Glen A. Wurden

Publications (243) View all

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  Available from: Glen A. Wurden

  Article: A bright, laser-neutron source based on relativistic transparency of solids

  M Roth, D Jung, K Falk, N Guler, O Deppert, M Devlin, A Favalli, J Fernandez, D Gautier, M Geissel, [......], G Schaumann, K Schoenberg, M Schollmeier, T Shimada, T Taddeucci, J L Tybo, F Wagner, S A Wender, C H Wilde, G A Wurden
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  ABSTRACT: Neutrons are unique particles to probe samples in many fields of research ranging from biology to material sciences to engineering and security applications. Access to bright, pulsed sources is currently limited to large accelerator facilities and there has been a growing need for compact sources over the recent years [1]. Short pulse laser driven neutron sources could be a compact and relatively cheap way to produce neutrons with energies in excess of 10 MeV. For more than a decade experiments have tried to obtain neutron numbers sufficient for applications [2–4]. Our recent experiments demonstrated an ion acceleration mechanism based on the concept of relativistic transparency. Using this new mechanism, we produced an intense beam of high energy (up to 170 MeV) deuterons directed into a Be converter to produce a forward peaked neutron flux with a record yield, on the order of 10 10 n/sr. We present results comparing the two acceleration mechanisms and the first short pulse laser generated neutron radiograph.
  Physical Review Letters 01/2013; 110:044802. · 7.37 Impact Factor
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  Available from: Glen A. Wurden

  Article: A multi-frame soft x-ray pinhole imaging diagnostic for single-shot applications

  G. A. Wurden, S. K. Coffey
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  ABSTRACT: For high energy density magnetized target fusion experiments at the Air Force Research Laboratory FRCHX machine, obtaining multi-frame soft x-ray images of the field reversed configuration (FRC) plasma as it is being compressed will provide useful dynamics and symmetry information. However, vacuum hardware will be destroyed during the implosion. We have designed a simple in-vacuum pinhole nosecone attachment, fitting onto a Conflat window, coated with 3.2 mg/cm2 of P-47 phosphor, and covered with a thin 50-nm aluminum reflective overcoat, lens-coupled to a multi-frame Hadland Ultra intensified digital camera. We compare visible and soft x-ray axial images of translating (∼200 eV) plasmas in the FRX-L and FRCHX machines in Los Alamos and Albuquerque.
  Review of Scientific Instruments 01/2012; 83(10):10E516. · 1.37 Impact Factor
• Article: Pellet refuelling of the ZT-40M reversed field pinch

  G.A. Wurden, P.G. Weber, R.G. Watt, C.P. Munson, J.C. Ingraham, R.B. Howell, T.E. Cayton, K. Büchl, E.J. Nilles
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  ABSTRACT: The first pellet refuelling of a reversed field pinch has been successfully demonstrated in ZT-40M. By injecting a series of pellets, density increases of 600% have been observed, with no disruptions. Because of a coincidence of pellet transit time, Ohmic reheat time and particle confinement times (about 0.5 ms) a significant fraction of the plasma inventory 'leaks out' before pellet ablation is complete. Strong on-axis peaking of the density profile due to pellet fuelling is not typically observed; this is due to large poloidal and toroidal deflections observed in the pellet trajectory, beginning in the plasma edge. Asymmetric ablation of the pellet by a suprathermal electron population is suspected and simple modelling can account for the observed trajectories.
  Nuclear Fusion 01/2011; 27(5):857. · 4.09 Impact Factor
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  Available from: 144.206.159.178

  Article: Divertor IR thermography on Alcator C-Mod.

  J L Terry, B LaBombard, D Brunner, J Payne, G A Wurden
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  ABSTRACT: Alcator C-Mod is a particularly challenging environment for thermography. It presents issues that will similarly face ITER, including low-emissivity metal targets, low-Z surface films, and closed divertor geometry. In order to make measurements of the incident divertor heat flux using IR thermography, the C-Mod divertor has been modified and instrumented. A 6° toroidal sector has been given a 2° toroidal ramp in order to eliminate magnetic field-line shadowing by imperfectly aligned divertor tiles. This sector is viewed from above by a toroidally displaced IR camera and is instrumented with thermocouples and calorimeters. The camera provides time histories of surface temperatures that are used to compute incident heat-flux profiles. The camera sensitivity is calibrated in situ using the embedded thermocouples, thus correcting for changes and nonuniformities in surface emissivity due to surface coatings.
  The Review of scientific instruments 10/2010; 81(10):10E513. · 1.52 Impact Factor
• Article: Magnetic design calculation and FRC formation modeling for the field reversed experiment liner

  L. A. Dorf, T. P. Intrator, T. Awe, R. Renneke, S. C. Hsu, G. A. Wurden, R. Siemon, V. E. Semenov
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  ABSTRACT: Integrated magnetic modeling and design are important to meet the requirements for (1) formation, (2) translation, and (3) compression of a field reversed configuration (FRC) for magnetized target fusion. Off-the-shelf solutions do not exist for many generic design issues. A predictive capability for time-dependent magnetic diffusion in realistically complicated geometry is essential in designing the experiment. An eddy-current code was developed and used to compute the mutual inductances between driven magnetic coils and passive magnetic shields (flux excluder plates) to calculate the self-consistent axisymmetric magnetic fields during the first two stages. The plasma in the formation stage was modeled as an immobile solid cylinder with selectable constant resistivity and magnetic flux that was free to readjust itself. It was concluded that (1) use of experimentally obtained anomalously large plasma resistivity in magnetic diffusion simulations is sufficient to predict magnetic reconnection and FRC formation, (2) comparison of predicted and experimentally observed timescales for FRC Ohmic decay shows good agreement, and (3) for the typical range of resistivities, the magnetic null radius decay rate scales linearly with resistivity. The last result can be used to predict the rate of change in magnetic flux outside of the separatrix (equal to the back-emf loop voltage), and thus estimate a minimum θ -coil loop voltage required to form an FRC.
  Journal of Applied Physics 11/2008; · 2.17 Impact Factor