New version of the small-angle x-ray equipment for studying biological structures at the station DICSI in the Kurchatov center of synchrotron radiation and nanotechnologies

The results of modernization implemented at the DICSI x-ray small-angle station (the Kurchatov Center of Synchrotron Radiation and Nanotechnologies) are presented. Certain parameters of the hardware and software environment have been successfully tested using the operating channel of the VEPP-3 storage ring (the Siberian Center of Synchrotron Radiation), where the time-resolved diffractometry (“diffraction cinema”) technique was used to study the dynamic and static behavior of living biological structures in different modes of data accumulation. The circuit designs and the basic parameters of x-ray optical schemes are justified theoretically. The results of test experiments with biological samples are presented.     

Ultra-Low-Emittance Light Sources

In this special issue, we delve into the subject of ultra-low-emittance storage ring light sources. While these go under various names, such as “diffraction-limited storage rings” and “ultimate storage rings,” perhaps the most universally applicable name is “fourth-generation storage rings” or 4GSRs. As this name suggests, these rings promise improvements in X-ray brightness that are comparable to those seen in the transition from second- to third-generation rings.     

Microanalysis station at the Kurchatov synchrotron radiation source

The REFRA station developed, fabricated, and put into operation at the Kurchatov Synchrotron Radiation Center is described. The station is placed on beamline 5.6 of the big storage ring. The station consists of a vertical beam position monitor, an operating shutter, vertical and horizontal slits for the white beam, a monochromator, an alignment stage, an intensity monitor, an EXAFS spectrometer unit, a diffractometer unit, detectors, and a data control and acquisition system. The station operating energy range is 5–30 keV. The station is fully-automated and has been operating with the SR beam since spring 2005. The station units can be reproducibly mounted on the SR beam to provide various research configurations.     

一种通用的时隙环网时隙调度机制

提出一种新颖的时隙环网公平机制——环分布式时隙调度(DTSR), 该机制是分布式的, 适合所有目的节点剥离业务的时隙环网。DTSR通过在单向信道上循环传输的时隙控制头(TCH)内增加一个简单的域, 实现对环上“饿死”节点信息的动态收集, 协调各个节点占用资源的时间, 确保各节点之间的公平性; 在发现环上有“饿死”节点后, DTSR利用时隙环网空间重用的特性, 调度相关节点向不经过“饿死”节点的其他节点发送数据, 充分利用了环网资源; 此外DTSR机制具有良好的算法收敛性, 且接入时延较传统算法更小。最后,对DTSR的性能进行仿真, 并和几个典型的时隙环网的公平机制进行了比较。     

Photofission of actinide nuclei in the nucleon-resonance region: First photonuclear experiment at the Siberia-2 storage ring

Results of an experiment performed to study ²³⁸U photofission with the aid of the initial section of the GAMMA channel of the Siberia-2 storage ring at the Kurchatov Institute are presented. These results are predominantly of a methodological value, because a photonuclear experiment was conducted for the first time in this channel. However, the data obtained in this way allowed us to evaluate an upper limit on the probability of the fast fission (fragmentation) of ²³⁸U nuclei that was induced by photons of energy up to 2.5 GeV. This is pertinent to the problem of the deviations of the total photoabsorption cross sections for actinide nuclei from a “universal curve.”     

Multimode X-ray tomography at the mediana Station of the Kurchatov synchrotron radiation source

The synchrotron radiation used in X-ray tomography enables us to vary the recording conditions within wide limits due to the continuous spectrum and the beam’s high brightness and collimation. The possibilities of multimode X-ray tomography at the Mediana station of the Kurchatov synchrotron radiation source, including tomography and microtomography based on white and “pink” beams, imaging with the help of a monochromatic beam, and measurements via axial and refractive phase-contrast methods, are described. The presented results of the reconstruction of different objects have been obtained under different recording conditions.     

X-ray stations based on cylindrical zoom lenses for nanostructural investigations using synchrotron radiation

The main results of the development of X-ray stations are presented. These stations are intended to solve problems concerning the structural biology of tissues at a high time resolution with the help of synchrotron radiation (SR) generated by the VEPP-3 storage ring (Siberian center of SR, Novosibirsk) and the Siberia-2 storage ring (National Research Centre Kurchatov Institute and the centre of nano-, bio-, information, and cognitive sciences, Moscow). The issues of selecting the optical scheme and basic parameters of X-ray optical systems are discussed. Photographs of the original designs of the constructed equipment are given. A modular approach to designing experimental facilities based on self-contained units and methods of focusing a monochromatic SR beam in the required spectral range have been developed. The technique of X-ray beam focusing by means of optical zoom lenses has been implemented. Experimental results that illustrate the possibilities of the SR-beamline hardware used for X-ray diffraction investigation of different biological objects with the help of different recording systems are presented.     

Focusing all the synchrotron radiation (2π radians) from an electron storage ring on a single point without time distortion

The geometrical-optical analysis of synchrotron radiation shows that it is possible to define a mirror able to focus all the emitted light by an electron storage ring on a single point lying anywhere in space, keeping unchanged the typical time patterns of the radiation. Because of the electron ultrarelativistic conditions, the electron “orbital path” is assimilated to an “underground bent photon path”. We prove then that the focusing condition is simply given by establishing the invariance of the photon path: “optical photon path” + “underground bent photon path” = constant. Some selected numerical examples show that it is possible to collect huge amounts of radiation producing extremely high excitation densities in a given small volume.     

Are interaction-free measurements interaction free?

In 1993, Elitzur and Vaidman introduced the concept of interaction-free measurements, which allowed finding objects without “touching” them. In the proposed method, since the objects were not touched, even by photons, thus, the interaction-free measurements can be called “seeing in the dark.” Since then, several experiments have been successfully performed and various modifications were suggested. Recently, however, the validity of the term “interaction-free” has been questioned. The criticism of the name is briefly reviewed and the meaning of the interaction-free measurements is clarified.     

Atomic Absorption Spectrophotometry with the Absorption Tube Technique

A device to increase the sensitivity of the atomic absorption spectrophotometric measurement by elongating the absorption path length has originally been developed by Fuwa and Vallee and the present authors called it “absorption tube technique”. Although the technique has been fully described in comparison with the flame photometry, and the behavior of the elements and the reactions in the tube were investigated for several elements, application of a newly designed ring burner to this technique and the detailed examination of the operating conditions have never beer, published.     

Comments on “Farewell to tachyons?”

We comment on the previous paper by L. Basano. In particular, we show that its Section 2 is kinematically incorrect (the dynamics of a two-body interaction through tachyon exchange, incidentally, has already been thoroughly expounded in one paper of ours). Its Section 1 is simply a rather subjective introduction. As to its Section 3, containing indeed interesting problems, we again briefly refer to our earlier work. Our conclusions are still in favor of “au revoir to tachyons!,” even if it is known that inside our cosmos tachyons are more likely to have a role in physics (e.g., in elementary particle and black-hole physics) as “exchanged objects” rather than as “asymptotically free” objects.     

Electron scattering based on a novel internal target technique: SCRIT

A novel technique for forming internal targets, named SCRIT (Self-Confining RI Ion Target), has been developed, which can make electron scattering off short-lived radioactive nuclei possible in an electron storage ring. SCRIT confines the ions of interest by utilizing the “ion trapping” phenomenon in the electron storage ring. Approximately 10⁷ stable ¹³³Cs ions were trapped in a three-dimensional configuration along the electron beam axis at an electron beam current of 75mA. The angular distribution of the electrons scattered from the trapped ¹³³Cs ions was successfully measured, and a collision luminosity of 10²⁶/(cm² s) was achieved.     

Surface-Enhanced Infrared Spectral Investigations of 2,3-Bis(chloromethyl)anthracene-1,4,9,10-tetraone on Copper Nanoparticles

ABSTRACT

Surface-enhanced infrared (IR) absorption spectroscopic technique has been employed to investigate the orientation of 2,3-bis(chloromethyl)anthracene-1,4,9,10-tetraone (BCMAT) on copper nanoparticles (NPs). Copper NPs have been prepared by the chemical reduction method. The observed ring stretching modes show higher downshifts, broader bandwidths, and higher enhancement. The observed features in out-of-plane and in-plane CH deformation modes indicate that the BCMAT molecules may be adsorbed in a “flat-on” orientation on the copper NPs. The observed lower enhancement factor of the in-plane C?O deformation mode and C?O stretching mode and the higher enhancement factor of out-of-plane C?O deformation mode elucidate that the BCMAT molecules are adsorbed on the copper NPs in a “flat-on” orientation. All these observations show that BCMAT is adsorbed on copper NPs through the π-anthraquinone ring system in a “flat-on” orientation.     

Synchrotron Stories from Stanford—From a Parking Lot to First Beam

Our journey in synchrotron radiation started in July 1972 when we joined a group at Stanford led by Seb Doniach and Bill Spicer to build a “Pilot Project” to test the feasibility of performing X-ray photoemission experiments on the newly commissioned SPEAR storage ring at SLAC. The SPEAR ring was expressly built for high-energy physics using colliding electron and positron beams (ultimately discovering the existence of quarks and garnering two Nobel prizes). As a result, anything we did could not interfere with the high-energy physics experiments.     

Status of the MAX IV Laboratory

On the day of the 2016 summer solstice, June 21, MAX IV, the new synchrotron radiation facility in Lund, Sweden, will be inaugurated. MAX IV is setting a new standard in terms of emittance, thereby providing beamlines with the best possible brilliance and coherence. At the same time, MAX IV continues a more than three-decades-long successful history of Swedish synchrotron-radiation-based research. The activities at the present MAX-lab, which officially started when the MAX I storage ring opened for users in 1986, have been concluded with a “last beamdump” ceremony for the MAX II and MAX III storage rings on December 13, 2015, Saint Lucy's Day. In Sweden, the winter solstice is celebrated with a festival of light.     

Scaling Law for Lattice Design of a Storage Ring

This paper describes and demonstrates the scaling law in the lattice design of a storage ring.When the size of the storage ring are enlarged or reduced according to a scale,the operating point ν and the beam emittance ε will be invarible.But while the energy of the storage ring is changed,the emittance will vary with the energy square.     

Applying the stochastic parallel gradient algorithm in the auto alignment problem for the amplifier channel of the UFL-2M facility

The procedure of automatic alignment of the four-pass amplifier channel of a UFL-2M facility has been simulated numerically in the presence of aberrations in the optical path. The alignment procedure is based on the “marker” or “reference” method. The control elements are directed by the stochastic parallel gradient algorithm. The order of executing the automatic alignment is determined. The numerical simulation shows the possibility of positioning the beam at the exit from the channel with an accuracy of 1% of the pinhole size in the far field and of 0.1% of the beam aperture size in the near field. It was established that the centering accuracy of the alignment beam in inner pinholes in the presence of optical inhomogeneities in the amplifier channel can be worse than at the exit of the channel. The possibility of symmetrizing the picture of far-field markers has been considered in the case where the position of the optical axis of the channel is unknown.     

Measurements of the Drift Current Oscillations in Thrusters with Closed Electron Drift

An induction method used to measure the drift current in thrusters with anode layer (TAL) has been applied for measuring the integral distortion of the magnetic field in the channel of a low-power stationary plasma thruster (SPT). Experiments are described in which the integral level of magnetic field oscillations in the narrow channel of a thruster with closed electron drift was determined. Experimental data show that when a discharge is ignited in an SPT, the drift current completely demagnetizes the discharge gap (the ratio between the self-magnetic and external fields reaches 90%). The same effect has been observed in TALs. In thrusters of both types, the total discharge current is one and a half order of magnitude higher than that typical of the stationary discharge and the plasma glow is observed not only inside but also outside the discharge channel. Drift current oscillations have been measured under steady-state conditions. It has been shown, in particular, that when the oscillations are intense (in weak magnetic fields on the order of 100 G), the drift-current-induced distortion of the magnetic field may reach 33%. Under rated operating conditions (200 G), the distortion does not exceed 8%. Beyond optimal operating conditions, the type of oscillation in SPTs and TALs and their performances differ. For example, in SPTs, a critical magnetic field at which the “turbulent” regime sets in is absent. In general, the discharge current is weakly dependent on the magnetic field.     

Numerical investigation of the air injection effect on the cavitating flow in Francis hydro turbine

At full and over load operating points, some Francis turbines experience strong self-excited pressure and power oscillations. These oscillations are occuring due to the hydrodynamic instability of the cavitating fluid flow. In many cases, the amplitude of such pulsations may be reduced substantially during the turbine operation by the air injection/ admission below the runner. Such an effect is investigated numerically in the present work. To this end, the hybrid one-three-dimensional model of the flow of the mixture “liquid?vapor” in the duct of a hydroelectric power station, which was proposed previously by the present authors, is augmented by the second gaseous component — the noncondensable air. The boundary conditions and the numerical method for solving the equations of the model are described. To check the accuracy of computing the interface “liquid?gas”, the numerical method was applied at first for solving the dam break problem. The algorithm was then used for modeling the flow in a hydraulic turbine with air injection below the runner. It is shown that with increasing flow rate of the injected air, the amplitude of pressure pulsations decreases. The mechanism of the flow structure alteration in the draft tube cone has been elucidated, which leads to flow stabilization at air injection.