Optimization of the RF Cavity Heat Load and Trip Rates for CEBAF at 12 GeV

The Continuous Electron Beam Accelerator Facility at JLab has 200 RF cavities in the north linac and the south linac respectively after the 12 GeV upgrade. The purpose of this work is to simultaneously optimize the heat load and the trip rate for the cavities and to reconstruct the pareto-optimal front in a timely manner when some of the cavities are turned down. By choosing an efficient optimizer and strategically creating the initial gradients, the pareto-optimal front for no more than 15 cavities down can be re-established within 20 seconds

Simulation Study on JLEIC High Energy Bunched Electron Cooling

In the JLab Electron Ion Collider (JLEIC) project the traditional electron cooling technique is used to reduce the ion beam emittance at the booster ring, and to compensate the intrabeam scattering effect and maintain the ion beam emittance during the collision at the collider ring. Different with other electron coolers using DC electron beam, the proposed electron cooler at the JLEIC ion collider ring uses high energy bunched electron beam, provided by an ERL. In this paper, we report some recent simulation study on how the electron cooling rate will be affected by the bunched electron beam properties, such as the correlation between the longitudinal position and momentum, the bunch size, and the Larmor emittance

GPU Accelerated Long-Term Simulations of Beam-Beam Effects in Colliders

We present an update on the development of the new code for long-term simulation of beam-beam effects in particle colliders. The underlying physical model relies on a matrix-based arbitrary-order particle tracking (including a symplectic option) for beam transport and the generalized Bassetti-Erskine approximation for beam-beam interaction. The computations are accelerated through a parallel implementation on a hybrid GPU/CPU platform. With the new code, previously computationally prohibitive long-term simulations become tractable. The new code will be used to model the proposed Medium-energy Electron-Ion Collider (MEIC) at Jefferson Lab

Nonequilibrium Green's function theory for transport and gain properties of quantum cascade structures

The transport and gain properties of quantum cascade (QC) structures are investigated using a nonequilibrium Green's function (NGF) theory which includes quantum effects beyond a Boltzmann transport description. In the NGF theory, we include interface roughness, impurity, and electron-phonon scattering processes within a self-consistent Born approximation, and electron-electron scattering in a mean-field approximation. With this theory we obtain a description of the nonequilibrium stationary state of QC structures under an applied bias, and hence we determine transport properties, such as the current-voltage characteristic of these structures. We define two contributions to the current, one contribution driven by the scattering-free part of the Hamiltonian, and the other driven by the scattering Hamiltonian. We find that the dominant part of the current in these structures, in contrast to simple superlattice structures, is governed mainly by the scattering Hamiltonian. In addition, by considering the linear response of the stationary state of the structure to an applied optical field, we determine the linear susceptibility, and hence the gain or absorption spectra of the structure. A comparison of the spectra obtained from the more rigorous NGF theory with simpler models shows that the spectra tend to be offset to higher values in the simpler theories.Comment: 44 pages, 16 figures, appearing in Physical Review B Dec 200

High-Fidelity Simulations of Long-Term Beam-Beam Dynamics on GPUs

Future machines such as the Electron Ion Collider (MEIC), linac-ring machines (eRHIC) or LHeC are particularly sensitive to beam-beam effects. This is the limiting factor for long-term stability and high luminosity reach. The complexity of the non-linear dynamics makes it challenging to perform such simulations typically requiring millions of turns. Until recently, most of the methods have involved using linear approximations and/or tracking for a limited number of turns. We have developed a framework which exploits a massively parallel Graphical Processing Units (GPU) architecture to allow for tracking millions of turns in a sympletic way up to an arbitrary order. The code is called GHOST for GPU-accelerated High-Order Symplectic Tracking. As of now, there is no other code in existence that can accurately model the single-particle non-linear dynamics and the beam-beam effect at the same time for a large enough number of turns necessary to verify the long-term stability of a collider. Our approach relies on a matrix-based arbitrary-order symplectic particle tracking for beam transport and the Bassetti-Erskine approximation for the beam-beam interaction

Rural and Urban Differences in the Adoption of New Health Information and Medical Technologies

Background This statewide survey sought to understand the adoption level of new health information and medical technologies, and whether these patterns differed between urban and rural populations. Methods A random sample of 7,979 people aged 18‐75 years, stratified by rural status and race, who lived in 1 of 34 Indiana counties with high cancer mortality rates and were seen at least once in the past year in a statewide health system were surveyed. Results Completed surveys were returned by 970 participants. Rural patients were less likely than urban to use electronic health record messaging systems (28.3% vs 34.5%, P = .045) or any communication technology (43.0% vs 50.8%, P = .017). Rural patients were less likely to look for personal health information for someone else's medical record (11.0% vs 16.3%, P = .022), look‐up test results (29.5% vs 38.3%, P = .005), or use any form of electronic medical record (EMR) access (57.5% vs 67.1%, P = .003). Rural differences in any use of communication technology or EMRs were no longer significant in adjusted models, while education and income were significantly associated. There was a trend in the higher use of low‐dose computed tomography (CT) scan among rural patients (19.1% vs 14.4%, P = .057). No significant difference was present between rural and urban patients in the use of the human papilloma virus test (27.1% vs 26.6%, P = .880). Conclusions Differences in health information technology use between rural and urban populations may be moderated by social determinants. Lower adoption of new health information technologies (HITs) than medical technologies among rural, compared to urban, individuals may be due to lower levels of evidence supporting HITs

Long-Term Simulations of Beam-Beam Dynamics on GPUs

Future machines such as the electron-ion colliders (JLEIC), linac-ring machines (eRHIC) or LHeC are particularly sensitive to beam-beam effects. This is the limiting factor for long-term stability and high luminosity reach. The complexity of the non-linear dynamics makes it challenging to perform such simulations which require millions of turns. Until recently, most of the methods used linear approximations and/or tracking for a limited number of turns. We have developed a framework which exploits a massively parallel Graphical Processing Units (GPU) architecture to allow for tracking millions of turns in a sympletic way up to an arbitrary order and colliding them at each turn. The code is called GHOST for GPU-accelerated High-Order Symplectic Tracking. As of now, there is no other code in existence that can accurately model the single-particle non-linear dynamics and the beam-beam effect at the same time for a large enough number of turns required to verify the long-term stability of a collider. Our approach relies on a matrix-based arbitrary-order symplectic particle tracking for beam transport and the Bassetti-Erskine approximation for the beam-beam interaction

On the growth of nonuniform lattices in pinched negatively curved manifolds

We study the relation between the exponential growth rate of volume in a pinched negatively curved manifold and the critical exponent of its lattices. These objects have a long and interesting story and are closely related to the geometry and the dynamical properties of the geodesic flow of the manifold

Near-field optical imaging of dielectric-loaded surface plasmon-polariton waveguides using optical feedback on erbium fiber laser

International audienceHeterodyne optical feedback on class-B solid state laser is applied for characterizing dielectric-loaded surface plasmon-polariton waveguides (DLSPPW) at telecom wavelength. Near-field optical images recorded on a series of DLSPPWs are compared to numerical models (mode-solver and finite-difference time-domain). IntroductionCompared to other surface plasmon-polariton (SPP) waveguides, DLSPPWs are characterized by a good compromise between efficient light squeezing on sub-wavelength structures and reasonably long propagation range [1]. DLSPPWs can be easily fabricated using e-beam or photolithography. Moreover the dielectric ridge on the top of the metal could also be structured to implement passive or active functionalities [2]. Therefore, DLSPPW are very promising components for high-density optical circuits or interconnects between integrated circuits and optical links. Improvements on DLSPPWs are still underway to further increase the propagation length in order to obtain very long-range DLSPPWs with propagation length exceeding few hundred microns [3]. Experimental setup and results Polymer layer (resin SAL 601 negative resist; thickness h stripe =600nm; refractive index n=1.68 @ 633nm) was spin-coated on 50-nm-thick gold film evaporated on a silica substrate. The polymer was micro-structured by e-beam lithography to pattern a series of rectangular micro-stripes with widths varying between w stripe =500nm up to 4µm. A funnel, located at the beginning of each stripe waveguide, was added for efficient light coupling thanks to adiabatic effective index matching (figure 1a)