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Fall 2011

Schedule Fall 2011

September 13

"New Multiscale Code for Simulation of Coherent Synchrotron Radiation"

Dr. Balsa Terzic

Jefferson Lab (CASA)

Coherent synchrotron radiation (CSR) is an effect of curvature-induced self-interaction of a microbunch with a high charge as it traverses a curved trajectory. It can cause a significant emittance degradation, as well as fragmentation and microbunching of the beam bunch. The development and optimization of the new designs for the existing and next-generation light sources crucially depends on accurate, high-resolution numerical simulations of this effect.

Direct computation of CSR wakefields in 2D and 3D are prohibitively costly in terms of efficiency and memory requirements, as they require integration over the entire history of the bunch. Consequently, the present CSR codes employ a number of approximations and simplifications that are often inadequate for resolving essential physics in many realistic situations. These situations where existing CSR codes fail are expected to become commonplace as the design of next-generation light sources commences.

This provides a strong impetus for the development of the new CSR codes that are both accurate and efficient.

In this talk, I will present the progress report on the development of the fundamentally new, particle-in-cell, multiscale code for modeling CSR. The code will exploit advantages afforded by the mathematical formulation of the problem in wavelet basis: (i) retaining information about the dynamics over the hierarchy of scales spanned by the wavelet expansion; (ii) natural removal of numerical noise (denoising) by thresholding of the wavelet coefficients; (iii) compact representation of relevant data sets and operators. The resulting algorithm will be numerically optimized to run efficiently on graphical processing units (GPUs), and will be capable of modeling a number of different machines.

As a proof-of-principle, we present the early benchmark result -- a comparison against the analytical results for a rigid-line bunch.

October 18

"Using Atomic Physics to Create the Coldest Plasmas Ever"

Dr. Steve Rolston

University of Maryland/JQI

Plasma is the most ubiquitous state of matter in the universe, ranging in temperatures from 15 million K in the core of the sun to 200 K in the ionosphere, and densities of 10^30 cm^-3 in a white dwarf to 1 particle per cm^-3. Using laser cooling and photoionization, we can now create neutral plasmas in the lab, orders of magnitude colder, down to sub-Kelvin temperatures. In this talk I will discuss some of the features of these novel plasmas, ranging from three-body recombination collisions that are used to make anti-hydrogen, to collective modes and the effects of magnetic fields.

October 25

"The Evolution of Conformal Therapy with Particles"

Dr. Jay Flanz

Technical Director, Burr Proton Therapy Center
Massachusetts General Hospital

Harvard Medical School

The evolution of radiation therapy is characterized by the goal of delivering as much energy as needed to the disease and minimizing the energy deposited elsewhere. Various forms of ionizing radiation delivery systems have been conceived over the past 50 years or more including the more recent rise of particle therapy systems. The technology used in these systems will be described including the accelerators and the beam delivery systems that have been and are planned to be used. This modality has shifted from laboratory based to vendor provided equipment in Hospital settings. Some of the promises and perils of these systems will be discussed.

November 15

"Laser Frequency Combs for Precision Astrophysical Spectroscopy"

Dr. Ron Walsworth


Precision astrophysical spectroscopy is a crucial tool for the discovery and study of planets around other stars (exoplanets) via the periodic Doppler shift of stellar lines induced by orbiting planets. However, the sensitivity of broadband astrophysical spectrographs to low-mass planets is currently limited by the stability and precision of existing wavelength calibration sources. In particular, to find a one-Earth-mass planet in an Earth-like orbit around a Sun-like star, an order of magnitude improvement in wavelength calibration is necessary. I will describe our ongoing efforts to use laser frequency combs to solve this problem.

November 29

Dr. Michael Pennington

Jefferson Lab