Weishi Wan

Generation of Picosecond X-Ray Pulses in the ALS Using RF Orbit Deflection

A scheme is proposed for producing ps length pulses of x-ray radiation from the Advanced Light Source (ALS) using two RF deflecting cavities. The cavities create vertical displacements of electrons correlated with their longitudinal position in the bunch. The two cavities separated by 180 degrees of vertical phase advance. This allows the vertical kick from one cavity to be compensated by the vertical kick of the other. The location of the cavities corresponds to the end of one straight section and the beginning of the following straight section. Halfway between the cavities a bending magnet source is located. The radiation from the bend can be compressed to ∼ 1 ps in duration.

FEL design for power beaming

We are reporting on the current design status of the 200 kW average power FEL at a 0.84 micron wavelength for power beaming of satellites. The project includes a cw RF photocathode gun injector, a cw linear accelerator, achromatic beam transport lines and an FEL amplifier. Problems that are specific to our design are considered.

COMPLETION OF THE BRIGHTNESS UPGRADE OF THE ALS

The Advanced Light Source (ALS) at Berkeley Lab remains one of the brightest sources for soft x-rays worldwide. A multiyear upgrade of the ALS is underway, which includes new and replacement x-ray beamlines, a replacement of many of the original insertion devices and many upgrades to the accelerator. The accelerator upgrade that affects the ALS performance most directly is the ALS brightness upgrade [1], which reduces the horizontal emittance from 6.3 to 2.0 nm (2.5 nm effective). Magnets for this upgrade were installed in late 2012 and early 2013 followed by user operation with the reduced emittance.

Simulation of the Effect of an in-Vacuum Undulator on the Beam Dynamics of ALS

The femtoslicing project at the Advanced Light Source (ALS) requires that a short period (3 cm) and narrow gap (5 mm) in vacuum undulator to be installed. The combination of the short period and the narrow gap raised concern of the impact on the beam dynamics. A 3D field model was established based on numerical data using 8 longitudinal and 4 transverse harmonics. At first fourth-order symplectic integrator was used. It was to our surprise that the dynamic aperture decreased by 30%. To understand the cause of the drastic change in the dynamic aperture, the field model was implemented in a differential algebraic code and the Taylor map of the undulator was obtained. Tracking result using the Taylor map showed little change in the dynamic aperture, which was latter corroborated using the symplectic integrator with 150 slices per period (as opposed to 10 before). Yet it is simply too time consuming to use the symplectic integrator with such thin slices. For this case, Taylor proves to be a much faster alternative.

Optimization of the ALS-U Storage Ring Lattice

The Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory is proposing the upgrade of its synchrotron light source to reach soft x-ray diffraction limits within the present ALS footprint. The storage ring lattice design and optimization of this light source is one of the challenging aspects for this proposed upgrade. The candidate upgrade lattice needs not only to fulfill the physics design requirements such as brightness, injection efficiency and beam lifetime, but also to meet engineering constraints such as space limitations, maximum magnet strength as well as beamline port locations. In this paper, we will present the approach that we applied to design and optimize a multi-bend achromat based storage ring lattice for the proposed ALS upgrade.

Physics Design Progress towards a Diffraction Limited Upgrade of the ALS

Improvements in brightness and coherent flux of more than two orders of magnitude are possible using multi bend achromat lattice designs [1]. These improvements can be implemented as upgrades of existing facilities, like the proposed upgrade of the Advanced Light Source. We will describe the progress in the physics design of this upgrade, including lattice evolution, error tolerance studies, simulations of collective effects, and intra beam scattering.

R+ D Progress Towards a Diffraction Limited Upgrade of the ALS

Author(s): Steier, C; Anders, A; Byrd, J; Chow, K; Duarte, R; Jung, J; Luo, T; Nishimura, H; Oliver, T; Osborn, J; Padmore, H; Pappas, C; Robin, D; Sannibale, F; De Santis, S; Schlueter, R; Sun, C; Swenson, C; Venturini, M; Waldron, W; Wallen, E; Wan, W; Yang, Y | Abstract: Copyright

Successful Completion of the Top-off Upgrade of the Advanced Light Source

An upgrade of the Advanced Light Source to enable top-off operation has been completed during the last four years. The final work centered around radiation safety aspects, culminating in a systematic proof that top-off operation is equally safe as decaying beam operation. Commissioning and transition to full user operations happened in late 2008 and early 2009. Top-off operation at the ALS provides a very large increase in time-averaged brightness (by about a factor of 10) as well as improvements in beam stability. The following sections provide an overview of the radiation safety rationale, commissioning results, as well as experience in user operations.