Insertion devices–recent developments and future trends

The first Ultrafast X-ray Summer School, organized and chaired by Nora Berrah (WMU), was held June 18–22, 2007, at the Stanford University's PULSE Center, located at the Stanford Linear Accelerator Center (SLAC). With the advent of 4^th generation X-ray light sources, and in particular, the Linac Coherent Light Source (LCLS) under construction at SLAC, it was timely to begin the process of building a competitive community of scientists. It was also primordial to communicate to everyone the excitement many of us have about these new tools and to help raise awareness of the opportunities in ultrafast X-ray research.     

A compact warm ring for industrial applications

The ultrafast, high brightness X-ray free electron laser (XFEL) sources of the future have the potential to revolutionize the study of time-dependent phenomena in the natural sciences. These linear accelerator (linac) sources will generate femtosecond (fs) X-ray pulses with peak flux comparable to conventional lasers, and far exceeding all other X-ray sources. The Stanford Linear Accelerator Center (SLAC) has pioneered the development of linac science and technology for decades, and since 2000 SLAC and the Stanford Synchrotron Radiation Laboratory (SSRL) have focused on the development of linac based ultrafast electron and X-ray sources.     

Practical application of cross correlation technique to measure jitter of master-oscillator-power-amplifier (MOPA) laser system

The Linac coherent light source (LCLS) at the SLAC National Accelerator Laboratory (SLAC) is the world’s first hard X-ray free electron laser (XFEL) and is capable of producing high-energy, femtosecond duration X-ray pulses. A common technique to study fast timescale physical phenomena, various “pump/probe” techniques are used. In these techniques there are two lasers, one optical and one X-ray, that work as a pump and as a probe to study dynamic processes in atoms and molecules. In order to resolve phenomena that occur on femtosecond timescales, it is imperative to have very precise timing between the optical lasers and X-rays (on the order of ～20 fs or better). The lasers are synchronized to the same RF source that drives the accelerator and produces the X-ray laser. However, elements in the lasers cause some drift and time jitter, thereby de-synchronizing the system. This paper considers cross-correlation technique as a way to quantify the drift and jitter caused by the regenerative amplifier of the ultrafast optical laser.     

2009 SSRL School on X-ray Spectroscopy Techniques in Environmental and Materials Sciences: Theory and Application

More than 50 students, post-docs, and career scientists from US national laboratories, academic institutions, and the international user community participated in this four-day school, held from June 2–5, 2009, which delved deeply into theoretical and practical aspects of synchrotron X-ray spectroscopy. The fourth annual school on synchrotron techniques in environmental and materials sciences, organized by the Stanford Synchrotron Radiation Lightsource (SSRL) at the SLAC National Accelerator Laboratory, was designed to introduce new and prospective users to theoretical underpinnings and capabilities of the techniques, data collection procedures, and data analysis approaches. More advanced topics, particularly in data analysis, were also discussed to reinforce and clarify important concepts that are fundamental to data interpretation. Although the school focused principally on applications in environmental and materials sciences, diverse and cross-cutting disciplinary backgrounds were represented, from environmental remediation science and geochemistry, to heterogeneous catalysis and bioinorganic chemistry, to materials sciences and applied physics.     

Coherent X-ray diffraction radiation produced by microbunched beams passing close to the edge of a slab

With use of formulas for single-particle X-ray transition and diffraction radiation (XTR and XDR), we obtain expressions for spectral-angular distributions and total numbers of emitted quanta in coherent X-ray transition radiation (CXTR2) and coherent X-ray diffraction radiation (CXDR) arising when a microbunched beam of electrons, respectively, intersects the interfaces of a slab or flies at small distance from the edge of the slab. Comparison of obtained results with those known for CXTR from a single interface is performed. It is shown on the basis of numerical calculations that experimental study of CXDR is at present possible on the Linac Coherent Light Source (LCLS, SLAC).     

FOREWORD

<正>The "International Workshop on e+e- collisions from phi to psi" (PHIPSI09), was held at Institute of High Energy Physics (IHEP), Chinese Academy of Sciences (CAS), Beijing, China, from Tuesday, October 13 to Friday,     

Second User Workshop on High-Power Lasers at the Linac Coherent Light Source

The second international workshop on the physics enabled by the unique combination of high-power lasers with the world-class Linac Coherent Light Source (LCLS) free-electron X-ray laser beam was held in Stanford, CA, on October 7–8, 2014. The workshop was co-organized by UC Berkeley, Lawrence Berkeley, Lawrence Livermore, and SLAC National Accelerator Laboratories. More than 120 scientists, including 40 students and postdoctoral scientists who are working in high-intensity laser-matter interactions, fusion research, and dynamic high-pressure science came together from North America, Europe, and Asia. The focus of the second workshop was on scientific highlights and the lessons learned from 16 new experiments that were performed on the Matter in Extreme Conditions (MEC) instrument since the first workshop was held one year ago.     

XFELO Scientific Opportunities Retreat

The first XFELO Science Workshop was held at SLAC National Accelerator Laboratory, Menlo Park, CA, from June 29 to July 1, 2016. The main purpose was the discussion of scientific opportunities an XFELO extension of the LCLS-II complex in the future would enable. Chaired by Jerry Hastings (SLAC), it brought together more than 40 researchers from institutes around the world.     

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.     

Dynamics of Self-Organized and Self-Assembled Structures,by Rashmi C. Desai and Raymond Kapral

The arrival of the first hard X-ray free electron laser facilities promises new advances in structural dynamics and nanoscale imaging that will have impact across the sciences. This introductory review is intended to cover the basic physics behind this potential and illustrate the current state-of-the-art by discussing a number of recent findings from the LCLS facility at the Stanford Linear Accelerator Centre (SLAC). We concentrate on the new science using these light sources rather than the new light source technology itself, although a brief introduction to the operation of LCLS is given. Emphasis is placed upon the new regime of high intensity X-ray matter interaction physics with ultrashort X-ray pulses. We discuss how the unique combination of X-ray parameters will open new opportunities for time resolved structural studies and how the high brightness enables a new class of coherent diffraction X-ray imaging. The potential importance of this new imaging method in the study of nanostructures and biological systems at the sub-cellular and molecular level will be outlined.     

Experimental Study on the Spatial Performance of Photorefractive X-ray Semiconductor Ultrafast Response ChipEI北大核心CSCD

The traditional ultrafast electric vacuum devices are usually based on the mechanism of photoelectric conversion, and their performance is restricted by factors such as material response and space-charge effect. It is difficult for the devices like microchannel plate framing cameras, Dilation X-ray Imager (DIXI) , streak cameras to achieve high temporal resolution (100 fs similar to 1 ps) and spatial resolution (similar to mu m) two-dimensional imaging. Ultrafast imaging technology based on photorefractive effect is a new ultrafast diagnostic technology, which has the advantages of high spatiotemporal resolution, all-optical, all and anti radiation. The nonequilibrium carrier lifetime of low temperature grown AlGaAs (LT-AlGaAs) can reach ps-level. The Ultrafast Response Chip (URC) made of LT-AlGaAs has the characteristics of high temporal resolution, meanwhile, good spatial performance is the other key factor for its application. In this paper, the spatial performance of LT-AlGaAs URC is experimentally studied using X-ray, generated by high-energy nanosecond pulsed laser-produced plasma, as the signal. The results show that the URC has the ability of high spatial resolution and large-scale imaging in the X-ray energy dynamic range of 120: 1. The optimal spatial resolution is >= 35 1p/mm (R) MTF = 0.1, and the imaging frame can reach 6.7 mm x 6.7 mm. The results further verify the feasibility of ultrafast diagnostic technology based on photorefractive materials. In the future, LT-AIGaAs URC will be combined with ultrafast framing technologies such as dispersion framing and polarization chirp framing to realize multi-frames and high spatiotemporal resolution two-dimensional imaging.     

Modeling and analysis of SLED

SLED(SLAC Energy Doubler) is a crucial component for the C-band microwave acceleration unit of a soft X-ray Free Electron Laser(SXFEL). To study the behavior of SLED, a mathematical model is commonly built and analyzed. In this paper, a new method is proposed to build the model of SLED at the Shanghai Institute of Applied Physics. With this method, the parameters of the two cavities can be analyzed separately. Also it is suitable to study parameter optimization of SLED and analyze the effect from the parameters variations. Simulation results of our method are also presented.     

FERMION COHERENT STATE AND QUARK CONFINEMENT

Two characteristics of the Fermion coherent state are given in this paper. One is the duality of the Fermion coherent state. The other is the indefiniteness of their eigenvalues. The SLAC bag model is also discussed by using the Fermion coherent state methodology. Our zesults agree with the SLAC bounded state iolutions, so that quark confinement can be phenomenally, illustrated.In addition, rje have found a gluon-ball solution and a non-bounded state solution, which are absent from the SLAC theory. Hence,the method of the Fermion coherent state is effective.     

X-ray pump optical probe cross-correlation study of GaAs

Ultrafast dynamics in atomic, molecular and condensed-matter systems are increasingly being studied using optical-pump, X-ray probe techniques where subpicosecond laser pulses excite the system and X-rays detect changes in absorption spectra and local atomic structure(1-3). New opportunities are appearing as a result of improved synchrotron capabilities and the advent of X-ray free-electron lasers(4,5). These source improvements also allow for the reverse measurement: X-ray pump followed by optical probe. We describe here how an X-ray pump beam transforms a thin GaAs specimen from a strong absorber into a nearly transparent window in less than 100 ps, for laser photon energies just above the bandgap. We find the opposite effect-X-ray induced optical opacity-for photon energies just below the bandgap. This raises interesting questions about the ultrafast many-body response of semiconductors to X-ray absorption, and provides a new approach for an X-ray/optical cross-correlator for synchrotron and X-ray free-electron laser applications.     

User Workshop on High-Power Lasers at the Linac Coherent Light Source

A two-day international workshop on the physics and integration of high-power lasers with the Linac Coherent Light Source was held in Stanford, California, USA, on October 1–2, 2013. The workshop was co-organized by UC Berkeley, Lawrence Berkeley, Lawrence Livermore, and SLAC National Accelerator Laboratories. More than 150 scientists, including 30 students and postdocs who are working in high-intensity laser-matter interactions, fusion research, and dynamic high-pressure science, came together from North America, Europe, and Asia. The group discussed the most promising and important new physics experiments that will be enabled by the unique combination of high-power lasers and the world-class LCLS free-electron laser X-ray beam.     

Excited-state dynamics of magnesium phthalocyanine thin film

Ultrafast excitation relaxation dynamics of magnesium phthalocyanine (MgPc) thin film were investigated by femtosecond pump-probe spectroscopy. The excited state dynamics of MgPc's Q-band were found to be strongly dependent on the probe wavelength. Ultrafast exciton–exciton annihilation with a t^−1/2 time dependence of the excited-state population was observed.     

The fast show with x‐rays and electrons

On October 20–26, 2004, more than 350 people participated in the 31st Annual Stanford Synchrotron Radiation Laboratory (SSRL) Users' Meeting, workshops, and social events. The presentation by SSRL Director Keith Hodgson in the opening session focused on the success in 2004 in getting SPEAR3 and the SSRL beam lines operating and productive. Looking towards the future, he discussed the exciting new opportunities at the Linac Coherent Light Source (LCLS), an X-ray free electron laser. Hodgson emphasized the importance of safety when conducting experiments at SSRL, a point strongly reiterated by SLAC Director Jonathan Dorfan.     

Strong coupling constant from scaling violations in fragmentation functions

We present a new determination of the strong coupling constant alpha(s) through the scaling violations in the fragmentation functions for charged pions, charged kaons, and protons. In our fit we include the latest e+e- annihilation data from CERN LEP1 and SLAC SLC on the Z-boson resonance and older, yet very precise, data from SLAC PEP at center-of-mass energy sqaure root of s = 29 GeV. At next-to-leading order, we find alpha(s)(5)(M(Z)) = 0.1170+/-0.0073. A new world average of alpha(s) is given.     

Mixing of P wave axial vector resonances

An analysis is given of the mixing of the axial vector kaon resonances by use of new data from SLAC. Mass values, decay widths and branching ratios of the SLAC work may be compatible with SU(3) and/or “pair creation model” classifications for a mixing angle λ ≈ ?35° ± 10°. The mass values and coupling strengths proposed by Basdevant and Berger, from a different parametrization of the same data, can be fitted in an SU(3) and/or broken SU(6)_w model with a larger mixing angle λ ≈ ?80°. Such a mixing would mean that the lower kaonic state is closely related to the 1^+? nonet in contrast to expectations from duality and/or one-gluon exchange mixing schemes. We also discuss the mixing of the charmed D meson states.     

Progress in the applicability of plasma X-ray lasers

Proposed as satellite-based weapons during the 1980s, X-ray lasing was for a long time only achieved with enormous amounts of pump energy in either nuclear explosions or at kilojoule-class laser installations. During the last few years a tremendous development was achieved, most visible in the realisation of the FEL lasers at DESY and SLAC. As important for a wider applicability is the enormous reduction in pump energy for laser pumped plasma X-ray lasers, which now brings such devices into the range of applications for diagnostics and spectroscopy even in smaller laboratories. Main developments were the transient excitation scheme and the optimized pumping concepts. This paper concentrates on developments at the GSI Helmholtzcenter at Darmstadt aiming towards reliable X-ray laser sources in the range from 50 to several 100 eV. The main driving forces for the laser development at GSI are the possible application for the spectroscopy of Li-like ions in the storage ring ESR and the future storage ring NESR at FAIR, and the interest in novel plasma diagnostics.