Light Source Storage Ring Research Articles

Design modelling and measured performance of the vacuum system of the Diamond Light Source storage ring

A one-dimensional diffusion model of the Diamond Light Source storage ring vacuum system is described and its predictions are compared with actual measured static (without beam) and dynamic (with beam) pressures over more than 2000 A h of beam conditioning at 3 GeV. An average specific thermal outgassing yield of 1·10−11 mbar l/(s cm2) during initial beam circulation is obtained, which reduces to 2·10−12 mbar l/(s cm2) after an accumulated beam dose of 1000 A h and an elapsed time of 769 days. In the presence of stored electron beam, the pressure rises as expected due to photon stimulated desorption (PSD). The PSD yield reduces with beam dose according to a (−2/3) power law as was applied in the model. Predicted and measured dynamic pressures generally agree within a factor of 2 over the whole range of beam conditioning dose studied.

Generation of laser Compton gamma-rays in the SAGA light source storage ring

A medium-scale synchrotron light source of GeV-class equipped with an infrared high-power laser can generate stable high-flux gamma-rays at several MeV via laser Compton scattering . We constructed an experimental setup for high-flux gamma-ray generation in the SAGA light source storage ring. A head-on collision between a 1.4 GeV electron beam and laser photons with a 10.6 μ m wavelength produced gamma-rays up to a maximum energy of 3.5 MeV. Since the laser Compton scattering does not influence the beam quality, these gamma-rays can be generated in conjunction with user time for synchrotron radiation research. The event rate was designed to be 1.4 × 10 8 s − 1 with a beam current of 300 mA and a laser power of 10 W. As a first step in high-flux gamma-ray generation, we performed beam tests at a low beam current to evaluate the characteristics of the gamma-rays. Gamma-ray generation with no reduction in beam lifetime was confirmed by these tests. The experimental results show that the effective gamma-ray flux was almost 40% of the design value. The laser Compton gamma-ray was also applied to measure the machine parameters of the storage ring. The beam energy was successfully determined with relative uncertainties on the order of 10 −3 by analyzing the gamma-ray spectrum for the stored beam, which ranged in energy from 0.6 to 1.4 GeV.

Design of a Superconducting Wiggler for the Saga Light Source Storage Ring

A hybrid three-pole wiggler for generating hard X-rays in the range 4-40 keV was designed for the 1.4-GeV storage ring of a synchrotron radiation facility, i.e., the Saga Light Source. The wiggler consists of a superconducting main pole with a peak field of 4 T and two normal-conducting side poles with peak fields of 1 T. The normal-conducting side poles were used to reduce the heat load on the cryogenic system for the wiggler. A cryogen-free system was used to ensure long-term operational stability of the wiggler system. The superconducting coil and iron poles of the main pole are cooled by a Gifford-McMahon cryocooler via mechanical contact. To suppress the first and second field integrals of the main pole, we designed the main pole with relatively large field clamps and with no transverse return yoke. This pole structure was effective in suppressing beam displacement due to the wiggler field and in reducing the side pole volume. The beam effects due to the multipole fields of the wiggler were estimated and were found to be small or controllable. Based on these results, the storage ring with the designed wiggler is considered to be an effective hard-X-ray source.

PEP-X: Concepts for a Future Light Source for SSRL

In a world where new storage ring light sources are pushing electron beam emittances to the nanometer-radian scale and below, producing photon beam brightness exceeding 1021 (ph/s/mm2/mrad2/0.1% BW) for multi-keV photons, the long-term future of the Stanford Synchrotron Radiation Lightsource (SSRL) may depend on a much higher performing light source than that provided by the 3-GeV SPEAR3 storage ring. SPEAR3, having an emittance of 10 nm-rad and commissioned in 2003, produces an order of magnitude lower brightness than these new sources, although with 500-mA stored beam current it is a prodigious source for flux-limited applications such as many spectroscopy applications. Incremental improvements to the machine over the next few years, which include reducing the emittance by another factor of two, will enhance science capabilities even further. Nevertheless, the lab is looking forward to a future source that far exceeds the performance of SPEAR3, enabling advanced capabilities in imaging and other areas made possible with very high coherence and brightness, and that could establish a new state of the art for performance from a ring-based light source.

A double bend achromat lattice for the Pohang Light Source to reduce emittance and increase number of insertion devices

The Pohang Light Source (PLS) storage ring is a synchrotron light source with the emittance of 18.9 nm at 2.5 GeV and has delivered vacuum ultraviolet and soft x-rays during the past 15 years. We investigate a lattice design for the 3 GeV ring for an upgrade project that keeps the existing tunnel. We investigate a double bend achromat (DBA) structure that provides the reduction of emittance by a factor of 3 and the increase of the number of straight section by a factor of 2 than the existing PLS lattice. We present several characteristics on the beam dynamics, dynamic aperture, and optics matching in the low-emittance lattice which includes squeezed space between magnets. Present PLS lattice has 12 long straight sections of 6.8 m long and the lattice is modified to provide the additional 12 short straight sections of 3.7 m long by eliminating a bending magnet in the middle of the cell of the present triplet bending achromat lattice. Thus, the new lattice consists of a total of 24 straight sections that consist of 12×6.8 and 12×3.7 m long straight sections, which can provide the spaces for the 4- and 2-m-long insertion devices. We present the design results in detail for a DBA lattice in 281.82 m long circumference. It is shown that the emittance of 6.2 nm in the lattice can be achieved by allowing nonzero dispersions in the straight sections. The lattice provides high brilliance at the photon energy of a few 10 keV that meets the requirements by synchrotron radiation users; however, it may require a strong focusing and become sensitive to machine errors and effects of insertion devices. Thus, we investigated the dynamic aperture in the lattice by a simulation method and achieved an optimal tune under the strength of sextupole magnets of 500 T/m(2) for the low-emittance ring. We also performed the lattice tunings to restore the optics due to the errors in the low-emittance ring. In result, our designed lattice shows a good optimization in terms of emittance, brilliance, and circumference as a light source for a 3 GeV.

Kinoform optics applied to X-ray photon correlation spectroscopy

Moderate-demagnification higher-order silicon kinoform focusing lenses have been fabricated to facilitate small-angle X-ray photon correlation spectroscopy (XPCS) experiments. The geometric properties of such lenses, their focusing performance and their applicability for XPCS measurements are described. It is concluded that one-dimensional vertical X-ray focusing via silicon kinoform lenses significantly increases the usable coherent flux from third-generation storage-ring light sources for small-angle XPCS experiments.

Storage Ring Light Sources

This article outlines the development and evolution of storage ring light sources, focusing on the latest, third generation light sources. After making brief historical remarks, it describes the current status, the performance, and the technological advancements of third generation light sources. The future developments of the ultimate storage ring as the next generation light source are envisioned.

Beam dynamics and expected performance of Sweden’s new storage-ring light source: MAX IV

MAX IV will be Sweden's next-generation high-performance synchrotron radiation source. The project has recently been granted funding and construction is scheduled to begin in 2010. User operation for a broad and international user community should commence in 2015. The facility is comprised of two storage rings optimized for different wavelength ranges, a linac-based short-pulse facility and a free-electron laser for the production of coherent radiation. The main radiation source of MAX IV will be a 528 m ultra-low emittance storage ring operated at 3 GeV for the generation of high-brightness hard X-rays. This storage ring was designed to meet the requirements of state-of-the-art insertion devices which will be installed in nineteen 5 m long dispersion-free straight sections. The storage ring is based on a novel multi-bend achromat design delivering an unprecedented horizontal bare lattice emittance of 0.33 nm rad and a vertical emittance below the 8 pm rad diffraction limit for 1 A radiation. In this paper we present the beam dynamics considerations behind this storage ring design and detail its expected unique performance. (Less)

Tune optimization of the third generation light source storage ring based on Frequency Map Analysis

Tune optimization is necessary to optimize the nonlinearity of the third generation light source storage ring. In this paper we summarize the common strategies for choosing a tune and discuss tune optimization. Frequency Map Analysis (FMA) is applied as a tune scanning tool to reveal information about nonlinear resonances and guide the tune optimization. The Shanghai Synchrotron Radiation Facility (SSRF) storage ring is taken as a test lattice, and the optimum solutions are presented in this paper. Moreover, the third order regular structural resonances excited by sextupoles are particularly investigated, and it is found that these resonances distort the tune shifts with amplitude and show a stop-band like the linear structural resonances.

New chromaticity compensation approach and dynamic aperture increase in the SSRF storage ring**Supported by SSRF Project

Strong chromatic sextupoles used to compensate natural chromaticities in the third generation light source storage ring usually reduce dynamic aperture drastically. Many optimization methods can be used to find solutions that provide large dynamic apertures. This paper discusses a new optimization approach of sextupole strengths with step-by-step procedure, which is applied in the SSRF storage ring, and a better solution is obtained. Investigating driving terms generated by the sextupoles in every step can analyze their convergences and guide the weight setting among different terms in object function of the single resonance approach based on the perturbation theory.

Conceptual design of the vacuum system of the Spanish synchrotron light source (ALBA) storage ring

ALBA will be a third generation synchrotron light facility to be built near Barcelona (Spain). The design phase of ALBA is almost completed and the first components are ready to be ordered. Commissioning of the storage ring is foreseen to start at the end of 2008. The circumference of the storage ring of ALBA is 268.8 m and it will be divided into 16 vacuum sections by ultra high vacuum (UHV) gate valves. The vacuum chamber will be made of stainless steel with vertical aperture of 28 mm and 72 mm width. The vacuum chamber will be connected to an antechamber with a slot of 10 mm height. The antechamber will have the crotch absorbers which will absorb the unwanted synchrotron radiation. The pumping will be by sputter ion pumps (SIP), NEG pumps and titanium sublimation pumps (TSP), with an overall pumping speed from SIP of 57,400 l/s. This will maintain an average dynamic pressure of around 1 × 10 −9 mbar to achieve a beam lifetime >15 h at the designed current.

Commissioning of the diamond light source storage ring vacuum system

The Diamond storage ring has been operating with a 3 GeV electron beam since September 2006 and 190 A.h of beam dose have been accumulated. The pressure in the storage ring is 4.2 10-10 mbar without beam, rising to 7.9 10-10 mbar with 125 mA of stored beam. Data on the storage ring vacuum performance and experience from commissioning and beam conditioning are presented.

A multipole superconducting wiggler for Canadian light source

A contract for multipole superconducting wiggler design and fabrication between The University of Saskatchewan and Budker Institute of Nuclear Physics was signed in October 2003. A wiggler with the photons energy range 4 to 40 keV, the maximum field 1.9 T, and the period length as small as possible was required for the micro-XAFS beamline. In 2004 the 2 T 63-pole superconducting wiggler with the average period length 34 mm was fabricated in BINP. To eliminate the undulator-type spectrum, the periodicity of the wiggler was broken. A new approach to the cryostat design enabled long-time (up to 6 months) machine operation without liquid helium refilling (LHe consumption <0.03 l/h). After successful tests the wiggler was installed on the Canadian Light Source (CLS) storage ring with the energy 2.9 GeV in January 2005. The main parameters of the magnet and the cryogenic systems, as well as magnet measurements data, cryogenic system test data, and experimental results during machine operation on the CLS storage ring are presented.

Design of a low-emittance 2.5-GeV pohang light source lattice

The Pohang Light Source (PLS) storage ring is a synchrotron light source with the emittance of 18.9 nm at 2.5 GeV. We designed a new lattice with an achromat of the emittance of 13 nm that may provide more brilliant synchrotron radiation. We investigated dependence of the dynamic aperture on the betatron tune to search for large dynamic aperture in the low-emittance lattice by a simulation method. We examined the dynamic apertures by a tune survey within a specified tune space without and with machine errors. It is also shown that how large is the dynamic aperture in the storage ring after correction of a closed orbit distortion. The operating tune for the low-emittance lattice can be chosen on the view point of dynamic apertures obtained from a tune survey. The low-emittance lattice with the achromat shows the reduced horizontal and vertical beam sizes by 10% and 29% in the positions of insertion devices and by 31% and 52% in the bending magnets than the present lattice, respectively. It is also shown that the low-emittance lattice with 13 nm may provide sufficient dynamic aperture without changing of configuration of magnets in the storage ring.

A new small angle X-ray scattering station at NSRRC

Using the X-ray source generated by a newly installed superconducting wavelength shifter at the Taiwan Light Source storage ring of the National Synchrotron Radiation Research Center (NSRRC), we have constructed an X-ray beamline equipped with a small angle X-ray scattering (SAXS) station for nanostructure research. This beamline can deliver a photon flux of ∼3×1011photons/s in the energy range of 5–22keV, with a beam divergence of ∼0.3mrad in vertical direction. With the new SAXS end station we have studied PtRu nanoparticles embedded in fine carbon grains using anomalous SAXS. We illustrate other features of the SAXS instrument with a few more measurements on phase transitions of diblock-polymers, structural evolution of aluminium alloys under an artificial aging at high temperature, and folding and unfolding of lysozyme in aqueous solutions.

Simulation and analysis of using deflecting cavities to produce short x-ray pulses with the Advanced Photon Source

We present detailed simulations and analysis of Zholents’s [A. Zholents, P. Heimann, M. Zolotorev, and J. Byrd, Nucl. Instrum. Methods Phys. Res., Sect. A 425, 385 (1999).] concept for using deflecting cavities in a synchrotron light source storage ring for the purpose of producing short x-ray pulses. In particular, we look at the optimization and performance of such a system for the Advanced Photon Source. We find the concept is practical and that x-ray pulse durations of about 1.5 ps FWHM should be achievable with more than 15% of the original intensity retained. Issues covered include lattice design, emittance degradation, lifetime, photon beam modeling, errors, and optimum choice of rf parameters.

Dependence of Dynamic Aperture on Betatron Tune at 2.5 GeV Pohang Light Source Storage Ring

The Pohang Light Source (PLS) storage ring is a synchrotron light source that has been operated using a 2.5 GeV full energy injection from a linac since October 2002. It is necessary to search for betatron tunes that can realize large dynamic apertures in a 2.5 GeV full energy injection. Accordingly, we investigated dependence of dynamic aperture on the betatron tune to obtain large dynamic apertures in the storage ring by a simulation method. We examined dynamic apertures by a tune survey within a specified tune space with and without machine errors. It is also shown how large are the dynamic apertures in the storage ring recovered are after the correction of a closed orbit distortion. The operating tune is examined from the viewpoint of dynamic apertures obtained by a tune survey.

Impedance Estimations from Bunch Lengthening in the Pohang Light Source

Bunch lengthening in the Pohang Light Source storage ring has been investigated. With the three kinds of impedance models, the impedances of the storage ring are estimated by fitting the solutions of the Haïssinski equation and the measured bunch lengthening. The ring impedances estimated by a series R+L impedance model indicate an inductance of L=13.7±3.5 nH and a resistance of R=743±84 Ω. The behaviors of the measured bunch lengthening are compared with those obtained from the estimated impedances. These results show a good agreement. The threshold beam current is estimated to be 7.4 mA. The scaling law for the bunch lengthening above microwave instability threshold is obtained as σx=0.437I1/3.35. Using the Keil–Schnell criterion, longitudinal broadband impedance of the ring is estimated to be 0.24 Ω.

Design consideration for Tohoku light source storage ring equipped with UV free electron laser

An integrated photon source facility has been planed at Laboratory of Nuclear Science, Tohoku University. A 1.5 GeV main ring designed as a synchrotron light source of VUV and soft X-ray region contains straight sections with very low beta function to accept high field superconducting wigglers for X-ray. One of two 8-m long straight sections is allocated for storage ring free electron laser (SRFEL) in the UV region. The beam property in the ring is evaluated and then the beam quality for the SRFEL oscillation is also discussed including possibility of coherent higher harmonic generation by showing results of numerical simulation.

New Ceramic Chambers for the HLS Storage Ring

The new injection bump system of Hefei light source (HLS) storage ring is firstly introduced. The new system set a strict error limit to the rise time delay of the pulsed magnetic field, which is caused by the coating of the ceramic chamber. The error allowance is studied and the results are summarized. A new method of coating ceramic chambers was developed. The method, which employs Mo metallization techniques, is quite different from existing methods. Important issues of coating these chambers are presented. A unique, two-coil pulsed magnetic field measurement system was set up. Rise time delay of the pulsed field at different positions inside the ceramic chambers was measured. The rise time deviations inside a pair of chambers proved to be within the range of /spl plusmn/4 ns. A vacuum pressure of 2/spl times/10/sup -8/ Pa of the ceramic chambers was obtained after the installation in the storage ring. The chambers performed well. An average injection rate of 2-6 mA/s was obtained.