High-resolution soft X-ray emission spectrograph at advanced light source

The progress of valence electronic spectroscopy with X-rays has been largely limited by the challenge of fine instrumentation. Relatively weak scattering cross-section and/or limited (coarse) energy resolution restrict X-ray spectroscopy to address fundamental issues in condensed-matter electron physics. Depending on the nature of excitations, high brightness photon beam from third-generation synchrotron facilities helps raise the count rates to a detectable limit over the noise level. Over the past decade, it has been realized that high-resolution resonant inelastic soft X-ray scattering has the potential to play an important role in understanding complex phenomena observed in highly correlated systems. Driven by such demand, we have developed a soft X-ray emission spectrograph based on variable line spacing (VLS) gratings to work in the soft X-ray and deep UV (the M edge of transition metals) regime. The slit-less design coupled with high quality optical elements and a high quantum efficiency (QE) in-vacuum CCD detector greatly improves the overall throughput. The M edge spectrograph has been demonstrated to have a resolving power better than 10,000 and will be used in conjunction with meV-resolution beamline (MERLIN) at the Advanced Light Source at Lawrence Berkeley National Laboratory.     

High pressure X-ray emission spectroscopy at the advanced photon source

ABSTRACT

The structural, electronic, and magnetic properties of materials under high pressure are of fundamental interest in physics, chemistry, materials science, and earth sciences. Among several hard X-ray-based techniques, X-ray emission spectroscopy (XES) provides a powerful tool to probe element-specific information for understanding the electronic and magnetic properties of materials under high pressure. Here, we discuss on the particular requirements and instrumentation used in high pressure XES experiments. We then present several examples to illustrate the recent progress in high pressure XES studies at the Advanced Photon Source, followed by an outlook toward future development in high pressure XES.     

TW Laser system for Thomson scattering X-ray light source at Tsinghua University

A TW (Tera Watt) laser system based on Ti:sapphire mainly for the Tsinghua Thomson scattering X-ray light source (TTX) is being built. Both UV (ultraviolet) laser pulse for driving the photocathode radiofrequency (RF) gun and the IR (infrared) laser pulse as the electron-beam-scattered-light are provided by the system. Efforts have also been made in laser pulse shaping and laser beam transport to optimize the high-brightness electron beam production by the photocathode RF gun.     

TW Laser system for Thomson scattering X-ray light source at Tsinghua University

A TW (Tera Watt) laser system based on Ti:sapphire mainly for the Tsinghua Thomson scattering X-ray light source (TTX) is being built. Both UV (ultraviolet) laser pulse for driving the photocathode radio-frequency (RF) gun and the IR (infrared) laser pulse as the electron-beam-scattered-light are provided by the system. Efforts have also been made in laser pulse shaping and laser beam transport to optimize the high-brightness electron beam production by the photocathode RF gun.     

Conceptual design of Hefei advanced light source

The conceptual of Hefei Advanced Light Source, which is an advanced VUV and Soft X-ray source, was developed at NSRL of USTC. According to the synchrotron radiation user requirements and the trends of SR source development, some accelerator-based schemes were considered and compared; furthermore storage ring with ultra low emittance was adopted as the baseline scheme of HALS. To achieve ultra low emittance, some focusing structures were studied and optimized in the lattice design. Compromising of emittance, onmomentum and off-momentum dynamic aperture and ring scale, five bend acromat (FBA) was employed. In the preliminary design of HALS, the emittance was reduced to sub nm·rad, thus the radiation up to water window has full lateral coherence. The brilliance of undulator radiation covering several eVs to keVs range is higher than that of HLS by several orders. The HALS should be one of the most advanced synchrotron radiation light sources in the world.     

Conceptual design of Hefei advanced light source

The conceptual of Hefei Advanced Light Source, which is an advanced VUV and Soft X-ray source, was developed at NSRL of USTC. According to the synchrotron radiation user requirements and the trends of SR source development, some accelerator-based schemes were considered and compared; furthermore storage ring with ultra low emittance was adopted as the baseline scheme of HALS. To achieve ultra low emittance, some focusing structures were studied and optimized in the lattice design. Compromising of emittance, on-momentum and off-momentum dynamic aperture and ring scale, five bend acromat (FBA) was employed. In the preliminary design of HALS, the emittance was reduced to sub nm·rad, thus the radiation up to water window has full lateral coherence. The brilliance of undulator radiation covering several eVs to keVs range is higher than that of HLS by several orders. The HALS should be one of the most advanced synchrotron radiation light sources in the world.     

Infrared facility at the Canadian light source

The Canadian Light Source (CLS) is constructing two beamlines for Infrared Spectroscopy using synchrotron radiation (IRSR). One will supply mid-Infrared (2–25 μ) light to a Fourier Transform Infrared (FTIR) spectrometer and microscope for biological applications. The second will have a high resolution FTIR spectrometer for gas-phase and surface spectroscopy in the far-Infrared (beyond 25 μ). The Infrared beamlines will use dipole bending magnet radiation from a special bend magnet port design which provides a 50 mrad square acceptance. Issues with the first mirror and photon mask design, as well as the beamline layout and features are discussed.     

The resistive-heating characterization of laser heating system and LaB6 characterization of X-ray diffraction of beamline 12.2.2 at advanced light source

X-ray diffraction from LaB₆ standards document a precision of 478 ppm in lattice-parameter determinations for beamline 12.2.2 at Lawrence Berkeley National Laboratory′s Advanced Light Source, a facility for characterizing materials at high pressures and temperatures using laser- and resistance-heated diamond cells. Melting of Ni, Mo, Pt and W, resistively heated at 1 atm pressure in Ar, provides a validation of the beamline spectroradiometric system that is used to determine sample temperatures. The known melting temperatures, which range from 1665 to 3860 K for these metals, are all reproduced to within ±80 K.     

Backscatter tolerant squeezed light source for advanced gravitational-wave detectors

We report on the performance of a dual-wavelength resonant, traveling-wave optical parametric oscillator to generate squeezed light for application in advanced gravitational-wave interferometers. Shot noise suppression of 8.6±0.8 dB was measured across the detection band of interest to Advanced LIGO, and controlled squeezing measured over 5900 s. Our results also demonstrate that the traveling-wave design has excellent intracavity backscattered light suppression of 47 dB and incident backscattered light suppression of 41 dB, which is a crucial design issue for application in advanced interferometers.     

PULSE Ultrafast X-ray Summer School

The Third Annual Ultrafast X-ray Summer School (UXSS 2009) was held from June 15–19, 2009, at the SLAC National Accelerator Laboratory (SLAC) and sponsored by the PULSE Institute for Ultrafast Energy Science. The summer school was a weeklong residential event that brought together about 100 students, post-doctoral researchers, and other young and established scientists from diverse backgrounds. Particular emphasis was given to new scientific opportunities enabled by the world's first hard X-ray free electron laser, the Linac Coherent Light Source (LCLS), which underwent a spectacular start-up only months before.     

Ultrafast X-ray sources and applications

The recent development of ultrafast X-ray sources makes conceivable the analysis of subpicosecond transient structures. This paper describes these new techniques and reports the first experiments dedicated to the analysis of atomic motions on this time-scale.     

Ultrafast laser-based thermal X-ray sources

The effects of hot electrons on the thermal radiative properties (brightness, duration and spectral shape) and dynamics of solid density plasmas, generated during the interaction of a femtosecond laser and a solid target, are assessed. Line and broadband thermal emissions with duration between 500 fs and 700 fs, have been successfully produced with peak power between 1 and 10 MW, when the fraction of laser energy in the hot electron population was less than 2%, and when the hot electron energy density at the target surface was less than 1 KJ / cm ² .     

先进光源磁铁支撑基座稳定性的实验研究

基座作为磁铁支架的基础,其制作工艺以及与地面连接固定方式的不同将影响磁铁与支架的稳定性。基于先进光源对磁铁支撑系统稳定性的极高要求,开展了基座安装浇筑实验,选取工程上常用的几种混凝土施工工艺,制作统一外形尺寸的实验件,通过锤击法逐一测试其固有频率,评估其稳定性,得到二次灌浆可有效提高稳定性、环氧基灌浆料获得的稳定性优于水泥基灌浆料等结论。基于固有频率测试结果,以HEPS支撑系统为例分析了不同的基座安装方式对系统模态的影响。     

Ultrafast electron microscopy in material science

Recent advances in the ultrafast transmission electron microscope(UTEM), with combined spatial and temporal resolutions, have made it possible to directly visualize the atomic, electronic, and magnetic structural dynamics of materials.In this review, we highlight the recent progress of UTEM techniques and their applications to a variety of material systems.It is emphasized that numerous significant ultrafast dynamic issues in material science can be solved by the integration of the pump–probe approach with the well-developed conventional transmission electron microscopy(TEM) techniques. For instance, UTEM diffraction experiments can be performed to investigate photoinduced atomic-scale dynamics, including the chemical reactions, non-equilibrium phase transition/melting, and lattice phonon coupling. UTEM imaging methods are invaluable for studying, in real space, the elementary processes of structural and morphological changes, as well as magnetic-domain evolution in the Lorentz TEM mode, at a high magnification. UTEM electron energy-loss spectroscopic techniques allow the examination of the ultrafast valence states and electronic structure dynamics, while photoinduced near-field electron microscopy extends the capability of the UTEM to the regime of electromagnetic-field imaging with a high real space resolution.     

X‐ray microscopy at the advanced photon source

In modern third generation synchrotron sources, undulators have become the principal source of X-rays and today a brilliance close to 10²¹ photons/sec?mm²?mrad?0.1%BW is routinely attained for photon energies of 10 keV. However, generating brilliant beams of photons with energies of 50 keV and above leads to conflicting choices for the undulator parameters as the following analysis shows.     

Intense, broadband, pulsed I-R source at the national synchrotron light source

We describe a broadband (1 m–1 mm) synchrotron radiation infrared source, pulsed each 20–180 nseconds and delivering about 10¹⁵ photons/sec/1% bandpass into f10 optics. The source size is diffraction limited. This source is thus 100–1000 times brighter than a 2000°K black body, very stable and capable of being used for calibration.Work supported by the U.S. Department of Energy.     

The impact on the X-ray phase contrast imaging clarity of the light source area

Based on the partially coherent optical theory, a new theoretical model is established about the X-ray light source radius of X-ray phase contrast imaging system. Through the integral phase contrast modulation transfer function, a comprehensive analysis about the light source radius is made. Then the light source radius selection methods are investigated. Finally, an actual imaging experiment is shown to confirm the choice method of light source radius in X-ray phase contrast imaging system.     

Global dynamics of the advanced light source revealed through experimental frequency map analysis

Frequency map analysis was first used for the dynamical study of numerical simulations of physical systems (solar system, galaxies, particle accelerators). Here it is applied directly to the experimental results obtained at the Advanced Light Source. For the first time, the network of coupling resonances is clearly visible in an experiment, in a similar way as in the numerical simulation. Excellent agreement between numerical and experimental results leads us to propose this technique as a tool for improving numerical models and actual behavior of particle accelerators. Moreover, it provides a model-independent diagnostic for the evaluation of the dynamical properties of the beam.