A proof-of-principle echo-enabled harmonic generation experiment at SLAC

In this paper we describe the technical design of an ongoing proof-of-principle echo-enabled harmonic generation (EEHG) experiment at the Next Linear Collider Test Accelerator (NLCTA) at SLAC. We present the design considerations and the technical details of the experiment

A test of NLC-type beam loading in the SLAC linac

The linac at the Stanford Linear Accelerator (SLAC) runs routinely with a beam loading of around 12% for the fixed target experiment E-158. Typical energy spread and energy jitter are 0.1% and 0.05%. To explore the conditions for the Next Linear Collider (NLC) the linac was operated with 20% beam loading. This was attained by increasing the beam charge from 5·1011 to 9·1011 particles and increasing the pulse length from 250 ns to 320ns. Although the beam loading compensation was more difficult to achieve, a reliable operating point was found with a similar energy spread and energy jitter as at the lower loading. Furthermore, using the sub-harmonic buncher (SHB), the beam was bunched at 178.5 MHz instead of the nominal 2.8 GHz so that the charge from 16 adjacent buckets was combined into one. Increased transverse instability and beam losses along the linac were observed indicating the possible onset of beam break-up

Start-to-end simulation of the shot-noise driven microbunching instability experiment at the Linac Coherent Light Source

The shot-noise driven microbunching instability can significantly degrade electron beam quality in x-ray free electron laser light sources. Experiments were carried out at the Linac Coherent Light Source (LCLS) to study this instability. In this paper, we present start-to-end simulations of the shot-noise driven microbunching instability experiment at the LCLS using the real number of electrons. The simulation results reproduce the measurements quite well. A microbunching self-heating mechanism is also illustrated in the simulation, which helps explain the experimental observation

Start-to-end simulation of the shot-noise driven microbunching instability experiment at the Linac Coherent Light Source

The shot-noise driven microbunching instability can significantly degrade electron beam quality in x-ray free electron laser light sources. Experiments were carried out at the Linac Coherent Light Source (LCLS) to study this instability. In this paper, we present start-to-end simulations of the shot-noise driven microbunching instability experiment at the LCLS using the real number of electrons. The simulation results reproduce the measurements quite well. A microbunching self-heating mechanism is also illustrated in the simulation, which helps explain the experimental observation

Plasma wakefield acceleration experiments at FACET

FACET-Facilities for Accelerator science and Experimental Test beams at SLAC-will provide high-energy-density electron and positron beams with peak currents of roughly 20 kA that will be focused down to a 10 μm × 10μm transverse spot size at an energy of ∼23 GeV. With FACET, the SLAC linac will support a unique program concentrating on second-generation research in plasma wakefield acceleration. Topics include high-gradient electron acceleration with a narrow energy spread and preserved emittance, beam loading and high-gradient positron acceleration. This paper describes the FACET facility, summarizes the state of the art for plasma wakefield accelerators and discusses the plasma wakefield accelerator program to be conducted at FACET over the next five years. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft

Multi-dimensional optimization of a terawatt seeded tapered Free Electron Laser with a Multi-Objective Genetic Algorithm

There is a great interest in generating high-power hard X-ray Free Electron Laser (FEL) in the terawatt (TW) level that can enable coherent diffraction imaging of complex molecules like proteins and probe fundamental high-field physics. A feasibility study of producing such X-ray pulses was carried out employing a configuration beginning with a Self-Amplified Spontaneous Emission FEL, followed by a “self-seeding” crystal monochromator generating a fully coherent seed, and finishing with a long tapered undulator where the coherent seed recombines with the electron bunch and is amplified to high power. The undulator tapering profile, the phase advance in the undulator break sections, the quadrupole focusing strength, etc. are parameters to be optimized. A Genetic Algorithm (GA) is adopted for this multi-dimensional optimization. Concrete examples are given for LINAC Coherent Light Source (LCLS) and LCLS-II-type systems. Analytical estimate is also developed to cross check the simulation and optimization results as a quick and complimentary tool