR-emitting plasma; (4) the bolometric radiated energy over the full duration of the event; (5) the energy in flare-accelerated electrons above 20 keV and in flare-accelerated ions above 1 MeV; (6) the kinetic and potential energies of the coronal mass ejection (CME); (7) the energy in solar energetic particles (SEPs) observed in interplanetary space; and (8) the amount of free (nonpotential) magnetic energy estimated to be available in the pertinent active region. Major conclusions include: (1) the energy radiated by the SXR-emitting plasma exceeds, by about half an order of magnitude, the peak energy content of the thermal plasma that produces this radiation; (2) the energy content in flare-accelerated electrons and ions is sufficient to supply the bolometric energy radiated across all wavelengths throughout the event; (3) the energy contents of flare-accelerated electrons and ions are comparable; (4) the energy in SEPs is typically a few percent of the CME kinetic energy (measured in the rest frame of the solar wind); and (5) the available magnetic energy is sufficient to power the CME, the flare-accelerated particles, and the hot thermal plasma.
Cholesterol-lowering properties of Ganoderma lucidum in vitro, ex vivo, and in hamsters and minipigs
A Berger, D Rein, E Kratky, I Monnard, H Hajjaj, I Meirim, C Piguet-Welsch, J Hauser, K Mace, P Niederberger
Lipids in Health and Disease , 2004, DOI: 10.1186/1476-511x-3-2
Abstract: Organic fractions containing oxygenated lanosterol derivatives inhibited cholesterol synthesis in T9A4 hepatocytes. In hamsters, 5% Gl did not effect LDL; but decreased total cholesterol (TC) 9.8%, and HDL 11.2%. Gl (2.5 and 5%) had effects on several fecal neutral sterols and bile acids. Both Gl doses reduced hepatic microsomal ex-vivo HMG-CoA reductase activity. In minipigs, 2.5 Gl decreased TC, LDL- and HDL cholesterol 20, 27, and 18%, respectively (P < 0.05); increased fecal cholestanol and coprostanol; and decreased cholate.Overall, Gl has potential to reduce LDL cholesterol in vivo through various mechanisms. Next steps are to: fully characterize bioactive components in lipid soluble/insoluble fractions; evaluate bioactivity of isolated fractions; and examine human cholesterol lowering properties. Innovative new cholesterol-lowering foods and medicines containing Gl are envisioned.In Kampo Chinese folk medicine, mushrooms have been known to have medicinal properties since AD1200 [1].In recent years, there has been interest in the cholesterol lowering properties of mushrooms, including Ganoderma lucidum (Reishi-, Longevity-, or Phantom mushrooms, Biladi Top, Young-zhi, The King Of Herbs, Ling Zhi in Chinese, Saru-no-koshikake and Mannendake in Japanese) [2,3], Pleurotus ostreatus (Oyster mushroom) [4-8], Volvariella volvacea (Straw mushroom) [9], Agaricus bisporus (champignon) [10], Agaricus campestris [11], Auricularia auricula (Tree-ear), Tremella fuciformis (White-jelly leaf) [12,13], Grifola frondosa (Maitake mushroom) [14,15], Lentinus erodes (Shiitake) and isolated fractions [14,16], and Polyporus confluens (Ningyotake) [17]. In an earlier work, Kaneda and Tokuda [18] studied cholesterol lowering properties of ether-, water- and ethanol extracts from caps and stems from Lentinus edodes, Auricularia polytricha (Jews-ear), Flammulina velutipes, and Agaricus bisporus. The majority of these studies were performed in rats. The cholesterol lowering properties o
Experimental evidence for electric surface resistance in niobium
Tobias Junginger,Wolfgang Weingarten,Carsten P. Welsch
Physics , 2013,
Abstract: Identifying the loss mechanisms of niobium cavities enables an accurate determination of applications for future accelerator projects and points to research topics required to mitigate current limitations. For several cavities an increasing surface resistance above a threshold field, saturating at higher field has been observed. Measurements on samples give evidence that this effect is caused by the surface electric field. The measured temperature and frequency dependence is consistent with a model that accounts for these losses by interface tunnel exchange between localized states in oxides formed along grain boundaries and the adjacent superconductor.
A Qualitative Dynamical Modelling Approach to Capital Accumulation in Unregulated Fisheries
K. Eisenack,H. Welsch,J. P. Kropp
Computer Science , 2002, DOI: 10.1016/j.jedc.2005.08.004
Abstract: Capital accumulation has been a major issue in fisheries economics over the last two decades, whereby the interaction of the fish and capital stocks were of particular interest. Because bio-economic systems are intrinsically complex, previous efforts in this field have relied on a variety of simplifying assumptions. The model presented here relaxes some of these simplifications. Problems of tractability are surmounted by using the methodology of qualitative differential equations (QDE). The theory of QDEs takes into account that scientific knowledge about particular fisheries is usually limited, and facilitates an analysis of the global dynamics of systems with more than two ordinary differential equations. The model is able to trace the evolution of capital and fish stock in good agreement with observed patterns, and shows that over-capitalization is unavoidable in unregulated fisheries.
A plasma wakefield acceleration experiment using CLARA beam
G. Xia,D. Angal-Kalinin,J. Clarke,J. Smith,E. Cormier-Michel,J. Jones,P. H. Williams,J. W. Mckenzie,B. L. Militsyn,K. Hanahoe,O. Mete,A. Aimidula,C. P. Welsch
Physics , 2014, DOI: 10.1016/j.nima.2013.10.092
Abstract: We propose a Plasma Accelerator Research Station (PARS) based at proposed FEL test facility CLARA (Compact Linear Accelerator for Research and Applications) at Daresbury Laboratory. The idea is to use the relativistic electron beam from CLARA, to investigate some key issues in electron beam transport and in electron beam driven plasma wakefield acceleration, e.g. high gradient plasma wakefield excitation driven by a relativistic electron bunch, two bunch experiment for CLARA beam energy doubling, high transformer ratio, long bunch self-modulation and some other advanced beam dynamics issues. This paper presents the feasibility studies of electron beam transport to meet the requirements for beam driven wakefield acceleration and presents the plasma wakefield simulation results based on CLARA beam parameters. Other possible experiments which can be conducted at the PARS beam line are also discussed.
The Coronal Global Evolutionary Model: Using HMI Vector Magnetogram and Doppler Data to Model the Buildup of Free Magnetic Energy in the Solar Corona
George H. Fisher,William. P. Abbett,David J. Bercik,Maria D. Kazachenko,Benjamin J. Lynch,Brian T. Welsch,J. Todd Hoeksema,Keiji Hayashi,Yang Liu,Aimee A. Norton,Alberto Sainz Dalda,Xudong Sun,Marc L. DeRosa,Mark C. M. Cheung
Physics , 2015, DOI: 10.1002/2015SW001191
Abstract: The most violent space weather events (eruptive solar flares and coronal mass ejections) are driven by the release of free magnetic energy stored in the solar corona. Energy can build up on timescales of hours to days, and then may be suddenly released in the form of a magnetic eruption, which then propagates through interplanetary space, possibly impacting the Earth's space environment. Can we use the observed evolution of the magnetic and velocity fields in the solar photosphere to model the evolution of the overlying solar coronal field, including the storage and release of magnetic energy in such eruptions? The objective of CGEM, the Coronal Global Evolutionary Model, funded by the NASA/NSF Space Weather Modeling program, is to develop and evaluate such a model for the evolution of the coronal magnetic field. The evolving coronal magnetic field can then be used as a starting point for magnetohydrodynamic (MHD) models of the corona, which can then be used to drive models of heliospheric evolution and predictions of magnetic field and plasma density conditions at 1AU.
Page 1 /374476
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.