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We present a flexible and compact experimental setup that combines an in vacuum liquid jet with an x-ray emission spectrometer to enable static and femtosecond time-resolved resonant inelastic soft x-ray scattering (RIXS) measurements from liquids at free electron laser (FEL) light sources. We demonstrate the feasibility of this type of experiments with the measurements performed at the Linac Coherent Light Source FEL facility. At the FEL we observed changes in the RIXS spectra at high peak fluences which currently sets a limit to maximum attainable count rate at FELs. The setup presented here opens up new possibilities to study the structure and dynamics in liquids.

A Wien filter was designed for and tested with a room temperature electron beam ion source (EBIS). Xenon charge state spectra up to the charge state Xe46+ were resolved as well as the isotopes of krypton using apertures of different sizes. The complete setup consisting of an EBIS and a Wien filter has a length of less than 1 m substituting a complete classical beamline setup. The Wien filter is equipped with removable permanent magnets. Hence total beam current measurements are possible via simple removal of the permanent magnets. In dependence on the needs of resolution a weak (0.2 T) or a strong (0.5 T) magnets setup can be used. In this paper the principle of operation and the design of the Wien filter meeting the requirements of an EBIS are briefly discussed. The first ion beam extraction and separation experiments with a Dresden EBIS are presented.

A dopant-enhanced atmospheric pressure direct current glow discharge ionization source for ion mobility spectrometry (APDCGD-IMS) has been described. It is shown that the ion intensity can be greatly increased by addition of species with ionization energy lower than that of buffer gas when the direction of the electric field between the target electrode and the extraction electrode was opposite to that of the drift field. With N(2) as the buffer gas, adding O(2) (or air), acetone, and CH(2)Cl(2) with certain concentration can enhanced the ion intensity more than one order of magnitude, and for O(2), it was found that the enhancement depending on both the concentration of O(2) and the flow rate of the carrier gas, and the largest enhancements of the signal intensity for electron in negative mode and reaction ion in positive mode reached at O(2) concentration about 1.5%-2%. The main physicochemical processes were summarized and discussed, and a zero-dimensional reaction rate model was set up to simulate the corresponding results. It was proposed that the enhancement of signal intensity was ascribed to the various ionization processes and reactions in APDCGD.

The distribution of photoelectrons acquired in angle-resolved photoemission spectroscopy can be mapped onto the energy-momentum space of the Bloch electrons in the crystal. The explicit forms of the mapping function f depend on the configuration of the apparatus as well as on the type of the photoelectron analyzer. We show that the existence of the analytic forms of f−1 is guaranteed in a variety of setups. The variety includes the case when the analyzer is equipped with a photoelectron deflector. Thereby, we provide a demonstrative mapping program implemented by an algorithm that utilizes both f and f−1. The mapping methodology is also usable in other spectroscopic methods such as momentum-resolved electron-energy loss spectroscopy. [ABSTRACT FROM AUTHOR]

Doppler-free saturation spectroscopy provides a very powerful method to obtain detailed information about the electronic structure of the atom through measurement of the spectral line profile. This is achieved through a significant decrease in the Doppler broadening and essentially an elimination of the instrument broadening inherent to passive spectroscopic techniques. In this paper we present the technique and associated physics of Doppler-free saturation spectroscopy in addition to how one selects the appropriate transition. Simulations of Hδ spectra are presented to illustrate the increased sensitivity to both electric field and electron density measurements. [ABSTRACT FROM AUTHOR]

We have developed an efficient spectrometer capable of performing a wide variety of coherent multidimensional measurements at optical wavelengths. The two major components of the largely automated device are a spatial beam shaper which controls the beam geometry and a spatiotemporal pulse shaper which controls the temporal waveform of the femtosecond pulse in each beam. We describe how to construct, calibrate, and operate the device, and we discuss its limitations. We use the exciton states of a semiconductor nanostructure as a working example. A series of complex multidimensional spectra-displayed in amplitude and real parts-reveals increasingly intricate correlations among the excitons. [ABSTRACT FROM AUTHOR]

Design, characterization, and selected applications of a novel electron detector dedicated to conventional perpendicular- and low-angle-incidence conversion electron Mössbauer spectroscopy are presented. The setup is suitable for varying the incident angle and external magnetic fields on Mössbauer source and absorber. Test experiments were performed on α-57Fe films using a conventional single-line 57Co(Rh) and magnetically split, 57Co(α-Fe) Mössbauer sources. The integral “blackness effect” in conversion-electron Mössbauer spectra of 57Fe isotope-enriched absorbers is demonstrated and shown to be pronounced at shallow angles of incidence. In order to determine the alignment and sign of the hyperfine field in an isotope-enriched absorber, the blackness effect is accounted for in a semiempirical way by using single-line source/absorber experimental relative intensities determined independently. This method works with high accuracy for linear polarimetry; however it is only a rough approximation in the case of nearly circular polarimetry. [ABSTRACT FROM AUTHOR]

The scanning probe electron energy spectra for micron-sized Ag islands on highly ordered pyrolytic graphite substrate are measured. One- and two-dimensional relative intensity distributions for Ag or graphite plasmon peaks have been acquired and a lateral resolution of 4.8±2.4 μm has been achieved. It is the first time for the scanning probe electron energy spectroscopy technique to obtain the spatially resolved electron energy spectra with elemental contrast for a surface, which demonstrates the possibility of the element identification for the scanning tunneling microscope. [ABSTRACT FROM AUTHOR]

We have developed a cold-target recoil-ion momentum spectroscopy apparatus dedicated to the experiments using the extreme-ultraviolet light pulses at the free-electron laser facility, SPring-8 Compact SASE Source test accelerator, in Japan and used it to measure spatial distributions of fundamental, second, and third harmonics at the end station. [ABSTRACT FROM AUTHOR]

In this article, a novel time-of-flight spectrometer for two-electron-emission (e,2e/γ,2e) correlation spectroscopy from surfaces at low electron energies is presented. The spectrometer consists of electron optics that collect emitted electrons over a solid angle of approximately 1 sr and focus them onto a multichannel plate using a reflection technique. The flight time of an electron with kinetic energy of Ekin≃25 eV is around 100 ns. The corresponding time- and energy resolution are typically ≈1 ns and ≈0.65 eV, respectively. The first (e,2e) data obtained with the present setup from a LiF film are presented. [ABSTRACT FROM AUTHOR]

Experiments on the multiterawatt (MTW) laser at the Laboratory for Laser Energetics will study the effect of the focal-spot shape on the forward acceleration and collimation of electrons. A compact electron spectrometer has been developed to record the energy spectra of electrons ejected in the interaction of the laser at multiple angular locations simultaneously. The modular system with replaceable magnets provides an adjustable energy band, currently 0.2–6 MeV. The detector is an array of imaging plates. The device is designed to operate in the high-noise environment (bremsstrahlung and Compton x rays, gamma rays, and scattered electrons), while being compact enough to fit in the 30 cm radius MTW target chamber. The detector geometry and shielding were optimized with the particle/radiation transport code GEANT4. Calibration was performed with beta sources. The required dynamic range, sensitivity, and resolution were confirmed with initial MTW experimental data. [ABSTRACT FROM AUTHOR]

Spin noise spectroscopy in semiconductors is an optical method that allows nearly perturbation free measurements of the spin dynamics of electrons in thermal equilibrium. The article explains the basic principles of spin noise spectroscopy and introduces an optimized experimental setup which promotes spin noise spectroscopy to an extraordinary sensitive tool. Exemplary measurements on n-doped bulk GaAs yield the temperature dependence of the electron spin relaxation time and the electron Landé g factor and reveal a dependence of the spin relaxation time on the laser probe wavelength. The magnitude and wavelength dependence of the measured spin noise signal compares well to basic calculations. [ABSTRACT FROM AUTHOR]

A power switching system has been developed to reverse the voltage polarity on the sample holder of PISCES-B from negative to positive potential in the microsecond time scale. Positive biasing draws electrons from the steady-state plasma through the sample, creating Ohmic heating on the surface. This pulsed biasing is used to replicate the transient heat loads that will be seen on plasma facing components during transient events, such as edge localized modes, in a device such as ITER. Surface temperatures are measured using two pyrometry techniques, a fast two-color system and a slower, more sensitive spectral system. [ABSTRACT FROM AUTHOR]

Simulations indicate that during flattop current discharges the optimal angles for the aiming of the National Spherical Torus Experiment (NSTX) antennae are quite rugged and basically independent of time. The time development of electron Bernstein wave emission (EBWE) at particular frequencies as well as the frequency spectrum of EBWE as would be seen by the recently installed NSTX antennae are computed. The simulation of EBWE at low frequencies (e.g., 16 GHz) agrees well with the recent preliminary EBWE measurements on NSTX. At high frequencies, the sensitivity of EBWE to magnetic field variations is understood by considering the Doppler broadened electron cyclotron harmonics and the cutoffs and resonances in the plasma. Significant EBWE variations are seen if the magnetic field is increased by as little as 2% at the plasma edge. The simulations for the low frequency antenna are compared to preliminary experimental data published separately by Diem et al. [Rev. Sci. Instrum.77 (2006)] [ABSTRACT FROM AUTHOR]

We developed a time-of-flight electron spectrometer optimized for the detection of photoelectrons generated with femtosecond laser-generated extreme ultraviolet pulses. The low number of electrons requires an electrostatic lens design with a very high transmission over a broad energy range. We show that with an asymmetric lens geometry the chromatic aberration can be reduced and the overall transmission be increased. The setup can be further optimized employing a closed-loop optimization with an evolutionary algorithm to increase the throughput by varying the voltages applied to the lens plates. [ABSTRACT FROM AUTHOR]

A PC based data acquisition cum control system has been developed using a general purpose interface bus (GPIB/IEEE-488/IEC-625) plug in card and GPIB interfaceable NIM electronics for use in experiments on absorption spectroscopy studies of molecules using laser-induced fluorescence (LIF), resonance multiphoton ionization (REMPI), electron impact ionization and dissociative attachment from the ground state as well as from excited states, to name a few examples. Unlike commercially available multichannel scalers, this system can handle several parameters as the acquisition parameter (e.g., dye laser) is scanned over the desired wavelength in preselected segments saving precious data acquisition time. This system has been tested on laser excited dissociative electron attachment experiments. [ABSTRACT FROM AUTHOR]

Velocity focusing of electrons is combined with photoelectron photoion coincidence (PEPICO) spectroscopy to achieve a true threshold PEPICO signal without contributions from energetic electrons. Ions are generated by a continuous vacuum ultraviolet light source. Electrons, extracted by a field of 20 V/cm, pass through a 13 cm drift region and are dispersed in space on a multichannel plate detector by velocity focusing optics. The ions are extracted in the opposite direction by the same electric field, further accelerated by a second field, and collected after passing through a 30 cm drift region. Ions are measured in coincidence with electrons collected from the central 3.2 mm electrode as well as a ring electrode (inner and outer diameters of 5.6 and 8.1 mm). The central ring electrode contains mostly true threshold electrons along with a background of "hot" electrons, whereas the outer ring electrode collects only hot electrons. By subtracting the latter from the former, true threshold photoelectron photoion coincidence spectra are obtained. The major advantages of this approach are the high electron energy resolution with the use of high direct current extraction fields, and the complete suppression of energetic electrons. [ABSTRACT FROM AUTHOR]

Describes the design and the operation of an original, high transmission, electrostatic 'double toroidal' electron energy analyzer. High resolution and high luminosity simultaneous measurement of the kinetic energy and angular distribution of electrons; Use of a two-dimensional position sensitive detector; Shape of the electrodes deduced from analytical and numerical electron trajectory calculations.

We describe the construction and operation of a UHV system for bremsstrahlung isochromat spectroscopy in the x-ray regime (1463 eV) with spin-polarized electrons. The performance of the system is illustrated with measurements on Ni(110). The implications of this new technique to study magnetic properties through the spin-resolved electronic structure of the (near) surface are discussed. [ABSTRACT FROM AUTHOR]

A microwave ion source is one of the long-life ion sources. In this paper, we report on the characteristics of the extracted Ar ion beam produced by a microwave ion source under various conditions, in terms of magnetic flux distribution and mass flow, and the stability of the ion beam. The measured spectra show that, under the experimental condition, almost all of produced ions were Ar+ ions. For more than 6 h, the ion beam was stable. [ABSTRACT FROM AUTHOR]

This paper presents the results of time-of-flight mass spectrometry studies of the elemental and mass-to-charge state compositions of metal ion beams produced by a vacuum arc ion source with compound cathode (WC–Co0.5, Cu–Cr0.25, Ti–Cu0.1). We found that the ion beam composition agrees well with the stoichiometric composition of the cathode material from which the beam is derived, and the maximum ion charge state of the different plasma components is determined by the ionization capability of electrons within the cathode spot plasma, which is common to all components. The beam mass-to-charge state spectrum from a compound cathode features a greater fraction of multiply charged ions for those materials with lower electron temperature in the vacuum arc cathode spot, and a smaller fraction for those with higher electron temperature within the spot. We propose a potential diagram method for determination of attainable ion charge states for all components of the compound cathodes. [ABSTRACT FROM AUTHOR]

A new experimental setup for probing multielectron processes in molecular inner-shell ionization regions has been developed. Symmetry-resolved zero-kinetic-energy (ZEKE) spectra have been measured by scanning the photon energy along with monitoring the intensity of the coincidence signals between ZEKE electrons and fragment ions detected at 0° and 90° relative to the electric vector of the light. The actual performance of the method is illustrated by using it to reveal the symmetry decomposition of the multielectron processes, such as double excitations and shake-up satellites, in the K-shell ionization region of nitrogen. [ABSTRACT FROM AUTHOR]

Spherically bent mica and quartz crystals have provided time-integrated spectra and monochromatic images in self-radiation of wire array z-pinch implosions on the MAGPIE generator (1 MA, 240 ns) at Imperial College. Diagnostics based on spherically bent crystals offer higher efficiencies than those based on flat or convex dispersion elements, allowing positioning far from the pinch with good debris shielding. A mica crystal spectrometer produced an image of the pinch in each emission line with about 100 μm axial resolution. Combining the results of monochromatic imaging and spectra confirmed the presence of bright spots, probably generated by energetic electrons inside the pinch. [ABSTRACT FROM AUTHOR]

The effect of strongly magnetized electrons on the spectrum of collective electron density fluctuations can be used to measure the magnetic field direction in a plasma with laser light scattering. The application of this method to measure the poloidal field in tokamaks is discussed. It is shown that noncircular beam cross sections will increase the angular resolution without loss in spatial resolution. In experiments to measure the ion temperature this technique results in an increase of scattered power received. The magnetic field direction was measured for the first time in a laboratory plasma using a pulsed CO[sub 2] laser and coherent detection. [ABSTRACT FROM AUTHOR]