Design and performance of BOREAS,the beamline for resonant X‐ray absorption and scattering experiments at the ALBA synchrotron light source

The optical design of the BOREAS beamline operating at the ALBA synchrotron radiation facility is described. BOREAS is dedicated to resonant X‐ray absorption and scattering experiments using soft X‐rays, in an unusually extended photon energy range from 80 to above 4000 eV, and with full polarization control. Its optical scheme includes a fixed‐included‐angle, variable‐line‐spacing grating monochromator and a pair of refocusing mirrors, equipped with benders, in a Kirkpatrick–Baez arrangement. It is equipped with two end‐stations, one for X‐ray magnetic circular dichroism and the other for resonant magnetic scattering. The commissioning results show that the expected beamline performance is achieved both in terms of energy resolution and of photon flux at the sample position.     

A multiplexed high‐resolution imaging spectrometer for resonant inelastic soft X‐ray scattering spectroscopy

The optical design of a two‐dimensional imaging soft X‐ray spectrometer is described. A monochromator will produce a dispersed spectrum in a narrow vertical illuminated stripe (～2 µm wide by ～2 mm tall) on a sample. The spectrometer will use inelastically scattered X‐rays to image the extended field on the sample in the incident photon energy direction (vertical), resolving the incident photon energy. At the same time it will image and disperse the scattered photons in the orthogonal (horizontal) direction, resolving the scattered photon energy. The principal challenge is to design a system that images from the flat‐field illumination of the sample to the flat field of the detector and to achieve sufficiently high spectral resolution. This spectrometer provides a completely parallel resonant inelastic X‐ray scattering measurement at high spectral resolution (～30000) over the energy bandwidth (～5 eV) of a soft X‐ray absorption resonance.     

软X射线条纹相机静态能量响应的绝对标定

软X光扫描相机是对软X光时间特性进行研究的主要诊断工具.利用同步辐射作为光源,采用美国NIST的标准,对它的静态能谱响应进行了绝对标定,给出了X光条纹相机在100—1000eV能区的绝对谱响应,不确定度小于23%.     

X光CCD响应特性

在北京同步辐射源上建立了Ｘ光ＣＣＤ量子效率实验标定方法,获得了１５０ｅＶ～１５００ｅＶ能区范围多个Ｘ光能点的量子效率实验结果,发展了Ｘ光ＣＣＤ量子效率简化计算模型,并对Ｘ光ＣＣＤ表面油沾污对量子效率的影响进行了实验研究和修正。     

p型掺杂Si/Ge量子点的电子拉曼散射(英文)

在本文中我们首次报道了p型掺杂的自组织Si/Ge量子点中空穴能级子带间的电子拉曼散射,此电子跃迁的能量为105meV。Si/Ge量子点Ge Ge模的共振拉曼散射表明此空穴能级间的电子拉曼散射与Γ点附近的E0(≈2.52eV)发生了共振,而E1的能量小于2.3eV.变温实验和偏振实验进一步证实了我们的指认。所有观测的实验数据与6 bandk·p能带结构理论的计算结果吻合得很好。     

A scanning transmission X‐ray microscope at the Pohang Light Source

A scanning transmission X‐ray microscope is operational at the 10A beamline at the Pohang Light Source. The 10A beamline provides soft X‐rays in the photon energy range 100–2000 eV using an elliptically polarized undulator. The practically usable photon energy range of the scanning transmission X‐ray microscopy (STXM) setup is from ～150 to ～1600 eV. With a zone plate of 25 nm outermost zone width, the diffraction‐limited space resolution, ～30 nm, is achieved in the photon energy range up to ～850 eV. In transmission mode for thin samples, STXM provides the element, chemical state and magnetic moment specific distributions, based on absorption spectroscopy. A soft X‐ray fluorescence measurement setup has been implemented in order to provide the elemental distribution of thicker samples as well as chemical state information with a space resolution of ～50 nm. A ptychography setup has been implemented in order to improve the space resolution down to 10 nm. Hardware setups and application activities of the STXM are presented.     

Extragalactic electromagnetic cascades as a possible instrument for the study of background radio emission

We analyzed the diffuse gamma-ray emission generated in the interactions between cosmic rays of ultrahigh energies and the background radiation in extragalactic space. The intensity of gamma-ray emission was calculated within a simplified model for energies E ≈ 10¹⁴ eV in different assumptions concerning the cosmic ray sources with the use of different estimates of nonthermal background radiation. It was shown that the gamma-ray radiation intensity in this energy range depends on the background radio emission and that under different assumptions concerning the radio background it can differ tens of times. It was concluded that gamma-ray emission can serve as a test for the models of background radio-frequency radiation.     

高能量分辨率的平面晶体位置灵敏谱仪

平面晶体波长色散位置灵敏谱仪是一新型高能量分辨率的X射线分析装置,可用于高能量分辨的元素分析、化学态及原子物理等研究中.这里简要介绍所研制的位置灵敏谱仪装置及其性能,以及位置灵敏谱仪与其核心部件──位置灵敏正比计数器的基本原理.所研制位置灵敏谱仪对55Fe,Ti和Si所达到的能量分辨率(FWHM)分别为25eV,15eV及7eV.因此,它将可以用作高分辨的元素分析.     

Spectral and diffraction properties of microchannel plates in the long-wavelength X-Ray range

The spatial distribution of the intensity and spectra of X rays at the output of microchannel plates is studied both experimentally and theoretically. A model of planar antenna array is used for radiation transmitted through an ordered system of through hollow microchannels for the energy range of 90–2000 eV. The results of the calculations are in good agreement with experimental data obtained with the parallel beams of monochromatic synchrotron radiation. The energy characteristics of the output radiation whose fine spectral structure corresponds to the reflection and fluorescence spectra near the Si L- and Si K-absorption edges are presented.     

激光等离子体脉冲软X光标定源

 利用神光Ⅱ上激光与等离子体相互作用得到的软X光,建立了基于多层镜的四通道软X光单色器系统。研究了光源的性能,测量了光源强度、单色器系统稳定性、相应通道的一致性。研究表明,采用多层镜作为脉冲光源的分光元件,可以得到具有较好单色性的强脉冲软X 光标定源。光源的光子能量为253 eV和820 eV,两能道的光源强度分别为1.8×10¹⁹ photon/(s·cm²)和3.2×10¹⁹ photon/(s·cm²)。在该标定源上可以实现XRD、平面镜、多层镜、透射光栅和滤片的标定。     

Observation of synchrotron radiation from electrons accelerated in a petawatt-laser-generated plasma cavity

The dynamics of plasma electrons in the focus of a petawatt laser beam are studied via measurements of their x-ray synchrotron radiation. With increasing laser intensity, a forward directed beam of x rays extending to 50 keV is observed. The measured x rays are well described in the synchrotron asymptotic limit of electrons oscillating in a plasma channel. The critical energy of the measured synchrotron spectrum is found to scale as the Maxwellian temperature of the simultaneously measured electron spectra. At low laser intensity transverse oscillations are negligible as the electrons are predominantly accelerated axially by the laser generated wakefield. At high laser intensity, electrons are directly accelerated by the laser and enter a highly radiative regime with up to 5% of their energy converted into x rays.     

Transition radiation of fast electrons as a broadband vacuum-ultraviolet radiation source

The characteristics of a possible radiation source in the vacuum-ultraviolet and soft X-ray range based on the transition radiation of electrons with an energy of about 100 keV are calculated. The possibilities of enhancing the radiation yield in the geometry of the glancing interaction of electrons with a target are analyzed. The possibility of creating a source with a yield on the order of 10^?5 photon/(eV sr) per electron is demonstrated.     

Photoemission studies of the energy dependence of the bulk plasmon loss intensity in Si and Al

Photoemission, using synchrotron radiation in the photon energy range 100 to 600 eV, has been utilized to study the energy dependence of the bulk plasmon loss intensity in Si and Al. The results are compared to the predictions of an extrinsic model for plasmon creation.     

Formation of Ti and TiN ultra-thin films on Si by ion beam sputter deposition

Ultra-thin titanium and titanium nitride films on silicon substrate were obtained by ion beam sputtering of titanium target in vacuum and nitrogen atmosphere, using argon ions with energy of 5 keV and 15 μA target current. Elemental composition and chemical state of obtained films were investigated by X-ray photoelectron spectroscopy with using Mg-Kα X-ray radiation (photon energy 1253.6 eV). It was shown that it is possible to form both ultra-thin titanium films (sputtering in vacuum) and ultra-thin titanium nitride films (sputtering in nitrogen atmosphere) in the same temperature conditions. Photoelectron spectra of samples surface, obtained in different steps of films synthesis, detailed spectra of photoelectron emission from Si 2p, Ti 2p, N 1s core levels and also X-ray photoelectron spectra of Auger electrons emission are presented.     

Large-angle channeling radiation from relativistic electrons in optically transparent crystals

In the work within the frame of quantum electrodynamics are obtained new formulae describing the large-angle photon emission from channeled electrons with taking into account of the dispersion of refractive index. Calculations based on these formulae show that the spectral and angular distributions of large-angle optical and ultraviolet radiation from planar channeled sub-GeV electrons in optically transparent crystal reflect the band structure of transverse energy levels of channeled electrons. Comparison with ordinary Cherenkov radiation spectrum reveals that channeling (depending on the beam energy) leads to sufficient change of the large-angle emission spectrum.     

Generation of characteristic x rays by a terawatt femtosecond chromium-forsterite laser

Characteristic K _α x rays arising when a metallic target is irradiated by femtosecond infrared pulses that are generated by a terawatt chromium-forsterite laser system (1240 nm, 90 mJ, 80 fs) are studied. The absolute yield (up to 3 × 10⁸ photons/sr pulse) and the coefficient of the transformation of laser radiation to K _α radiation (maximum value ≈0.03%) are measured for an iron target. The dependence of the radiation intensity on the angle of incidence of p polarized laser radiation is analyzed. The mechanisms of the production of fast electrons responsible for generating characteristic x rays are discussed.     

基于14 MeV中子的烧氚历史诊断模拟研究

针对直接测量16.7 MeV进行烧氚历史诊断所需聚变产额高的情况,模拟研究了利用14 MeV中子与副靶作用产生的非弹伽马进行烧氚历史诊断的情况,计算了几种材料14 MeV中子作用产生的次级伽马能谱以及切伦科夫辐射阈能之上的非弹伽马数目,对副靶材料和厚度进行了选择。计算了14 MeV中子产生的切伦科夫光子时间谱,分析了光电转换器件处伽马、电子以及正电子等噪声信号,分析了气体切伦科夫系统测量统计涨落与聚变中子产额之间的关系,确定了气体切伦科夫系统所适用的最低聚变中子产额,通过测量14 MeV中子与副靶产生的非弹伽马进行烧氚历史诊断较直接测量16.7 MeV伽马可将测量所需聚变中子产额降低2个量级。     

Photoemission electron microscopy as a tool for the investigation of optical near fields

Photoemission electron microscopy was used to image the electrons photoemitted from specially tailored Ag nanoparticles deposited on a Si substrate (with its native oxide SiO(x)). Photoemission was induced by illumination with a Hg UV lamp (photon energy cutoff homega(UV) = 5.0 eV, wavelength lambda(UV) = 250 nm) and with a Ti:sapphire femtosecond laser (homega(l) = 3.1 eV, lambda(l) = 400 nm, pulse width below 200 fs), respectively. While homogeneous photoelectron emission from the metal is observed upon illumination at energies above the silver plasmon frequency, at lower photon energies the emission is localized at tips of the structure. This is interpreted as a signature of the local electrical field therefore providing a tool to map the optical near field with the resolution of emission electron microscopy.     

上海软X光胶片响应的相对标定

介绍了在同步辐射源上用透射光栅对“上海”软Ｘ光胶片进行相对标定的方法，初步研究了“上海”胶片的特性，得到了在２７６ｅＶ和９３０ｅＶ两能点的胶片黑密度与相对曝光量的关系曲线；应用标定结果。