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Jun 2012

Volume 83, Issue 6, Articles (06xxxx)

Issue Cover Spotlight Figure

Rev. Sci. Instrum. 83, 061101 (2012); http://dx.doi.org/10.1063/1.4720102 (35 pages)

Marcel Lucas and Elisa Riedo

Versatility from combining scanning probe microscopy with optical spectroscopy. Scanning probe microscopy can characterize (top, left to right) mechanical properties, topography, transport properties and chemical composition of the sample. Optical spectroscopy (bottom, left to right) can probe chemical composition, crystal structure, and deformation, and map them in hyperspectral images.

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Invited Review Article: Combining scanning probe microscopy with optical spectroscopy for applications in biology and materials science

Marcel Lucas and Elisa Riedo

Rev. Sci. Instrum. 83, 061101 (2012); http://dx.doi.org/10.1063/1.4720102 (35 pages) | Cited 4 times

Online Publication Date: 7 June 2012

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This is a comprehensive review of the combination of scanning probe microscopy (SPM) with various optical spectroscopies, with a particular focus on Raman spectroscopy. Efforts to combine SPM with optical spectroscopy will be described, and the technical difficulties encountered will be examined. These efforts have so far focused mainly on the development of tip-enhanced Raman spectroscopy, a powerful technique to detect and image chemical signatures with single molecule sensitivity, which will be reviewed. Beyond tip-enhanced Raman spectroscopy and/or topography measurements, combinations of SPM with optical spectroscopy have a great potential in the characterization of structure and quantitative measurements of physical properties, such as mechanical, optical, or electrical properties, in delicate biological samples and nanomaterials. The different approaches to improve the spatial resolution, the chemical sensitivity, and the accuracy of physical properties measurements will be discussed. Applications of such combinations for the characterization of structure, defects, and physical properties in biology and materials science will be reviewed. Due to the versatility of SPM probes for the manipulation and characterization of small and/or delicate samples, this review will mainly focus on the apertureless techniques based on SPM probes.
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07.79.-v Scanning probe microscopes and components
82.80.Gk Analytical methods involving vibrational spectroscopy
87.64.Dz Scanning tunneling and atomic force microscopy
87.80.Dj Spectroscopies
87.64.kp Raman
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back to top Optics; Atoms and Molecules; Spectroscopy; Photon Detectors

Velocity-map imaging at low extraction fields

Daniel A. Horke, Gareth M. Roberts, Julien Lecointre, and Jan R. R. Verlet

Rev. Sci. Instrum. 83, 063101 (2012); http://dx.doi.org/10.1063/1.4724311 (6 pages) | Cited 3 times

Online Publication Date: 5 June 2012

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We present a velocity-map imaging (VMI) setup for photoelectron imaging that utilizes low electric extraction fields. This avoids any complications that could arise from electrostatic interactions between the extraction field and the molecular properties that are probed and has a minimal effect on the trajectory of ions in ion beam experiments. By using an attractive potential supplied to the detector, and keeping the electrodes at ground (zero) potential, we show that fringe fields between the VMI arrangement and the vacuum chamber can be eliminated, which is important in experiments on ions.
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07.81.+a Electron and ion spectrometers

A compact collinear polarization gating scheme for many cycle laser pulses

G. Kolliopoulos, P. A. Carpeggiani, D. Rompotis, D. Charalambidis, and P. Tzallas

Rev. Sci. Instrum. 83, 063102 (2012); http://dx.doi.org/10.1063/1.4725590 (4 pages)

Online Publication Date: 8 June 2012

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We demonstrate the generation of a broadband coherent continuum extreme-ultraviolet (XUV) radiation produced by the interaction of gases with a many-cycle infrared (IR) laser field, utilizing a compact collinear many cycle-polarization gating (CMC-PG) device. The spectral width of the XUV radiation can support isolated pulses of 200 asec duration. The CMC-PG device forms a high energy content ultra-short temporal gate in a many-cycle laser pulse, within which the XUV emission is taking place. The gate width has been measured and is in agreement with the theoretical calculations. The simplicity, the compactness, the long term stability, and the high IR energy output within the gate, make the CMC-PG device an ideal tool for generating energetic isolated attosecond pulses and measure the carrier-envelope phase of a high-power many-cycle laser field.
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42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.72.Bj Visible and ultraviolet sources

On-line determination of Förster resonance energy transfer efficiency in drying latex films: Correlation of interdiffusion and particle deformation

K. Pohl, B. Kussmaul, J. Adams, and D. Johannsmann

Rev. Sci. Instrum. 83, 063103 (2012); http://dx.doi.org/10.1063/1.4726025 (6 pages)

Online Publication Date: 8 June 2012

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An instrument is described, which measures the efficiency of Förster resonance energy transfer (FRET) in parallel to the sample's turbidity. The instrument was used to study the film formation from polymer latex dispersions. In this context, the FRET efficiency reflects the diffusion of polymer chains across the interparticle boundaries, while the loss of turbidity reflects the progress of particle deformation. Particle deformation causes tensile in-plane stress, while polymer interdiffusion creates cohesion and thereby helps to prevent cracking. The relative timing between the two therefore is of fundamental importance for successful film formation. The on-line determination of FRET efficiency while the film dries is complicated by the fact that the fluorescence lifetime of the donor, τD, depends on the water content in the vicinity of the donor. In the established procedure for data analysis, drifts in τD induce corresponding artifical drifts in the values of the FRET efficiency. A novel algorithm for the analysis of fluorescence decay profiles is proposed, which makes use of the method of moments. The FRET efficiency is quantified by the upward curvature of the fluorescence decay curve in log-linear display. In the application example, interdiffusion is delayed relative to particle deformation by about 10 min. For successful film formation, this delay should be as small as possible.
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82.35.Lr Physical properties of polymers
68.35.Fx Diffusion; interface formation

High energy resolution five-crystal spectrometer for high quality fluorescence and absorption measurements on an x-ray absorption spectroscopy beamline

Isabelle Llorens, Eric Lahera, William Delnet, Olivier Proux, Aurélien Braillard, Jean-Louis Hazemann, Alain Prat, Denis Testemale, Quentin Dermigny, Frederic Gelebart, Marc Morand, Abhay Shukla, Nathalie Bardou, Olivier Ulrich, Stéphan Arnaud, et al.

Rev. Sci. Instrum. 83, 063104 (2012); http://dx.doi.org/10.1063/1.4728414 (9 pages) | Cited 3 times

Online Publication Date: 12 June 2012

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Fluorescence detection is classically achieved with a solid state detector (SSD) on x-ray absorption spectroscopy (XAS) beamlines. This kind of detection however presents some limitations related to the limited energy resolution and saturation. Crystal analyzer spectrometers (CAS) based on a Johann-type geometry have been developed to overcome these limitations. We have tested and installed such a system on the BM30B/CRG-FAME XAS beamline at the ESRF dedicated to the structural investigation of very dilute systems in environmental, material and biological sciences. The spectrometer has been designed to be a mobile device for easy integration in multi-purpose hard x-ray synchrotron beamlines or even with a laboratory x-ray source. The CAS allows to collect x-ray photons from a large solid angle with five spherically bent crystals. It will cover a large energy range allowing to probe fluorescence lines characteristic of all the elements from Ca (Z = 20) to U (Z = 92). It provides an energy resolution of 1–2 eV. XAS spectroscopy is the main application of this device even if other spectroscopic techniques (RIXS, XES, XRS, etc.) can be also achieved with it. The performances of the CAS are illustrated by two experiments that are difficult or impossible to perform with SSD and the complementarity of the CAS vs SSD detectors is discussed.
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07.85.Nc X-ray and γ-ray spectrometers

On-line thermal dependence study of the main solar cell electrical photoconversion parameters using low thermal emission lamps

J. J. Gallardo, J. Navas, R. Alcántara, C. Fernández-Lorenzo, T. Aguilar, and J. Martín-Calleja

Rev. Sci. Instrum. 83, 063105 (2012); http://dx.doi.org/10.1063/1.4729118 (8 pages)

Online Publication Date: 13 June 2012

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This paper presents a non-conventional methodology and an instrumental system to measure the effect of temperature on the photovoltaic properties of solar cells. The system enables the direct measurement of the evolution of open-circuit voltage and short-circuit current intensity in relation to a continuously decreasing temperature. The system uses a high-intensity white light-emitting diode light source with low emissions of radiation in the infrared region of the electromagnetic spectrum, resulting in a reduced heating of the photovoltaic devices by the irradiation source itself. To check the goodness of the system and the methodology designed, several measurements were performed with monocrystalline silicon solar cells, dye-sensitized solar cells, and thin-film amorphous silicon solar cells, showing similar tendencies to those reported in the literature.
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88.40.jj Silicon solar cells
85.60.Jb Light-emitting devices

Performance of a short “magnetic bottle” electron spectrometer

M. Mucke, M. Förstel, T. Lischke, T. Arion, A. M. Bradshaw, and U. Hergenhahn

Rev. Sci. Instrum. 83, 063106 (2012); http://dx.doi.org/10.1063/1.4729256 (9 pages) | Cited 1 time

Online Publication Date: 14 June 2012

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In this article, a newly constructed electron spectrometer of the magnetic bottle type is described. The instrument is part of an apparatus for measuring the electron spectra of free clusters using synchrotron radiation. Argon and helium outer valence photoelectron spectra have been recorded in order to investigate the characteristic features of the spectrometer. The energy resolution (E/ΔE) has been found to be ∼30. Using electrostatic retardation of the electrons, it can be increased to at least 110. The transmission as a function of kinetic energy is flat, and is not impaired much by retardation with up to 80% of the initial kinetic energy. We have measured a detection efficiency of most probably 0.6−0.1+0.05, but at least of 0.4. Results from testing the alignment of the magnet, and from trajectory simulations, are also discussed.
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07.81.+a Electron and ion spectrometers
79.60.-i Photoemission and photoelectron spectra

Frequency stabilization of an external-cavity diode laser to metastable argon atoms in a discharge

P. Douglas, C. Maher-McWilliams, and P. F. Barker

Rev. Sci. Instrum. 83, 063107 (2012); http://dx.doi.org/10.1063/1.4729793 (5 pages) | Cited 1 time

Online Publication Date: 21 June 2012

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A laser stabilization scheme using magnetic dichroism in a RF plasma discharge is presented. This method has been used to provide a frequency stable external-cavity diode laser that is locked to the 4s[math]2 → 4p[math]3 argon laser cooling transition at 811.53 nm. Using saturated absorption spectroscopy, we lock the laser to a Doppler free peak which gave a locking range of 20 MHz when the slope of the error signal was maximized. The stability of the laser was characterized by determining the square root Allan variance of laser frequency fluctuations when the laser was locked. A stability of 129 kHz was measured at 1 s averaging time for data acquired over 6000 s.
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42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems
42.60.Fc Modulation, tuning, and mode locking
back to top Particle Sources, Optics and Acceleration; Particle Detectors

Absolute energy calibration for relativistic electron beams with pointing instability from a laser-plasma accelerator

H. J. Cha, I. W. Choi, H. T. Kim, I J. Kim, K. H. Nam, T. M. Jeong, and J. Lee

Rev. Sci. Instrum. 83, 063301 (2012); http://dx.doi.org/10.1063/1.4725530 (9 pages)

Online Publication Date: 7 June 2012

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The pointing instability of energetic electron beams generated from a laser-driven accelerator can cause a serious error in measuring the electron spectrum with a magnetic spectrometer. In order to determine a correct electron spectrum, the pointing angle of an electron beam incident on the spectrometer should be exactly defined. Here, we present a method for absolutely calibrating the electron spectrum by monitoring the pointing angle using a scintillating screen installed in front of a permanent dipole magnet. The ambiguous electron energy due to the pointing instability is corrected by the numerical and analytical calculations based on the relativistic equation of electron motion. It is also possible to estimate the energy spread of the electron beam and determine the energy resolution of the spectrometer using the beam divergence angle that is simultaneously measured on the screen. The calibration method with direct measurement of the spatial profile of an incident electron beam has a simple experimental layout and presents the full range of spatial and spectral information of the electron beams with energies of multi-hundred MeV level, despite the limited energy resolution of the simple electron spectrometer.
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29.30.Aj Charged-particle spectrometers: electric and magnetic
29.30.Ep Charged-particle spectroscopy
06.20.fb Standards and calibration
41.75.Ht Relativistic electron and positron beams

Electrical shielding box measurement of the negative hydrogen beam from Penning ion gauge ion source

T. Wang, Z. Yang, P. Dong, J. D. long, X. Z. He, X. Wang, K. Z. Zhang, and L. W. Zhang

Rev. Sci. Instrum. 83, 063302 (2012); http://dx.doi.org/10.1063/1.4725534 (5 pages)

Online Publication Date: 8 June 2012

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The cold-cathode Penning ion gauge (PIG) type ion source has been used for generation of negative hydrogen (H−) ions as the internal ion source of a compact cyclotron. A novel method called electrical shielding box dc beam measurement is described in this paper, and the beam intensity was measured under dc extraction inside an electrical shielding box. The results of the trajectory simulation and dc H− beam extraction measurement were presented. The effect of gas flow rate, magnetic field strength, arc current, and extraction voltage were also discussed. In conclusion, the dc H− beam current of about 4 mA from the PIG ion source with the puller voltage of 40 kV and arc current of 1.31 A was extrapolated from the measurement at low extraction dc voltages.
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84.37.+q Measurements in electric variables (including voltage, current, resistance, capacitance, inductance, impedance, and admittance, etc.)
29.25.Ni Ion sources: positive and negative
29.20.dg Cyclotrons

Synchrotron-based ultrafast x-ray diffraction at high repetition rates

H. Navirian, R. Shayduk, W. Leitenberger, J. Goldshteyn, P. Gaal, and M. Bargheer

Rev. Sci. Instrum. 83, 063303 (2012); http://dx.doi.org/10.1063/1.4727872 (7 pages)

Online Publication Date: 8 June 2012

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We present a setup for ultrafast x-ray diffraction (UXRD) based at the storage ring BESSY II, in particular, a pump laser that excites the sample using 250 fs laser-pulses at repetition rates ranging from 208 kHz to 1.25 MHz. We discuss issues connected to the high heat-load and spatio-temporal alignment strategies in the context of a UXRD experiment at high repetition rates. The spatial overlap between laser pump and x-ray probe pulse is obtained with 10 μm precision and transient lattice changes can be recorded with an accuracy of δa/a0 = 10−6. We also compare time-resolved x-ray diffraction signals from a laser excited LSMO/STO superlattice with phonon dynamics simulations. From the analysis we determine the x-ray pulse duration to 120 ps in standard operation mode and below 10 ps in low-α mode.
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61.05.C- X-ray diffraction and scattering

Influence of ion source configuration and its operation parameters on the target sputtering and implantation process

K. V. Shalnov, V. R. Kukhta, K. Uemura, and Y. Ito

Rev. Sci. Instrum. 83, 063304 (2012); http://dx.doi.org/10.1063/1.4731009 (8 pages)

Online Publication Date: 27 June 2012

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In the work, investigation of the features and operation regimes of sputter enhanced ion-plasma source are presented. The source is based on the target sputtering with the dense plasma formed in the crossed electric and magnetic fields. It allows operation with noble or reactive gases at low pressure discharge regimes, and, the resulting ion beam is the mixture of ions from the working gas and sputtering target. Any conductive material, such as metals, alloys, or compounds, can be used as the sputtering target. Effectiveness of target sputtering process with the plasma was investigated dependently on the gun geometry, plasma parameters, and the target bias voltage. With the applied accelerating voltage from 0 to 20 kV, the source can be operated in regimes of thin film deposition, ion-beam mixing, and ion implantation. Multi-component ion beam implantation was applied to α-Fe, which leads to the surface hardness increasing from 2 GPa in the initial condition up to 3.5 GPa in case of combined N2-C implantation. Projected range of the implanted elements is up to 20 nm with the implantation energy 20 keV that was obtained with XPS depth profiling.
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52.50.Dg Plasma sources
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
61.72.U- Doping and impurity implantation
52.77.Dq Plasma-based ion implantation and deposition

A very sensitive ion collection device for plasma-laser characterization

S. Cavallaro, L. Torrisi, M. Cutroneo, A. Amato, F. Sarta, and L. Wen

Rev. Sci. Instrum. 83, 063305 (2012); http://dx.doi.org/10.1063/1.4730594 (4 pages)

Online Publication Date: 29 June 2012

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In this paper a very sensitive ion collection device, for diagnostic of laser ablated-target plasma, is described. It allows for reducing down to few microvolts the signal threshold at digital scope input. A standard ion collector is coupled to a transimpedance amplifier, specially designed, which increases data acquisition sensitivity by a gain ≈1100 and does not introduce any significant distortion of input signal. By time integration of current intensity, an amount of charge as small as 2.7 × 10−2 pC can be detected for photopeak events.
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42.62.-b Laser applications
52.38.Mf Laser ablation
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.75.-d Plasma devices
back to top Nuclear Physics, Fusion and Plasmas

A linear helicon plasma device with controllable magnetic field gradient

Kshitish K. Barada, P. K. Chattopadhyay, J. Ghosh, Sunil Kumar, and Y. C. Saxena

Rev. Sci. Instrum. 83, 063501 (2012); http://dx.doi.org/10.1063/1.4723816 (6 pages) | Cited 2 times

Online Publication Date: 1 June 2012

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Current free double layers (CFDLs) are localized potential structures having spatial dimensions – Debye lengths and potential drops of more than local electron temperature across them. CFDLs do not need a current for them to be sustained and hence they differ from the current driven double layers. Helicon antenna produced plasmas in an expanded chamber along with an expanding magnetic field have shown the existence of CFDL near the expansion region. A helicon plasma device has been designed, fabricated, and installed in the Institute for Plasma Research, India to study the role of maximum magnetic field gradient as well as its location with respect to the geometrical expansion region of the chamber in CFDL formation. The special feature of this machine consisting of two chambers of different radii is its capability of producing different magnetic field gradients near the physical boundary between the two chambers either by changing current in one particular coil in the direction opposite to that in other coils and/or by varying the position of this particular coil. Although, the machine is primarily designed for CFDL experiments, it is also capable of carrying out many basic plasma physics experiments such as wave propagation, wave coupling, and plasma instabilities in a varying magnetic field topology. In this paper, we will present the details of the machine construction, its specialties, and some preliminary results about the production and characterization of helicon plasma in this machine.
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52.75.-d Plasma devices
52.25.Fi Transport properties
52.40.Fd Plasma interactions with antennas; plasma-filled waveguides
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)

Magnetic bucket for rotating unmagnetized plasma

Noam Katz, Cami Collins, John Wallace, Mike Clark, David Weisberg, Jon Jara-Almonte, Ingrid Reese, Carl Wahl, and Cary Forest

Rev. Sci. Instrum. 83, 063502 (2012); http://dx.doi.org/10.1063/1.4723820 (6 pages)

Online Publication Date: 1 June 2012

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A new experiment is described which generates flow in unmagnetized plasma. Confinement is provided by a cage of permanent magnets, arranged to form an axisymmetric, high-order, multipolar magnetic field. This field configuration—sometimes called a “magnetic bucket”—has a vanishingly small field in the core of the experiment. Toroidal rotation is driven by J × B forces applied in the magnetized edge. The cross-field current that is required for this forcing flows from anodes to thermionic cathodes, which are inserted between the magnet rings. The rotation at the edge reaches 3 km/s and is viscously coupled to the unmagnetized core plasma. We describe the conditions necessary for rotation, as well as a 0-dimensional power balance used to understand plasma confinement in the experiment.
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52.55.Lf Field-reversed configurations, rotamaks, astrons, ion rings, magnetized target fusion, and cusps
52.30.-q Plasma dynamics and flow
52.25.Fi Transport properties

Surface analysis using a new plasma assisted desorption/ionisation source for mass spectrometry in ambient air

A. Bowfield, D. A. Barrett, M. R. Alexander, C. A. Ortori, F. M. Rutten, T. L. Salter, I. S. Gilmore, and J. W. Bradley

Rev. Sci. Instrum. 83, 063503 (2012); http://dx.doi.org/10.1063/1.4729120 (7 pages) | Cited 1 time

Online Publication Date: 12 June 2012

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The authors report on a modified micro-plasma assisted desorption/ionisation (PADI) device which creates plasma through the breakdown of ambient air rather than utilising an independent noble gas flow. This new micro-PADI device is used as an ion source for ambient mass spectrometry to analyse species released from the surfaces of polytetrafluoroethylene, and generic ibuprofen and paracetamol tablets through remote activation of the surface by the plasma. The mass spectra from these surfaces compare favourably to those produced by a PADI device constructed using an earlier design and confirm that the new ion source is an effective device which can be used to achieve ambient mass spectrometry with improved spatial resolution.
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82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
52.75.-d Plasma devices

Calibration of the neutron detectors for the cluster fusion experiment on the Texas Petawatt Laser

W. Bang, H. J. Quevedo, G. Dyer, J. Rougk, I. Kim, M. McCormick, A. C. Bernstein, and T. Ditmire

Rev. Sci. Instrum. 83, 063504 (2012); http://dx.doi.org/10.1063/1.4729121 (7 pages) | Cited 2 times

Online Publication Date: 13 June 2012

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Three types of neutron detectors (plastic scintillation detectors, indium activation detectors, and CR-39 track detectors) were calibrated for the measurement of 2.45 MeV DD fusion neutron yields from the deuterium cluster fusion experiment on the Texas Petawatt Laser. A Cf-252 neutron source and 2.45 MeV fusion neutrons generated from laser-cluster interaction were used as neutron sources. The scintillation detectors were calibrated such that they can detect up to 108 DD fusion neutrons per shot in current mode under high electromagnetic pulse environments. Indium activation detectors successfully measured neutron yields as low as 104 per shot and up to 1011 neutrons. The use of a Cf-252 neutron source allowed cross calibration of CR-39 and indium activation detectors at high neutron yields (∼1011). The CR-39 detectors provided consistent measurements of the total neutron yield of Cf-252 when a modified detection efficiency of 4.6×10−4 was used. The combined use of all three detectors allowed for a detection range of 104 to 1011 neutrons per shot.
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29.40.-n Radiation detectors
06.20.fb Standards and calibration
29.25.Dz Neutron sources

Soft x-ray tomography for real-time applications: present status at Tore Supra and possible future developments

D. Mazon, D. Vezinet, D. Pacella, D. Moreau, L. Gabelieri, A. Romano, P. Malard, J. Mlynar, R. Masset, and P. Lotte

Rev. Sci. Instrum. 83, 063505 (2012); http://dx.doi.org/10.1063/1.4730044 (14 pages)

Online Publication Date: 21 June 2012

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This paper is focused on the soft x-ray (SXR) tomography system setup at Tore Supra (DTOMOX) and the recent developments made to automatically get precise information about plasma features from inverted data. The first part describes the main aspects of the tomographic inversion optimization process. Several observations are made using this new tool and a set of shape factors is defined to help characterizing the emissivity field in a real-time perspective. The second part presents a detailed off-line analysis comparing the positions of the magnetic axis obtained from a magnetic equilibrium solver, and the maximum of the reconstructed emissivity field for ohmic and heated pulses. A systematic discrepancy of about 5 cm is found in both cases and it is shown that this discrepancy increases during sawtooth crashes. Finally, evidence of radially localized tungsten accumulation with an in–out asymmetry during a lower hybrid current drive pulse is provided to illustrate the DTOMOX capabilities for a precise observation of local phenomena.
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52.55.Fa Tokamaks, spherical tokamaks
52.70.La X-ray and γ-ray measurements
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.50.Nr Plasma heating by DC fields; ohmic heating, arcs

Source characterization and modeling development for monoenergetic-proton radiography experiments on OMEGA

M. J.-E. Manuel, A. B. Zylstra, H. G. Rinderknecht, D. T. Casey, M. J. Rosenberg, N. Sinenian, C. K. Li, J. A. Frenje, F. H. Séguin, and R. D. Petrasso

Rev. Sci. Instrum. 83, 063506 (2012); http://dx.doi.org/10.1063/1.4730336 (9 pages) | Cited 4 times

Online Publication Date: 22 June 2012

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A monoenergetic proton source has been characterized and a modeling tool developed for proton radiography experiments at the OMEGA [T. R. Boehly et al., Opt. Comm. 133, 495 (1997)]10.1016/S0030-4018(96)00325-2 laser facility. Multiple diagnostics were fielded to measure global isotropy levels in proton fluence and images of the proton source itself provided information on local uniformity relevant to proton radiography experiments. Global fluence uniformity was assessed by multiple yield diagnostics and deviations were calculated to be ∼16% and ∼26% of the mean for DD and D3He fusion protons, respectively. From individual fluence images, it was found that the angular frequencies of ≳50 rad−1 contributed less than a few percent to local nonuniformity levels. A model was constructed using the Geant4 [S. Agostinelli et al., Nuc. Inst. Meth. A 506, 250 (2003)]10.1016/S0168-9002(03)01368-8 framework to simulate proton radiography experiments. The simulation implements realistic source parameters and various target geometries. The model was benchmarked with the radiographs of cold-matter targets to within experimental accuracy. To validate the use of this code, the cold-matter approximation for the scattering of fusion protons in plasma is discussed using a typical laser-foil experiment as an example case. It is shown that an analytic cold-matter approximation is accurate to within ≲10% of the analytic plasma model in the example scenario.
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52.50.Dg Plasma sources
52.65.-y Plasma simulation
52.70.La X-ray and γ-ray measurements
02.60.Gf Algorithms for functional approximation

A new method for determining the plasma electron density using three-color interferometer

Hiroyuki Arakawa, Yasunori Kawano, and Kiyoshi Itami

Rev. Sci. Instrum. 83, 063507 (2012); http://dx.doi.org/10.1063/1.4731651 (7 pages) | Cited 1 time

Online Publication Date: 28 June 2012

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A new method for determining the plasma electron density using the fractional fringes on three-color interferometer is proposed. Integrated phase shift on each interferometer is derived without using the temporal history of the fractional fringes. The dependence on the fringe resolution and the electrical noise are simulated on the wavelengths of CO2 laser. Short-time integrations of the fractional fringes enhance the reliability of this method.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
42.60.-v Laser optical systems: design and operation
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy
07.60.Ly Interferometers
52.25.-b Plasma properties
back to top Microscopy and Imaging

High-speed Lissajous-scan atomic force microscopy: Scan pattern planning and control design issues

A. Bazaei, Yuen K. Yong, and S. O. Reza Moheimani

Rev. Sci. Instrum. 83, 063701 (2012); http://dx.doi.org/10.1063/1.4725525 (10 pages) | Cited 3 times

Online Publication Date: 4 June 2012

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Tracking of triangular or sawtooth waveforms is a major difficulty for achieving high-speed operation in many scanning applications such as scanning probe microscopy. Such non-smooth waveforms contain high order harmonics of the scan frequency that can excite mechanical resonant modes of the positioning system, limiting the scan range and bandwidth. Hence, fast raster scanning often leads to image distortion. This paper proposes analysis and design methodologies for a nonlinear and smooth closed curve, known as Lissajous pattern, which allows much faster operations compared to the ordinary scan patterns. A simple closed-form measure is formulated for the image resolution of the Lissajous pattern. This enables us to systematically determine the scan parameters. Using internal model controllers (IMC), this non-raster scan method is implemented on a commercial atomic force microscope driven by a low resonance frequency positioning stage. To reduce the tracking errors due to actuator nonlinearities, higher order harmonic oscillators are included in the IMC controllers. This results in significant improvement compared to the traditional IMC method. It is shown that the proposed IMC controller achieves much better tracking performances compared to integral controllers when the noise rejection performances is a concern.
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07.79.Lh Atomic force microscopes
42.30.Va Image forming and processing
84.30.Ng Oscillators, pulse generators, and function generators

Design and performance of a combined secondary ion mass spectrometry-scanning probe microscopy instrument for high sensitivity and high-resolution elemental three-dimensional analysis

Tom Wirtz, Yves Fleming, Mathieu Gerard, Urs Gysin, Thilo Glatzel, Ernst Meyer, Urs Wegmann, Urs Maier, Aitziber Herrero Odriozola, and Daniel Uehli

Rev. Sci. Instrum. 83, 063702 (2012); http://dx.doi.org/10.1063/1.4724308 (9 pages) | Cited 1 time

Online Publication Date: 6 June 2012

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State-of-the-art secondary ion mass spectrometry (SIMS) instruments allow producing 3D chemical mappings with excellent sensitivity and spatial resolution. Several important artifacts however arise from the fact that SIMS 3D mapping does not take into account the surface topography of the sample. In order to correct these artifacts, we have integrated a specially developed scanning probe microscopy (SPM) system into a commercial Cameca NanoSIMS 50 instrument. This new SPM module, which was designed as a DN200CF flange-mounted bolt-on accessory, includes a new high-precision sample stage, a scanner with a range of 100 μm in x and y direction, and a dedicated SPM head which can be operated in the atomic force microscopy (AFM) and Kelvin probe force microscopy modes. Topographical information gained from AFM measurements taken before, during, and after SIMS analysis as well as the SIMS data are automatically compiled into an accurate 3D reconstruction using the software program “SARINA,” which was developed for this first combined SIMS-SPM instrument. The achievable lateral resolutions are 6 nm in the SPM mode and 45 nm in the SIMS mode. Elemental 3D images obtained with our integrated SIMS-SPM instrument on Al/Cu and polystyrene/poly(methyl methacrylate) samples demonstrate the advantages of the combined SIMS-SPM approach.
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07.79.Lh Atomic force microscopes
42.30.Va Image forming and processing
07.75.+h Mass spectrometers

A multi-view time-domain non-contact diffuse optical tomography scanner with dual wavelength detection for intrinsic and fluorescence small animal imaging

Eric Lapointe, Julien Pichette, and Yves Bérubé-Lauzière

Rev. Sci. Instrum. 83, 063703 (2012); http://dx.doi.org/10.1063/1.4726016 (14 pages) | Cited 1 time

Online Publication Date: 11 June 2012

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We present a non-contact diffuse optical tomography (DOT) scanner with multi-view detection (over 360°) for localizing fluorescent markers in scattering and absorbing media, in particular small animals. It relies on time-domain detection after short pulse laser excitation. Ultrafast time-correlated single photon counting and photomultiplier tubes are used for time-domain measurements. For light collection, seven free-space optics non-contact dual wavelength detection channels comprising 14 detectors overall are placed around the subject, allowing the measurement of time point-spread functions at both excitation and fluorescence wavelengths. The scanner is endowed with a stereo camera pair for measuring the outer shape of the subject in 3D. Surface and DOT measurements are acquired simultaneously with the same laser beam. The hardware and software architecture of the scanner are discussed. Phantoms are used to validate the instrument. Results on the localization of fluorescent point-like inclusions immersed in a scattering and absorbing object are presented. The localization algorithm relies on distance ranging based on the measurement of early photons arrival times at different positions around the subject. This requires exquisite timing accuracy from the scanner. Further exploiting this capability, we show results on the effect of a scattering hetereogenity on the arrival time of early photons. These results demonstrate that our scanner provides all that is necessary for reconstructing images of small animals using full tomographic reconstruction algorithms, which will be the next step. Through its free-space optics design and the short pulse laser used, our scanner shows unprecedented timing resolution compared to other multi-view time-domain scanners.
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87.57.-s Medical imaging
42.30.Wb Image reconstruction; tomography
42.79.Ls Scanners, image intensifiers, and image converters
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
85.60.Ha Photomultipliers; phototubes and photocathodes
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy

Nanomanipulation and nanofabrication with multi-probe scanning tunneling microscope: From individual atoms to nanowires

Shengyong Qin, Tae-Hwan Kim, Zhouhang Wang, and An-Ping Li

Rev. Sci. Instrum. 83, 063704 (2012); http://dx.doi.org/10.1063/1.4727878 (4 pages) | Cited 1 time

Online Publication Date: 13 June 2012

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The wide variety of nanoscale structures and devices demands novel tools for handling, assembly, and fabrication at nanoscopic positioning precision. The manipulation tools should allow for in situ characterization and testing of fundamental building blocks, such as nanotubes and nanowires, as they are built into functional devices. In this paper, a bottom-up technique for nanomanipulation and nanofabrication is reported by using a 4-probe scanning tunneling microscope (STM) combined with a scanning electron microscope (SEM). The applications of this technique are demonstrated in a variety of nanosystems, from manipulating individual atoms to bending, cutting, breaking carbon nanofibers, and constructing nanodevices for electrical characterizations. The combination of the wide field of view of SEM, the atomic position resolution of STM, and the flexibility of multiple scanning probes is expected to be a valuable tool for rapid prototyping in the nanoscience and nanotechnology.
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07.07.Tw Servo and control equipment; robots
81.16.-c Methods of micro- and nanofabrication and processing
81.40.Lm Deformation, plasticity, and creep

Balanced detection for interferometry with a noisy source

E. C. Robinson, J. Trägårdh, I. D. Lindsay, and H. Gersen

Rev. Sci. Instrum. 83, 063705 (2012); http://dx.doi.org/10.1063/1.4729474 (6 pages)

Online Publication Date: 20 June 2012

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Optical properties of nanostructures depend on size, shape, material, and local environment. These characteristics can be probed interferometrically, given a broadband source. However, broadband supercontinuum sources are intrinsically noisy, limiting the measurement sensitivity. In this article we describe the application of an auto-balancing technique to reduce the noise in a broadband supercontinuum source, thus increasing the signal to noise ratio. We show a noise reduction of 41 dB allowing optical powers as small as 0.01 pW to be interferometrically detected with a 5 ms integration time.
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07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
42.65.-k Nonlinear optics
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