Tuesday, February 19, 2019 at 4:00 pm

Speaker: Vitaly Yakimenko, SLAC

Title: Collider of Fields : On the Prospect of Studying Fully Non-Perturbative QED with Beam-Beam Collisions

Abstract:

The talk will discuss how modern accelerator technology can probe a fundamentally different regime of physics – fully Non-Perturbative QED – for the first time. The key idea is to employ compressed bunches that are shorter than the average photon emission length to probe unprecedented extreme field strengths, which facilitate fully Non-Perturbative QED experiments with a 100 GeV-class particle collider. In addition, it also has multiple important implications for different areas of physics. For example, this approach to the mitigation of radiative energy losses (“beamstrahlung”), which is a critical limitation of existing linear collider designs like ILC and CLIC, represents an opportunity to reduce the power consumption of these machines significantly. The Energy frontier in electron/positron particle physics could then reach energies prohibited by the beam power requirement in conventional collisions of flat bunches.

Tuesday, April 16, 2019 at 4:00 pm

Speaker: Flicie Albert, Lawerence Livermore National Laboratory

Title: X-ray sources from laser-plasma acceleration: development and applications for high energy density sciences

Abstract:

Bright sources of x-rays, such as synchrotrons and x-ray free electron lasers (XFEL) are transformational tools for many fields of science. They are used for biology, material science, medicine, or industry. Such sources rely on conventional particle accelerators, where electrons are accelerated to gigaelectronvolts (GeV) energies. The accelerating particles are also wiggled in magnetic structures to emit x-ray radiation that is commonly used for molecular crystallography, fluorescence studies, chemical analysis, medical imaging, and many other applications. One of the drawbacks of synchrotrons and XFELs is their size and cost, because electric field gradients are limited to about a few 10s of MeV/M in conventional accelerators. This seminar will review particle acceleration in laser-driven plasmas as an alternative to generate x-rays. A plasma is an ionized medium that can sustain electrical fields many orders of magnitude higher than that in conventional radiofrequency accelerator structures. When short, intense laser pulses are focused into a gas, it produces electron plasma waves in which electrons can be trapped and accelerated to GeV energies. This process, laser-wakefield acceleration (LWFA), is analogous to a surfer being propelled by an ocean wave. Betatron x-ray radiation, driven by electrons from laser-wakefield acceleration, has unique properties that are analogous to synchrotron radiation, with a 1000-fold shorter pulse. This source is produced when relativistic electrons oscillate during the LWFA process. An important use of x-rays from laser plasma accelerators we will discuss is in High Energy Density (HED) science. This field uses large laser and x-ray free electron laser facilities to create in the laboratory extreme conditions of temperatures and pressures that are usually found in the interiors of stars and planets. To diagnose such extreme states of matter, the development of efficient, versatile and fast (sub-picosecond scale) x-ray probes has become essential. In these experiments, x-ray photons can pass through dense material, and absorption of the x-rays can be directly measured, via spectroscopy or imaging, to inform scientists about the temperature and density of the targets being studied.

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