TY - CONF AU - Smith, S.J. AU - Biedron, S. AU - Bolin, T.B. AU - Carlsten, B.E. AU - Cary, J.R. AU - Cheatham, D.M. AU - Krawczyk, F.L. AU - Sosa Guitron, S.I. ED - Boland, Mark ED - Tanaka, Hitoshi ED - Button, David ED - Dowd, Rohan ED - Schaa, Volker RW ED - Tan, Eugene TI - Exploration of High-Gradient Structures for 4th Generation Light Sources J2 - Proc. of IPAC2019, Melbourne, Australia, 19-24 May 2019 CY - Melbourne, Australia T2 - International Particle Accelerator Conference T3 - 10 LA - english AB - As the energy, scale and therefore the cost of large-scale accelerator projects, such as X-ray free-electron lasers (XFELs) increases, new technologies must be developed in order to minimize costs and maximize efficiency wherever possible. One obvious way to reduce costs is to reduce the length of accelerating sections by utilizing higher accelerating gradients. Here we present the results of a study into the various structure options for FEL linacs, contrasting different frequencies, geometries and operating modes. An investigation into the possibility of using cryo-cooled travelling wave (TW) electron structures which allow for higher gradient operation by exploiting the anomalous skin effect is also detailed. Finally, we give simulation results from a number of commercial codes including VSim 9, for a hypothetical TW high gradient C-band structure design employing cryo-cooled technology. Breakdown effects, pulsed heating, tolerances, efficiencies and potential rf sources are also explored, all within the framework of typical FELs and their requirements. PB - JACoW Publishing CP - Geneva, Switzerland SP - 1155 EP - 1157 KW - cavity KW - FEL KW - linac KW - cryogenics KW - electron DA - 2019/06 PY - 2019 SN - 978-3-95450-208-0 DO - DOI: 10.18429/JACoW-IPAC2019-MOPTS117 UR - http://jacow.org/ipac2019/papers/mopts117.pdf ER - TY - CONF AU - Smith, S.J. AU - Bethoney, P.G. AU - Biedron, S. AU - Bolin, T.B. AU - Cary, J.R. AU - Cheatham, D.M. AU - Curtin, M.S. AU - Elfrgani, A.M.N. AU - Hartman, B. AU - Pressnall, T. AU - Schamiloglu, E. AU - Sosa Guitron, S.I. AU - Swenson, D.A. ED - Boland, Mark ED - Tanaka, Hitoshi ED - Button, David ED - Dowd, Rohan ED - Schaa, Volker RW ED - Tan, Eugene TI - 3D Electromagnetic/PIC Simulations for a Novel RFQ/RFI Linac Design J2 - Proc. of IPAC2019, Melbourne, Australia, 19-24 May 2019 CY - Melbourne, Australia T2 - International Particle Accelerator Conference T3 - 10 LA - english AB - Using the commercial software VSim 9, a highly parallelized particle-in-cell/finite difference time-domain modeling code, the performance of an existing novel RFQ/RFI linac structure designed by Ion Linac Systems is evaluated. This effort is aimed towards having an up to date full 3D start-to-end simulation of the accelerator system, which does not exist currently. The structure used is an efficient 200-MHz, 2.5-MeV, CW-RFQ/RFI proton linac. The methods employed in VSim for modelling and parameter setup are presented, along with the simulation procedures for both the Electromagnetic and PIC solver. The important figures of merit for the structure are given including the Q-factor, field distributions, shunt impedance, and important beam properties. These are then contrasted with the initial design values and analytical calculations. PB - JACoW Publishing CP - Geneva, Switzerland SP - 1158 EP - 1160 KW - rfq KW - linac KW - simulation KW - neutron KW - operation DA - 2019/06 PY - 2019 SN - 978-3-95450-208-0 DO - DOI: 10.18429/JACoW-IPAC2019-MOPTS118 UR - http://jacow.org/ipac2019/papers/mopts118.pdf ER - TY - CONF AU - Averkin, S.N. AU - Veitzer, S.A. ED - Boland, Mark ED - Tanaka, Hitoshi ED - Button, David ED - Dowd, Rohan ED - Schaa, Volker RW ED - Tan, Eugene TI - Global Model of Multi-Chamber Negative Hydrogen Ion Sources with Updated Hydrogen Plasma Chemistry J2 - Proc. of IPAC2019, Melbourne, Australia, 19-24 May 2019 CY - Melbourne, Australia T2 - International Particle Accelerator Conference T3 - 10 LA - english AB - Global models of plasma discharges are used to calculate volume averaged number densities and temperatures of plasma components. The wall fluxes are estimated based on heuristic expressions that "patch" together analytic and semi-analytic solutions covering from low-pressure to high-pressure regimes. Due to the nature of the wall fluxes estimation, the global models are limited to single chamber designs. We present the extension of the Global Enhanced Vibrational Kinetic Model (GEVKM) * for the multi-chamber design with the updated hydrogen plasma chemistry **. The extended GEVKM consists of separate global models for macroscopic parameters of all species in each chamber coupled through interface boundary conditions. We compare our model with fluid simulation results for a plasma composition and species temperatures in the negative hydrogen ion source developed at IPP Garching. PB - JACoW Publishing CP - Geneva, Switzerland SP - 2144 EP - 2146 KW - simulation KW - plasma KW - ion-source KW - electron KW - interface DA - 2019/06 PY - 2019 SN - 978-3-95450-208-0 DO - DOI: 10.18429/JACoW-IPAC2019-TUPTS095 UR - http://jacow.org/ipac2019/papers/tupts095.pdf ER - TY - CONF AU - Veitzer, S.A. AU - Stoltz, P. ED - Boland, Mark ED - Tanaka, Hitoshi ED - Button, David ED - Dowd, Rohan ED - Schaa, Volker RW ED - Tan, Eugene TI - Fluid Models of Inductively Coupled Plasma Sources for Negative Hydrogen Ion Sources J2 - Proc. of IPAC2019, Melbourne, Australia, 19-24 May 2019 CY - Melbourne, Australia T2 - International Particle Accelerator Conference T3 - 10 LA - english AB - Negative hydrogen ion sources are widely used to produce neutron beams via spallation both for neutron science in its own right, and as neutron sources for fusion devices. Numerical modeling is a useful tool for trying to optimize negative hydrogen ion sources. However there are significant numerical and computational challenges that have to be overcome, including code performance and resolution of separation of time scales between ion and electron motions. One method is to utilize fluid models to simulate inductively coupled ion sources (ICPs). We have been developing algorithms to simulate negative hydrogen production in high-power, external-antenna ICP sources. We present simulation results using the USim*,** framework to model plasma chemistry that produces negative hydrogen, and model the effects of electron temperature on overall production rates. The numerical plasma chemistry models include processes of ionization, dissociation, recombination, as well as reactive dissociation of vibrationally resolved states and de-excitation of atomic hydrogen. We benchmark our plasma chemistry model results using plasma parameters relevant to experiments being carried out at the D-Pace Ion Source Test Facility. We have also been developing fluid-based drift/diffusion models for multi-component plasmas, such as those in negative hydrogen sources. These simulation results demonstrate enhancement of the effective diffusion rates in plasmas that contain both electrons and negative ions. PB - JACoW Publishing CP - Geneva, Switzerland SP - 2147 EP - 2149 KW - plasma KW - electron KW - ion-source KW - simulation KW - neutron DA - 2019/06 PY - 2019 SN - 978-3-95450-208-0 DO - DOI: 10.18429/JACoW-IPAC2019-TUPTS096 UR - http://jacow.org/ipac2019/papers/tupts096.pdf ER -