GeV Electron Storage Ring Research Articles

A machine learning approach to electron orbit control at the 1.5 GeV synchrotron light source DELTA

Machine learning (ML) methods have found their application in a wide range of particle accelerator control tasks. Among other possible use cases, neural networks (NNs) can also be utilized for automated beam position control (orbit correction). ML studies on this topic, which were initially based on simulations, were successfully transferred to real accelerator operation at the 1.5–GeV electron storage ring of the DELTA accelerator facility. For this purpose, classical fully connected multi-layer feed-forward NNs were trained by supervised learning on measured orbit data to apply local and global beam position corrections. The supervised NN training was carried out with various conjugate gradient backpropagation learning algorithms. Afterwards, the ML-based orbit correction performance was compared with a conventional, numerical-based computing method. Here, the ML-based approach showed a competitive orbit correction quality in a fewer number of correction steps.

SPring-8 LEPS2 beamline: A facility to produce a multi-GeV photon beam via laser Compton scattering

We have constructed a new laser-Compton-scattering facility, called the LEPS2 beamline, at the 8 GeV electron storage ring, SPring-8. This facility provides a linearly polarized photon beam in a tagged energy range of 1.3–2.4 GeV. Thanks to a small divergence of the low-emittance storage-ring electrons, the tagged photon beam has a size (σ) suppressed to about 4 mm even after it travels about 130 m to the experimental building that is independent of the storage ring building and contains large detector systems. This beamline is designed to achieve a photon beam intensity higher than that of the first laser-Compton-scattering beamline at SPring-8 by adopting the simultaneous injection of up to four high-power laser beams and increasing a transmittance for the long photon-beam path up to about 77%. The new beamline is under operation for hadron photoproduction experiments.

Development of 200 MeV linac for the SKIF light source injector

The new fourth-generation synchrotron light source SKIF is under development in Novosibirsk, Russia. It consists of a 3 GeV electron storage ring with extremely low emittance, a booster synchrotron, and a linear accelerator. The paper discusses essential aspects of the design of the 200 MeV linear accelerator for SKIF, its main characteristics, and parameters in different operation modes. Description of the linac systems is presented.

Beam-based characterization of higher-order-mode driven coupled-bunch instabilities in a fourth-generation storage ring

Longitudinal coupled-bunch instabilities are driven by monopole higher-order modes (HOMs) in the active and passive radio-frequency (rf) cavities at the MAX IV 3 GeV electron storage ring. By combining different beam and rf-based techniques, we have performed a systematic survey of the properties of these resonant modes as a function of cavity temperatures and fundamental mode frequency. This information was then used to setup a HOM model that allowed us to infer optimized temperature ranges for the cavities. An important feature of the optimization method is that it takes into account not only the need to minimize the growth rates (given by the resistive component of the sum of HOM impedances) from each individual cavity but also aims to minimize the total reactive component of the impedance of HOMs that are present in more than one cavity. The resulting small real coherent tune shifts allow the coupled-bunch modes driven by these HOMs to be effectively Landau damped. Further optimization of the cavity temperatures was performed by minimizing the measured electron beam energy spread within the temperature ranges defined by the HOM model. The optimum temperature search was performed at 300 mA stored beam current and in multi-bunch mode using the RCDS (Robust Conjugate Direction Search) algorithm and succeeded in bringing the electron energy spread to within 10% of the zero current value determined solely by quantum excitation and radiation damping.

Commissioning and operation status of the MAX IV 3 GeV storage ring vacuum system.

The 3 GeV electron storage ring of the MAX IV laboratory is the first storage-ring-based synchrotron radiation facility with the inner surface of almost all the vacuum chambers along its circumference coated with non-evaporable getter (NEG) thin film. The coating provides a low dynamic outgassing rate and pumping of active gases. As the NEG coating was applied on an unprecedented scale, there were doubts concerning the storage ring performance. Fast conditioning of the vacuum system and over five years of reliable accelerator operation have demonstrated that the chosen design proved to be good and does not impose limits on the operation. The vacuum system performance is comparable with or better than that of other similar facilities around the world, where conventional designs were implemented. Observed pressure levels are low, and the electron beam lifetime is long and not limited by residual gas density. A summary of the vacuum performance is presented.

HIPPIE: a new platform for ambient-pressure X-ray photoelectron spectroscopy at the MAX IV Laboratory.

HIPPIE is a soft X-ray beamline on the 3 GeV electron storage ring of the MAX IV Laboratory, equipped with a novel ambient-pressure X-ray photoelectron spectroscopy (APXPS) instrument. The endstation is dedicated to performing in situ and operando X-ray photoelectron spectroscopy experiments in the presence of a controlled gaseous atmosphere at pressures up to 30 mbar [1 mbar = 100 Pa] as well as under ultra-high-vacuum conditions. The photon energy range is 250 to 2200 eV in planar polarization and with photon fluxes >1012 photons s-1 (500 mA ring current) at a resolving power of greater than 10000 and up to a maximum of 32000. The endstation currently provides two sample environments: a catalysis cell and an electrochemical/liquid cell. The former allows APXPS measurements of solid samples in the presence of a gaseous atmosphere (with a mixture of up to eight gases and a vapour of a liquid) and simultaneous analysis of the inlet/outlet gas composition by online mass spectrometry. The latter is a more versatile setup primarily designed for APXPS at the solid-liquid (dip-and-pull setup) or liquid-gas (liquid microjet) interfaces under full electrochemical control, and it can also be used as an openport for ad hoc-designed non-standard APXPS experiments with different sample environments. The catalysis cell can be further equipped with an IR reflection-absorption spectrometer, allowing for simultaneous APXPS and IR spectroscopy of the samples. The endstation is set up to easily accommodate further sample environments.

The eRHIC spin rotator and the beam optics of the 400 MeV transfer line to RCS

The 400 MeV LINAC1 of the proposed eRHIC collider1 is the first acceleration stage of the 18 GeV electron accelerator. The second acceleration stage of the electron accelerator is the Rapid Cycling Synchrotron (RCS), which can increase the energy of the electron bunches to 18 GeV and subsequently extract transfer and inject the 18 GeV electron bunches into the 18 GeV electron Storage Ring (SR) to collide with the hadron bunches of the existing (Relativistic Heavy Ion Collider (RHIC)) accelerator. This paper describes the beam optics of the transfer line between the 400 MeV LINAC and the RCS accelerator (LtRCS). The function of the LtRCS line is twofold, first to transfer the electron beam from the exit of the 400 MeV LINAC to the injection point of the RCS1 and second to rotate the stable spin direction of the polarized electrons from the longitudinal direction to the vertical. A detailed description of the constraints to be satisfied by the LtRCS transfer line will be given. A section will also be devoted to discuss the spin rotator2.

High-Resolution Infrared Synchrotron Investigation of (HCN)2 and a Semi-Experimental Determination of the Dissociation Energy D0.

The high‐resolution infrared absorption spectrum of the donor bending fundamental band ν 61 of the homodimer (HCN)2 has been collected by long‐path static gas‐phase Fourier transform spectroscopy at 207 K employing the highly brilliant 2.75 GeV electron storage ring source at Synchrotron SOLEIL. The rovibrational structure of the ν 61 transition has the typical appearance of a perpendicular type band associated with a Σ–Π transition for a linear polyatomic molecule. The total number of 100 assigned transitions are fitted employing a standard semi‐rigid linear molecule Hamiltonian, providing the band origin ν 0 of 779.05182(50) cm−1 together with spectroscopic parameters for the degenerate excited state. This band origin, blue‐shifted by 67.15 cm−1 relative to the HCN monomer, provides the final significant contribution to the change of intra‐molecular vibrational zero‐point energy upon HCN dimerization. The combination with the vibrational zero‐point energy contribution determined recently for the class of large‐amplitude inter‐molecular fundamental transitions then enables a complete determination of the total change of vibrational zero‐point energy of 3.35±0.30 kJ mol−1. The new spectroscopic findings together with previously reported benchmark CCSDT(Q)/CBS electronic energies [Hoobler et al. ChemPhysChem. 19, 3257–3265 (2018)] provide the best semi‐experimental estimate of 16.48±0.30 kJ mol−1 for the dissociation energy D 0 of this prototypical homodimer.

Commissioning and first-year operational results ofthe MAX IV 3 GeV ring.

The MAX IV 3 GeV electron storage ring in Lund, Sweden, is the first of a new generation of light sources to make use of the multibend-achromat lattice (MBA) to achieve ultralow emitance and hence ultrahigh brightness and transverse coherence. The conceptual basis of the MAX IV 3 GeV ring project combines a robust lattice design with a number of innovative engineering choices: compact, multifunctional magnet blocks, narrow low-conductance NEG-coated copper vacuum chambers and a 100 MHz radio-frequency system with passively operated third-harmonic cavities for bunch lengthening. In this paper, commissioning and first-year operational results of the MAX IV 3 GeV ring are presented, highlighting those aspects that are believed to be most relevant for future MBA-based storage rings. The commissioning experience of the MAX IV 3 GeV ring offers in this way an opportunity for validation of concepts that are likely to be essential ingredients of future diffraction-limited light sources.

Simulation of fast beam ion instability (FBII) in Indus-2 and its experimental observation

Indus-2 is a 2.5 GeV electron storage ring and a national facility for synchrotron radiation users in India providing the photon beam in round the clock mode. Recently, the electron beam emittance of Indus-2 was reduced to one third of the normal operating optics (130 nm rad) with improved beam optics. Due to this reduced emittance, likelihood of fast beam ion instability (FBII) enhances, and that was explored using simulation study. FBII is generated due to the cascading interaction of electron beam with ions that comes across in the path of the beam. This interaction induces oscillation in center of mass of bunches of electron beam and that process increases the transverse beam size, which spoils the effort made in achieving the reduction in beam emittance. For correct understanding of this instability, simulations have been performed with different ring average pressure and considering different per bunch current values. Further, studies have been carried out for two sets of beam optics used for normal emittance and reduced emittance of the electron beam. The simulation method and results are presented in this paper. To observe the signature of this instability, an experiment has been conducted in Indus-2 and its limitations due to operational gas pressure are discussed.

Nsls-II Boster

The National Synchrotron Light Source II is a third generation light source, which was constructed at Brookhaven National Laboratory. This project includes a highly-optimized 3 GeV electron storage ring, linac preinjector, and full-energy synchrotron injector. Budker Institute of Nuclear Physics built and delivered the booster for NSLS-II. The commissioning of the booster was successfully completed. This paper reviews fulfilled work by participants.

The high luminosity interaction region for a ring–ring Large Hadron Electron Collider

The Large Hadron Electron Collider (LHeC) project is a proposal for high luminosity TeV-scale electron–proton (ep) collisions at the LHC. The LHeC Conceptual Design Report presented an early overview of the machine, including an electron linac solution and a solution involving a 60 GeV electron storage ring. Here we present a new complete solution for the collision insertion of this electron ring, incorporating all constraints including those imposed by the LHC and, for the first time, proving the feasibility of ep collisions at a luminosity of ∼1033 cm−2s−1 in the LHC era. The solution presented offers high luminosity while maintaining the large detector coverage required by the particle physics programme. This negates the earlier need for two separate interaction region designs, one optimized for high luminosity at the cost of detector coverage, and the other for lower luminosity but higher coverage. Synchrotron radiation emission is also a major factor in electron accelerator design, and studies are presented showing the feasibility of the design in this regard. The design is found to be technically viable, solving the problem of TeV-scale, high luminosity and high coverage ep collisions at a ring–ring LHeC.

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.

Grazing incidence X-ray absorption spectroscopy under non-ambient conditions: Investigations of liquid surfaces at DELTA beamline 8

A setup for the investigation of liquid surfaces using grazing incidence X-ray absorption spectroscopy has been installed at the hard X-ray beamline BL 8 at the 1.5 GeV electron storage ring DELTA. While the 6-axis diffractometer endstation of the beamline accommodates a Langmuir trough, the double mirror device which is originally used for the harmonic rejection of low energy beams was used to deflect the beam downwards, defining thereby the incidence angle for the reflection and fluorescence mode EXAFS experiments in a Θ-Θ-geometry. Results obtained during the biomineralization of iron oxides on a Langmuir film of stearic acid show the feasibility of grazing incidence EXAFS measurements that may provide valuable information about the molecular structure of the formed iron oxide phases.

A simultaneous multiple angle-wavelength dispersive X-ray reflectometer using a bent-twisted polychromator crystal

An X-ray reflectometer has been developed, which can simultaneously measure the whole specular X-ray reflectivity curve with no need for rotation of the sample, detector or monochromator crystal during the measurement. A bent-twisted crystal polychromator is used to realise a convergent X-ray beam which has continuously varying energy E (wavelength λ) and glancing angle α to the sample surface as a function of horizontal direction. This convergent beam is reflected in the vertical direction by the sample placed horizontally at the focus and then diverges horizontally and vertically. The normalized intensity distribution of the reflected beam measured downstream of the specimen with a two-dimensional pixel array detector (PILATUS 100K) represents the reflectivity curve. Specular X-ray reflectivity curves were measured from a commercially available silicon (100) wafer, a thin gold film coated on a silicon single-crystal substrate and the surface of liquid ethylene glycol with data collection times of 0.01 to 1000 s using synchrotron radiation from a bending-magnet source of a 6.5 GeV electron storage ring. A typical value of the simultaneously covered range of the momentum transfer was 0.01-0.45 Å(-1) for the silicon wafer sample. The potential of this reflectometer for time-resolved X-ray studies of irreversible structural changes is discussed.

The first microbeam synchrotron X-ray fluorescence beamline at the Siam Photon Laboratory

The first microbeam synchrotron X-ray fluorescence (µ-SXRF) beamline using continuous synchrotron radiation from Siam Photon Source has been constructed and commissioned as of August 2011. Utilizing an X-ray capillary half-lens allows synchrotron radiation from a 1.4 T bending magnet of the 1.2 GeV electron storage ring to be focused from a few millimeters-sized beam to a micrometer-sized beam. This beamline was originally designed for deep X-ray lithography (DXL) and was one of the first two operational beamlines at this facility. A modification has been carried out to the beamline in order to additionally enable µ-SXRF and synchrotron X-ray powder diffraction (SXPD). Modifications included the installation of a new chamber housing a Si(111) crystal to extract 8 keV synchrotron radiation from the white X-ray beam (for SXPD), a fixed aperture and three gate valves. Two end-stations incorporating optics and detectors for µ-SXRF and SXPD have then been installed immediately upstream of the DXL station, with the three techniques sharing available beam time. The µ-SXRF station utilizes a polycapillary half-lens for X-ray focusing. This optic focuses X-ray white beam from 5 mm × 2 mm (H × V) at the entrance of the lens down to a diameter of 100 µm FWHM measured at a sample position 22 mm (lens focal point) downstream of the lens exit. The end-station also incorporates an XYZ motorized sample holder with 25 mm travel per axis, a 5× ZEISS microscope objective with 5 mm × 5 mm field of view coupled to a CCD camera looking to the sample, and an AMPTEK single-element Si (PIN) solid-state detector for fluorescence detection. A graphic user interface data acquisition program using the LabVIEW platform has also been developed in-house to generate a series of single-column data which are compatible with available XRF data-processing software. Finally, to test the performance of the µ-SXRF beamline, an elemental surface profile has been obtained for a piece of ancient pottery from the Ban Chiang archaeological site, a UNESCO heritage site. It was found that the newly constructed µ-SXRF technique was able to clearly distinguish the distribution of different elements on the specimen.

XAS at the materials science X-ray beamline BL8 at the DELTA storage ring

The hard X-ray beamline BL 8 at the 1.5 GeV electron storage ring DELTA is described, and experimental data of different fields of research are presented. Making use of the intense X-ray beam emitted by a superconducting wiggler, the beamline is dedicated to X-ray absorption experiments. Three different monochromator crystal pairs are permanently available for experiments in the spectral range from about 1 keV to ca. 25 keV photon energy. Results of reference materials show that high quality EXAFS data can be obtained using Si(111) and Si(311) monochromators. First measurements in the energy range between 1.2 and 5 keV have been accomplished using YB66(400) monochromator crystals. The experimental hutch accommodates a unique 6-axis diffractometer which is well suited for all kinds of diffraction and absorption experiments, including the grazing incidence geometry. The diffractometer can carry heavy loads related to non-ambient sample environments such as e.g. ultrahigh vacuum sample stages or cryostats. Here we present typical results obtained at BL8 in different areas of materials science including investigations of dilute alloys by fluorescence mode EXAFS and the study of the structural changes associated with temperature induced spin transitions of metallo-supramolecular polyelectrolyte-amphiphile-complexes.

Current status and progresses of SSRF project

The Shanghai Synchrotron Radiation Facility (SSRF), a third generation light source, comprises a 3.5GeV electron storage ring, a full energy booster, a 150 MeV linac, and seven beamlines in Phase I of the project. Beginning at the end of 2004 with a groundbreaking ceremony, the accelerators were installed in ten months from November 2006, and were successfully tested and commissioned in the past a couple of months. On December 21, 2007, storing electron beams in the storage ring was realized, and the first synchrotron radiations were observed three days later on the front-end of Beamline BL16B of the facility. Now, it runs 3 GeV 100 mA beams with a lifetime of 8∼10 hours. Meanwhile, construction of the first seven beamlines (five ID beamlines and two bending magnet beamlines) is progressing on schedule.

Bunch purity measurement for Diamond

Measurement of the fill pattern of synchrotron storage rings is important for several reasons, including checking the quality of the injection system and the generation of special fill patterns for time-resolved experiments. For the new national X-ray facility based on the Diamond 3 GeV electron storage ring, it is planned to measure the beam quality in a short time of several minutes by using a time-correlated single photon counting method. The method has very good time resolution (50 ps) and high dynamic range (more than six orders of magnitude). In this paper, we describe our experimental setup, a series of tests to evaluate the system limitations using short pulse lasers on laboratory test benches, the existing SRS national X-ray facility, and the third-generation synchrotron radiation facility SLS. Taking all these results together, we are able to predict the system performance for Diamond.

Structure quality in deep X-ray lithography applying commercial polyimide-based masks

The structure quality of deep X-ray lithography components strongly depends on the quality of the applied X-ray mask. In this article we compare the results obtained with two different mask types. Sophisticated working masks generated by e-beam lithography, soft X-ray lithography and electroplating of gold absorbers on a titanium mask membrane have been fabricated at the Institute for Microstructure Technology, Research Center, Karlsruhe (FZK/IMT), Germany. Prototype masks generated by e-beam lithography, optical lithography and electroplating of gold absorbers on a polyimide mask membrane have been fabricated by Optnics Precision, Japan, with the aim to offer commercially available low cost masks. Both mask types were applied to pattern PMMA resist layers of 300–750 μm thickness at the 2.5 GeV electron storage ring ANKA, Germany, using comparable process parameters. FZK/IMT masks provide microstructures with significantly better structure quality. The layout area, however, is currently limited to 12 cm2, and the Ti mask membrane tends to lead to a slight resist surface attack, such as rounding of the resist edges. Optnics masks provide microstructures with reduced structure quality due to sidewall striations (sidewall roughness up to 2 μm) and thermal distortions (of up to 3–5 μm) which limit the potential scope of applications. They could nevertheless potentially be applied as low quality, low cost X-ray masks. High resolution and high accuracy applications, however, require more sophisticated but also more expensive masks, like the Ti-masks from FZK/IMT.