Vertical emittance reduction and preservation in electron storage rings via resonance driving terms correction

Very few experimental techniques are useful for the direct observation of ultralow vertical emittance in electron storage rings. In this work, quantitative measurements of ultralow (pm rad) electron beam vertical emittance using a vertical undulator are presented. An undulator radiation model was developed using the measured magnetic field of the APPLE-II type undulator. Using calibrated experimental apparatus, a geometric vertical emittance of ε y ¼ 0.9 AE 0.3 pm rad has been observed. These measurements could also inform modeling of the angular distribution of undulator radiation at high harmonics, for proposed diffraction-limited storage ring light sources.

Section: Introductionmentioning

confidence: 99%

Measurement of ultralow vertical emittance using a calibrated vertical undulator

Wootton

Boland

Rassool

2014

“…First experiments were proposed and conducted in [1,2] at electron machines about a decade ago. The issue is of special interest for increasing the performance of x-ray free electron lasers and advanced approaches to emittance repartitioning are under conceptual and experimental investigation [3][4][5][6][7][8]. Flat hadron beams could facilitate the process of multiturn injection into circular machines, which imposes different requirements on the horizontal and vertical emittance of the incoming beam.…”

Section: Introductionmentioning

confidence: 99%

Single-knob beam line for transverse emittance partitioning

Xiao

Kester

Groening

et al. 2013

Flat beams feature unequal emittances in the horizontal and vertical phase space. Such beams were created successfully in electron machines by applying effective stand-alone solenoid fringe fields in the electron gun. Extension of this method to ion beams was proposed conceptually. The present paper is on the decoupling capabilities of an ion beam emittance transfer line. The proposed beam line provides a single-knob tool to partition the horizontal and vertical rms emittances, while keeping the product of the two emittances constant as well as the transverse rms Twiss parameters ( x;y and x;y ) in both planes. It is shown that this single knob is the solenoid field strength.

“…The influence of betatron coupling on these three transverse emittances has been described using the resonance driving term formalism in Ref. [19]. For a coupling free lattice, these three quantities coincide, E ¼ ε ¼ ϵ.…”

Section: Minimizing the Vertical Beam Size In Spear3mentioning

confidence: 99%

“…Smaller vertical beam sizes in a storage ring can produce higher photon brilliance. Therefore, there have been several results reported for achieving ultralow vertical beam size or emittance recently [19]. To construct the GA, we use 13 skew quadrupoles in the SPEAR3 storage ring as decision variables and the average vertical beam size as the objective function.…”

Section: Introductionmentioning

confidence: 99%

Machine based optimization using genetic algorithms in a storage ring

Tian

Safranek

Yan

2014

The genetic algorithm (GA) has been a popular technique in optimizing the design of particle accelerators. As a population based algorithm, GA requires a large number of evaluations of the objective functions, which can be time consuming. One can benefit from parallel computing with significantly reduced computing time when fulfilling the function evaluation by a numerical machine model in simulation codes. Indeed, this is the most common approach in GA applications. In this paper, instead of applying GA in the conventional numerical calculations as described above, we present a successful experimental demonstration of implementing GA in real machine based optimization. We conduct the minimization of the average vertical beam size of the SPEAR3 storage ring using GA. Beam loss rate is chosen as the sole objective function because it is inversely proportional to the vertical beam size and can be measured instantaneously in SPEAR3. The decision variables are the strengths of SPEAR3 skew quadrupoles, by varying which we can change both the betatron coupling and the vertical dispersion while searching for the minimum beam size. The results in this paper can shed light on new applications of GAs in the particle accelerator community, for example, optimizing the luminosity of a high energy collider or the injection efficiency of a diffraction limited storage ring in real time.