Second generation X-ray lasers

Laser and Particle Beams, 2002

Recent experiments undertaken at the Rutherford Appleton Laboratory to produce X-ray lasing over the 5–30 nm wavelength range are reviewed. The efficiency of lasing is optimized when the main pumping pulse interacts with a preformed plasma. Experiments using double 75-ps pulses and picosecond pulses superimposed on 300-ps background pulses are described. The use of travelling wave pumping with the approximately picosecond pulse experiments is necessary as the gain duration becomes comparable to the time for the X-ray laser pulse to propagate along the target length. Results from a model taking account of laser saturation and deviations from the speed of light c of the travelling wave and X-ray laser group velocity are presented. We show that X-ray laser pulses as short as 2–3 ps can be produced with optical pumping pulses of ≈1-ps.

2009

Hyperfine Interactions, 2010

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

IEEE Journal of Selected Topics in Quantum Electronics, 1999

Recent realization of saturated X-ray lasers (XRL's) has considerably extended the range of optical properties of soft X-ray sources toward high brightness and large coherence length. Consequently, new results may be expected from studies previously experienced with traditional sources such as synchrotron radiation. On the other hand, XRL's open new fields of research owing to their high brightness. In this paper, we present some of the first experiments utilizing XRL sources.

Instruments, 2019

Fine time-resolved analysis of matter—i.e., spectroscopy and photon scattering—in the linear response regime requires fs-scale pulsed, high repetition rate, fully coherent X-ray sources. A seeded Free Electron Laser (FEL) driven by a Linac based on Super Conducting cavities, generating 10 8 – 10 10 coherent photons at 2–5 keV with 0.2–1 MHz of repetition rate, can address this need. Three different seeding schemes, reaching the X-ray range, are described hereafter. The first two are multi-stage cascades upshifting the radiation frequency by a factor of 10–30 starting from a seed represented by a coherent flash of extreme ultraviolet light. This radiation can be provided either by the High Harmonic Generation of an optical laser or by an FEL Oscillator operating at 12–14 nm. The third scheme is a regenerative amplifier working with X-ray mirrors. The whole chain of the X-ray generation is here described by means of start-to-end simulations.

Soft X-Ray Lasers and Applications VIII, 2009

Two novel schemes for efficient x-ray laser generation from laser-produced plasma and capillary discharge-driven plasmas are described. The combination of nano-structured targets with the high energy ultrashort pulse lasers can result in the generation of laser-produced plasmas that could lead to high brightness sources of incoherent multi-KeV radiation and x-ray lasers of short pulse duration at shorter wavelengths. The generation of 0.5-1 keV x-ray laser radiation from a Ni-like U plasma created using excitation from a Petawatt laser is analyzed. The efficient excitation of capillary discharge plasmas in micro-capillary discharge channels is discussed.

The European Physical Journal H, 2012

The successful lasing at the SLAC National Accelerator Laboratory of the Linear Coherent Light Source (LCLS), the first X-ray free-electron laser (X-ray FEL), in the wavelength range 1.5 to 15Å, pulse duration of 60 to few femtoseconds, number of coherent photons per pulse from 10 13 to 10 11 , is a landmark event in the development of coherent electromagnetic radiation sources. Until now electrons traversing an undulator magnet in a synchrotron radiation storage ring provided the best X-ray sources. The LCLS has set a new standard, with a peak X-ray brightness higher by ten orders of magnitudes and pulse duration shorter by three orders of magnitudes. LCLS opens a new window in the exploration of matter at the atomic and molecular scales of length and time. Taking a motion picture of chemical processes in a few femtoseconds or less, unraveling the structure and dynamics of complex molecular systems, like proteins, are some of the exciting experiments made possible by LCLS and the other X-ray FELs now being built in Europe and Asia. In this paper, we describe the history of the many theoretical, experimental and technological discoveries and innovations, starting from the 1960s and 1970s, leading to the development of LCLS.

SPIE Newsroom, 2009

The use of x-ray radiation has driven the development of synchrotron sources and, more recently, x-ray free-electron lasers (FELs). These microwave-based facilities are huge and expensive, yet governments are prepared to support them (usually one per nation) because of their great value to industry, academia, and society. However, laser-wakefield accelerators (LWFAs) are now advancing to the point where compact radiation sources could be developed into a new, complementary, or even disruptive technology. In addition to reductions in scale and cost-by a factor of up to 1000-x-ray pulse durations are significantly shorter than those of conventional lasers, which could facilitate probing of ultrafast dynamic processes. The Advanced Laser-Plasma High-Energy Accelerators towards X-rays (ALPHA-X) project, based at the University of Strathclyde, is developing laser-plasma accelerators as drivers of radiation sources. 1 The first demonstration of a compact synchrotron source based on an LWFA was recently demonstrated using a conventional undulator and a diverging electron beam. 2 Our challenge is to develop a compact x-ray FEL. Here we focus on developments to improve the electron-beam properties and discuss the suitability of LWFAs as drivers of FELs. Our work shows that the once-distant prospect of a compact x-ray FEL is now within reach. On the ALPHA-X accelerator beam line (see Figure 1), electrons are accelerated in a relativistically self-guiding plasma channel formed in a hydrogen-gas jet by a 35fs titaniumsapphire laser pulse with a power of 1J. Electrons are selfinjected from the background plasma into the density wake that trails behind the laser pulse (through the combined action

Nature Communications, 2015

The X-ray free-electron laser has opened a new era for photon science, improving the X-ray brightness by ten orders of magnitude over previously available sources. Similar to an optical laser, the spectral and temporal structure of the radiation pulses can be tailored to the specific needs of many experiments by accurately manipulating the lasing medium, that is, the electron beam. Here we report the generation of mJ-level two-colour hard X-ray pulses of few femtoseconds duration with an XFEL driven by twin electron bunches at the Linac Coherent Light Source. This performance represents an improvement of over an order of magnitude in peak power over state-of-the-art two-colour XFELs. The unprecedented intensity and temporal coherence of this new two-colour X-ray free-electron laser enable an entirely new set of scientific applications, ranging from X-ray pump/X-ray probe experiments to the imaging of complex biological samples with multiple wavelength anomalous dispersion.

1989

A high power, short pulse ultraviolet laser system (Powerful Picosecond-Laser) has been developed at the Princeton Plasma Physics Laboratory (PPPL) as part of experiments designed to generate shorter wavelength X-ray lasers. With the addition of pulse compression and a final KrF amplifier the laser output is expected to have reached 1/3-1/2 TW (10 12 watts) levels. The laser system, particularly the final amplifier, is described along with some initial soft X-ray spectra front laser-target experiments. The front end of the PP-Laser provides an output of 20-30 CW (10 9 watts) and can be focussed to intensities of •v 10 1 * W/CBI Z. Experiments using this output to examine the effects of a prepulse on laser-target interaction are described.