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The National Synchrotron Light Source-II (NSLS-II) at Brookhaven National Lab (BNL) is a third-generation medium-energy storage ring with 3 GeV and sub-nm-rad horizontal emittance, equipped with a top-off capability of 500 mA. It is designed to deliver an extremely intense photon beam across a wide spectral range, from the far-infrared to the very hard X-ray region. This outstanding performance is achieved through a combination of bending magnets (BM), three-pole wigglers (3 PW), and advanced insertion device (ID) sources. Six three-pole wigglers have been constructed at the NSLS-II IDs Lab. These devices are used to produce broadband radiation with lower angular power density and to monitor the electron beam emittance and energy spread. This paper describes the R&D activities focused on developing the required magnetic and mechanical designs, along with magnetic field optimization and the final magnetic measurement results. It also covers the spectral brightness, flux, power density, spatial and angular output properties of the 3 PWs, including their commissioning results and their effects on the performance of the NSLS-II storage ring. [ABSTRACT FROM AUTHOR]

The High Energy Photon Source (HEPS) is a 6 GeV diffraction-limited synchrotron light source under construction in Beijing. It will use five 166.6 MHz superconducting radio frequency (rf) cavities to accelerate the 200 mA electron beam in the storage ring. In the current lattice design, each straight section is 6 meters long to accommodate two 166.6 MHz cavities. The cavity adopts β =1 quarter-wave geometry, and the damping of the higher order modes is realized by using an enlarged cavity beam pipe to 505 mm and a ferrite absorber installed on the beam pipe. The low rf frequency, as well as the large beam aperture, added great challenges to the design of the 166.6 MHz cavity module to fit into a strictly limited longitudinal space. In addition, heat load optimization for the transition from room temperature to the cryogenic temperature, smooth tapering from the 505 mm beam aperture to the small diameter of the gate valves for impedance control, proper collimation of the synchrotron light to prevent thermal damage of delicate components, are also demanding requirements for a compact design. Accessibilities are also preserved for tuners and vacuum components to enable online maintenance. Finally, rf field leakage in the vacuum seal groove of the cavity is carefully examined to prevent overheating on the superconducting flange, which, in the worst scenario, may cause a thermal runaway, thus limiting the achievable accelerating gradient of the cavity. This paper presents the first compact design of the 166.6 MHz srf section for HEPS. [ABSTRACT FROM AUTHOR]

The capability of providing full-charge bunches has become an important requirement for quite a few boosters used in ultralow-emittance storage rings based synchrotron light sources. The transverse single-bunch instabilities may limit the single-bunch charge in these type of boosters. The relatively weak synchrotron radiation damping makes the bunch more unstable at the injection energy than at the extraction energy. Therefore, studies of the transverse single-bunch instabilities are carried out first at the injection energy, with the chromaticity varied, to understand how the threshold changes accordingly. Our studies show that the single-bunch threshold current tends to drop when the chromaticity becomes nonzero at the injection energy of the used booster lattice. The corresponding simulation results are presented and analyzed. Furthermore, the transverse single-bunch instabilities during the energy ramping process are also studied. [ABSTRACT FROM AUTHOR]

We designed a normal-conducting (NC) 1.5 GHz harmonic cavity that can be used in a future synchrotron light source at High Energy Accelerator Research Organization (KEK). By utilizing a higher TM020 mode for beam acceleration, this cavity has lower R/Q and higher unloaded Q as compared to those of conventional NC cavities. These features are advantageous in reducing the fluctuations in harmonic RF voltages when the bunch gaps are introduced. Harmful parasitic modes other than the TM020 mode can be heavily damped using coaxial slots located at the node of the TM020 mode. We made a concerted effort to lower the coupling impedances of parasitic modes while maintaining high Q value of the accelerating mode. We found that maintaining the axial symmetry of the cavity is essential for minimizing the leakage power of the accelerating mode into the coaxial slots. In this article, we present the optimization of the cavity shape, low-power measurement, and the basic design of a high-power model. [ABSTRACT FROM AUTHOR]

Fast Orbit Feedback System (FOFB) can be installed in a synchrotron light source to eliminate undesired disturbances and to improve the stability of beam orbit. The design and implementation of an accurate and reliable Fast Corrector Power Supply (FCPS) is essential to realize the effectiveness and availability of the FOFB. A reliability assessment for the FCPSs in the FOFB of Taiwan Photon Source (TPS) considering MOSFETs’ temperatures is represented in this paper. The FCPS is composed of a full-bridge topology and a low-pass filter. A Hybrid Pulse Width Modulation (HPWM) requiring two MOSFETs in the full-bridge circuit to be operated at high frequency and the other two be operated at the output frequency is adopted to control the implemented FCPS. Due the characteristic of HPWM, the conduction loss and switching loss of each MOSFET in the FCPS is not same. Two of the MOSFETs in the full-bridge circuit will suffer higher temperatures and therefore the circuit reliability of FCPS is reduced. A Modified PWM Scheme (MPWMS) designed to average MOSFETs’ temperatures and to improve circuit reliability is proposed in this paper. Experimental results measure the MOSFETs’ temperatures of FCPS controlled by the HPWM and the proposed MPWMS. The reliability indices under different PWM controls are then assessed. From the experimental results, it can be observed that the reliability of FCPS using the proposed MPWMS can be improved because the MOSFETs’ temperatures are closer. Since the reliability of FCPS can be enhanced, the availability of FOFB can also be improved. [ABSTRACT FROM AUTHOR]

At many storage rings for synchrotron light production there is demand for serving both high-flux and timing users simultaneously. Today this is most commonly achieved by operating inhomogeneous fill patterns, but this is not preferable for rings that employ passive harmonic cavities to damp instabilities and increase Touschek lifetime. For these rings, inhomogeneous fill patterns could severely reduce the effect of the harmonic cavities. It is therefore of interest to develop methods to serve high-flux and timing users simultaneously without requiring gaps in the fill pattern. One such method is pseudo-single-bunch (PSB), where one bunch in the bunch train is kicked onto another orbit by a fast stripline kicker. The light emitted from the kicked bunch can then be separated by an aperture in the beamline. Due to recent developments in fast kicker design, PSB operation in multibunch mode is within reach for rings that operate with a 100 MHz RF system, such as the MAX IV and Solaris storage rings. This paper describes machine requirements and resulting performance for such a mode at the MAX IV 1.5 GeV storage ring. A solution for serving all beamlines is discussed as well as the consequences of beamline design and operation in the soft X-ray energy range. [ABSTRACT FROM AUTHOR]

We present a detailed study using the skew quadrupoles in the Canadian Light Source storage ring lattice to control the parameters of a coupled lattice. We calculate the six-dimensional beam envelop matrix and use it to produce a variety of objective functions for optimization using the Multi-Objective Particle Swarm Optimization (MOPSO) algorithm. MOPSO produces a number of skew quadrupole configurations that we apply to the storage ring. We use the X-ray synchrotron radiation diagnostic beamline to image the beam and we make measurements of the vertical dispersion and beam lifetime. We observe satisfactory agreement between the measurements and simulations. These methods can be used to adjust phase space coupling in a rational way and have applications to fine-tuning the vertical emittance and Touschek lifetime and measuring the gas scattering lifetime. [ABSTRACT FROM AUTHOR]

To realize the full benefits of the high brightness and ultra-small beam sizes of NSLS-II, it is essential that the photon beams are exceedingly stable. In the circumstances of implementing local bumps, changing ID gaps, and long term drifting, the fast orbit feedback (FOFB) requires shifting the fast corrector strengths to the slow correctors to prevent the fast corrector saturation and to make the beam orbit stable in the sub-micron level. As the result, a reliable and precise technique of fast-to-slow corrector strength shift has been developed and tested at NSLS-II. This technique is based on the fast corrector response to the slow corrector change when the FOFB is on. In this article, the shift technique is described and the result of proof-of-principle experiment carried out at NSLS-II is presented. The maximum fast corrector current was reduced from greater than 0.45 A to less than 0.04 A with the orbit perturbation within ± 1 μ m. [ABSTRACT FROM AUTHOR]

The MAX IV 3 GeV storage ring is presently being commissioned and crucial parameters such as machine functions, emittance, and stored current have either already been reached or are approaching their design specifications. Once the baseline performance has been achieved, a campaign will be launched to further improve the brightness and coherence of this storage ring for typical X-ray users. During recent years, several such improvements have been designed. Common to these approaches is that they attempt to improve the storage ring performance using existing hardware provided for the baseline design. Such improvements therefore present more short-term upgrades. In this paper, however, we investigate medium-term improvements assuming power supplies can be exchanged in an attempt to push the brightness and coherence of the storage ring to the limit of what can be achieved without exchanging the magnetic lattice itself. We outline optics requirements, the optics optimization process, and summarize achievable parameters and expected performance. [ABSTRACT FROM AUTHOR]

The MAX IV 3 GeV storage ring is the first light source to make use of a multibend achromat lattice to reach ultralow emittance. After extensive commissioning efforts, the storage ring is now ramping up its user program. We present results from beam commissioning of the MAX IV 3 GeV storage ring as well as a summary of the beam dynamics studies that have so for been carried out. We report on injection and accumulation using a single dipole kicker, top-up injection, slow orbit feedback, restoring the linear optics to design, effects of in-vacuum undulators with closed gaps, adjusting nonlinear optics to achieve design chromaticity correction and dynamic aperture sufficient for high injection efficiency and large Touschek lifetime. [ABSTRACT FROM AUTHOR]

We report on the production and testing of an array of active edge silicon sensors as a prototype of a large array. Four Medipix3RX.1 chips were bump bonded to four single chip sized Advacam active edge n-on-n sensors. These detectors were then mounted into a 2 by 2 array and tested on B16 at Diamond Light Source with an x-ray beam spot of 2um. The results from these tests, compared with optical metrology demonstrate that this type of sensor is sensitive to the physical edge of the silicon, with only a modest loss of efficiency in the final two rows of pixels. We present the efficiency maps recorded with the microfocus beam and a sample powder diffraction measurement. These results give confidence that this sensor technology can be used effectively in larger arrays of detectors at synchrotron light sources. [ABSTRACT FROM AUTHOR]

The effects of temperature changes on the particle orientation of a consolidated kaolin are studied using XRD experiments. Two sets of equipment were utilized in this study: a benchtop equipment, and a synchrotron beamline at the National Synchrotron Light Source II (NSLS-II) at Brookhaven National Laboratory. The kaolin specimens tested in the benchtop XRD were subjected to elevated and freezing temperatures ex-situ, while those used for the NSLS-II experiment were exposed to the temperature changes in-situ. The temperatures considered in this study range from freezing (− 10 °C) to elevated temperature below boiling (90 °C). The thermally-induced reorientation of clay mineral particles is highly dependent on the relative orientation of the clay mineral particles with respect to the applied thermal gradient. For example, kaolin samples with kaolinite particles oriented perpendicular to the thermal gradient, and to the expected thermally-induced pore water flow, experience much higher particles reorientations compared to samples with particles initially oriented parallel to the thermal gradient. Moreover, freezing kaolin preserved its microstructure as ice crystals form. [ABSTRACT FROM AUTHOR]

Picosecond-long x-ray pulses of moderate intensity and high repetition rate are highly sought after by the light sources community, e.g. for time-resolved investigations of matter in the linear response regime. We investigate the upgrade of a diffraction-limited storage ring light source to a short X-ray pulse scheme. Short pulses are emitted by electron bunches magnetically compressed in the injection chain, with no impact on the simultaneous standard emission from long bunches. The ultimate performance, limits and operational aspects of the scheme are discussed in terms of soft X-ray undulator emission. [ABSTRACT FROM AUTHOR]

Fourth-generation storage rings enabled by multi-bend achromat lattices are being inaugurated worldwide and many more are planned for the next decade. These sources deliver stable ultra-high brightness radiation with unmatched levels of transverse coherence by virtue of their highly advanced magnetic lattices. Optimization of these challenging and strongly nonlinear lattices with many degrees of freedom bounded by extensive sets of constraints and multiple often conflicting optimization goals is highly demanding and requires application of the most advanced numerical tools available to the community. While multi-objective genetic algorithms have been very successful in supporting these optimization efforts, the algorithms suffer from a fundamental limitation of their stochastic nature: an exceedingly vast number of candidate lattices, most of which eventually are rejected, has to be fully evaluated. This comes at immense computational cost and thus drives excessive runtime despite use of large supercomputing clusters. We therefore propose to employ deep learning techniques and iterative retraining of neural networks to massively accelerate such lattice evaluation, thereby allowing lattice optimization to rely on far fewer a priori assumptions, open up to larger search ranges, and include right from the start and in parallel multiple error distributions to find truly global optima, all while completing a full optimization campaign in weeks rather than months. In this paper we present the neural network designs, the deep learning approach, iterative retraining procedures, and demonstrate how these machine learning techniques can be incorporated into existing state-of-the-art optimization workflows with only minimal changes applied to the optimization pipeline itself and none at all to the employed tracking codes. [ABSTRACT FROM AUTHOR]

The tolerances for the alignment of the magnets on the girders of the proposed particle accelerator of the Brazilian Synchrotron Light Laboratory (LNLS), Sirius, are as small as 40 μm for translations and 0.3 mrad for rotations. The functional axis of the magnets is measured by the vibrating wire technique, which employs conductive wires of diameters of approx. 0.1 mm. Since the alignment has to be performed targeting these magnetic axes, rather than their geometric centrelines, non-contact measuring sensors mounted on a coordinate measuring machine have been chosen to measure the relative deviations between magnets. To better the measurement accuracy for that specific measuring task, to allow interim checks on multiple coordinate measuring systems, and to provide effective traceability to the SI unit of length, a multipurpose geometrical artefact has been devised. The reasoning behind this development and the first measurement results are described in this paper. [ABSTRACT FROM AUTHOR]

The tolerances for the alignment of the magnets in the girders of the next machine of the Brazilian Synchrotron Light Laboratory (LNLS), Sirius, are as small as 40 µm for translations and 0.2 mrad for rotations. Therefore, a novel approach to the well-known vibrating wire technique has been developed and tested for the precise fiducialization of magnets. The alignment bench consists of four commercial linear stages, a stretched wire, a commercial lock-in amplifier working with phase-locked loop (PLL), a coordinate measuring machine (CMM) and a vibration sensor for the wire. This novel sensor has been designed for a larger linear region of operation. For the mechanical metrology step of the fiducialization of quadrupoles an innovative technique, using the vision system of the CMM, is presented. While the work with pitch and yaw orientations is still ongoing with promising partial results, the system already presents an uncertainty level below 10 µm for translational alignment. [ABSTRACT FROM AUTHOR]

It is shown that two radio frequency deflecting cavities with slightly different frequencies can be used to produce time-dependent orbit deflection to a few special electron bunches circulating in a synchrotron without affecting the majority of the electron bunches. These special bunches produce an x-ray pulse in which transverse position or angle, or both, are correlated with time. The x-ray pulse is then shortened, either with an asymmetrically cut crystal that acts as a pulse compressor, or with an angular aperture such as a narrow slit positioned downstream. The implementation of this technique creates a highly flexible environment for synchrotrons in which users of most beamlines will be able to easily select between the x-rays originated by the standard electron bunches and the short x-ray pulses originated by the special electron bunches carrying a time-dependent transverse correlation. [ABSTRACT FROM AUTHOR]

The on-axis swap-out injection scheme is promising for diffraction-limited storage rings, mainly because it can significantly reduce the requirement of dynamic aperture. However, this scheme requires the injection of full-charge bunches. Therefore, it may suffer from the reduction of injection efficiency caused by the so-called "injection transient instability" when high-charge bunches are needed. The idea of implementing RF modulation in a booster before extraction, driving the second-order parametric resonance to suppress the "injection transient instability" in the storage ring, was proposed and demonstrated previously. Here, we mainly present studies of third-order parametric resonance driven by RF phase modulation. Derivation of the modulated Hamiltonian around the third-order parametric resonance, the coordinates of both stable and unstable fixed points, and the 'island tune' are presented in detail. To double check the correctness of the theoretical results, numerical tests and tracking studies were carried out and presented. Furthermore, the results from comprehensive simulations are presented to demonstrate the improvement of injection efficiency by the proper settings of the RF phase modulation. [ABSTRACT FROM AUTHOR]

Abstract: Injection into the two MAX IV storage rings will not make use of a 4-kicker local injection bump. Instead, pulsed multipole injection will be used for initial filling as well as top-up injection. Since commissioning a pulsed multipole magnet for injection into a storage ring is non-trivial, it has been decided to install a single dipole kicker magnet into the storage rings to provide a simple method for injection during early commissioning. Design studies have revealed that injection with a single dipole kicker into the MAX IV storage rings is not only efficient, but also allows for accumulation of beam. Although this accumulation cannot be made transparent to users (i.e. it is not compatible with user top-up operation), it does provide a simple and robust injection method during commissioning. In addition, the dipole kicker can be used as a pinger magnet during machine studies with a single-bunch filling. This paper reports on the design studies performed for dipole kicker injection into the MAX IV storage rings and presents a summary of the expected performance of such an injection scheme. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: An upgrade project is under way to further improve the brightness of the Advanced Light Source at Berkeley Lab by reducing its horizontal emittance from 6.3 to 2.2nm (effective emittance in the straights from 6.4 to 2.5nm). This will result in a brightness increase by a factor of three for bend magnet beamlines and at least a factor of two for insertion device beamlines and will keep the ALS competitive with newer sources. This paper presents an overview of the upgrade project with emphasis on the nonlinear beam dynamics simulations. It also discusses in a more general way the techniques used at LBNL for finding optimum lattices (e.g. the ones with maximum brightness) and optimizing the particle dynamics, thereby increasing beam lifetime and stability. [Copyright &y& Elsevier]

Abstract: This paper is the report of the working group on Ultimate Storage Rings at the Department of Energy''s Basic Energy Sciences Workshop on Physics of Future Light Sources, which took place in Gaithersburg, Maryland on September 15–17, 2009. In this report we address the accelerator design issues related to the next generation of storage ring light sources, deemed “ultimate” storage rings. In our estimation, storage rings have the potential to provide an increase in photon brightness and coherent flux that is two orders of magnitude above that projected for rings currently under construction. In addition to photon brightness and coherent flux, we discuss other directions, such as shorter pulses, tailored bunches, and partial lasing, in which rings could evolve. For the most part we envision ultimate storage rings as an evolutionary advance from existing rings that faces no fundamental technological obstacles. Nevertheless we identify several important areas of R&D that should be pursued to enable the realization of the full potential of ultimate ring light sources. [Copyright &y& Elsevier]

Abstract: Successive improvements have been performed on the vacuum system for the Photon Factory Advanced Ring (PF-AR) at the High Energy Accelerator Research Organization (KEK). The main purpose is to prolong electron beam lifetime for stable operation as an intense pulsed X-ray source. In the past three years, a total of 61 sputter ion pumps (SIPs) were additionally installed, and the increased effective pumping speed amounts to 13% of total. Comparison between calculated and observed beam lifetimes indicates that the lifetime is restricted mainly by the residual gas scatterings and that improvement of the vacuum will realize still longer lifetime. Sudden beam lifetime drops caused by dust trappings have been investigated for many years. The frequency of the lifetime drops has decreased as operation time elapsed after a large-scale reconstruction. Effect of distributed ion pumps (DIPs) on the lifetime drops has also been investigated experimentally. [Copyright &y& Elsevier]

Abstract: A new bunch cleaning system has been designed and is currently in operation in the storage ring of the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory. The new system provides for high bunch purity, arbitrary filling patterns, and is compatible with the various ALS user operation modes. Design details and performance results of the new system will be described. [Copyright &y& Elsevier]

Abstract: Insertion devices (IDs) of various types provide light of high brilliance to experimenters at the Swiss Light Source (SLS) beamlines. However, changes in the photon energy and polarization by movement of the ID gap and phase shift cause orbit distortions that result in a displacement of the photon beam in both angle and position at the beamline. A feed-forward correction scheme has been developed to quantify and precisely correct these effects using designated correctors local to the photon source. The settings for these correctors are determined using an orbit configuration consisting of 73 digital beam position monitors (DBPMs) and associated correctors; recently commissioned X-ray beam position monitors (XBPMs) located at the beamline front-end are also included in the correction algorithm to further constrain the photon beam to its specified position. The feed-forward correction procedure is finally implemented at the local processor level and applied at a rate of 10Hz. A photon pointing stability at the sub-microradian level is achieved. The entire gap scan, feed-forward generation and subsequent verification can be completed from within a few minutes to several hours depending on the complexity of the ID. The methodology of the procedure is described and the results from several ID analyses are presented. The effect of the ID on the betatron tune is also discussed. Both feed-forward and feedback procedures have been implemented to maintain the horizontal and vertical components of the tune at the desired working points. [Copyright &y& Elsevier]

Abstract: Two examples of low-emittance light-source lattices are discussed. Both use similar building blocks consisting of 7-bend achromats. The small emittances generated by these lattices are further reduced by the introduction of insertion devices (IDs), resulting in beam emittance values ranging from 0.2 to 0.9nmrad, depending on the number of achromats chosen. The two examples discussed here are rings with 12 and 20 achromats. The performances of any intermediate number of achromats can easily be estimated. A higher number of achromats of this type seems to result in an uncomfortably small dynamic aperture. The Touschek losses and Intra Beam Scattering (IBS) effect are calculated together with some means to reduce their impact. To calculate this impact, certain technical solutions are assumed, which are described. Other technical solutions could naturally be chosen. The impact of emittance on brilliance is also discussed and the brilliance curves for the two cases are presented and compared with the zero-emittance case (“ultimate source”). [Copyright &y& Elsevier]

Abstract: The Siam Photon Source (SPS) is an accelerator complex with a 1.2-GeV electron storage ring optimized for the generation of synchrotron radiation. The storage ring was originally designed to operate at 1.0-GeV electron beam energy, and was later upgraded for 1.2-GeV operation in 2005. The intent of this report is to present the overview of current machine performance, which includes user beam availability and problems which lead to machine downtime. In order to address the growing user demand for improved beam stability and machine reliability, several progresses has been made recently, with more machine improvements planned that will be carried out in the near future. These activities will also be discussed in this paper. [Copyright &y& Elsevier]

Abstract: A short overview is given on the status of SSLS, its four operational and one forthcoming experimental facilities and their use for material science exemplified by selected work on electromagnetic metamaterials, arrays of nanorods for near-IR photonics, thin films of low dielectric constant materials for semiconductor manufacturing, nanoparticles and art objects. [Copyright &y& Elsevier]

It is well known that the electron beam emittance can be lowered by keeping positive dispersion in the insertion straight section of an otherwise double bend achromat lattice. But the fact that the beam size at the straight section is not simply determined by the emittance any more has made the scheme suspicious. There was even a claim that the minimum electron beam size in the straight section remains unchanged regardless of the dispersion. It is shown in this article that the electron beam size can really be decreased by the positive dispersion of the straight section. It is also shown that the minimum of σ2/β of the dispersive straight section is 0.64 of that of the minimum double bend achromat lattice. [Copyright &y& Elsevier]

In order to accommodate the luminosity improvement strategy, two superconducting 499.8 MHz radio frequency (rf) cavities have been adopted for the Upgrade project of Beijing Electron Positron Collider (BEPCII), a double-ring electron–positron collider as well as a synchrotron radiation (SR) light source. The in-house development of the 499.8 MHz superconducting cavity system was initiated at IHEP since 2008. One prototype niobium cavity with all the parts except for the flanges and the pickup port formed by spinning was fabricated and then vertical-tested successfully in July 2011. Four prototype input couplers were manufactured and high-power tested with one reaching a maximum rf power of continuous wave (cw) 420 kW. One prototype HOM damper with a satisfactory absorbing efficiency at the desired frequency band was also constructed and high power tested up to cw 4.4 kW. In the meanwhile, a frequency tuner consisting of a stepping motor and a piezoelectric oscillator was developed. Finally, the bare cavity was dressed with one input coupler, two HOM dampers and one frequency tuner, mounted in a domestic-developed cryostat and then high-power tested successfully in Oct. 2011. The achieved accelerating voltage is 2.2 MV with corresponding Q 0 measured to be 5.8 × 10 8 , beyond the designed goal. This is the first in-house developed 499.8 MHz HOM-damped superconducting cavity system in China. The design, fabrication, post processing and tests of the niobium bare cavity and its auxiliaries, as well as the horizontal high-power test of the cavity system are presented. [ABSTRACT FROM AUTHOR]

We discuss recent work on the construction of a numerical simulation of the fast orbit feedback system at NSLS-II. The simulation operates in the time domain and also includes the spatial domain, i.e. all beam position monitors (BPMs) and correctors. It can accept inputs of the real beam orbit and the measured orbit response matrix. It can also add errors to every stage of the calculation. We present methods to verify the simulation results by comparing the simulation results with experimental data collected at NSLS-II. The results are in very good agreement. The effects of errors from BPMs and correctors, as well as the amplitude of excitation, on the feedback performance, are also explored. This simulation can be used to predict the behavior and performance of the system for a future upgrade. [ABSTRACT FROM AUTHOR]

Detector prototypes are commonly characterised in testbeams, either using charged particles or X-rays. Charged particles are used to quantify detector performance in terms of absolute efficiency, while X-rays can provide additional information about the detector structure. This paper presents an alternative approach to calculating charged particle efficiencies, using the results of an X-ray testbeam of the mini-MALTA CMOS prototype at Diamond Light Source, and additional laboratory measurements. Results are presented for an unirradiated and an irradiated sample and compared to the results of charged particle testbeams at SPS and ELSA. The extrapolated efficiencies are in agreement with the measured values. Additionally, the extrapolated efficiency maps provide more insight about the location of the pixel inefficiencies, due to the better spatial resolution of the X-ray testbeam. [ABSTRACT FROM AUTHOR]

This paper discusses improvements made to the fast orbit feedback (FOFB) system at NSLS-II in 2019. We first characterized the system by measuring the transfer function and the closed-loop gain of the system. We also constructed a model to predict the performance, which was based on physical behaviors. After finding and fixing the sources of the latency, we improved the closed-loop gain's bandwidth from 250 Hz to 400 Hz in the horizontal plane and 250 Hz to 300 Hz in the vertical plane. The orbit beam instability improved by 30% and 10% in the horizontal and vertical planes, respectively. [ABSTRACT FROM AUTHOR]

This paper outlines the results of investigations into the effects of radiation damage in the mini-MALTA depleted monolithic pixel sensor prototype. Measurements were carried out at Diamond Light Source using a micro-focus X-ray beam, which scanned across the surface of the device in 2 μ m steps. This allowed the in-pixel photon response to be measured directly with high statistics. Three pixel design variations were considered: one with the standard continuous n − layer layout and front-end, and extra deep p-well and n − gap designs with a modified front-end. Five chips were measured: one unirradiated, one neutron irradiated, and three proton irradiated. The standard design showed a decrease of 12% in pixel response after irradiation to 1e15 n eq ∕ cm 2 . For the two new designs the pixel response did not decrease significantly after irradiation. A decrease of pixel response at high biasing voltages was observed. The charge sharing in the chip was quantified and found to be in agreement with expectations. [ABSTRACT FROM AUTHOR]

A low-frequency quarter-wave superconducting β = 1 structure has been proposed as a main accelerating cavity for the newly planned storage ring light source with ultra-low emittance. In the development of High Energy Photon Source, a 6 GeV diffraction-limited light source at the Institute of High Energy Physics, a compact 166.6 MHz proof-of-principle cavity was designed. By optimizing its geometry, the cavity's mechanical properties have been significantly improved with a focus on stress, pressure sensitivity, Lorentz-force detuning, microphonics and tuning capabilities. The cavity was later fabricated, post-processed and tested in a vertical manner at cryogenic temperatures. High peak electromagnetic fields have been achieved with an excellent cryogenic performance, largely exceeding the design goal and project specifications. In addition, the measured mechanical parameters are in good accordance with simulation results. Small Lorentz coefficients and low pressure sensitivities were measured during the tests. This constitutes the first demonstration of a solid low-frequency β = 1 superconducting cavity design with compact geometry and favorable mechanical properties. [ABSTRACT FROM AUTHOR]