Synchrotron Radiation Light Research Articles

Thermodynamically revealing the effect mechanism of Cu on the interfacial metallurgical reaction for Al/steel welding-brazing joint

Developing excellent mechanical properties of Al/steel welding-brazing joint adding alloy elements for vehicle structure lightweight is in immediate need to reveal the effect mechanism of alloy elements on the interfacial metallurgical reaction. Here, the Al/steel welding-brazing joints with different Cu-coating thicknesses were designed to determine the effect rule of Cu on mechanical properties and interfacial microstructure evolution. More importantly, the action mechanism of Cu element on diffusion behavior of interfacial elements was clarified by synchrotron radiation light source and thermodynamic models. The results showed that appropriate Cu could improve the tensile strength of joints. And the Cu could efficiently inhibit the growth of interfacial brittle intermetallic compounds (IMCs) and the Fe diffusion into molten pool. Because the chemical potential of Fe in the molten pool increased with an increasing Cu content, which weakened the driving force of Fe diffusion. Besides, Cu and Al would react with each other to form Al 2 Cu with a lower Gibbs free energy under higher Cu content, which deteriorated the tensile strength of joints. Unambiguously, this work will deepen the understanding of the effect mechanism of Cu on the interfacial metallurgical reaction, which will be beneficial to the development and application of excellent properties of Al/Cu-coating/steel welding joints.

Lattice optimization of a fourth-generation synchrotron radiation light source in Novosibirsk

We discuss the choice of the magnetic lattice and parameter optimization of the fourth-generation light source SKIF (Russian acronym for Siberian Circular Photon Source) under construction in Novosibirsk. The study compares several basic lattice cells to procure one with low emittance and large dynamic aperture. The result is a developed lattice of SKIF with 72 pm natural emittance (at zero beam current and absent betatron coupling) at 3 GeV beam energy and 476 m circumference. Only two families of sextupoles provide horizontal and vertical dynamic apertures of 12 mm and 3.5 mm, respectively, and energy acceptance more than 5%. To check the potential of the found solution, we used slightly modified SKIF lattice to design 6 GeV light source and reached 33 pm natural emittance for 1075 m circumference with 40 straight sections. Again, only two sextupole families ensure sufficient dynamic aperture (7 mm horizontal and 4 mm vertical) and energy acceptance more than 5% for simple efficient injection and sufficient beam lifetime.

Abstract 14132: The Crystal Structures Of Human Cytochrome P450 2C9 Provide Insights Into The Effect Of Genetic Variation And The Binding Of Losartan

The human cytochrome P450 2C9 (CYP2C9) enzyme metabolizes many of the currently available medications that include anti-coagulant warfarin, anti-hypertensive losartan, anti-diabetics tolbutamide and glimepiride. Genetic variations in CYP2C9 that include the common alleles *2 and *3 have resulted in reduced enzyme activity leading to altered metabolism of various drug substrates compared with the wild-type (WT). The CYP2C9*2 genetic variant represent an amino acid change from arginine to cysteine at position 144. The crystal structure of CYP2C9 WT and the *2 variant complexed with losartan were recently published. However, the structure of these enzymes in the absence of any ligand or losartan is not available. Thus, the aim was to determine the ligand free structure of these enzymes and assess the hypothesis that the drug binding orchestrates the conformational change and leads to reorientation of amino acid sidechains to interact with losartan in the active site. The data for the CYP2C9 WT and the CYP2C9*2 crystals in the absence of any ligands was collected remotely at the Stanford Synchrotron Radiation Light Source and the structures were solved using x-ray crystallography. The ligand-free structure of the *2 variant revealed markedly different conformation compared to the recently published structure in complex with losartan. The changes in the F, F’, G and G’ helices indicate an open conformation in the absence of losartan compared to the losartan complex. Whereas the ligand-free structure of the WT illustrated similarity in the overall conformation to the previously published structures with losartan bound. Comparison of the ligand free structure of the CYP2C9 WT or the *2 variant with the losartan bound structure identified the amino acid sidechains important for interaction with the drug in the active site. Furthermore, the structure of the *2 variant in the absence or presence of losartan provided a useful framework to investigate the effect of amino acid substitution that leads to altered binding of the drug. In conclusion, the structural characterization of the CYP2C9 WT and the *2 variant yield insights into the conformational changes that occur upon binding of losartan and help understand the effect of genetic polymorphisms on drug metabolism.

Active vibration control method of double crystal monochromator of P2 protein crystallography beam line at SSRF

The angular stability of the double-crystal monochromator (DCM) directly affects the positional stability of the focused spot. This paper describes the active vibration control (AVC) method of the DCM of P2 Experimental Station at SSRF based on the adaptive filtering algorithm and the AVC system improves the performance of by optimizing the filter weight estimation algorithm. The simulation results show that the amplitude of the crystal in the pitch direction is greatly reduced by the AVC method, the RMS value of the angular displacement in the pitch direction of the crystal is 1.23 nrad, which is 91.93% lower than the passive vibration control (the RMS value of the angular displacement in the pitch direction is 15.25 nrad); the RMS value of the angular displacement in the pitch direction of the optimized AVC system is 0.233 nrad, which is 98.47% lower than that of the passive vibration control method. The AVC method can effectively ensure the angular stability of the DCM in the pitch direction, which is of great significance for the key equipment of the new generation of synchrotron radiation light source to achieve nano-radian stability.

Micro telecom computing architecture.4-based beam position monitor electronics design for storage ring of Hefei advanced light facility.

The Hefei Advanced Light Facility (HALF) is a fourth-generation vacuum ultraviolet and x-ray diffraction limit synchrotron radiation (DLSR) light source now under preliminary research. To achieve ultralow beam emittance and small beam size, the orbit of the beam in the DLSR storage ring should meet the stability requirement at submicrometer scale. The beam position monitor (BPM) electronics measures the orbit and is hence an essential part of the beam orbit control system. In this article, we designa BPM electronics based on the MicroTCA.4 (Micro Telecom Computing Architecture) standards platform, which consists of a MicroTCA.4 module (including a chassis, a power supply, and a digital board), a customized RF front end module, and a frequency synthesizer. In-phase and quadrature sampling and digital signal processing algorithms are implemented to obtain turn-by-turn data, fast acquisition data at a 10 kHz rate, and slow acquisition data at a 10Hz rate. To evaluate the performance and function of BPM electronics, we conducted offline tests in the laboratory and beam tests based on the storage ring of Hefei Light Source II (HLS II), a light source similar to the HALF as an alternative. Test results indicate that the performance of MicroTCA.4-based BPM electronics can meet the requirements of the HALF storage ring.

The development of the 499.8 MHz superconducting cavity system for BEPCII

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 Q0 measured to be 5.8 × 108, 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.

Application of machine learning in orbital correction of storage ring

Synchrotron light source is one of the most powerful tools in modern science and technology. Shanghai Synchrotron Radiation Facility (SSRF), located in Shanghai, China, is an advanced 3.5 GeV 3rd-generation medium energy light source. The 3rd-generation synchrotron radiation light source will provide high brilliance and high stability synchrotron radiation to fulfill the advanced experimental conditions in frontier researches. To achieve highly stable radiation, it is important to have highly stable beam orbit. Thus we adopted machine learning method to control and feedback the orbit. Using this neural network-based orbit correction method, which doesn’t rely on the response matrix, we can establish a nonlinear mapping relationship between correctors and the orbit distortions and perform continuous online retraining. This new method can significantly improve the orbit stability of SSRF.

A robust smoothing analysis strategy for improving particle accelerator alignment and installation accuracy and efficiency based on HALF design

The fourth-generation synchrotron radiation light source under construction has a higher requirement for alignment measurement than former-generation light sources, including the accuracies and efficiencies. In this paper, a robust smoothing analysis strategy that aims to reduce relative position errors is introduced to smooth the magnetic centers’ orbit. First, we pre-process the original data based on gross error detection. Then, we do a smooth analysis of the data of the magnetic centers’ orbit and iteration by using the curve fitting of the Parzen-window function. Finally, the physical accelerator calculation is utilized to terminate the iteration. Simulation results based on the Hefei Advanced Light Facility show that the comparison between the physical calculation results before and after using this strategy verifies that it can dramatically improve beam quality, which has a slight improvement concerning existing methods. Besides, this strategy requires lower quantities of magnets that need to be adjusted, less than that of other methods. This research can provide a robust technical guarantee for the construction of the fourth-generation light source.

The application of confocal depth-resolved micro-X-ray absorption spectroscopy to study colorant copper in ancient lead-silica glassy system at the Beijing Synchrotron Radiation Facility

A new mobilizable confocal fluorescence end-station for depth-resolved micro-X-ray absorption spectroscopy being setup with optimal settings and applied to copper in lead-based glaze and pigment of ancient Chinese ceramics. The major equipment of the confocal micro-spots system included two polycapillary half-lens: one is defines the incident beam path and another polycapillary half-lens at 90°defines the probe sample volume, and operate with an efficient automatic alignment program by evolutionary algorithm. This depth-resolved system was examined on a general X-ray absorption spectroscopy (XAS) beamline at the Beijing Synchrotron Radiation Facility (BSRF, 1W1A/1W2B). The application in this case report that the status of copper in various lead-silica amorphous materials and speciation in different depth of lead-rich glassy layer from aged China. The results shown that this equipment working well and can obtaining equal data from surface to certain depth of copper colorant. Also, although the large number of lead component existing in the various glassy matrix but due to high-intensity of synchrotron radiation light and optimize-designed structure of facility, the results still revealing the preeminent ability of spatially resolution as well. As a mobilizable end-station with advantage, such as non-destructive and adjustable micro-spots, this confocal system in BSRF can improve the function and flexibility of general XAS beamlines, and indicating their capabilities to applicating to archaeological and cultural heritage field more deeply and widely in further.

Visible-Light-Driven Nitrogen Fixation Catalyzed by Bi5O7Br Nanostructures: Enhanced Performance by Oxygen Vacancies.

Photocatalytic nitrogen fixation represents a green alternative to the conventional Haber-Bosch process in the conversion of nitrogen to ammonia. In this study, a series of Bi5O7Br nanostructures were synthesized via a facile, low-temperature thermal treatment procedure, and their photocatalytic activity toward nitrogen fixation was evaluated and compared. Spectroscopic measurements showed that the tubular Bi5O7Br sample prepared at 40 °C (Bi5O7Br-40) exhibited the highest electron-transfer rate among the series, producing a large number of O2.- radicals and oxygen vacancies under visible-light photoirradiation and reaching a rate of photocatalytic nitrogen fixation of 12.72 mM·g-1·h-1 after 30 min of photoirradiation. The reaction dynamics was also monitored by in situ infrared measurements with a synchrotron radiation light source, where the transient difference between signals in the dark and under photoirradiation was analyzed and the reaction pathway of nitrogen fixation was identified. This was further supported by results from density functional theory calculations. The reaction energy of nitrogen fixation was quantitatively estimated and compared by building oxygen-enriched and anoxic models, where the change in the oxygen vacancy concentration was found to play a critical role in determining the nitrogen fixation performance. Results from this study suggest that Bi5O7Br with rich oxygen vacancies can be used as a high-performance photocatalyst for nitrogen fixation.

Physics issues of the diffraction-limited storage ring light source

<p indent=0mm>The synchrotron radiation light source based on electron storage ring is the most widely used high-performance X-ray source in the field of basic scientific research in the 20th century, and has undergone three generations of development. One important direction of the new generation light source, i.e., the fourth generation light source, is the so-called diffraction-limited storage ring (DLSR) light source. DLSR, with ultra-high average brightness, high repetition frequency, multi-user, high stability, complementary to the free electron laser (FEL), has a great development in recent decades. By adopting lattice design based on compact multi-bend achromats (MBAs), DLSR allows to achieve one or two orders of magnitude lower emittance approaching the diffraction limit of X-rays, and much higher brightness and coherence than available in the third generation light source, while inheriting the high brightness, multi-user and high stability advantages of existing ring light sources. In this paper, the progress made in the last few decades in physics design and optimization of the DLSR, especially on the ultralow-emittance lattice and injection schemes, will be overviewed. To achieve an ultralow emittance, lattice structures of standard MBA and hybrid MBA, and novel magnets of high-gradient quadrupole, antibend, longitudinal gradient dipole and complex bend, have been proposed. To obtain optimized beam dynamics in a DLSR, theoretical and numerical methods have been developed to date. Due to the fact that the nonlinearities are extremely high in a DLSR and the nonlinear dynamics is greatly coupled with the linear optics, the most effective and most commonly used way is global and stochastic optimization of the ring performance evaluated by numerical tracking. To deal with the challenges of injecting to a DLSR with small dynamic acceptance, different injection schemes, such as, pulsed multipole injection, on-axis swap-out injection and on-axis longitudinal injection, have been proposed. Collective effects, especially the intra beam scattering and the Touschek effects, become significant as emittance decreases, requiring methods of bunch lengthening and transverse feedback to ensure the stability of the particle motion at a high beam current. Besides, a few developing topics in DLSR physics will be discussed. Machine learning, the method of transferring disorder data into useful information, is an important branch of artificial intelligence, and has been used in accelerator control system and beam commissioning. This method would be very useful and helpful in the design and optimization, initial commissioning and daily operation of a DLSR. A rational combination of machine learning and multi-objective optimization algorithm, like multi-objective genetic algorithm and multi-objective particle swarm algorithm, can effectively improve the optimization performance, and has been successfully applied in nonlinear optimization of light sources. In addition, improving the performance of synchrotron radiation by combining the beam physics of DLSR and the principle of FEL is one developing research topic which might be able to provide base for further development of the DLSR. Combined with bypass and transverse gradient undulator, high gain FEL could be achieved in the storage ring. Besides, double ring light source, divided into two loops, the inner ring is DLSR, and the other is FEL with more long straight sections, was proposed to improve the utilization rate of the beams.

Thermionic microwave gun for terahertz and synchrotron light sources.

Conventional thermionic microwave and radio frequency (RF) guns can offer high average beam current, which is important for synchrotron light and terahertz (THz) radiation source facilities, as well as for industrial applications. For example, the Advanced Photon Source at Argonne National Laboratory is a national synchrotron-radiation light source research facility that utilizes thermionic RF guns. However, these existing thermionic guns are bulky, difficult to handle and install, easily detuned, very sensitive to thermal expansion, and due for a major upgrade and replacement. In this paper, we present the design of a new, more stable, and reliable gun with optimized electromagnetic performance, improved thermal engineering, and a more robust cathode mounting technique, which is a critical step to improve the performance of existing and future light sources, industrial accelerators, and electron beam-driven THz sources. We will also present a fabricated gun prototype and show results of high-power and beam tests.

Demonstration of stimulated emission depletion phenomenon in luminescence of solid-state scintillator excited by soft X-rays

Although imaging techniques using soft X-rays (SXs) are being developed as the available photon flux increases because of the continuing development of synchrotron light sources, it will be necessary to downsize the pixel size of the SX camera to produce finer SX images. Application of the stimulated emission depletion (STED) method to a scintillator plate followed by use of this plate as a sensor is one promising method to reduce the pixel size of SX cameras. A STED phenomenon occurred in the luminescence of a Ce-doped Lu2SiO5 crystal (Ce:LSO) excited using ultraviolet (UV) light when the scintillator was irradiated with azimuthally polarized laser light in the photon energy range from 1.97 eV (630 nm) to 2.58 eV (480 nm). When the excitation light source changed to synchrotron radiation (SR) light with photon energy of 800 eV, the same STED phenomenon occurred. The spot size of the luminescence was reduced by the STED phenomenon and this spot size decreased as the STED laser’s photon energy increased. The energy dependence of the Ce:LSO luminescence levels can be used to explain the change in the spot size at the luminescence point.

Optimizations of nonlinear kicker injection for synchrotron light sources

The concept of using a single nonlinear kicker (NLK) to inject electron beams into a storage ring has been proposed and tested in several synchrotron radiation light source facilities. Different from pulsed dipole kicker magnets used in a conventional local-bump injection, the single nonlinear kicker provides a nonlinear distribution of magnetic fields which has a maximum value off axis where the injected beam arrives and a zero or near-zero value at the center where the stored beam passes by. Therefore, the injected beam will receive a kick from the NLK and lose its transverse momentum, and will be eventually captured by the storage ring. In the meantime the stored beam at the center will receive no kick or less kick, which significantly reduces the injection perturbations on the stored beam. In addition, the NLK injection requires less space for the kicker and removes the complications of synchronizing four pulsed kicker magnets. Because of these advantages, several light source facilities are either proposing or already using this NLK injection as a replacement of the conventional local-bump injection scheme. In this paper, we will discuss the working principal of this NLK injection, and use both Advanced Light Source and Advanced Light source Upgrade as examples to optimize the NLK injections. By optimizing the NLK design and injection conditions, we could achieve maximum injection efficiencies for both facilities with a large injected beam from the existing ALS booster.

Fast corrector power supply design for HEPS

High-energy photon source under construction is a fourth-generation synchrotron radiation light source with energy of 6 Gev and ultra-low emittance (lower than 0.1 nm rad). The ultra-low beam emittance requires high beam stability. In order to meet this requirement of low beam emittance, the fast close orbit correction system is used to keep beam on the right orbit. The fast close orbit correction system need fast corrector power supply to drive the calibration magnet to complete track correction. So, a fast corrector power supply prototype with high bandwidth and low current ripple to improve the performance of the fast close orbit correction system to prove the high beam stability had been developed. The prototype use a novel multilevel switch-mode structure to provide the dynamic requirement. The prototype adopts FPGA for full-digital control and use high-speed ADC with temperature control. By using a precision sampling circuit (ADC+DCCT), the prototype outputs current ripple can meet the requirement. The designed for HEPS meet the design requirement. Through test, the prototype has a small signal bandwidth of 10 kHz and output current ripple lower than 20 ppm.

Preliminary Research of HOM for 100MHz Superconducting Cavity in the Pre-research Project of HALS

A 100MHz QWR superconducting cavity is researched in the pre-research project of Hefei Advanced Light Source (HALS). Higher order modes (HOM) damping is a big challenge for synchrotron radiation light source. In this paper, we first apply the novel choke mode structure to the 100MHz QWR (quarter wave resonator) cavity in order to damp the HOM. We identify the main harmful higher order modes. The HOMs in the QWR cavity are suppressed by optimizing the choke dimensions. The broadband HOM impedance spectrum of the cavity was also evaluated by calculating the beam induced wake potential in time domain. The results show that choke mode structure has a good HOM damping effect on the QWR cavity.

Establishing A Laser Treatment To Suppress The Sec-Ondary Electron Emission

Laser treatment has a significant influence on suppressing the secondary electron emission (SEE) in electron storage rings. A new synchrotron radiation light source, the Hefei Advanced Light Source(HALS), is under consideration and it has a strict requirement to suppress the SEE. In this paper, we used a laser with the wavelength of 355nm to process with copper sample. After the laser treatment, the secondary electron yield (SEY) reduces from 2.05 to 0.86. We also used the scanning electron microscope (SEM) to analysis the surface of the sample after the laser treatment. This paper reports the experiment set up and preliminary results.

A Fast-Response and High-Stability Power Supply for a Corrector Magnet in HALS

The beam quality of the new synchrotron radiation light source Hefei Advanced Light Source (HALS) requires a fast-responding, high-stability, magnet power supply (MPS). Inspired by the commercial electronic load and audio amplifier circuits, we designed a bipolar power supply that utilizes the linear amplification characteristics of the metal–oxide–semiconductor field-effect transistor (MOSFET) to improve the balance between the response speed and the resolution of the switching power supply. The frequency response of the designed power supply can reach 10 kHz and the long-term stability can reach 5 ppm. In addition, the ±10-A rated output power supply can resolve current changes of 0.1 mA. This article describes in detail the topology of the power supply, the feedback control strategy, and the design of the digital control card. Finally, the test platform construction, performance test methods, and final experimental results of the prototype are presented.

The shielding design of the radio frequency cavity in the storage ring of the Thailand synchrotron radiation light source

The radio frequency (RF) cavity provides an electric field in direction of electron beam in the synchrotron radiation machine to accelerate electron beam or compensate electron beam energy loss. Thailand synchrotron radiation machine has installed a second RF systems in the straight ring since August 2016. The RF cavity of the system can provide a maximum accelerating voltage of 300 kV at its accelerating gap. During the commissioning of the cavity in August 2016, there was a high radiation detected outside the shielding wall of the storage ring. The local shielding was installed for the safe operation of RF cavity at 185 kV. There will be a new insertion device installed in storage ring during a machine shutdown period in August 2018. This insertion device requires an operation of the RF cavity higher than 185 kV, which increases the radiation. The new design of RF cavity local shielding will also be installed. The radiation from RF cavity was investigated and the local shielding was designed using Mote Carlo simulations. This paper presents a detailed investigation and design of a local shielding together with a radiation survey results after the installation of shielding.

Multi-dimensional characterization and controlling of microstructure evolution during solidification of metallic alloys

Metallic alloys are important structural and functional materials and have been widely applied in industry. The performance of metallic alloys strongly depends on the microstructures after solidification. Many effective methods are introduced to control the microstructure evolution during solidification, including grain refining, adding rare earth (RE) elements, applying electric current and/or magnetic field, etc. However the inherent mechanisms affecting the microstructure formation are still unclear due to the limitation of real time and multidimensional characterization technique. With the development of the third generation synchrotron radiation light source, a real time imaging technology in 2D (two dimensional) or 3D (three dimensional) view with strong penetrability, high spatial and temporal resolution, nondestructive features has been developed to break those limitations. In this paper, some application cases during solidification performed in our group are reported in different alloys and using different solidification controlling techniques. Different solidification behaviors in those cases are revealed and discussed.