Low Emittance Light Sources Research Articles

Suppression of emittance variation in extremely low emittance light source storage rings

A passive method based on an optimized quasiachromatic condition effectively suppresses emittance variation during the independent tuning of insertion devices (IDs), which is one of the major obstacles for conducting precise experiments in extremely low emittance light source storage rings. This method, simple and easy to apply to any light source storage ring, reduces the emittance variation to potentially less than 1% by carefully optimizing dispersion leakage at the straight sections where the IDs are installed according to an actual condition of the ID independent tuning.

Erratum: Source size measurement options for low-emittance light sources [Phys. Rev. Accel. Beams 23 , 024801 (2020)

Erratum: Source size measurement options for low-emittance light sources [Phys. Rev. Accel. Beams <b>23</b> , 024801 (2020)

Propagation of partially coherent radiation using Wigner functions

Undulator radiation from synchrotron light sources must be transported down a beamline from the source to the sample. A partially coherent photon beam may be represented in phase space using a Wigner function, and its transport may use some similar techniques as is familiar in particle beam transport. We describe this process in the case that the beamline is composed of linear focusing and defocusing sections as well as apertures. We present a compact representation of the beamline map involving linear transformations and convolutions. We create a 1:1 imaging system (4f system) with a single slit on the image plane and observe the radiation downstream to it. We propagate a Gaussian beam and undulator radiation down this sample beamline, drawing parameters from current and future ultra low emittance light sources. We derive an analytic expression for the partially coherent Gaussian case including passage through a single slit aperture. We benchmark the Wigner function calculation against the analytical expression and a partially coherent calculation in the Synchrotron Radiation Workshop (SRW) code.

Source size measurement options for low-emittance light sources

Radiation-based techniques for measuring electron source sizes are widely used as emittance diagnostics at existing synchrotron sources. Three of these techniques, namely, pinhole imaging, double-slit interferometry, and a K-edge filter-based beam position and size monitor system (ps-BPM), are evaluated for measuring source sizes at low-emittance storage rings. Each technique is reviewed with a detailed system description, design optimization, and practical considerations targeted for small source sizes. Pinhole imaging has the simplest setup and gives the beam profile in both transverse dimensions but with limited resolution. Double-slit interferometry has the highest resolution but with a limited detectable size range. The ps-BPM system shows reasonable resolution for monitoring small source sizes and divergence and can give real-time information of the source position and angle. New facilities may consider an integrated system that combines some or all of these techniques.

Application of a phase space beam position and size monitor for synchrotron radiation source characterization

A phase space beam position and size monitor (ps-BPM) system was introduced previously to measure the electron source vertical position and angular motion along with the vertical source size and angular size at a single location in a synchrotron bend magnet beam line. The system was validated experimentally at the Canadian Light Source and demonstrated by a simulation that it is suitable for low-emittance light sources. In this work, the potential practicality of the ps-BPM system is explored with real-case studies. By combining the analysis in the time and frequency domain, information on the beam motion and size can be extracted and identified from both the source and the beam-line optics. Applications of the ps-BPM system at the Canadian Light Source are demonstrated by studying beam vibrations and machine insertion device field changes. Results of these studies provide guidelines for implementing a dedicated ps-BPM system at existing and planned synchrotron facilites.

Optimization of a phase-space beam position and size monitor for low-emittance light sources.

The recently developed vertical phase-space beam position and size monitor (ps-BPM) system has proven to be able to measure the electron-source position, angle, size and divergence simultaneously in the vertical plane at a single location of a beamline. The optimization of the ps-BPM system is performed by ray-tracing simulation to maximize the instrument sensitivity and resolution. The contribution of each element is studied, including the monochromator, the K-edge filter, the detector and the source-to-detector distance. An optimized system is proposed for diffraction-limited storage rings, such as the Advanced Photon Source Upgrade project. The simulation results show that the ps-BPM system can precisely monitor the source position and angle at high speed. Precise measurements of the source size and divergence will require adequate resolution with relatively longer integration time.

Magnetic Field Measurements of Full-Scale Conduction-Cooled Superconducting-Undulator-Coils

The Institute for Beam Physics and Technology (IBPT) of the Karlsruhe Institute of Technology (KIT), and the Babcock Noell GmbH are collaborating to develop superconducting undulators for ANKA and low-emittance light sources. The collaboration is now focusing on a superconducting undulator with a period length of 20 mm (SCU20) planned to be the source of the NANO beamline at ANKA. The local magnetic field and the field integrals of the SCU20 1.5-m-long-coils have been characterized in a conduction-cooled horizontal test facility developed at KIT IBPT. Here we complement the main results reported in a previous work with a more detailed analysis, including the measurements of the geometrical deviations from the ideal case of the undulator coils at room temperature used to simulate the magnetic field profile with the program Radia and a quantitative explanation of the magnetic field measurements in cold conditions. A comparison of the photon spectrum calculated from the measured field with the one from the field simulated with Radia considering the geometry measured at room temperature is also presented.

Field quality of 1.5 m long conduction cooled superconducting undulator coils with 20 mm period length

The Institute for Beam Physics and Technology (IBPT) at the Karlsruhe Institute of Technology (KIT) and the industrial partner Babcock Noell GmbH (BNG) are collaborating since 2007 on the development of superconducting undulators both for ANKA and low emittance light sources. The first full length device with 15 mm period length has been successfully tested in the ANKA storage ring for one year. The next superconducting undulator has 20 mm period length (SCU20) and is also planned to be installed in the accelerator test facility and synchrotron light source ANKA. The SCU20 1.5 m long coils have been characterized in a conduction cooled horizontal test facility developed at KIT IBPT. Here we present the local magnetic field and field integral measurements, as well as their analysis including the expected photon spectrum.

Performance of SCU15: The New Conduction-Cooled Superconducting Undulator for ANKA

Superconducting undulators (SCUs) have the potential to reach higher brilliance and flux with respect to the state-of-the-art permanent-magnet insertion devices. Babcock Noell GmbH (BNG) and the ANKA synchrotron radiation facility at Karlsruhe Institute of Technology (KIT) are collaborating to realize NbTi conduction cooled planar devices for ANKA and low-emittance light sources. Here the features of the first full-size, 1.5 m long device with a 15 mm period length installed in the ANKA storage ring since December 2014 are briefly described, followed by the main results of the tests performed, with a focus on the cryogenic behavior and operation at nominal current.

Compact low emittance light sources based on longitudinal gradient bending magnets

The horizontal emittance of a storage ring beam can be reduced below the theoretical minimum of a given magnet structure if a variation of the longitudinal field is introduced in the bending magnets. The optimum longitudinal field variation for the generation of the lowest emittance has been calculated numerically – and analytically for different classes of simple functions: exponential-, power-, hyperbolic- and step-function. Constraints have been introduced for the maximum field and the minimum beta function in the magnet. The distribution of the deflection angles to the different magnet types has been optimized. The optimization results have been applied to an exemplary design of a lattice for a light source with limited circumference as for instance the Swiss Light Source.

Test of Short Mockups for Optimization of Superconducting Undulator Coils

ANKA and Babcock Noell GmbH (BNG) collaborate to develop planar superconducting undulators for ANKA and low emittance light sources. We report here on the results of the training and magnetic field measurements on short mockup coils with 15- and 20-mm period length performed in the test facility CASPER I, that have qualified the wire and different winding schemes as promising to be applied to longer undulator coils.

Sirius: A 5BA Low-Emittance Lattice with Superbends for the New Brazilian Synchrotron Light Source

Starting in the late 1980s and into the 1990s, Brazil developed its own technology for the production of synchrotron light, designing and building UVX, a light source based on a 1.37 GeV electron storage ring with a circumference of 93 m and natural emittance of 100 nm.rad [1]. Over more than 15 years of routine operation for users, the expansion capabilities for this light source, either in terms of new beamlines or upgrades to its accelerators, have reached fundamental limits that can no longer be overcome. The first discussions about a new low-emittance light source for Brazil started in 2006 among the scientific and accelerator communities during the 16th LNLS Annual Users Meeting. In November 2008, a decision by the Brazilian Federal Government was taken to fund preliminary studies for this new source, leading to the final decision to fund the whole project in 2011. The proposed new synchrotron light source, Sirius, is based on a 3 GeV electron storage ring with a circumference of 518 m, a natural emittance of 0.28 nm.rad, and a total of 20 straight sections, of which 18 are for insertion devices. The new facility is being built at the same LNLS site as shown in Figure 1.

Calculations of synchrotron radiation emission in the transverse coherent limit

We present approximations for the synchrotron radiation emission for low emittance light sources, which provide a connection between user needs and the electron beam parameters. The results and calculations are a consequence of the phase coherence in the emission from the electrons. We derive the remarkable result that if the electron beam is energetic enough, the emitted flux is independent of the photon energy, electron beam energy, or bending radius in the transverse coherent limit. Similarly the brightness is identical for all machines at a given current.

Nonlinear dynamics with sextupoles in low-emittance light source storage rings

Abstract An analysis is made of the nonlinear particle motions arising from sextupoles in low-emittance light source rings. By employing the single-resonance approximation to the Hamiltonian expanded into harmonics, boundaries of the stable motion brought about by 1st- and 3rd-order resonances are calculated analytically. These are used together with the second-order tune shifts with amplitude as guidelines of the analysis and of the optimization of sextupoles to improve the dynamic aperture. The application is made to two typical lattices of the light source rings, the Chasman-Green and the triple-bend achromat lattice, to pursue the lattice dependence of the nonlinear characteristics. Apart from the cases where the stability is determined by the lowest-order resonances, studies using particle tracking indicate that the motion is very often driven by higher-order resonances for which further considerations are required. Two approaches are discussed in this context. One is to interpret the phenomena as a combined effect of the lowest-order resonances, which is verified numerically by a fictitious tracking. Another is the perturbative method. The theory developed by Poincare and von Zeipel is used to analyze the horizontal dynamics, which is worked up to 4th order in amplitude. Examples that satisfactorily reproduce the phase-space structure are shown, although it is also found that perturbations of many of the sextupoles required for these low-emittance rings are even higher than 4th order.