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Jan 2010

Volume 81, Issue 1, Articles (01xxxx)

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back to top Optics; Atoms and Molecules; Spectroscopy; Photon Detectors

Applying genetic algorithm optimization to a folded geometry acousto-optic modulated spatial pulse shaper

Amit Nag, Prasad A. Chaphekar, and Debabrata Goswami

Rev. Sci. Instrum. 81, 013101 (2010); http://dx.doi.org/10.1063/1.3276682 (9 pages) | Cited 1 time

Online Publication Date: 4 January 2010

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A folded geometry acousto-optic modulator spatial pulse shaper has been designed for shaping individual pulses from a high power amplified laser. The design preserves the capability of computer programmable amplitude and phase modulation of femtosecond laser pulses. An additional application of genetic algorithm optimization approach for compressing a stretched pulse is also demonstrated for such a pulse shaper. Spectrally and temporally resolved optical gating technique is used to characterize the shaped pulses.
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42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.60.-v Laser optical systems: design and operation
02.60.Pn Numerical optimization

Velocity distribution function of sputtered Cu atoms obtained by time resolved optical absorption spectroscopy

Namjun Kang, Soo-ghee Oh, Freddy Gaboriau, and André Ricard

Rev. Sci. Instrum. 81, 013102 (2010); http://dx.doi.org/10.1063/1.3284528 (5 pages) | Cited 4 times

Online Publication Date: 14 January 2010

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A new method based on time resolved optical absorption spectroscopy is proposed to determine the velocity distribution function of sputtered Cu atoms in a magnetron plasma discharge. The method consists of applying a short pulse of 1.5 μs and of recording time variations in copper atom density in off pulse at different positions (1, 2, and 3 cm) from target surface under 3–30 mTorr. The time evolution of the density is then converted into velocity distribution. We estimate that only sputtered atoms with radial velocity component lower than 0.5 km/s are detected. The average velocity of Cu atoms is evaluated as the first order moment of the velocity distribution functions. The velocity distribution functions become the more dispersive the farther from target surface. The average velocities vary in the range of 2.5–3 km/s at the vicinity of target surface whereas at 3 cm a decrease from 2.5 to 1.2 km/s is observed at 30 mTorr.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.25.Os Emission, absorption, and scattering of electromagnetic radiation
52.40.Hf Plasma-material interactions; boundary layer effects
52.80.Vp Discharge in vacuum

Construction, figures of merit, and testing of a single-cell fluorescence excitation spectroscopy system

Laura S. Hill, Tammi L. Richardson, Luisa T. M. Profeta, Timothy J. Shaw, Christopher J. Hintz, Benjamin S. Twining, Evelyn Lawrenz, and Michael L. Myrick

Rev. Sci. Instrum. 81, 013103 (2010); http://dx.doi.org/10.1063/1.3270251 (13 pages)

Online Publication Date: 15 January 2010

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Characterization of phytoplankton community composition is critical to understanding the ecology and biogeochemistry of the oceans. One approach to taxonomic characterization takes advantage of differing pigmentation between algal taxa and thus differences in fluorescence excitation spectra. Analyses of bulk water samples, however, may be confounded by interference from chromophoric dissolved organic matter or suspended particulate matter. Here, we describe an instrument that uses a laser trap based on a Nikon TE2000-U microscope to position individual phytoplankton cells for confocal fluorescence excitation spectroscopy, thus avoiding interference from the surrounding medium. Quantitative measurements of optical power give data in the form of photons emitted per photon of exposure for an individual phytoplankton cell. Residence times for individual phytoplankton in the instrument can be as long as several minutes with no substantial change in their fluorescence excitation spectra. The laser trap was found to generate two-photon fluorescence from the organisms so a modification was made to release the trap momentarily during data acquisition. Typical signal levels for an individual cell are in the range of 106 photons/s of fluorescence using a monochromated 75 W Xe arc lamp excitation source with a 2% transmission neutral density filter.
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07.60.Rd Visible and ultraviolet spectrometers
87.64.kv Fluorescence
93.85.-q Instruments and techniques for geophysical research: Exploration geophysics
92.20.-h Chemical and biological oceanography

Development of a new rectangular NaI(Tl) scintillator and spectroscopy of low-energy charged particles

Hidehito Nakamura, Hisashi Kitamura, and Ryuta Hazama

Rev. Sci. Instrum. 81, 013104 (2010); http://dx.doi.org/10.1063/1.3276691 (4 pages) | Cited 3 times

Online Publication Date: 20 January 2010

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Standard NaI(Tl) scintillators have only one optical window and are housed in airtight protective enclosures to protect against hygroscopicity from moisture in the air. For these reasons, NaI(Tl) scintillators are unsuitable for the collection of scintillation photons or for the detection of low-energy (<1 MeV) charged particles. To overcome these disadvantages, a rectangular NaI(Tl) scintillator has been newly developed. In this paper, we estimate the photon response of this new scintillator. The energy resolution was ΔE (Full Width at Half Maximum) = 7.5±0.2% for 662 keV gamma rays from a maths standard source. The number of photoelectrons was 3,686 for the photoelectric peak. Good energy resolution and photon collection were therefore confirmed for this specialized form of NaI(Tl) scintillator. The ability of this scintillator to detect low-energy particles was confirmed by successful measurement of low-energy charged particles (250–700 keV region) from a maths thin film radioisotope source.
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29.40.Mc Scintillation detectors
07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
29.25.Rm Sources of radioactive nuclei

A slow atom source using a collimated effusive oven and a single-layer variable pitch coil Zeeman slower

S. C. Bell, M. Junker, M. Jasperse, L. D. Turner, Y.-J. Lin, I. B. Spielman, and R. E. Scholten

Rev. Sci. Instrum. 81, 013105 (2010); http://dx.doi.org/10.1063/1.3276712 (7 pages) | Cited 7 times

Online Publication Date: 22 January 2010

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We describe a simple slow atom source for loading a rubidium magneto-optical trap. The source includes an effusive oven with a long heated collimation tube. Almost all components are standard vacuum parts. The heating elements and thermocouples are external to the vacuum, protecting them from the hostile hot alkali environment and allowing repair without breaking vacuum. The thermal source is followed by a Zeeman slower with a single-layer coil of variable winding pitch. The single-layer design is simple to construct and has low inductance which allows for rapid switching of the magnetic field. The coil pitch was determined by fitting the analytic form of the magnetic field for a variable winding pitch to the desired magnetic field profile required to slow atoms. The measured magnetic field for the constructed coil is in excellent agreement with the desired field. The source produces atoms at 35 m/s with a flux up to 2×1010 cm−2 s−1 at 200 °C.
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78.20.Ls Magneto-optical effects
07.20.Dt Thermometers

Time-resolved x-ray scattering from laser-molten indium antimonide

R. Nüske, C. v. Korff Schmising, A. Jurgilaitis, H. Enquist, H. Navirian, P. Sondhauss, and J. Larsson

Rev. Sci. Instrum. 81, 013106 (2010); http://dx.doi.org/10.1063/1.3290418 (4 pages) | Cited 3 times

Online Publication Date: 22 January 2010

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We demonstrate a concept to study transient liquids with picosecond time-resolved x-ray scattering in a high-repetition-rate configuration. Femtosecond laser excitation of crystalline indium antimonide (InSb) induces ultrafast melting, which leads to a loss of the long-range order. The remaining local correlations of the liquid result in broad x-ray diffraction rings, which are measured as a function of delay time. After 2 ns the liquid structure factor shows close agreement with that of equilibrated liquid InSb. The measured decay of the liquid scattering intensity corresponds to the resolidification rate of 1 m/s in InSb.
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61.05.cf X-ray scattering (including small-angle scattering)
61.05.cp X-ray diffraction
78.70.Ck X-ray scattering
61.25.-f Studies of specific liquid structures
64.70.dj Melting of specific substances
78.47.J- Ultrafast spectroscopy (<1 psec)

An electrostatic autoresonant ion trap mass spectrometer

A. V. Ermakov and B. J. Hinch

Rev. Sci. Instrum. 81, 013107 (2010); http://dx.doi.org/10.1063/1.3276686 (8 pages) | Cited 3 times

Online Publication Date: 25 January 2010

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A new method for ion extraction from an anharmonic electrostatic trap is introduced. Anharmonicity is a common feature of electrostatic traps which can be used for small scale spatial confinement of ions, and this feature is also necessary for autoresonant ion extraction. With the aid of ion trajectory simulations, novel autoresonant trap mass spectrometers (ART-MSs) have been designed based on these very simple principles. A mass resolution ∼ 60 is demonstrated for the prototypes discussed here. We report also on the pressure dependencies, and the (mV) rf field strength dependencies of the ART-MS sensitivity. Importantly the new MS designs do not require heavy magnets, tight manufacturing tolerances, introduction of buffer gases, high power rf sources, nor complicated electronics. The designs described here are very inexpensive to implement relative to other instruments, and can be easily miniaturized. Possible applications are discussed.
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07.75.+h Mass spectrometers

Broadband 308 nm vibrational Raman spectroscopy of gaseous species using a potassium hydrogen phthalate liquid filter and polarization fluorescence suppression

J. E. A. Saunders and M. H. Davy

Rev. Sci. Instrum. 81, 013108 (2010); http://dx.doi.org/10.1063/1.3276683 (6 pages) | Cited 2 times

Online Publication Date: 26 January 2010

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Broadband XeCl excimer lasers operating at 308 nm are not currently used in the field of gas phase vibrational Raman spectroscopy (VRS). An explanation as to why alternative wavelengths, and in particular tuneable, narrowband lasers are currently preferred for gas phase VRS is presented in addition to demonstrating a setup which makes the XeCl laser a viable alternative when considering excitation sources for VRS. A solution of potassium hydrogen phthalate is shown to be a practical low-pass liquid filter and to reduce substantially the effects of Rayleigh scattering on collected Raman spectra. The use of a commercial beam polarizer is also shown to be effective in suppressing background fluorescence that otherwise necessitates the use of expensive tuneable, narrowband lasers when performing VRS with sources of background fluorescence. Finally, an unconventional excitation beam arrangement is shown to produce viable Raman spectra from which species concentrations and distributions can be determined.
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42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy
42.55.Lt Gas lasers including excimer and metal-vapor lasers
42.60.By Design of specific laser systems
07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
42.60.Fc Modulation, tuning, and mode locking
42.79.Ci Filters, zone plates, and polarizers

Optical lattices for atom-based quantum microscopy

Andreas Klinger, Skyler Degenkolb, Nathan Gemelke, Kathy-Anne Brickman Soderberg, and Cheng Chin

Rev. Sci. Instrum. 81, 013109 (2010); http://dx.doi.org/10.1063/1.3274813 (6 pages) | Cited 4 times

Online Publication Date: 27 January 2010

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We describe new techniques in the construction of optical lattices to realize a coherent atom-based microscope, comprised of two atomic species used as target and probe atoms, each in an independently controlled optical lattice. Precise and dynamic translation of the lattices allows atoms to be brought into spatial overlap to induce atomic interactions. For this purpose, we have fabricated two highly stable, hexagonal optical lattices, with widely separated wavelengths but identical lattice constants using diffractive optics. The relative translational stability of 12 nm permits controlled interactions and even entanglement operations with high fidelity. Translation of the lattices is realized through a monolithic electro-optic modulator array, capable of moving the lattice smoothly over one lattice site in 11 μs, or rapidly on the order of 100 ns.
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07.60.Pb Conventional optical microscopes
42.50.Wk Mechanical effects of light on material media, microstructures and particles

Subwavenumber charge-coupled device spectrometer calibration using molecular iodine laser-induced fluorescence

Joseph G. Lambert, Carlos Hernandez-Diaz, and J. Charles Williamson

Rev. Sci. Instrum. 81, 013110 (2010); http://dx.doi.org/10.1063/1.3287951 (11 pages)

Online Publication Date: 28 January 2010

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Spectrometers configured with charge-coupled devices (CCD) or other array-based detectors require calibration to convert from the pixel coordinate to a spectral coordinate. A CCD calibration method well suited for Raman spectroscopy has been developed based on the 514.5 nm Ar+ laser-induced fluorescence (LIF) spectrum of room-temperature molecular iodine vapor. Over 360 primary and secondary I2 LIF calibration lines spanning 510–645 nm were identified as calibrant peaks using an instrumental resolution of 1 cm−1. Two instrument calibration functions were evaluated with these peaks: a second-order polynomial and a function derived from simple optomechanical considerations. The latter function provided better fitting characteristics. Calibration using I2 LIF was tested with measurements of both laser light scattering and Raman spectra. The I2 LIF reference spectra and the signal spectra were recorded simultaneously, with no cross talk, by separating the two signals spatially along the vertical axis of the CCD imager. In this way, every CCD image could be independently calibrated. An accuracy and a precision of ±0.05 cm−1 were achieved with this calibration technique.
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07.81.+a Electron and ion spectrometers
42.55.Lt Gas lasers including excimer and metal-vapor lasers
06.20.fb Standards and calibration

Fast shuttling of ions in a scalable Penning trap array

D. R. Crick, S. Donnellan, S. Ananthamurthy, R. C. Thompson, and D. M. Segal

Rev. Sci. Instrum. 81, 013111 (2010); http://dx.doi.org/10.1063/1.3276699 (5 pages) | Cited 3 times

Online Publication Date: 29 January 2010

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We report on the design and testing of an array of Penning ion traps made from printed circuit board. The system enables fast shuttling of ions from one trapping zone to another, which could be of use in quantum information processing. We describe simulations carried out to determine the optimal potentials to be applied to the trap electrodes for enabling this movement. The results of a preliminary experiment with a cloud of laser cooled calcium ions demonstrate a round-trip shuttling efficiency of up to 75%.
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37.10.Ty Ion trapping
42.50.Wk Mechanical effects of light on material media, microstructures and particles
Author Select

A novel merged beams apparatus to study anion-neutral reactions

H. Bruhns, H. Kreckel, K. Miller, M. Lestinsky, B. Seredyuk, W. Mitthumsiri, B. L. Schmitt, M. Schnell, X. Urbain, M. L. Rappaport, C. C. Havener, and D. W. Savin

Rev. Sci. Instrum. 81, 013112 (2010); http://dx.doi.org/10.1063/1.3280227 (10 pages) | Cited 7 times

Online Publication Date: 29 January 2010

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We have developed a novel laboratory instrument for studying gas phase, anion-neutral chemistry. To the best of our knowledge, this is the first such apparatus which uses fast merged beams to investigate anion-neutral chemical reactions. As proof-of-principle we have detected the associative detachment reaction H−+H→H2+e−. Here we describe the apparatus in detail and discuss related technical and experimental issues.
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82.30.Nr Association, addition, insertion, cluster formation
82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions
back to top Particle Sources, Optics and Acceleration; Particle Detectors

Production of negative osmium ions by laser desorption and ionization

D. Rodríguez, V. Sonnenschein, K. Blaum, M. Block, H.-J. Kluge, A. M. Lallena, S. Raeder, and K. Wendt

Rev. Sci. Instrum. 81, 013301 (2010); http://dx.doi.org/10.1063/1.3276685 (4 pages) | Cited 2 times

Online Publication Date: 6 January 2010

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The interest to produce negative osmium ions is manifold in the realm of high-accuracy ion trap experiments: high-resolution nearly Doppler-free laser spectroscopy, antihydrogen formation in its ground state, and contributions to neutrino mass spectrometry. Production of these ions is generally accomplished by sputtering an Os sample with Cs+ ions at tens of keV. Though this is a well-established method commonly used at accelerators, these kind of sources are quite demanding and tricky to operate. Therefore, the development of a more straightforward and cost effective production scheme will be of benefit for ion trap and other experiments. Such a scheme makes use of desorption and ionization with pulsed lasers and identification of the ions by time-of-flight mass spectrometry. First investigations of negative osmium ion production using a pulsed laser for desorption and ionization and a commercial matrix-assisted laser desorption/ionization time-of-flight system for identification has demonstrated the suitability of this technique. More than 103 negative osmium ions per shot were registered after bombarding pure osmium powder with a 5 ns pulse width Nd:yttrium aluminum garnet laser. The limitation in the ion number was imposed by the detection limit of the microchannel plate detector.
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68.43.Tj Photon stimulated desorption
79.20.La Photon- and electron-stimulated desorption
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Design and development of indirectly heated solid cathode for strip type electron gun

Namita Maiti, S. Mukherjee, Bhunesh Kumar, U. D. Barve, V. B. Suryawanshi, and A. K. Das

Rev. Sci. Instrum. 81, 013302 (2010); http://dx.doi.org/10.1063/1.3271539 (10 pages) | Cited 1 time

Online Publication Date: 7 January 2010

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Design analysis of a high power indirectly heated solid cathode (for a 200 kW, 45 kV, and 270° bent strip type electron gun) has been presented. The design approach consists of simulation followed by extensive experimentation with different cathode configurations. The preferred cathode is of trapezoidal section (8×4×2 mm3) with an emitting area of 110×4 mm2 made up of tantalum operating at about 2500 K. The solid cathode at the operating temperature of 2500 K generated a well defined electron beam. Electromagnetic and thermomechanical simulation is used to optimize the shape of the beam. Thermal modeling has also been used to analyze the temperature and stress distribution on the electrodes. The simulation results are validated by experimental measurement.
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84.47.+w Vacuum tubes

Highly efficient pulsed power supply system with a two-stage LC generator and a step-up transformer for fast capillary discharge soft x-ray laser at shorter wavelength

Yusuke Sakai, Shnsuke Takahashi, Takanori Komatsu, Inho Song, Masato Watanabe, and Eiki Hotta

Rev. Sci. Instrum. 81, 013303 (2010); http://dx.doi.org/10.1063/1.3276705 (3 pages) | Cited 8 times

Online Publication Date: 14 January 2010

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Highly efficient and compact pulsed power supply system for a capillary discharge soft x-ray laser (SXRL) has been developed. The system consists of a 2.2 μF two-stage LC inversion generator, a 2:54 step-up transformer, a 3 nF water capacitor, and a discharge section with a few tens of centimeter length capillary. Adoption of the pulsed transformer in combination with the LC inversion generator enables us to use only one gap switch in the circuit for charging the water capacitor up to about 0.5 MV. Furthermore, step-up ratio of a water capacitor voltage to a LC inversion generator initial charging voltage is about 40 with energy transfer efficiency of about 50%. It also leads to good reproducibility of a capillary discharge which is necessary for lasing a SXRL stably. For the study of the possibility of lasing a SXRL at shorter wavelength in a small laboratory scale, high-density and high-temperature plasma column suitable for the laser can be generated relatively easily with this system.
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42.55.Vc X- and γ-ray lasers
84.30.Sk Pulse and digital circuits
84.30.Jc Power electronics; power supply circuits

A laser-Compton scattering prototype experiment at 100 MeV linac of Shanghai Institute of Applied Physics

W. Luo, W. Xu, Q. Y. Pan, X. Z. Cai, J. G. Chen, Y. Z. Chen, G. T. Fan, G. W. Fan, W. Guo, Y. J. Li, W. H. Liu, G. Q. Lin, Y. G. Ma, W. Q. Shen, X. C. Shi, et al.

Rev. Sci. Instrum. 81, 013304 (2010); http://dx.doi.org/10.1063/1.3282445 (9 pages) | Cited 3 times

Online Publication Date: 19 January 2010

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As a prototype of the Shanghai Laser Electron Gamma Source in the Shanghai Synchrotron Radiation Facility, an x-ray source based on laser-Compton scattering (LCS) has been installed at the terminal of the 100 MeV linac of the Shanghai Institute of Applied Physics. LCS x-rays are generated by interactions between Q-switched Nd:yttrium aluminum garnet laser pulses [with wavelength of 1064 nm and pulse width of 21 ns (full width at half maximum)] and electron bunches [with energy of 108 MeV and pulse width of 0.95 ns (rms)] at an angle of 42° between laser and electron beam. In order to measure the energy spectrum of LCS x-rays, a Si(Li) detector along the electron beam line axis is positioned at 9.8 m away from a LCS chamber. After background subtraction, the LCS x-ray spectrum with the peak energy of 29.1±4.4∣stat±2.1∣syst keV and the peak width (rms) of 7.8±2.8∣stat±0.4∣syst keV is observed. Normally the 100 MeV linac operates with the electron macropulse charge of 1.0 nC/pulse, and the electron and laser collision repetition rate of 20 Hz. Therefore, the total LCS x-ray flux of (5.2±2.0)×102 Hz can be achieved.
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29.20.Ej Linear accelerators
41.75.Fr Electron and positron beams
29.27.Eg Beam handling; beam transport
29.25.Bx Electron sources
07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors

Physics design of a 100 keV acceleration grid system for the diagnostic neutral beam for international tokamak experimental reactor

M. J. Singh and H. P. L. De Esch

Rev. Sci. Instrum. 81, 013305 (2010); http://dx.doi.org/10.1063/1.3271535 (13 pages) | Cited 4 times

Online Publication Date: 20 January 2010

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This paper describes the physics design of a 100 keV, 60 A H− accelerator for the diagnostic neutral beam (DNB) for international tokamak experimental reactor (ITER). The accelerator is a three grid system comprising of 1280 apertures, grouped in 16 groups with 80 apertures per beam group. Several computer codes have been used to optimize the design which follows the same philosophy as the ITER Design Description Document (DDD) 5.3 and the 1 MeV heating and current drive beam line [ R. Hemsworth, H. Decamps, J. Graceffa, B. Schunke, M. Tanaka, M. Dremel, A. Tanga, H. P. L. De Esch, F. Geli, J. Milnes, T. Inoue, D. Marcuzzi, P. Sonato, and P. Zaccaria, Nucl. Fusion 49, 045006 (2009) ]. The aperture shapes, intergrid distances, and the extractor voltage have been optimized to minimize the beamlet divergence. To suppress the acceleration of coextracted electrons, permanent magnets have been incorporated in the extraction grid, downstream of the cooling water channels. The electron power loads on the extractor and the grounded grids have been calculated assuming 1 coextracted electron per ion. The beamlet divergence is calculated to be 4 mrad. At present the design for the filter field of the RF based ion sources for ITER is not fixed, therefore a few configurations of the same have been considered. Their effect on the transmission of the electrons and beams through the accelerator has been studied. The OPERA-3D code has been used to estimate the aperture offset steering constant of the grounded grid and the extraction grid, the space charge interaction between the beamlets and the kerb design required to compensate for this interaction. All beamlets in the DNB must be focused to a single point in the duct, 20.665 m from the grounded grid, and the required geometrical aimings and aperture offsets have been calculated.
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52.70.-m Plasma diagnostic techniques and instrumentation
52.55.Fa Tokamaks, spherical tokamaks
52.80.-s Electric discharges
52.65.-y Plasma simulation

High quality single shot diffraction patterns using ultrashort megaelectron volt electron beams from a radio frequency photoinjector

P. Musumeci, J. T. Moody, C. M. Scoby, M. S. Gutierrez, H. A. Bender, and N. S. Wilcox

Rev. Sci. Instrum. 81, 013306 (2010); http://dx.doi.org/10.1063/1.3292683 (3 pages) | Cited 12 times

Online Publication Date: 22 January 2010

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Single shot diffraction patterns using a 250-fs-long electron beam have been obtained at the UCLA Pegasus laboratory. High quality images with spatial resolution sufficient to distinguish closely spaced peaks in the Debye–Scherrer ring pattern have been recorded by scattering the 1.6 pC 3.5 MeV electron beam generated in the rf photoinjector off a 100-nm-thick Au foil. Dark current and high emittance particles are removed from the beam before sending it onto the diffraction target using a 1 mm diameter collimating hole. These results open the door to the study of irreversible phase transformations by single shot MeV electron diffraction.
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61.05.J- Electron diffraction and scattering
72.40.+w Photoconduction and photovoltaic effects
41.75.Fr Electron and positron beams

Absolute response of Fuji imaging plate detectors to picosecond-electron bunches

K. Zeil, S. D. Kraft, A. Jochmann, F. Kroll, W. Jahr, U. Schramm, L. Karsch, J. Pawelke, B. Hidding, and G. Pretzler

Rev. Sci. Instrum. 81, 013307 (2010); http://dx.doi.org/10.1063/1.3284524 (6 pages) | Cited 10 times

Online Publication Date: 26 January 2010

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The characterization of the absolute number of electrons generated by laser wakefield acceleration often relies on absolutely calibrated FUJI imaging plates (IP), although their validity in the regime of extreme peak currents is untested. Here, we present an extensive study on the dependence of the sensitivity of BAS-SR and BAS-MS IP to picosecond electron bunches of varying charge of up to 60 pC, performed at the electron accelerator ELBE, making use of about three orders of magnitude of higher peak intensity than in prior studies. We demonstrate that the response of the IPs shows no saturation effect and that the BAS-SR IP sensitivity of 0.0081 photostimulated luminescence per electron number confirms surprisingly well data from previous works. However, the use of the identical readout system and handling procedures turned out to be crucial and, if unnoticed, may be an important error source.
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41.75.Jv Laser-driven acceleration
52.25.Tx Emission, absorption, and scattering of particles
29.20.Ej Linear accelerators
52.38.Kd Laser-plasma acceleration of electrons and ions
41.75.Fr Electron and positron beams
back to top Nuclear Physics, Fusion and Plasmas

Dynamic programming based time-delay estimation technique for analysis of time-varying time-delay

Deepak K. Gupta, George R. McKee, and Raymond J. Fonck

Rev. Sci. Instrum. 81, 013501 (2010); http://dx.doi.org/10.1063/1.3280161 (8 pages)

Online Publication Date: 6 January 2010

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A new time-delay estimation (TDE) technique based on dynamic programming is developed to measure the time-varying time-delay between two signals. The dynamic programming based TDE technique provides a frequency response five to ten times better than previously known TDE techniques, namely, those based on time-lag cross-correlation or wavelet analysis. Effects of frequency spectrum, signal-to-noise ratio, and amplitude of time-delay on response of the TDE technique (represented as transfer function) are studied using simulated data signals. The transfer function for the technique decreases with increase in noise in signal; however it is independent of signal spectrum shape. The dynamic programming based TDE technique is applied to the beam emission spectroscopy diagnostic data to measure poloidal velocity fluctuations, which led to the observation of theoretically predicted zonal flows in high-temperature tokamak plasmas.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
02.60.Pn Numerical optimization
52.55.Fa Tokamaks, spherical tokamaks
52.30.-q Plasma dynamics and flow

Controllable optical emission spectroscopy diagnostic system for analysis of process chemistries

P. L. Stephan Thamban, Jimmy Hosch, and M. J. Goeckner

Rev. Sci. Instrum. 81, 013502 (2010); http://dx.doi.org/10.1063/1.3276706 (4 pages) | Cited 2 times

Online Publication Date: 8 January 2010

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Optical emission spectroscopy (OES) diagnostics have been employed for many years in plasma etch end point detection schemes. Unfortunately some newer process systems have much lower optical emission or limited optical access. To overcome such limitations, an OES diagnostic system making use of variable e-beam has been developed. That system is described and initial experimental results are presented. A strong correlation is observed between the optical emission intensity and e-beam current, a measurable electrical parameter. This correlation offers means to normalize optical signal and to be used as a feedback input to the electronics that control the plasma source. In addition there is a measurable response from the different lines due to energy of the electrons, indicating a new degree of freedom in the diagnostic that can be tapped for more precise analysis of end point.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
82.33.Xj Plasma reactions (including flowing afterglow and electric discharges)
52.50.Dg Plasma sources
52.40.Mj Particle beam interactions in plasmas

An experiment for the investigation of forces on microparticles in ion beams

Viktor Schneider, Thomas Trottenberg, Iulian Teliban, and Holger Kersten

Rev. Sci. Instrum. 81, 013503 (2010); http://dx.doi.org/10.1063/1.3271536 (5 pages) | Cited 6 times

Online Publication Date: 12 January 2010

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A novel experiment for the study of forces on microparticles in ion beams is presented. A broad beam ion source provides a vertically upward directed beam wherein 100 μm hollow glass spheres are injected. The particles are illuminated by a diode laser and recorded with a charge-coupled device camera. From the trajectories the acceleration and the net force on the particles are determined. Information on energetic neutral atoms is achieved, which is not accessible by electrostatic methods.
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52.40.Mj Particle beam interactions in plasmas
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.27.Lw Dusty or complex plasmas; plasma crystals

Cherenkov-type diamond detectors for measurements of fast electrons in the TORE-SUPRA tokamak

L. Jakubowski, M. J. Sadowski, J. Zebrowski, M. Rabinski, K. Malinowski, R. Mirowski, Ph. Lotte, J. Gunn, J-Y. Pascal, G. Colledani, V. Basiuk, M. Goniche, and M. Lipa

Rev. Sci. Instrum. 81, 013504 (2010); http://dx.doi.org/10.1063/1.3280221 (9 pages) | Cited 3 times

Online Publication Date: 14 January 2010

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The paper presents a schematic design and tests of a system applicable for measurements of fast electron pulses emitted from high-temperature plasma generated inside magnetic confinement fusion machines, and particularly in the TORE-SUPRA facility. The diagnostic system based on the registration of the Cherenkov radiation induced by fast electrons within selected solid radiators is considered, and electron low-energy thresholds for different radiators are given. There are some estimates of high thermal loads, which might be deposited by intense electron beams upon parts of the diagnostic equipment within the TORE-SUPRA device. There are some proposed measures to overcome this difficulty by the selection of appropriate absorption filters and Cherenkov radiators, and particularly by the application of a fast-moving reciprocating probe. The paper describes the measuring system, its tests, as well as some results of the preliminary measurements of fast electrons within TORE-SUPRA facility.
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52.70.-m Plasma diagnostic techniques and instrumentation
52.55.-s Magnetic confinement and equilibrium
52.55.Fa Tokamaks, spherical tokamaks
52.25.-b Plasma properties

Heavy ion beam probe coordinate mapping and calibration at WEGA stellarator

Y. Podoba, M. Otte, F. Wagner, L. Krupnik, and A. Zhezhera

Rev. Sci. Instrum. 81, 013505 (2010); http://dx.doi.org/10.1063/1.3280176 (5 pages) | Cited 1 time

Online Publication Date: 19 January 2010

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The heavy ion beam probe (HIBP) is an established nonperturbing diagnostic for high spatially and temporary resolved measurements of magnetically confined plasma parameters such as potential, density, and temperature. These quantities can be determined from the change in the ion beam parameters (charge, intensity, and trajectory) passing through a plasma volume due to collisions with electrons and interaction with the confining magnetic field. One of the problems that should be solved during HIBP installation and tuning is the coordinate matching. Conventionally the coordinate mapping of the HIBP measurement point is provided by ray tracing calculations of the ion beam in the magnetic field. However, it is very difficult to include all physical effects and uncertainties in the model. Thus, the result of the calculations may differ from the real probing position. In order to improve the mapping precision of the HIBP installed at the WEGA stellarator an additional measurement of the beam position is provided using a primary beam detector array inside the vacuum vessel. This allows comparing the measured and calculated ion beam positions in order to prove the calculated coordinate precision and include adjustments in the calculation code if necessary. The principle and the results of this calibration, which is not specific to WEGA but could be adapted to other experiments as well, are presented in this work.
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52.40.Mj Particle beam interactions in plasmas
52.20.Fs Electron collisions
52.70.Nc Particle measurements
06.20.fb Standards and calibration
52.55.Jd Magnetic mirrors, gas dynamic traps
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A method of particle transport study using supersonic molecular beam injection and microwave reflectometry on HL-2A tokamak

W. W. Xiao, X. L. Zou, X. T. Ding, J. Q. Dong, L. H. Yao, S. D. Song, Z. T. Liu, Y. D. Gao, B. B. Feng, X. M. Song, Q. W. Yang, L. W. Yan, Yi Liu, X. R. Duan, C. H. Pan, et al.

Rev. Sci. Instrum. 81, 013506 (2010); http://dx.doi.org/10.1063/1.3274201 (6 pages) | Cited 3 times

Online Publication Date: 25 January 2010

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A method of the particle transport study using supersonic molecular beam injection (SMBI) and microwave reflectometry is reported in this paper. Experimental results confirm that pulsed SMBI is a good perturbation source with deeper penetration and better localization than the standard gas puffing. The local density modulation is induced using the pulsed SMBI and the perturbation density is measured by the microwave reflectometry. Using Fourier transform analysis for the local density perturbation, radial profiles of the amplitude and phase of the density modulation can be obtained. The experimental results in HL-2A show that the particle injected by SMBI is located at about r/a = 0.65–0.75. The position of the main particle source can be determined through three aspects: the minimum of the phase of the first harmonic of the Fourier transform of the modulated density measured by microwave reflectometry; the Ha intensity profile and the local density increase ratio. The maximum of the amplitude of the first harmonic shifts often inward relative to the particle source location, which indicates clearly there is an inward particle pinch in this area. Good agreement has been found between the experimental results and the simulation using analytical transport model. The particle diffusivity D and the particle convection velocity V have been obtained by doing this simulation. The sensitivity in the transport coefficients of the amplitude and the phase of the density modulation has been discussed.
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52.55.Fa Tokamaks, spherical tokamaks
52.55.-s Magnetic confinement and equilibrium
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