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.     

Berkeley and Its Physics Heritage

I first sketch the settlement of Berkeley, California, the founding of the University of California at Berkeley, and the origin of its Department of Physics. I then discuss the pivotal role that Ernest O. Lawrence (1901–1958) and his invention and subsequent development of the cyclotron played in physics at Berkeley after his arrival there in 1928 through the Second World War and beyond. I close by commenting on the Lawrence Hall of Science, the educational center and science museum conceived as a living memorial to Lawrence.     

Gerson Goldhaber: A Life in Science

I draw on my interviews in 2005–2007 with Gerson Goldhaber (1924–2010), his wife Judith, and his colleagues at Lawrence Berkeley National Laboratory. I discuss his childhood, early education, marriage to his first wife Sulamith (1923–1965), and his further education at the Hebrew University in Jerusalem (1942–1947) and his doctoral research at University of Wisconsin at Madison (1947–1950). He then was appointed to an instructorship in physics at Columbia University (1950–1953) before accepting a position in the physics department at the University of California at Berkeley and the Radiation Laboratory (later the Lawrence Berkeley Laboratory, today the Lawrence Berkeley National Laboratory), where he remained for the rest of his life. He made fundamental contributions to physics, including to the discovery of the antiproton in 1955, the GGLP effect in 1960, the psi particle in 1974, and charmed mesons in 1977, and to cosmology, including the discovery of the accelerating universe and dark energy in 1998. Beginning in the late 1960s, he also took up art, and he and his second wife Judith, whom he married in 1969, later collaborated in illustrating and writing two popular books. Goldhaber died in Berkeley, California, on July 19, 2010, at the age of 86.     

A high aperture beamline for vacuum ultraviolet circular dichroism on the srs

The three-day international workshop Actinide-XAS-2006 was held at Forschungszentrum Karlsruhe (FZK), Germany, from September 18–20, 2006. Actinide-XAS-2006 was the fourth workshop on speciation, techniques, and facilities for radioactive materials at synchrotron light sources. The Actinide-XAS series addresses the specialized field of the application of synchrotron techniques for investigating radioactive materials and is a forum for teaching and scientific discussion in this field, thereby strengthening existing and establishing new transnational cooperative scientific networks. The first and second workshops, Actinide-XAS-1998 and Actinide-XAS-2000, were held in Grenoble at the ESRF. The third and last workshop, Actinide-XAS-2004, was held at Lawrence Berkeley National Laboratory.     

Spring school on magnetic properties of condensed matter

The sixth joint Stanford-Berkeley summer school on synchrotron radiation and its applications in physical science was held on August 17?22, 2008, at the Stanford Linear Accelerator Center (SLAC). The Stanford-Berkeley summer school is jointly organized by the Stanford University, University of California Berkeley, Lawrence Berkeley National Laboratory (LBNL), and the Stanford Synchrotron Radiation Lightsource (SSRL). Anders Nilsson (Stanford) and Dave Attwood (Berkeley) have been the organizers of this one-week summer school since 2001. It alternates between Stanford and Berkeley. The summer school provides lecture programs on synchrotron radiation and its broad range of scientific applications in the physical science, visits to the Stanford Synchrotron Radiation Lightsource and the Advanced Light Source, where the students also have the opportunity to join a beamline. The program is designed to introduce students and postdocs to the fundamental properties of synchrotron radiation and how to understand and use spectroscopic, scattering and microscopy techniques in various scientific applications. Particular emphasis is given to examples from physics, chemistry, and material science.     

Second International Workshop on Ambient Pressure X-ray Photoelectron Spectroscopy

The Second International Workshop on Ambient Pressure X-ray Photoelectron Spectroscopy (APXPS) was held at Lawrence Berkeley National Laboratory (LBNL) in Berkeley, CA, from December 7–9, 2015. It brought together more than 100 participants from 17 countries. The workshop followed the inaugural meeting at the French synchrotron SOLEIL in December 2014, which was organized by François Rochet. The strong interest in these workshops reflects the growth of the APXPS community over the last decade, with instruments now operational at more than 12 synchrotrons around the world (see SRN, Vol. 27, No. 2, pp. 14–23 (2014)), and a steady increase in the number of laboratory instruments. APXPS has established itself as an important method for the investigation of surfaces and interfaces under in situ and operando conditions, including liquid/vapor and liquid/solid interfaces.     

Efficient High-Power High-Energy Neutral Beams for the Reference Mirror Reactor

The neutral beams for the reference mirror reactor are provided via four separate injectors using negative ions created by charge exchange in a cesium-vapor cell and neutralized by photodetachment. Each of the injectors delivers the equivalent of 1800 A of the desired mixture of 150-keV deuterium and tritium neutrals. Each injector consists of 23 ion sources of a modified Lawrence Berkeley Laboratory/Lawrence Livermore Laboratory type, with an associated cesium-vapor cell that converts 20 percent of the positive-ion output into negative ions D- and T-. The negative ions are accelerated to the desired energy and subsequently pass through a photodetachment cell that is continuously illuminated by eight columns of iteratively pulsed lasers. As much as 95 percent of the negative ions are stripped, producing fast neutrals that pass between the cryopumps and shielding into the reactor. Innovations required to attain an overall efficiency of 81.2 percent include a continuously operating cathode for the ion source, a negative-ion beam line with cooled gids, a high-voltage accelerator with insulators shielded from the neutron and gamma flux, cryopanels that cycle between pumping and outgassing modes, and recovery of the waste thermal energy and charged beam energy.     

高功率超短脉冲激光与新奇物理现象

 CPA（Chirped Pulse Amplification）技术,掺钛蓝宝石晶体材料与高功率固体激光器相结合,产生了新一代激光器,把已有高功率固体激光器的脉冲宽度缩短了3~4个数量级,输出功率提高了2~3个数量级,超过1PW,聚焦功率密度高达10²¹ W/cm²。激光技术这一划时代的进展打开了一个新奇的物理学世界,科学家们观察到了许多意想不到的新现象,也在探索和思考其令人鼓舞的应用前景。     

National school on Neutron and X‐ray scattering alumni presentations

The 4th joint Stanford–Berkeley summer school on synchrotron radiation and its applications in physical science was held June 12–17, 2005, at the Stanford Linear Accelerator Center (SLAC). The Stanford–Berkeley summer school is jointly organized by Stanford University, University of California Berkeley, Lawrence Berkeley National Laboratory (LBNL), and the Stanford Synchrotron Radiation Laboratory (SSRL). Since 2001, Anders Nilsson (Stanford/SSRL) and Dave Attwood (UC Berkeley) have been the organizers of this annual weeklong summer school, which alternates each year between Stanford and Berkeley. The summer school provides lecture programs on synchrotron radiation and its broad range of scientific applications in the physical science as well as visits to the Stanford Synchrotron Radiation Laboratory and the Advanced Light Source (ALS), where the students also have the opportunity to experience a beam line.     

On-line isotope separation of projectile fragments produced in relativistic heavy-ion reactions

A new on-line isotope separator was constructed and used successfully for the study on short-lived isotopes at the Bevalac at Lawrence Berkeley Laboratory. The isotopes were produced through projectile fragmentation processes of high energy heavy-ion reactions. Various isotopes were rigidity-separated by use of a beam line and, finally, the desired single isotope was range analyzed to stop in a catcher. A large number of β-emitting²¹F nuclei were successfully collected and the nuclear lifetime was determined by detecting β-rays.     

大功率半导体激光器发展及相关技术概述

激光被称为"最快的刀"、"最准的尺"、"最亮的光",与原子能、计算机、半导体并称为20世纪新四大发明。大功率半导体激光器在工业加工、医疗美容、光纤通信、无人驾驶、智能机器人等方面有着广泛的应用。如何实现大功率半导体激光光源,一直以来都是国际的研究前沿和学科热点。为此,简述了大功率半导体激光器的发展历史,综述了大功率半导体激光器的共用技术,包括大功率芯片技术和大功率合束技术,并对大功率半导体激光的发展方向进行了展望。     

Lightest isotope of Bh produced via the 209Bi(52Cr,n)260Bh reaction

The lightest isotope of Bh was produced in the new 209Bi(52Cr,n)260Bh reaction at the Lawrence Berkeley National Laboratory's 88-Inch Cyclotron. Positive identification was made by observation of eight correlated alpha particle decay chains in the focal plane detector of the Berkeley Gas-Filled Separator. 260Bh decays with a 35(-9)(+19) ms half-life by alpha particle emission mainly by a group at 10.16 MeV. The measured cross section of 59(-20)(+29) pb is compared to model predictions. The influence of the N=152 and Z=108 shells on alpha decay properties is discussed.     

高功率皮秒紫外激光器新进展

高功率皮秒紫外激光器在高精密加工、激光医疗、光电对抗和光伏产业等领域有重要应用,近年来成为固体激光新光源研究热点。本文对国内外基于和频技术的高功率皮秒紫外激光器研究新进展进行了归纳和总结。首先,阐述了和频工作原理,介绍了和频产生皮秒紫外激光的非线性晶体;然后,介绍了国内外高功率皮秒紫外激光器的新进展,包括:高功率皮秒紫外激光器、高峰值功率皮秒紫外激光器、高功率和高峰值功率皮秒紫外激光器。最后,展望了高功率皮秒紫外激光器的进一步发展及应用。归纳和总结表明:高功率皮秒紫外激光器在国外较成熟,国内在该领域的研究刚刚起步。光子晶体光纤和碟片激光器输出基频光的皮秒紫外激光器有突出的优势,已成为皮秒紫外激光产业的主力军。     

Collimation tester for ultrashort pulses and short coherence length lasers

A simple and easy-to-use collimation tester suitable for short coherence length lasers is described. The device is based on shearing interferometry using a compensation plate that enables a zero path length difference of the interfering beams and can be used for lasers of virtually vanishing coherence length, such as found in fs-lasers and high-power multimode lasers.     

High-power tunable IR Raman lasers

Physical principles, new ways and means of creation, schemes, characteristics and features of efficient high-power tunable pulse Raman lasers, operating in the near and middle ir are reviewed. The paper includes: tunable dye and Nd lasers as pump sources; promising active media and their optimal excitation methods; optical systems for producing spatially homogeneous pumping; the physics of Raman oscillators and their practical schemes, efficient high pulse energy liquid N₂ and compressed H₂ Raman oscillators, covering several bands in the range between 1.4 and 9.2 μm; the physics and construction of efficient tunable Raman amplifiers-convertors, amplifying in the saturation regime of spontaneously scattered or beforehand produced and collimated external Stokes signals, obtained in the spectral range between 0.83 μm and 18 μm. Raman laser using a, so-called, broadband pump where the linewidth of pumping light is broader than the spontaneous scattering linewidth, are also discussed. Features of both amplification and oscillation regimes of such broadband pumped Raman lasers are reported, and conditions for the efficient frequency conversion are determined.     

高功率掺镱双包层光纤激光器中光纤损伤及其理论分析

针对高功率掺镱双包层光纤激光器热效应引起的光纤损伤情况,由热传导方程,结合边界条件推导了两端泵浦情况下双包层光纤激光器光纤内的温度分布及热效应引起的应力分布,并对光纤内的温度分布和应力分布进行了数值模拟.结合模拟结果,对光纤的损伤进行了解释,分析了引起光纤热效应的主要因素.对两端泵浦情况的模拟与分析符合高功率光纤激光器的实际工作情况,这对优化高功率光纤激光器的设计有一定的参考价值.     

一种实现高功率输出的新型光纤激光器

介绍了一种实现光纤激光器高功率输出的新方法--采用螺旋芯光纤,这种光纤是在光纤制作过程中按照一定的弯曲半径使纤芯呈螺旋状排布在光纤包层中.介绍了这种螺旋芯光纤的原理和其提高输出功率的能力,以及目前的理论与实验研究现状.基于该光纤,提出了一种光纤激光器相干合成新思想.     

一种实现光纤激光器高功率输出的方法

 介绍了一种实现光纤激光器高功率输出的新方法——采用螺旋芯光纤，这种光纤是在光纤制作过程中按照一定的弯曲半径使纤芯呈螺旋状排布在光纤包层中。介绍了这种螺旋芯光纤的原理和其提高输出功率的能力，以及目前的理论与实验研究现状。基于该光纤，提出了一种光纤激光器相干合成新思想。     

Simulation of multilayer injection lasers with internal emission leaking

A mathematical model of multilayer injection lasers, based on the self-consistent kinetic problem taking into account the correlation between optical and electrical characteristics of a device is presented. The light-current characteristic of such laser is measured. A fast algorithm for computing complex eigenvalues of the wave equation is proposed. The calculation results are compared with experimentally measured light-current characteristics of diode lasers (fabricated by the GNOptics Company) with emission leaking to an optical cavity. The optical field profiles are determined in subthreshold and above-threshold modes for structures of high-power injection lasers with internal emission leaking. Good agreement between experimental and calculated data is achieved.