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Jan 2013

Volume 84, Issue 1, Articles (01xxxx)

Issue Cover Spotlight Figure

Rev. Sci. Instrum. 84, 011101 (2013); http://dx.doi.org/10.1063/1.4765055 (21 pages)

Trevor R. Ireland
An ion’s eye view of an electrostatic quadrupole lens and the mass spectrometer for which the lens was designed. SHRIMP RG is an ion microprobe mass spectrometer used for in situ isotopic analyses of geological materials.
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Invited Review Article: Recent developments in isotope-ratio mass spectrometry for geochemistry and cosmochemistry

Trevor R. Ireland

Rev. Sci. Instrum. 84, 011101 (2013); http://dx.doi.org/10.1063/1.4765055 (21 pages)

Online Publication Date: 2 January 2013

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Mass spectrometry is fundamental to measurements of isotope ratios for applications in isotope geochemistry, geochronology, and cosmochemistry. Magnetic-sector mass spectrometers are most common because these provide the best precision in isotope ratio measurements. Where the highest precision is desired, chemical separation followed by mass spectrometric analysis is carried out with gas (noble gas and stable isotope mass spectrometry), liquid (inductively coupled plasma mass spectrometry), or solid (thermal ionization mass spectrometry) samples. Developments in in situ analysis, including ion microprobes and laser ablation inductively coupled plasma mass spectrometry, have opened up issues concerning homogeneity according to domain size, and allow ever smaller amounts of material to be analyzed. While mass spectrometry is built solidly on developments in the 20th century, there are new technologies that will push the limits in terms of precision, accuracy, and sample efficiency. Developments of new instruments based on time-of-flight mass spectrometers could open up the ultimate levels of sensitivity per sample atom.
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91.67.-y Geochemistry
91.80.+d Geochronology
93.85.-q Instruments and techniques for geophysical research: Exploration geophysics
95.30.Dr Atomic processes and interactions
95.30.Ft Molecular and chemical processes and interactions
95.55.-n Astronomical and space-research instrumentation
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back to top Optics; Atoms and Molecules; Spectroscopy; Photon Detectors

A novel photonic Doppler velocimetry for transverse velocity measurement

Guanghua Chen, Detian Wang, Jun Liu, Jianhua Meng, Shouxian Liu, and Qingguo Yang

Rev. Sci. Instrum. 84, 013101 (2013); http://dx.doi.org/10.1063/1.4776186 (4 pages)

Online Publication Date: 18 January 2013

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A fiber interferometry for transverse velocity measurement has been developed. This diagnostic is similar to photonic Doppler velocimetry in the way in which laser propagates and couples. The interferometer mainly consists of a fiber coupler, an emitting probe, and two receiving probes. A pair of scattered laser beams mix in the coupler and generates fringes with frequency proportional to transverse velocity. Measurement of transverse velocity is independent of longitudinal velocity. The feasibility of the technique has been verified by rotating wheel experiment and shock loading experiment.
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06.30.Gv Velocity, acceleration, and rotation

Automation of an “Aculight” continuous-wave optical parametric oscillator

Alexander M. Morrison, Tao Liang, and Gary E. Douberly

Rev. Sci. Instrum. 84, 013102 (2013); http://dx.doi.org/10.1063/1.4776179 (8 pages) | Cited 2 times

Online Publication Date: 23 January 2013

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We report the automation of a continuous-wave, singly resonant, optical parametric oscillator (Lockheed-Martin Aculight ARGOS 2400-SF-15). This commercially available optical parametric oscillator (OPO) is capable of producing >1 W of continuously tunable idler output between 2.2 and 4.6 μm. An algorithm based on the feedback from a high accuracy wavemeter is implemented to synchronize three separate OPO tuning elements; the translation of a fan-out type periodically poled lithium niobate crystal, the rotation of an intracavity etalon, and the continuous tuning of the pump and idler wavelengths via piezoelectric strain of the tunable fiber pump laser. This allows for several hundred wavenumbers of efficient, automatic, continuous tuning of the idler wave. Continuous feedback from the wavemeter limits the absolute frequency accuracy to ±20 MHz. The broad, automatic tuning of the OPO is demonstrated via its implementation as a probe laser for the infrared action spectroscopy of methanol solvated in helium nanodroplets. LabVIEW virtual instruments for the automation of this OPO laser system are reported, along with detailed schematics of the associated hardware developed at the University of Georgia.
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42.65.Yj Optical parametric oscillators and amplifiers
07.60.Ly Interferometers
42.55.Rz Doped-insulator lasers and other solid state lasers
42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.60.Fc Modulation, tuning, and mode locking

Compensational scintillation detector with a flat energy response for flash X-ray measurements

Liang Chen, Xiaoping Ouyang, Bin Liu, Jinliang Liu, Lin Quan, and Zhongbing Zhang

Rev. Sci. Instrum. 84, 013103 (2013); http://dx.doi.org/10.1063/1.4788730 (5 pages)

Online Publication Date: 25 January 2013

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To measure the intensity of flash X-ray sources directly, a novel scintillation detector with a fast time response and flat energy response is developed by combining film scintillators of doped ZnO crystal and fast organic scintillator together. Through compensation design, the dual-scintillator detector (DSD) achieved a flat energy response to X-rays from tens of keV to several MeV, and sub-nanosecond time response by coupling to ultrafast photo-electronic devices. A prototype detector was fabricated according to the theoretical design; it employed ZnO:In and EJ228 with thicknesses of 0.3 mm and 0.1 mm, respectively. The energy response of this detector was tested on monoenergetic X-ray and γ-ray sources. The detector performs very well with a sensitivity fluctuation below 5% for 8 discrete energy points within the 40–250 keV energy region and for other energies of 662 keV and 1.25 MeV as well, showing good accordance with the theoretical design. Additionally, the detector works properly for the application to the flash X-ray radiation field absolute intensity measurement. This DSD may be very useful for the diagnosis of time-resolved dynamic physical processes of flash X-ray sources without knowing the exact energy spectrum.
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07.85.-m X- and γ-ray instruments

Adaptive femtosecond laser-induced breakdown spectroscopy of uranium

P. Ko, K. C. Hartig, J. P. McNutt, R. B. D. Schur, T. W. Jacomb-Hood, and I. Jovanovic

Rev. Sci. Instrum. 84, 013104 (2013); http://dx.doi.org/10.1063/1.4779042 (6 pages) | Cited 1 time

Online Publication Date: 25 January 2013

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Laser-induced breakdown spectroscopy (LIBS) is an established technique for material characterization applicable to a variety of problems in research, industry, environmental studies, and security. LIBS conducted with femtosecond laser pulses exhibits unique properties, arising from the characteristics of laser-matter interactions in this pulse width regime. The time evolution of the electric field of the pulse determines its interaction with sample materials. We present the design and performance of a femtosecond LIBS system developed to systematically optimize the technique for detection of uranium. Sample analysis can be performed in vacuum environment, and the spectral and temporal diagnostics are coupled through an adaptive feedback loop, which facilitates optimization of the signal-to-noise ratio by pulse shaping. Initial experimental results of LIBS on natural uranium are presented.
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06.60.Jn High-speed techniques (microsecond to femtosecond)
78.47.J- Ultrafast spectroscopy (<1 psec)
02.60.Pn Numerical optimization

Designing an optical set-up of differential laser triangulation for oil film thickness measurement on water

Ge Baozhen, Sun Jingbin, Liu Pengcheng, Lü Qieni, and Wu Di

Rev. Sci. Instrum. 84, 013105 (2013); http://dx.doi.org/10.1063/1.4788937 (6 pages)

Online Publication Date: 30 January 2013

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Based on the differential laser triangulation principle, an optical system configuration for measuring the oil film thickness on water is designed and developed. A semiconductor laser of 650 nm wavelength with the maximum power of 5 mW is used as a light source, the magnification of the imaging system is 1.4; the range of the measurement is 0.1 mm–10 mm; the resolution is 2.3 μm and the measurement accuracy is 10 μm theoretically. Experiments are conducted with block gauges and feeler gauges, and the experimental results, with absolute error less than ±25 μm and the maximal measurable thickness 12 mm, indicate that this system presented in this paper can fulfill high accuracy.
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06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
42.55.Px Semiconductor lasers; laser diodes
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy
47.80.-v Instrumentation and measurement methods in fluid dynamics
back to top Particle Sources, Optics and Acceleration; Particle Detectors

Development of a single-shot-imaging thin film for an online Thomson parabola spectrometer

H. Sakaki, M. Kanasaki, Y. Fukuda, M. Nishiuchi, T. Hori, A. Yogo, S. Jinno, and K. Niita

Rev. Sci. Instrum. 84, 013301 (2013); http://dx.doi.org/10.1063/1.4773546 (7 pages)

Online Publication Date: 9 January 2013

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A single-shot-imaging thin scintillator film was developed for an online Thomson parabola (TP) spectrometer and the first analysis of laser accelerated ions, using the online TP spectrometer, was demonstrated at the JAEA-Kansai Advanced Relativistic Engineering Laser System (J-KAREN). An energy spectrum of ∼4.0 MeV protons is obtained using only this imaging film without the need of a microchannel plate that is typically utilized in online ion analyses. A general-purpose Monte Carlo particle and heavy ion-transport code system, which consists of various quantum dynamics models, was used for the prediction of the luminescent properties of the scintillator. The simulation can reasonably predict not only the ion trajectories detected by the spectrometer, but also luminescence properties.
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07.81.+a Electron and ion spectrometers
61.82.-d Radiation effects on specific materials
72.15.Jf Thermoelectric and thermomagnetic effects

Characterization of Hall effect thruster propellant distributors with flame visualization

S. Langendorf and M. L. R. Walker

Rev. Sci. Instrum. 84, 013302 (2013); http://dx.doi.org/10.1063/1.4774049 (7 pages)

Online Publication Date: 9 January 2013

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A novel method for the characterization and qualification of Hall effect thruster propellant distributors is presented. A quantitative measurement of the azimuthal number density uniformity, a metric which impacts propellant utilization, is obtained from photographs of a premixed flame anchored on the exit plane of the propellant distributor. The technique is demonstrated for three propellant distributors using a propane-air mixture at reservoir pressure of 40 psi (gauge) (377 kPa) exhausting to atmosphere, with volumetric flow rates ranging from 15-145 cfh (7.2–68 l/min) with equivalence ratios from 1.2 to 2.1. The visualization is compared with in-vacuum pressure measurements 1 mm downstream of the distributor exit plane (chamber pressure held below 2.7 × 10−5 Torr-Xe at all flow rates). Both methods indicate a non-uniformity in line with the propellant inlet, supporting the validity of the technique of flow visualization with flame luminosity for propellant distributor characterization. The technique is applied to a propellant distributor with a manufacturing defect in a known location and is able to identify the defect and characterize its impact. The technique is also applied to a distributor with numerous small orifices at the exit plane and is able to resolve the resulting non-uniformity. Luminosity data are collected with a spatial resolution of 48.2–76.1 μm (pixel width). The azimuthal uniformity is characterized in the form of standard deviation of azimuthal luminosities, normalized by the mean azimuthal luminosity. The distributors investigated achieve standard deviations of 0.346 ± 0.0212, 0.108 ± 0.0178, and 0.708 ± 0.0230 mean-normalized luminosity units respectively, where a value of 0 corresponds to perfect uniformity and a value of 1 represents a standard deviation equivalent to the mean.
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47.70.Pq Flames; combustion
47.80.Fg Pressure and temperature measurements
47.80.Jk Flow visualization and imaging
47.85.Np Fluidics
47.70.Fw Chemically reactive flows

Current density distributions and sputter marks in electron cyclotron resonance ion sources

Lauri Panitzsch, Thies Peleikis, Stephan Böttcher, Michael Stalder, and Robert F. Wimmer-Schweingruber

Rev. Sci. Instrum. 84, 013303 (2013); http://dx.doi.org/10.1063/1.4774052 (8 pages) | Cited 1 time

Online Publication Date: 14 January 2013

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Most electron cyclotron resonance ion sources use hexapolar magnetic fields for the radial confinement of the plasma. The geometry of this magnetic structure is then—induced by charged particles—mapped onto the inner side of the plasma electrode via sputtering and deposition. The resulting structures usually show two different patterns: a sharp triangular one in the central region which in some cases is even sputtered deep into the material (referred to as thin groove or sharp structure), and a blurred but still triangular-like one in the surroundings (referred to as broad halo). Therefore, both patterns seem to have different sources. To investigate their origins we replaced the standard plasma electrode by a custom-built plasma electrode acting as a planar, multi-segment current-detector. For different biased disc voltages, detector positions, and source biases (referred to the detector) we measured the electrical current density distributions in the plane of the plasma electrode. The results show a strong and sharply confined electron population with triangular shape surrounded by less intense and spatially less confined ions. Observed sputter- and deposition marks are related to the analysis of the results. Our measurements suggest that the two different patterns (thin and broad) indeed originate from different particle populations. The thin structures seem to be caused by the hot electron population while the broad marks seem to stem from the medium to highly charged ions. In this paper we present our measurements together with theoretical considerations and substantiate the conclusions drawn above. The validity of these results is also discussed.
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52.50.Dg Plasma sources
52.70.Ds Electric and magnetic measurements
52.77.Dq Plasma-based ion implantation and deposition
81.15.Cd Deposition by sputtering
06.30.Ka Basic electromagnetic quantities
52.25.Fi Transport properties

Performance of the Los Alamos National Laboratory spallation-driven solid-deuterium ultra-cold neutron source

A. Saunders, M. Makela, Y. Bagdasarova, H. O. Back, J. Boissevain, L. J. Broussard, T. J. Bowles, R. Carr, S. A. Currie, B. Filippone, A. García, P. Geltenbort, K. P. Hickerson, R. E. Hill, J. Hoagland, et al.

Rev. Sci. Instrum. 84, 013304 (2013); http://dx.doi.org/10.1063/1.4770063 (10 pages) | Cited 1 time

Online Publication Date: 14 January 2013

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In this paper, we describe the performance of the Los Alamos spallation-driven solid-deuterium ultra-cold neutron (UCN) source. Measurements of the cold neutron flux, the very low energy neutron production rate, and the UCN rates and density at the exit from the biological shield are presented and compared to Monte Carlo predictions. The cold neutron rates compare well with predictions from the Monte Carlo code MCNPX and the UCN rates agree with our custom UCN Monte Carlo code. The source is shown to perform as modeled. The maximum delivered UCN density at the exit from the biological shield is 52(9) UCN/cc with a solid deuterium volume of ∼1500 cm3.
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29.25.Dz Neutron sources
14.20.Dh Protons and neutrons

W(310) cold-field emission characteristics reflecting the vacuum states of an extreme high vacuum electron gun

Boklae Cho, Kokubo Shigeru, and Chuhei Oshima

Rev. Sci. Instrum. 84, 013305 (2013); http://dx.doi.org/10.1063/1.4776182 (7 pages)

Online Publication Date: 24 January 2013

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An extremely high vacuum cold-field electron emission (CFE) gun operating at pressures ranging from ∼10−8 Pa to ∼10−10 Pa was constructed. Only the CFE current emitting from W(310) surfaces revealed the existence of a “stable region” with high current angular density just after tip flash heating. In the “stable region,” the CFE current was damped very slowly. The presence of non-hydrogen gas eliminated this region from the plot. Improvement of the vacuum prolonged the 90% damping time of the CFE current from ∼10 min to 800 min. The current angular density I′ of CFE current was 60 and 250 μA/sr in the “stable region” for total CFE currents of 10 and 50 μA, respectively. These results were about three times larger than I′ when measured after the complete damping of the CFE current. The CFE gun generated bright scanning transmission electron microscopy images of a carbon nanotube at 30 kV.
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84.47.+w Vacuum tubes
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
79.70.+q Field emission, ionization, evaporation, and desorption

A test stand for off-line laser ion source development at TRIUMF

J. P. Lavoie, R. Li, P. Bricault, J. Lassen, O. Chachkova, and A. Teigelhöfer

Rev. Sci. Instrum. 84, 013306 (2013); http://dx.doi.org/10.1063/1.4788938 (5 pages) | Cited 1 time

Online Publication Date: 29 January 2013

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A test stand for ion source development and laser resonance ionization spectroscopy was built and commissioned at TRIUMF. The test stand is needed to develop efficient ion sources that can function reliably in the hostile, high temperature, high radiation environment of TRIUMF's isotope separator on-line (ISOL) production target ion source. In addition, it enables laser resonance ionization spectroscopy to develop laser excitation schemes suitable for the solid-state laser systems used with TRIUMF's resonant ionization laser ion source . Also, it allows for possible improvement of current ion sources and validation of new designs. The test stand employs a copy of the ion optics used on-line, so that results can be transferred directly to radioactive ion beam production. Due to space restrictions and the need for rapid mass scans, a quadrupole mass spectrometer is used as a mass separator. One of the first experiments conducted on the laser ion source test stand (LIS STAND) was resonant ionization spectroscopy of gallium to improve on the ionization scheme previously used on-line, so that low yield isotopes (e.g., 62Ga) become available for experiments. Different Rydberg series in gallium were observed and autoionizing states were searched for. The overall LIS STAND system performance, characteristics, and the first resonant ionization spectroscopy are described.
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42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy
07.75.+h Mass spectrometers
07.77.Ka Charged-particle beam sources and detectors
41.85.-p Beam optics

Multifunctional bulk plasma source based on discharge with electron injection

A. S. Klimov, A. V. Medovnik, A. V. Tyunkov, K. P. Savkin, M. V. Shandrikov, and A. V. Vizir

Rev. Sci. Instrum. 84, 013307 (2013); http://dx.doi.org/10.1063/1.4788939 (4 pages)

Online Publication Date: 30 January 2013

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A bulk plasma source, based on a high-current dc glow discharge with electron injection, is described. Electron injection and some special design features of the plasma arc emitter provide a plasma source with very long periods between maintenance down-times and a long overall lifetime. The source uses a sectioned sputter-electrode array with six individual sputter targets, each of which can be independently biased. This discharge assembly configuration provides multifunctional operation, including plasma generation from different gases (argon, nitrogen, oxygen, acetylene) and deposition of composite metal nitride and oxide coatings.
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52.50.Dg Plasma sources
52.80.Hc Glow; corona
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.80.Mg Arcs; sparks; lightning; atmospheric electricity
52.25.Fi Transport properties

Elimination of ghosting artifacts from wavelength-shifting fiber neutron detectors

C. L. Wang, L. G. Clonts, Y. Diawara, B. W. Hannan, and J. P. Hodges

Rev. Sci. Instrum. 84, 013308 (2013); http://dx.doi.org/10.1063/1.4789497 (6 pages)

Online Publication Date: 31 January 2013

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Misassignment of neutron position (ghosting) produces artifacts which have been observed in wavelength-shifting (WLS) fiber detectors developed for time-of-flight (TOF) neutron powder diffraction. In position-sensitive detectors (PSDs) with WLS fiber encoding, thermal and cold neutrons interact with a monolithic 6LiF/ZnS:Ag scintillator screen, and scintillation photons are generated and transported through the crossed fibers to photomultipliers (PMTs). The neutron position is determined by photon counts in the PMTs within a preset time window. Ghosting occurs when neutrons hit the group boundaries of two neighboring PMTs for x-position multiplexing, which is modeled as resulting from a long travel length (about 3–5 mm) of a small number of scintillation photons. This model is supported by the change observed in aperture images when the threshold number for photon-pulses was adjusted for neutron event determination. When the threshold number of photon-pulses was set above 10 for each PMT, the ghost peaks in the aperture images and TOF spectra of powder diffraction were strongly suppressed or completely eliminated, and the intrinsic background levels of the WLS detectors were significantly reduced. Our result indicates that WLS fiber detector is a promising alternative for 3He PSDs for neutron scattering.
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29.40.Gx Tracking and position-sensitive detectors
29.40.Mc Scintillation detectors
42.81.Pa Sensors, gyros
back to top Nuclear Physics, Fusion and Plasmas

High efficiency coupling of radio frequency beams from the dual frequency gyrotron with a corrugated waveguide transmission system

Yasuhisa Oda, Ken Kajiwara, Koji Takahashi, Yoshika Mitsunaka, and Keishi Sakamoto

Rev. Sci. Instrum. 84, 013501 (2013); http://dx.doi.org/10.1063/1.4772572 (6 pages)

Online Publication Date: 3 January 2013

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High efficiency coupling of the millimeter-wave output of the dual-frequency gyrotron with the transmission line was demonstrated. The dual-frequency gyrotron was design to produce similar beam profiles for two operation frequencies (170 GHz and 137 GHz). Using two RF beam reflecting mirrors in a matching optics unit (MOU), which are designed to transform the beam profile of the gyrotron output to the fundamental waveguide mode (HE11 mode) at 170 GHz, high efficiency coupling was demonstrated for two frequencies. The measured mode purity of HE11 mode was 96% at 170 GHz and 94% at 137 GHz operations with the identical mirrors at the fixed mirror position and angle. The results indicate that the significantly simple dual frequency system is realized by the gyrotron designed to output the similar beam profiles at different frequency operation.
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84.40.Ik Masers; gyrotrons (cyclotron-resonance masers)
42.79.Bh Lenses, prisms and mirrors
84.40.Az Waveguides, transmission lines, striplines

Covariance analysis of gamma ray spectra

R. Trainham and J. Tinsley

Rev. Sci. Instrum. 84, 013502 (2013); http://dx.doi.org/10.1063/1.4774047 (8 pages)

Online Publication Date: 10 January 2013

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The covariance method exploits fluctuations in signals to recover information encoded in correlations which are usually lost when signal averaging occurs. In nuclear spectroscopy it can be regarded as a generalization of the coincidence technique. The method can be used to extract signal from uncorrelated noise, to separate overlapping spectral peaks, to identify escape peaks, to reconstruct spectra from Compton continua, and to generate secondary spectral fingerprints. We discuss a few statistical considerations of the covariance method and present experimental examples of its use in gamma spectroscopy.
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29.30.Kv X- and γ-ray spectroscopy
02.50.-r Probability theory, stochastic processes, and statistics
07.05.-t Computers in experimental physics

High power continuous wave microwave test bench at 4.6 GHz for experimental advanced superconducting tokamak

Wendong Ma, Huaichuan Hu, Jiafang Shan, Handong Xu, Mao Wang, Zege Wu, and Liang Zhu

Rev. Sci. Instrum. 84, 013503 (2013); http://dx.doi.org/10.1063/1.4775486 (8 pages)

Online Publication Date: 11 January 2013

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The lower hybrid current drive (LHCD) is an effective approach for auxiliary heating and non-inductive current drive in the experimental advanced superconducting tokamak. The 6 MW/4.6 GHz LHCD system is being designed and installed with twenty-four 250 KW/4.6 GHz high power klystron amplifiers. The test bench operating at 250 KW/4.6 GHz in continuous wave mode has been set up, which can test and train microwave components for the 6 MW/4.6 GHz LHCD system. In this paper, the system architecture and software of the microwave test bench are presented. Moreover, the test results of these klystrons and microwave units are described here in detail. The long term operation of the test bench and improved performance of all microwave component samples indicated that the related technologies on test bench can be applied in the large scale LHCD systems.
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52.55.Fa Tokamaks, spherical tokamaks
84.40.Fe Microwave tubes (e.g., klystrons, magnetrons, traveling-wave, backward-wave tubes, etc.)
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
52.50.Sw Plasma heating by microwaves; ECR, LH, collisional heating

Toroidal magnetized plasma device with sheared magnetic field lines using an internal ring conductor

Th. Pierre

Rev. Sci. Instrum. 84, 013504 (2013); http://dx.doi.org/10.1063/1.4775487 (5 pages)

Online Publication Date: 11 January 2013

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In a new toroidal laboratory plasma device including a poloidal magnetic field created by an internal circular conductor, the confinement efficiency of the magnetized plasma and the turbulence level are studied in different situations. The plasma density is greatly enhanced when a sufficiently large poloidal magnetic field is established. Moreover, the instabilities and the turbulence usually found in toroidal devices without sheared magnetic field lines are suppressed by the finite rotational transform. The particle confinement time is estimated from the measurement of the plasma decay time. It is compared to the Bohm diffusion time and to the value predicted by different diffusion models, in particular neoclassical diffusion involving trapped particles.
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52.55.Jd Magnetic mirrors, gas dynamic traps
52.25.Fi Transport properties
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.35.Ra Plasma turbulence

Design and validation of the ball-pen probe for measurements in a low-temperature magnetized plasma

G. Bousselin, J. Cavalier, J. F. Pautex, S. Heuraux, N. Lemoine, and G. Bonhomme

Rev. Sci. Instrum. 84, 013505 (2013); http://dx.doi.org/10.1063/1.4775491 (8 pages)

Online Publication Date: 15 January 2013

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Ball-pen probes have been used in fusion devices for direct measurements of the plasma potential. Their application in low-temperature magnetized plasma devices is still subject to studies. In this context, a ball-pen probe has been recently implemented on the linear plasma device Mirabelle. Produced by a thermionic discharge, the plasma is characterized by a low electron temperature and a low density. Plasma confinement is provided by an axial magnetic field that goes up to 100 mT. The principle of the ball-pen probe is to adjust the saturation current ratio to 1 by reducing the electron current contribution. In that case, the floating potential of the probe is close to the plasma potential. A thorough study of the ball-pen probe operation is performed for different designs of the probe over a large set of plasma conditions. Comparisons between ball-pen, Langmuir, and emissive probes are conducted in the same plasma conditions. The ball-pen probe is successfully measuring the plasma potential in these specific plasma conditions only if an adapted electronics and an adapted probe size to the plasma characteristic lengths (λD, ρce) are used.
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52.70.Ds Electric and magnetic measurements
52.25.Fi Transport properties
52.55.-s Magnetic confinement and equilibrium

Effect of filament supports on emissive probe measurements

X. Wang, C. T. Howes, M. Horányi, and S. Robertson

Rev. Sci. Instrum. 84, 013506 (2013); http://dx.doi.org/10.1063/1.4776201 (3 pages)

Online Publication Date: 15 January 2013

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We have constructed an emissive probe with a thin tungsten filament spot-welded across two nickel wires insulated with ceramic paint. We show that the ceramic supports covering the nickel wires have a large effect on the potential measurements in low-density plasmas. It is found that the potential measured by the emissive probe is more negative than the potential derived from a Langmuir probe current-voltage (I-V) characteristic curve when the plasma density is so low that the emitting filament remains immersed in the sheaths of the ceramic supports. The length of the filament L needs to be larger than about 2 Debye lengths (L > 2λDe) in order to avoid the influence of the ceramic supports and to achieve reliable plasma potential measurements using emissive probes.
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52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.40.Kh Plasma sheaths
52.70.Ds Electric and magnetic measurements

Optimization of operation of a three-electrode gyrotron with the use of a flow-type calorimeter

Nikolay K. Kharchev, German M. Batanov, Leonid V. Kolik, Dmitrii V. Malakhov, Aleksandr Ye. Petrov, Karen A. Sarksyan, Nina N. Skvortsova, Vladimir D. Stepakhin, Vladimir I. Belousov, Sergei A. Malygin, and Yevgenii M. Tai

Rev. Sci. Instrum. 84, 013507 (2013); http://dx.doi.org/10.1063/1.4773544 (4 pages)

Online Publication Date: 16 January 2013

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Results are presented for measurements of microwave power of the Borets-75/0.8 gyrotron with recovery of residual electron energy, which were performed by a flow-type calorimeter. This gyrotron is a part of the ECR plasma heating complex put into operation in 2010 at the L-2M stellarator. The new calorimeter is capable of measuring microwave power up to 0.5 MW. Monitoring of the microwave power makes it possible to control the parameters of the gyrotron power supply unit (its voltage and current) and the magnetic field of the cryomagnet in order to optimize the gyrotron operation and arrive at maximum efficiency.
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52.50.Sw Plasma heating by microwaves; ECR, LH, collisional heating
84.40.Ik Masers; gyrotrons (cyclotron-resonance masers)
07.20.Fw Calorimeters

Response functions of Fuji imaging plates to monoenergetic protons in the energy range 0.6–3.2 MeV

T. Bonnet, M. Comet, D. Denis-Petit, F. Gobet, F. Hannachi, M. Tarisien, M. Versteegen, and M. M. Aleonard

Rev. Sci. Instrum. 84, 013508 (2013); http://dx.doi.org/10.1063/1.4775719 (6 pages)

Online Publication Date: 16 January 2013

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We have measured the responses of Fuji MS, SR, and TR imaging plates (IPs) to protons with energies ranging from 0.6 to 3.2 MeV. Monoenergetic protons were produced with the 3.5 MV AIFIRA (Applications Interdisciplinaires de Faisceaux d’Ions en Région Aquitaine) accelerator at the Centre d’Etudes Nucléaires de Bordeaux Gradignan (CENBG). The IPs were irradiated with protons backscattered off a tantalum target. We present the photo-stimulated luminescence response of the IPs together with the fading measurements for these IPs. A method is applied to allow correction of fading effects for variable proton irradiation duration. Using the IP fading corrections, a model of the IP response function to protons was developed. The model enables extrapolation of the IP response to protons up to proton energies of 10 MeV. Our work is finally compared to previous works conducted on Fuji TR IP response to protons.
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29.40.Gx Tracking and position-sensitive detectors
29.40.Wk Solid-state detectors

Implementation of focal zooming on the Nike KrF laser

D. M. Kehne, M. Karasik, Y. Aglitsky, Z. Smyth, S. Terrell, J. L. Weaver, Y. Chan, R. H. Lehmberg, and S. P. Obenschain

Rev. Sci. Instrum. 84, 013509 (2013); http://dx.doi.org/10.1063/1.4789313 (4 pages) | Cited 1 time

Online Publication Date: 29 January 2013

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In direct drive inertial confinement laser fusion, a pellet containing D-T fuel is imploded by ablation arising from absorption of laser energy at its outer surface. For optimal coupling, the focal spot of the laser would continuously decrease to match the reduction in the pellet's diameter, thereby minimizing wasted energy. A krypton-fluoride laser (λ = 248 nm) that incorporates beam smoothing by induced spatial incoherence has the ability to produce a high quality focal profile whose diameter varies with time, a property known as focal zooming. A two-stage focal zoom has been demonstrated on the Nike laser at the Naval Research Laboratory. In the experiment, a 4.4 ns laser pulse was created in which the on-target focal spot diameter was 1.3 mm (full width at half maximum) for the first 2.4 ns and 0.28 mm for the final 2 ns. These two diameters appear in time-integrated focal plane equivalent images taken at several locations in the amplification chain. Eight of the zoomed output beams were overlapped on a 60 μm thick planar polystyrene target. Time resolved images of self-emission from the rear of the target show the separate shocks launched by the two corresponding laser focal diameters.
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42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.57.-z Laser inertial confinement
back to top Microscopy and Imaging

Design and demonstration of multimodal optical scanning microscopy for confocal and two-photon imaging

Wanhee Chun, Dukho Do, and Dae-Gab Gweon

Rev. Sci. Instrum. 84, 013701 (2013); http://dx.doi.org/10.1063/1.4773232 (8 pages)

Online Publication Date: 7 January 2013

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We developed a multimodal microscopy based on an optical scanning system in order to obtain diverse optical information of the same area of a sample. Multimodal imaging researches have mostly depended on a commercial microscope platform, easy to use but restrictive to extend imaging modalities. In this work, the beam scanning optics, especially including a relay lens, was customized to transfer broadband (400–1000 nm) lights to a sample without any optical error or loss. The customized scanning optics guarantees the best performances of imaging techniques utilizing the lights within the design wavelength. Confocal reflection, confocal fluorescence, and two-photon excitation fluorescence images were obtained, through respective implemented imaging channels, to demonstrate imaging feasibility for near-UV, visible, near-IR continuous light, and pulsed light in the scanning optics. The imaging performances for spatial resolution and image contrast were verified experimentally; the results were satisfactory in comparison with theoretical results. The advantages of customization, containing low cost, outstanding combining ability and diverse applications, will contribute to vitalize multimodal imaging researches.
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07.60.Pb Conventional optical microscopes
42.15.Eq Optical system design
42.79.Bh Lenses, prisms and mirrors

Friction measurement on free standing plates using atomic force microscopy

X. S. Tang, Y. C. Loke, P. Lu, Sujeet K. Sinha, and S. J. O'Shea

Rev. Sci. Instrum. 84, 013702 (2013); http://dx.doi.org/10.1063/1.4773534 (9 pages)

Online Publication Date: 8 January 2013

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A method is introduced to measure friction on small, free standing objects, specifically microfabricated silicon plates, based on atomic force microscopy (AFM). An AFM tip is brought into contact with the plate resting on a substrate. The substrate is displaced laterally and, provided the AFM tip does not slide over the plate, the twisting of the AFM cantilever is used to measure the friction of the underlying plate-substrate interface. The method can measure nano-Newton to micro-Newton forces (both friction and applied load) and provides a means to measure friction of macroscopic structures at low load.
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07.10.Cm Micromechanical devices and systems
07.79.Lh Atomic force microscopes
81.40.Pq Friction, lubrication, and wear
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
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