LBNL, Berkeley, California
Funding: This work was supported by the Director, Office of Science, U. S. Department of Energy under Contract No. DE-AC02-05CH11231.
Beam stability is one of the most important properties for the users of a synchrotron light source. Beam stability includes the stability of orbit, beamsize, current (lifetime), energy, and energy spread. As light sources are generating higher brightnesses, adding fast switching variable polarization devices, and and producing smaller source sizes, there is a necessity for continuous improvements in beam stability. In this talk an overview of the state of the art in beam stabilization and remaining challenges for beam stability are presented.
LBNL, Berkeley, California
Funding: This work is supported by the Director, Office of Science, U. S. Department of Energy under Contract No. DE-AC02-05CH11231.
In 2006, the 30mm period In-Vacuum Insertion Device (IVID) was operational for the femtosecond phenomena beamline at the Advanced Light Source (ALS) of Lawrence Berkeley National Laboratory. Since then the IVID has been demonstrating unexpected behaviors especially at small gaps (minimum gap = 5.5mm). The main observations related to these issues are partial or total beam losses as well as sudden pressure increases while operating the IVID gap. This paper is reporting these observations and describes the investigations and the repair attempt performed on this insertion device.
LBNL, Berkeley, California
Funding: This work was supported by the Director, Office of Science, U. S. Department of Energy under Contract No. DE-AC02-05CH11231.
The upgrade of the Advanced Light Source to enable top-off operation has been ongoing for the last four years. Activities over the last year have centered around radiation safety aspects, culminating in a systematic proof that top-off operation is equally safe as decaying beam operation, followed by commissioning and full user operations. Top-off operation at the ALS provides a very large increase in time-averaged brightness to ALS users (by about a factor of 10) as well as improvements in beam stability. The presentation will provide an overview of the radiation safety rationale, commissioning results, as well as experience in user operations.
LBNL, Berkeley, California
Funding: This work was supported by the Director, Office of Science, U. S. Department of Energy under Contract No. DE-AC02-05CH11231.
The Advanced Light Source (ALS) is a third generation synchrotron light source that has been operating since 1993 at Berkeley Lab. Recently, the ALS was upgraded to achieve Top-Off Mode, which allows injection of 1.9GeV electron beam into the Storage Ring approximately every 30 seconds. Modifications required for Top-Off operation included replacing the booster dipole and quadrupole magnet power supplies to increase the peak booster beam energy from 1.5GeV to 1.9GeV. Each new power supply was originally controlled by an analog controller that performs the current feedback loop and, in concert with other modules in the control chassis, determines the output of the ramped power supply. The new digital power supply controller performs the current feedback loop digitally to provide greater output stability and resolution. In addition, it provides remote monitoring of feedback loop signals, interlocks, and status signals, as well as remote control of the power supply operation via Ethernet. This paper will present the ALS Digital Power Supply Controller module requirements and design.
LBNL, Berkeley, California
Funding: Supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
ALS has been upgraded by adding Top-Off Mode, a new mode of operation to the existing modes of Fill and Stored Beam. The Top-Off Mode permits injection of 1.9GeV electron beam into the Storage Ring, with the safety shutters open, once certain strict conditions are met and maintained. Top-Off Mode enables User operation without an interruption caused by mode switching between the Stored Beam Mode when safety shutters are open, to the Fill Mode with the safety shutters closed and back. The conditions necessary to permit Top-Off Mode are; stored beam is present, the energies are matched between the injector and storage ring, a select set of storage ring lattice magnets are operating at the correct current levels, and radiation losses are minimized. If certain combinations of these conditions are not met, a potentially dangerous condition of injecting electrons down a users beam line can exist. Therefore a system of mode control, energy match, lattice match and stored beam interlocks are needed to control the injected beam prohibiting potentially dangerous conditions. In this paper we will present the Top-Off Mode Beam Interlock system requirements, design, and operational parameters.
LBNL, Berkeley, California
Funding: This work was supported by the Director, Office of Science, U. S. Department of Energy under Contract No. DE-AC02-05CH11231.
The Touschek lifetime in low energy or small emittance lepton storage rings strongly depends on the particle density in bunches. In the usual parameter range, this dominates other effects and the lifetime gets shorter with higher the bunch density, i.e. with smaller beam emittance. However, once one gets to extremely small horizontal emittances, this is no longer the case. Since the Touschek scattering process is an energy transfer from the transverse plane to the longitudinal one, the Touschek lifetime actually increases, once the transverse temperature (i.e. emittance) gets small enough. In the usual Touschek lifetime formulas, this is accounted for with a complicated multiparameter function (form factor). This paper presents to our knowledge the first direct measurements of the Touschek lifetime in this region of reversed dependence on horizontal emittance, as well as comparison with theory. The measurements were carried out at the ALS at reduced beam energy and ultrasmall horizontal emittance.
LBNL, Berkeley, California
Funding: Work supported by the Director, Office of Science, U. S. Department of Energy under Contract No. DE-AC02-05CH11231.
Multiobjective optimization has been used in many fields including accelerator related projects. Here we use it as a powerful tool for lattice design and optimization, which includes betatron functions, brightness.
LBNL, Berkeley, California
Funding: This work was supported by the Director, Office of Science, U. S. Department of Energy under Contract No. DE-AC02-05CH11231.
Frequency map analysis is being widely used, nowadays, both in simulations to design or improve accelerator lattices, as well as in experiments to study the transverse nonlinear dynamics in accelerators. A significant challenge to the use of frequency map analysis in experiments is the usually very fast decoherence of transverse oscillations, caused by the large nonlinearities of state-of-the-art lattices. Due to the decoherence, the center of mass oscillations of bunches often disappear in less than 100 turns. A potential way to get around this limitation is the use of multiple BPMs distributed (symetrically) around the storage ring. The presentation will describe the challenges multi-BPM frequency map analysis poses as well as initial results using the ALS.
LBNL, Berkeley, California
Funding: Supported by DOE BES contract DE-AC03-76SF00098.
Recently there has been a proposal to use pulsed high order multipole elements for injection. One of the advantages of this proposed injection scheme would be that it would be less disruptive to the stored beam and thus advantageous for Top-off operation. In addition to Top-off, such novel injectors might open the door to operating storage rings in more desirable lattice settings. In this paper we will explore some of the possibilities for taking advantage of high order multipole pulsed kick injection.