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Dec 2009

Volume 80, Issue 12, Articles (12xxxx)

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Application of a simple asynchronous mechanical light chopper to multielectron coincidence spectroscopy

Kenji Ito, Francis Penent, Yasumasa Hikosaka, Eiji Shigemasa, Isao H. Suzuki, John H. D. Eland, and Pascal Lablanquie

Rev. Sci. Instrum. 80, 123101 (2009); http://dx.doi.org/10.1063/1.3258200 (9 pages) | Cited 7 times

Online Publication Date: 1 December 2009

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A simple asynchronous mechanical light chopper, based on modification of a turbo-molecular pump, has been developed to extend the interval between light pulses in single bunch operation at the Photon Factory storage ring. A pulse repetition rate of 80 kHz was achieved using a cylinder rotating at 48000 rpm, with 100 slits of 80 μm width. This allows absolute timing of particles up to 12.48 μs instead of the single-bunch period of 624 ns. We have applied the chopper together with a light pulse monitor to measure multielectron coincidence spectra using a magnetic bottle time-of-flight electron spectrometer. With such a system, the electron energies are determined without any ambiguity, the folding of coincidence spectra disappears and the effect of false coincidences is drastically reduced.
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07.81.+a Electron and ion spectrometers
41.85.-p Beam optics
42.50.Wk Mechanical effects of light on material media, microstructures and particles

Solid and liquid spectroscopic analysis (SALSA)–a soft x-ray spectroscopy endstation with a novel flow-through liquid cell

M. Blum, L. Weinhardt, O. Fuchs, M. Bär, Y. Zhang, M. Weigand, S. Krause, S. Pookpanratana, T. Hofmann, W. Yang, J. D. Denlinger, E. Umbach, and C. Heske

Rev. Sci. Instrum. 80, 123102 (2009); http://dx.doi.org/10.1063/1.3257926 (6 pages) | Cited 12 times

Online Publication Date: 3 December 2009

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We present a novel synchrotron endstation with a flow-through liquid cell designed to study the electronic structure of liquids using soft x-ray spectroscopies. In this cell, the liquid under study is separated from the vacuum by a thin window membrane, such that the sample liquid can be investigated at ambient pressure. The temperature of the probing volume can be varied in a broad range and with a fast temperature response. The optimized design of the cell significantly reduces the amount of required sample liquid and allows the use of different window membrane types necessary to cover a broad energy range. The liquid cell is integrated into the solid and liquid spectroscopic analysis (SALSA) endstation that includes a high-resolution, high-transmission x-ray spectrometer and a state-of-the-art electron analyzer. The modular design of SALSA also allows the measurement of solid-state samples. The capabilities of the liquid cell and the x-ray spectrometer are demonstrated using a resonant inelastic x-ray scattering map of a 25 wt % NaOD solution.
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07.85.Nc X-ray and γ-ray spectrometers
29.20.dk Synchrotrons
78.70.Ck X-ray scattering

Resonant photoacoustic cell for pulsed laser analysis of gases at high temperature

Tapio Sorvajärvi, Albert Manninen, Juha Toivonen, Jaakko Saarela, and Rolf Hernberg

Rev. Sci. Instrum. 80, 123103 (2009); http://dx.doi.org/10.1063/1.3266974 (5 pages) | Cited 3 times

Online Publication Date: 7 December 2009

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A new approach to high temperature gas analysis by means of photoacoustic (PA) spectroscopy is presented. The transverse modes of the resonant PA cell were excited with a pulsed laser and detected with a microphone. Changes in the properties of the PA cell resulting from a varying temperature are discussed and considered when processing the PA signal. The feasibility of the proposed method was demonstrated by studying PA response from saturated vapor of potassium chloride (KCl) in the temperature range extending from 410 to 691 °C. The PA spectrum, the detection limit, and the signal saturation of KCl vapor are discussed. At 245 nm excitation wavelength and 300 μJ pulse energy, the achieved detection limit for KCl is 15 ppb.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
07.20.Ka High-temperature instrumentation; pyrometers
43.58.Kr Spectrum and frequency analyzers and filters; acoustical and electrical oscillographs; photoacoustic spectrometers; acoustical delay lines and resonators
43.60.Qv Signal processing instrumentation, integrated systems, smart transducers, devices and architectures, displays and interfaces for acoustic systems
82.80.Kq Energy-conversion spectro-analytical methods (e.g., photoacoustic, photothermal, and optogalvanic spectroscopic methods)
85.50.-n Dielectric, ferroelectric, and piezoelectric devices

Frequency-agile terahertz-wave parametric oscillator in a ring-cavity configuration

Hiroaki Minamide, Tomofumi Ikari, and Hiromasa Ito

Rev. Sci. Instrum. 80, 123104 (2009); http://dx.doi.org/10.1063/1.3271039 (5 pages) | Cited 8 times

Online Publication Date: 7 December 2009

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We demonstrate a frequency-agile terahertz wave parametric oscillator (TPO) in a ring-cavity configuration (ring-TPO). The TPO consists of three mirrors and a MgO:LiNbO3 crystal under noncollinear phase-matching conditions. A novel, fast frequency-tuning method was realized by controlling a mirror of the three-mirror ring cavity. The wide tuning range between 0.93 and 2.7 THz was accomplished. For first demonstration using the ring-TPO, terahertz spectroscopy was performed as the verification of the frequency-agile performance, measuring the transmission spectrum of the monosaccharide glucose. The spectrum was obtained within about 8 s in good comparison to those of Fourier transform infrared spectrometer.
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42.65.Yj Optical parametric oscillators and amplifiers
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.79.Nv Optical frequency converters
42.65.Lm Parametric down conversion and production of entangled photons
42.79.Bh Lenses, prisms and mirrors
33.20.Bx Radio-frequency and microwave spectra

Absolute density-profile tomography of molecular beams using multiphoton ionization

N. E. Schofield, D. M. Paganin, and A. I. Bishop

Rev. Sci. Instrum. 80, 123105 (2009); http://dx.doi.org/10.1063/1.3264079 (7 pages)

Online Publication Date: 7 December 2009

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We describe an approach for the absolute density measurement of rotationally symmetric molecular beams via multiphoton ionization. This simple single-projection tomographic technique requires only knowledge of the spatial intensity profile and ionization characteristics of the focused laser beam that probes the pulsed molecular jet. Multiphoton ionization (MPI) of a xenon beam allowed tomographic reconstruction of a two-dimensional density profile with a peak density of (4.2±0.4)×1018 m−3, which was compared with the theoretical predictions of the sudden freeze model. An analytic solution to the Abel transform is derived for Gaussian projected density profiles which greatly simplifies the reconstruction of the absolute radial density. MPI is sufficiently general that this technique can be readily applied to atomic beams with a broad range of chemistries.
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37.20.+j Atomic and molecular beam sources and techniques
06.30.Dr Mass and density
33.80.Rv Multiphoton ionization and excitation to highly excited states (e.g., Rydberg states)

Frequency-resolved optical gating system with a tellurium crystal for characterizing free-electron lasers in the wavelength range of 10–30 μm

Hokuto Iijima, Ryoji Nagai, Nobuyuki Nishimori, Ryoichi Hajima, and Eisuke J. Minehara

Rev. Sci. Instrum. 80, 123106 (2009); http://dx.doi.org/10.1063/1.3265318 (5 pages)

Online Publication Date: 7 December 2009

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A second-harmonic generation frequency-resolved optical gating (SHG-FROG) system has been developed for the complete characterization of laser pulses in the wavelength range of 10–30 μm. A tellurium crystal is used so that spectrally resolved autocorrelation signals with a good signal-to-noise ratio are obtained. Pulses (wavelength ∼ 22 μm) generated from a free-electron laser are measured by the SHG-FROG system. The SHG intensity profile and the spectrum obtained by FROG measurements are well consistent with those of independent measurements of the pulse length and spectrum. The pulse duration and spectral width determined from the FROG trace are 0.6 ps and 5.2 THz at full width half maximum, respectively.
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41.60.Cr Free-electron lasers
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

Interferometric polarization pulse shaper stabilized by an external laser diode for arbitrary vector field shaping

Masaaki Sato, Takayuki Suzuki, and Kazuhiko Misawa

Rev. Sci. Instrum. 80, 123107 (2009); http://dx.doi.org/10.1063/1.3270254 (6 pages) | Cited 1 time

Online Publication Date: 11 December 2009

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We achieved reliable and stable generation of pulses with all possible polarization states by a Mach–Zehnder pulse shaper. This was realized by incorporating a stabilization mechanism using an external laser diode in the interferometric pulse shaper. This stabilization mechanism has overcome an inherent instability in the Mach–Zehnder interferometer, which caused serious distortion of shaped pulses. For a demonstration of polarization shaping, we generated and measured chiral pulses with a rotating major axis of polarizing orientations at arbitrary frequencies. We expect these chiral pulses enables us to study on new chirality-related light-matter interactions.
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42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.25.Ja Polarization
07.60.Ly Interferometers

Collinear laser spectroscopy of francium using online rubidium vapor neutralization and amplitude modulated lasers

J. F. Sell, K. Gulyuz, and G. D. Sprouse

Rev. Sci. Instrum. 80, 123108 (2009); http://dx.doi.org/10.1063/1.3271037 (5 pages)

Online Publication Date: 11 December 2009

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Performing collinear laser spectroscopy on low intensity radioactive beams requires sensitive detection techniques. We explain our apparatus to detect atomic resonances in neutralized 208–210Fr ion beams at beam energies of 5 keV and intensities of 105 s−1. Efficient neutralization ( ≥ 80%) is accomplished by passing the beam through a dense Rb vapor. Increased detection efficiency is achieved by amplitude modulating the exciting laser to decrease the scattered light background, allowing fluorescence detection only when the laser is near its minimum in the modulation cycle. Using this technique in a collinear geometry we achieve a background reduction by a factor of 180 and a signal-to-noise increase of 2.2, with the lifetime of the atomic state playing a role in the efficiency of this process. Such laser modulation will also produce sidebands on the atomic spectra which we illustrate.
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32.80.-t Photoionization and excitation
32.50.+d Fluorescence, phosphorescence (including quenching)

Time-delay compensated monochromator for the spectral selection of extreme-ultraviolet high-order laser harmonics

Luca Poletto, Paolo Villoresi, Fabio Frassetto, Francesca Calegari, Federico Ferrari, Matteo Lucchini, Giuseppe Sansone, and Mauro Nisoli

Rev. Sci. Instrum. 80, 123109 (2009); http://dx.doi.org/10.1063/1.3273964 (8 pages) | Cited 8 times

Online Publication Date: 15 December 2009

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The design and the characterization of a monochromator for the spectral selection of ultrashort high-order laser harmonics in the extreme ultraviolet are presented. The instrument adopts the double-grating configuration to preserve the length of the optical paths of different diffracted rays, without altering the extremely short duration of the pulse. The gratings are used in the off-plane mount to have high efficiency. The performances of the monochromator have been characterized in terms of spectral response, efficiency, photon flux, imaging properties, and temporal response. In particular, the temporal characterization of the harmonic pulses has been obtained using a cross-correlation method: Pulses as short as 8 fs have been measured at the output of the monochromators, confirming the effectiveness of the time-delay compensated configuration.
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42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
42.88.+h Environmental and radiation effects on optical elements, devices, and systems
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