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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 8 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 9 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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Multipurpose furnace for in situ studies of polycrystalline materials using synchrotron radiation

Hemant Sharma, Alix C. Wattjes, Murugaiyan Amirthalingam, Thim Zuidwijk, Nico Geerlofs, and S. Erik Offerman

Rev. Sci. Instrum. 80, 123301 (2009); http://dx.doi.org/10.1063/1.3262501 (7 pages) | Cited 4 times

Online Publication Date: 2 December 2009

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We report a multipurpose furnace designed for studies using synchrotron radiation on polycrystalline materials, namely, metals, ceramics, and (semi)crystalline polymers. The furnace has been designed to carry out three-dimensional (3D) x-ray diffraction measurements but can also be used for other types of synchrotron radiation research. The furnace has a very low thermal gradient across the specimen (<0.2 °C/mm). Accurate determination of the temperature can be carried out by welding a thermocouple to the specimen. The furnace can be rotated over an angle of 90° in order to determine the crystallographic orientation of each individual grain. It is possible to follow growth kinetics of all grains in the illuminated volume of the specimen. The specimen environment can be controlled varying from vacuum (up to 10−5 mbar) to gas or air filled. The maximum temperature of operation is 1500 °C, with the possibility of achieving high heating (up to 20 °C/s) and cooling rates (up to 30 °C/s without quenching gas). 3D maps of the microstructure of the specimen can be generated at elevated temperatures by bringing the high-resolution detector close to the specimen. We show an example of a simulation of the heat affected zone during the thermal cycle of a weld in a transformation-induced plasticity steel carried out using the furnace. The unique characteristics of the furnace open possibility of new fields in materials research using synchrotron radiation.
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07.20.Hy Furnaces; heaters
07.85.Jy Diffractometers

The quality factor of a superconducting rf resonator in a magnetic field

S. Ulmer, H. Kracke, K. Blaum, S. Kreim, A. Mooser, W. Quint, C. C. Rodegheri, and J. Walz

Rev. Sci. Instrum. 80, 123302 (2009); http://dx.doi.org/10.1063/1.3271537 (8 pages) | Cited 6 times

Online Publication Date: 11 December 2009

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The quality factor of a superconducting NbTi resonator at 1.6 MHz in a magnetic field up to 1.2 T as well as its temperature dependence is investigated. A hysteresis effect in the superconducting surface resistance as a function of the magnetic field is observed. An unloaded Q-value of the resonator of 40 500 is achieved at 3.9 K. It is shown that this Q-value is limited by dielectric losses in the FORMVAR insulation of the coils wire. The details of the Q-value optimization are discussed. In the temperature dependence of the Q-value a steep decrease is observed above T ≈ 7.5 K. Finally, the implications of these measurements for real trap experiments are discussed in detail.
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85.25.-j Superconducting devices

A new particle size analyzer

Ebrahim Abedini and Mahmoud Tabrizchi

Rev. Sci. Instrum. 80, 123303 (2009); http://dx.doi.org/10.1063/1.3272784 (4 pages)

Online Publication Date: 14 December 2009

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A new particle sizer which integrates the dispersion and detection parts is presented. Particles are dispersed based on charging between two parallel plates connected to a high voltage power source. The charged particles bounce between the two plates and escape into a measuring area where the size is determined by light scattering. The instrument is calibrated using standard powders. The data obtained from the new instrument are in good agreement with those obtained from a commercial particle size analyzer. The sizer works both for insulator and conductive powders.
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06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)

Observation of pulsed x-ray trains produced by laser-electron Compton scatterings

Kazuyuki Sakaue, Masakazu Washio, Sakae Araki, Masafumi Fukuda, Yasuo Higashi, Yosuke Honda, Tsunehiko Omori, Takashi Taniguchi, Nobuhiro Terunuma, Junji Urakawa, and Noboru Sasao

Rev. Sci. Instrum. 80, 123304 (2009); http://dx.doi.org/10.1063/1.3272789 (7 pages) | Cited 8 times

Online Publication Date: 17 December 2009

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X-ray generation based on laser-electron Compton scattering is one attractive method to achieve a compact laboratory-sized high-brightness x-ray source. We have designed, built, and tested such a source; it combines a 50 MeV multibunch electron linac with a mode-locked 1064 nm laser stored and amplified in a Fabry–Pérot optical cavity. We directly observed trains of pulsed x rays using a microchannel plate detector; the resultant yield was found to be 1.2×105 Hz in good agreement with prediction. We believe that the result has demonstrated good feasibility of linac-based compact x-ray sources via laser-electron Compton scatterings.
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29.20.Ej Linear accelerators
41.75.Fr Electron and positron beams
29.27.Eg Beam handling; beam transport
07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors

High intensity electron cyclotron resonance proton source for low energy high intensity proton accelerator

P. Roychowdhury and D. P. Chakravarthy

Rev. Sci. Instrum. 80, 123305 (2009); http://dx.doi.org/10.1063/1.3272786 (8 pages) | Cited 1 time

Online Publication Date: 28 December 2009

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Electron cyclotron resonance (ECR) proton source at 50 keV, 50 mA has been designed, developed, and commissioned for the low energy high intensity proton accelerator (LEHIPA). Plasma characterization of this source has been performed. ECR plasma was generated with 400–1100 W of microwave power at 2.45 GHz, with hydrogen as working gas. Microwave was fed in the plasma chamber through quartz window. Plasma density and temperature was studied under various operating conditions, such as microwave power and gas pressure. Langmuir probe was used for plasma characterization using current voltage variation. The typical hydrogen plasma density and electron temperature measured were 7×1011 cm−3 and 6 eV, respectively. The total ion beam current of 42 mA was extracted, with three-electrode extraction geometry, at 40 keV of beam energy. The extracted ion current was studied as a function of microwave power and gas pressure. Depending on source pressure and discharge power, more than 30% total gas efficiency was achieved. The optimization of the source is under progress to meet the requirement of long time operation. The source will be used as an injector for continuous wave radio frequency quadrupole, a part of 20 MeV LEHIPA. The required rms normalized emittance of this source is less than 0.2 π mm mrad. The simulated value of normalized emittance is well within this limit and will be measured shortly. This paper presents the study of plasma parameters, first beam results, and the status of ECR proton source.
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52.50.Dg Plasma sources
52.70.Ds Electric and magnetic measurements
52.25.-b Plasma properties
52.65.-y Plasma simulation
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Three-dimensional photogrammetric measurement of magnetic field lines in the WEGA stellarator

Peter Drewelow, Torsten Bräuer, Matthias Otte, Friedrich Wagner, and Andreas Werner

Rev. Sci. Instrum. 80, 123501 (2009); http://dx.doi.org/10.1063/1.3263820 (7 pages) | Cited 1 time

Online Publication Date: 7 December 2009

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The magnetic confinement of plasmas in fusion experiments can significantly degrade due to perturbations of the magnetic field. A precise analysis of the magnetic field in a stellarator-type experiment utilizes electrons as test particles following the magnetic field line. The usual fluorescent detector for this electron beam limits the provided information to two-dimensional cut views at certain toroidal positions. However, the technique described in this article allows measuring the three-dimensional structure of the magnetic field by means of close-range photogrammetry. After testing and optimizing the main diagnostic components, measurements of the magnetic field lines were accomplished with a spatial resolution of 5 mm. The results agree with numeric calculations, qualifying this technique as an additional tool to investigate magnetic field configurations in a stellarator. For a possible future application, ways are indicated on how to reduce experimental error sources.
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52.55.Jd Magnetic mirrors, gas dynamic traps
52.55.-s Magnetic confinement and equilibrium
52.70.-m Plasma diagnostic techniques and instrumentation

Compact multiwire proportional counters for the detection of fission fragments

Akhil Jhingan, P. Sugathan, K. S. Golda, R. P. Singh, T. Varughese, Hardev Singh, B. R. Behera, and S. K. Mandal

Rev. Sci. Instrum. 80, 123502 (2009); http://dx.doi.org/10.1063/1.3263911 (8 pages) | Cited 2 times

Online Publication Date: 7 December 2009

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Two large area multistep position sensitive (two dimensional) multiwire proportional counters have been developed for experiments involving study of fission dynamics using general purpose scattering chamber facility at IUAC. Both detectors have an active area of 20×10 cm2 and provide position signals in horizontal (X) and vertical (Y) planes, timing signal for time of flight measurements and energy signal giving the differential energy loss in the active volume. The design features are optimized for the detection of low energy heavy ions at very low gas pressures. Special care was taken in setting up the readout electronics, constant fraction discriminators for position signals in particular, to get optimum position and timing resolutions along with high count rate handling capability of low energy heavy ions. A custom made charge sensitive preamplifier, having lower gain and shorter decay time, has been developed for extracting the differential energy loss signal. The position and time resolutions of the detectors were determined to be 1.1 mm full width at half maximum (FWHM) and 1.7 ns FWHM, respectively. The detector could handle heavy ion count rates exceeding 20 kHz without any breakdown. Time of flight signal in combination with differential energy loss signal gives a clean separation of fission fragments from projectile and target like particles. The timing and position signals of the detectors are used for fission coincidence measurements and subsequent extraction of their mass, angular, and total kinetic energy distributions. This article describes systematic study of these fission counters in terms of efficiency, time resolution, count rate handling capability, position resolution, and the readout electronics. The detector has been operated with both five electrode geometry and four electrode geometry, and a comparison has been made in their performances.
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29.40.Cs Gas-filled counters: ionization chambers, proportional, and avalanche counters
29.40.Gx Tracking and position-sensitive detectors
07.68.+m Photography, photographic instruments; xerography
84.30.Qi Modulators and demodulators; discriminators, comparators, mixers, limiters, and compressors
84.30.Le Amplifiers

Flexible CO2 laser system for fundamental research related to an extreme ultraviolet lithography source

Y. Tao, M. S. Tillack, N. Amin, R. A. Burdt, S. Yuspeh, N. M. Shaikh, and F. Najmabadi

Rev. Sci. Instrum. 80, 123503 (2009); http://dx.doi.org/10.1063/1.3270257 (6 pages) | Cited 4 times

Online Publication Date: 10 December 2009

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A CO2 laser system with flexible parameters was developed for fundamental research related to an extreme ultraviolet (EUV) lithography source. The laser is a master oscillator and power amplifier (MOPA) system, consisting of a master oscillator, an externally triggered plasma switch, a preamplifier, a main amplifier, and electronic synchronization units. The laser pulse duration can be varied easily from 10 to 110 ns, with a constant peak power for pulse durations from 25 to 110 ns. The MOPA laser system can also be operated in dual-oscillator mode to produce laser pulse with pulse duration as long as 200ns and a train of laser pulses with flexible interval. The divergence of the laser beam is 1.3 times the diffraction limit. The laser intensity on the target surface can be up to 8×1010 W/cm2. Utilizing this CO2 MOPA laser system, high conversion efficiency from laser to in-band (2% bandwidth) 13.5 nm EUV emission has been demonstrated over a wide range of laser pulse durations.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.60.By Design of specific laser systems
42.62.-b Laser applications
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Hybrid radio-frequency/direct-current plasma-enhanced chemical vapor deposition system for deposition on inner surfaces of polyethylene terephthalate bottles

Jing Li, Xiubo Tian, Chunzhi Gong, Shiqin Yang, Ricky K. Y. Fu, and Paul K. Chu

Rev. Sci. Instrum. 80, 123504 (2009); http://dx.doi.org/10.1063/1.3273944 (4 pages)

Online Publication Date: 16 December 2009

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A hybrid radio-frequency (rf)/direct-current (dc) system has been developed to control the biasing effects during deposition of diamondlike carbon (DLC) films onto the inner wall of polyethylene terephthalate (PET) bottles. An additional dc bias is coupled to the rf electrode to produce the effect of equivalent rf self-biasing. This allows more flexible control of the deposition of the DLC films which are intended to improve the gas barrier characteristics. The experimental results demonstrate that the additional dc bias improves the adhesion strength between the DLC film and PET, although the enhancement in the gas barrier properties is not significantly larger compared to the one without dc bias. The apparatus and methodology have practical importance in the food and beverage industry.
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68.55.aj Insulators
61.41.+e Polymers, elastomers, and plastics
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
52.77.Dq Plasma-based ion implantation and deposition

Axial x-ray backlighting of wire-array Z-pinches using X pinches

I. C. Blesener, J. B. Greenly, S. A. Pikuz, T. A. Shelkovenko, S. Vishniakou, D. A. Hammer, and B. R. Kusse

Rev. Sci. Instrum. 80, 123505 (2009); http://dx.doi.org/10.1063/1.3271388 (5 pages) | Cited 3 times

Online Publication Date: 23 December 2009

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For the first time, a geometry has been developed to allow for an axial imaging system for wire-array Z-pinch experiments that produce high-resolution x-ray images. The new geometry required a significant redesign of the electrode hardware. Calibrated areal density measurements of the Z-pinch plasma including wire cores, coronal plasma, streaming plasma, and the precursor were obtained. The system used eight-wire molybdenum (Mo) X pinches in series with and directly below the Z-pinch axis to provide micron-scale x-rays sources for point-projection radiography. The images formed on the x-ray sensitive film had a 15 mm diameter field of view at the center height of the array and a magnification of about 7.5:1. Titanium (Ti) filters in front of the film transmitted radiation in the spectral range of 3–5 keV. For calibration, a separate film with the same thickness Ti filter was placed the same distance from the X pinch. This film had an unobstructed path that bypasses the Z-pinch but included step wedges for calibration of the Z-pinch plasma. The step wedges had thicknesses of tungsten (W) ranging from 0.015 to 1.1 μm to obtain areal density measurements of the W plasma from the wire-array. Images had subnanosecond temporal resolution and about 10 μm spatial resolution.
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52.75.-d Plasma devices
06.20.fb Standards and calibration
52.80.Hc Glow; corona
52.59.Qy Wire array Z-pinches
07.85.-m X- and γ-ray instruments

Fast scanning probe for the NSTX spherical tokamak

J. A. Boedo, N. Crocker, L. Chousal, R. Hernandez, J. Chalfant, H. Kugel, P. Roney, and J. Wertenbaker

Rev. Sci. Instrum. 80, 123506 (2009); http://dx.doi.org/10.1063/1.3266065 (10 pages) | Cited 2 times

Online Publication Date: 31 December 2009

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We describe a fast reciprocating Langmuir probe and drive system, which has four main new features: (1) use of high-temperature, vacuum, circuit boards instead of cables to reduce weight and increase to 21 the number of possible connections, (2) rotatable and removable shaft, (3) 10 tip construction with designed hardware bandwidth up to 10 MHz, and (4) a detachable and modular tip assembly for easy maintenance. The probe is mounted in a fast pneumatic drive capable of speeds ∼ 7 m/s and ∼ 20g’s acceleration in order to reach the scrape-off layer (SOL) and pedestal regions and remain inserted long enough to obtain good statistics while minimizing the heat deposition to the tips and head in a power density environment of 1–10 MW/m2. The National Spherical Torus Experiment SOL features electron temperature, Te ∼ 10–30 eV, and electron density, ne ∼ 0.1–5×1012 cm−3 while the pedestal features ne ∼ 0.5–1.5×1013 cm−3 and Te ∼ 30–150 eV. The probe described here has ten tips which obtain a wide spectrum of plasma parameters: electron temperature profile Te(r), electron density profile ne(r) and Mach number profile M(r), floating potential Vf(r), poloidal and radial electric field profiles Eθ(r) and Eρ(r), saturation current profile Isat(r), and their fluctuations up to 3 MHz. We describe the probe and show representative radial profiles of various parameters.
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52.70.Ds Electric and magnetic measurements
52.40.Hf Plasma-material interactions; boundary layer effects
52.55.Fa Tokamaks, spherical tokamaks

A high resolution Mirnov array for the Mega Ampere Spherical Tokamak

M. J. Hole, L. C. Appel, and R. Martin

Rev. Sci. Instrum. 80, 123507 (2009); http://dx.doi.org/10.1063/1.3272713 (10 pages) | Cited 3 times

Online Publication Date: 31 December 2009

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Over the past two decades, the increase in neutral-beam heating and α particle production in magnetically confined fusion plasmas has led to an increase in energetic particle driven mode activity, much of which has an electromagnetic signature which can be detected by the use of external Mirnov coils. Typically, the frequency and spatial wave number band of such oscillations increase with increasing injection energy, offering new challenges for diagnostic design. In particular, as the frequency approaches the megahertz range, care must be taken to model the stray capacitance of the coil, which limits the resonant frequency of the probe; model transmission line effects in the system, which if unchecked can produce system resonances; and minimize coil conductive shielding, so as to minimize skin currents which limit the frequency response of the coil. As well as optimizing the frequency response, the coils should also be positioned to confidently identify oscillations over a wide wave number band. This work, which draws on new techniques in stray capacitance modeling and coil positioning, is a case study of the outboard Mirnov array for high-frequency acquisition in the Mega Ampere Spherical Tokamak, and is intended as a roadmap for the design of high frequency, weak field strength magnetic diagnostics.
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52.55.Fa Tokamaks, spherical tokamaks
52.70.Ds Electric and magnetic measurements
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)
52.25.Fi Transport properties
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Antiproton, positron, and electron imaging with a microchannel plate/phosphor detector

G. B. Andresen, W. Bertsche, P. D. Bowe, C. C. Bray, E. Butler, C. L. Cesar, S. Chapman, M. Charlton, S. Seif El Nasr, J. Fajans, M. C. Fujiwara, D. R. Gill, J. S. Hangst, W. N. Hardy, R. S. Hayano, et al.

Rev. Sci. Instrum. 80, 123701 (2009); http://dx.doi.org/10.1063/1.3266967 (5 pages) | Cited 7 times

Online Publication Date: 1 December 2009

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A microchannel plate (MCP)/phosphor screen assembly has been used to destructively measure the radial profile of cold, confined antiprotons, electrons, and positrons in the ALPHA experiment, with the goal of using these trapped particles for antihydrogen creation and confinement. The response of the MCP to low energy (10–200 eV, <1 eV spread) antiproton extractions is compared to that of electrons and positrons.
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14.20.Dh Protons and neutrons
29.25.-t Particle sources and targets
14.60.Cd Electrons (including positrons)

A benchtop, ultrafast infrared spectroscopic imaging system for biomedical applications

Hemmel Amrania, Andrew McCrow, and Chris Phillips

Rev. Sci. Instrum. 80, 123702 (2009); http://dx.doi.org/10.1063/1.3262499 (6 pages) | Cited 2 times

Online Publication Date: 7 December 2009

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We discuss the potential biomedical applications for a novel infrared spectroscopic microimaging system. A tunable, table top solid-state laser has been coupled to a commercial infrared microscope, fitted with a modified high resolution infrared camera, to create a unique tool for midinfrared imaging. The system is capable of performing broadband imaging at a diffraction-limited spatial resolution, as is demonstrated here by spatially resolved spectroscopy of polymer test samples with a spectral resolution of 20 cm−1. The large pulse energies (tens of microjoules) offer previously unobtainable combinations of high signal-to-noise levels and rapid data collection times which are superior to current stand-alone laboratory instruments by many decades. Coupled with the short (100 ps) short pulse duration, these characteristics promise to make a wide range of time-resolved and reflection mode imaging experiments possible with live biological systems.
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87.63.lt Laser imaging
87.64.km Infrared
87.64.M- Optical microscopy
42.62.Be Biological and medical applications
87.57.cf Spatial resolution

Photoemission electron microscopy using extreme ultraviolet attosecond pulse trains

A. Mikkelsen, J. Schwenke, T. Fordell, G. Luo, K. Klünder, E. Hilner, N. Anttu, A. A. Zakharov, E. Lundgren, J. Mauritsson, J. N. Andersen, H. Q. Xu, and A. L’Huillier

Rev. Sci. Instrum. 80, 123703 (2009); http://dx.doi.org/10.1063/1.3263759 (7 pages) | Cited 14 times

Online Publication Date: 11 December 2009

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We report the first experiments carried out on a new imaging setup, which combines the high spatial resolution of a photoemission electron microscope (PEEM) with the temporal resolution of extreme ultraviolet (XUV) attosecond pulse trains. The very short pulses were provided by high-harmonic generation and used to illuminate lithographic structures and Au nanoparticles, which, in turn, were imaged with a PEEM resolving features below 300 nm. We argue that the spatial resolution is limited by the lack of electron energy filtering in this particular demonstration experiment. Problems with extensive space charge effects, which can occur due to the low probe pulse repetition rate and extremely short duration, are solved by reducing peak intensity while maintaining a sufficient average intensity to allow imaging. Finally, a powerful femtosecond infrared (IR) beam was combined with the XUV beam in a pump-probe setup where delays could be varied from subfemtoseconds to picoseconds. The IR pump beam could induce multiphoton electron emission in resonant features on the surface. The interaction between the electrons emitted by the pump and probe pulses could be observed.
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68.37.Xy Scanning Auger microscopy, photoelectron microscopy
06.60.Jn High-speed techniques (microsecond to femtosecond)
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
79.60.Jv Interfaces; heterostructures; nanostructures

Simple and efficient scanning tunneling luminescence detection at low-temperature

J. G. Keizer, J. K. Garleff, and P. M. Koenraad

Rev. Sci. Instrum. 80, 123704 (2009); http://dx.doi.org/10.1063/1.3274675 (5 pages)

Online Publication Date: 28 December 2009

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We have designed and built an optical system to collect light that is generated in the tunneling region of a low-temperature scanning tunneling microscope. The optical system consists of an in situ lens placed approximately 1.5 cm from the tunneling region and an ex situ optical lens system to analyze the emitted light, for instance, by directing the light into a spectrometer. As a demonstration, we measured tip induced photoluminescence spectra of a gold surface. Furthermore, we demonstrate that we can simultaneously record scanning tunneling microscope induced luminescence and topography of the surface both with atomic resolution.
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68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
42.79.Bh Lenses, prisms and mirrors
78.55.Hx Other solid inorganic materials
68.35.bd Metals and alloys
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