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Mar 2000

Volume 71, Issue 3, pp. 1243-1570

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back to top OPTICS; ATOMS and MOLECULES; SPECTROSCOPY

A novel intensity interferometer for synchrotron radiation in the vacuum ultraviolet and soft x-ray regions

RenZhong Tai, Yasuhiro Takayama, Noriko Takaya, Tsuneaki Miyahara, Shigeru Yamamoto, Hiroshi Sugiyama, Junji Urakawa, Hitoshi Hayano, and Masami Ando

Rev. Sci. Instrum. 71, 1256 (2000); http://dx.doi.org/10.1063/1.1150450 (8 pages) | Cited 3 times

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Based upon a method of Hanbury-Brown and Twiss, while considering the nonstationary characteristics of synchrotron radiation (SR), a novel optical intensity interferometer was constructed to extract the true two-photon correlation of soft x-ray SR. This intensity interferometer consists of an optical vacuum chamber, which includes a wire scanner, a beam divider, and a grating monochromator with a coherence time modulator, and of an electric correlator which completes the multiplication of two broadband electric currents. The technique of coherence time modulation, together with the two bandpass filters in the correlator, play an essential role to cancel a huge trivial correlation, which arises from the accidental coincidence between a pair of divided pulses being largely enhanced by the finite slow time response of the detection system compared to the coherence time of the photon. A preliminary performance test was conducted, and the results exhibit satisfactory functions of this interferometer. © 2000 American Institute of Physics.
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41.60.Ap Synchrotron radiation
07.85.Qe Synchrotron radiation instrumentation
42.72.-g Optical sources and standards
07.60.Ly Interferometers
42.50.Ar Photon statistics and coherence theory

Measurement of the beam size at the compact superconducting storage ring by the SR interferometer

I. Sakai, Y. Yamamoto, T. Mitsuhashi, D. Amano, and H. Iwasaki

Rev. Sci. Instrum. 71, 1264 (2000); http://dx.doi.org/10.1063/1.1150451 (4 pages) | Cited 2 times

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The beam size in the compact superconducting storage ring AURORA was measured using the SR interferometer developed by one of the present authors. The spatial coherence of the radiation beam in the visible range was derived from the visibility of the interferogram recorded by a CCD camera and its dependence on the spatial frequency has shown that the beam profile is described by a Gaussian. Analysis of the data has yielded the beam size to be 10.5 μm in the vertical direction, which is unexpectedly small for the storage ring having only a weak beam focusing system. © 2000 American Institute of Physics.
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29.27.Fh Beam characteristics
29.20.db Storage rings and colliders
07.85.Qe Synchrotron radiation instrumentation

Timing control of an intense picosecond pulse laser to the SPring-8 synchrotron radiation pulses

Yoshihito Tanaka, Toru Hara, Hideo Kitamura, and Tetsuya Ishikawa

Rev. Sci. Instrum. 71, 1268 (2000); http://dx.doi.org/10.1063/1.1150452 (7 pages) | Cited 11 times

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We have developed a control system to synchronize intense picosecond laser pulses to the hard x-ray synchrotron radiation (SR) pulses of SPring-8. A regeneratively amplified mode-locked Ti:sapphire laser is synchronized to 40 ps SR pulses by locking the laser to the radio frequency of the ring. The synchronization of the pulses is monitored by detecting both beams simultaneously on a gold photocathode of a streak camera. This method enabled us to make a precise measurement of the time interval between the beams, even if the trigger of the streak camera drifts. Synchronization between the laser and the SR pulses has been achieved with a precision of ±2 ps for some hours. The stable timing control ensures the possibility of making two-photon excitation and pump–probe experiments with time resolution of a few tens of ps (limited by the pulse duration of the SR). We have used this system to show that closing undulator gaps in the storage ring shifts the arrival time of the SR pulses, in accord with expectations for the increased power loss. © 2000 American Institute of Physics.
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07.05.Dz Control systems
07.85.Qe Synchrotron radiation instrumentation
41.60.Ap Synchrotron radiation
42.60.Fc Modulation, tuning, and mode locking
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

A frequency division multiplexed low-finesse fiber optic Fabry–Perot sensor system for strain and displacement measurements

T. Liu and G. F. Fernando

Rev. Sci. Instrum. 71, 1275 (2000); http://dx.doi.org/10.1063/1.1150453 (4 pages) | Cited 19 times

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We report a novel frequency multiplexing method for addressing low finesse fiber Fabry–Perot sensors using a white light source and a CCD based monochromator. The absolute optical path length imbalance of the sensors can be determined using this method. The concept was demonstrated with three fiber Fabry–Perot interferometers for strain and displacement measurements. The accuracy is better than 0.01 μm and the maximum range is approximately 1 mm. © 2000 American Institute of Physics.
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42.81.Pa Sensors, gyros
07.60.Ly Interferometers
06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
07.10.Pz Instruments for strain, force, and torque

Full-field x-ray fluorescence imaging microscope with a Wolter mirror

Akihisa Takeuchi, Sadao Aoki, Kimitake Yamamoto, Hidekazu Takano, Norio Watanabe, and Masami Ando

Rev. Sci. Instrum. 71, 1279 (2000); http://dx.doi.org/10.1063/1.1150454 (7 pages) | Cited 3 times

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Full-field x-ray fluorescence (XRF) and transmission x-ray microscopic images were obtained with a Wolter-type mirror (10× magnification). A synchrotron radiation white beam (4–20 keV) from a bending magnet beamline at the Photon Factory was used to obtain XRF images and a conventional laboratory x-ray source (8.04 keV) was used to obtain transmission x-ray images. The effects of the coherent and the incoherent scattering x rays on the contrast of an XRF image were estimated. The scattering angle between the incidence x ray and the optical axis of the XRF microscope should be 90° to obtain the highest contrast image when the incidence x ray is horizontally polarized. Observation of small metallic inclusions in the synthesized diamond showed that the contrast of the XRF image was better than that of the transmission x-ray image. © 2000 American Institute of Physics.
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07.85.Tt X-ray microscopes
42.79.Bh Lenses, prisms and mirrors
07.85.Qe Synchrotron radiation instrumentation

Improved measurements of noise and resolution of x-ray framing cameras at 1–2 keV

Carl J. Pawley and A. V. Deniz

Rev. Sci. Instrum. 71, 1286 (2000); http://dx.doi.org/10.1063/1.1150497 (10 pages) | Cited 9 times

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We describe x-ray framing cameras that were developed for experiments on the Nike laser system at the Naval Research Laboratory. These cameras have internal impedance matching to allow use of 50Ω pulsing systems from 100 ps to several nanoseconds, or for long pulse/dc operation. The cameras have been optimized for spatial resolution and low light scatter using aluminized phosphors. One of these cameras has been coupled to a charge coupled device camera and the total system was tested for resolution and image noise using both electrons and x rays. The spatial resolution was found to be well fitted to a Gaussian modulation transfer function with a value of 0.5 at 10 lp/mm. A detailed analysis of the noise in the images was performed for electrons and x rays. The noise in the images is determined by a detective quantum efficiency of approximately 10% for 1–2 keV x-ray photons.
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07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
85.60.Ha Photomultipliers; phototubes and photocathodes
52.70.La X-ray and γ-ray measurements
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
85.60.Gz Photodetectors (including infrared and CCD detectors)

Distributed-feedback dye laser for picosecond ultraviolet and visible spectroscopy

Perry P. Yaney, Dahv A. V. Kliner, Paul E. Schrader, and Roger L. Farrow

Rev. Sci. Instrum. 71, 1296 (2000); http://dx.doi.org/10.1063/1.1150455 (10 pages) | Cited 18 times

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We describe the design and operation of a tunable, picosecond laser system for use in time-resolved spectroscopic measurements in the visible and ultraviolet (UV) spectral region. The laser is designed for fine tuning and high wavelength stability. A Nd:YAG-pumped distributed-feedback dye laser (DFDL) generates pulses that are ∼100 ps in duration with a nearly transform-limited linewidth (∼5 GHz) at a 20 Hz repetition rate. The DFDL pulses are amplified in two bow-tie amplifiers, providing pulse energies of up to 3.0 mJ; the amplified pulses may be frequency doubled to the UV spectral region, providing up to 1.0 mJ. The DFDL wavelength is computer stabilized to within ±0.8 pm (±0.7 GHz, two standard deviations), allowing the wavelength to be stationed on a narrow atomic or molecular transition or permitting nearly continuous spectral scans. Application of the laser system to studies of OH energy transfer has been demonstrated; both laser-induced-fluorescence and degenerate-four-wave-mixing spectra have been recorded. © 2000 American Institute of Physics.
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42.60.By Design of specific laser systems
42.55.Mv Dye lasers
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
07.60.-j Optical instruments and equipment
42.65.Re Ultrafast processes; optical pulse generation and pulse compression
42.62.Fi Laser spectroscopy
07.60.Rd Visible and ultraviolet spectrometers
42.60.Fc Modulation, tuning, and mode locking
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
back to top CHARGED PARTICLE SOURCES, OPTICS and ACCELERATION

Characterization of a Hadamard transform time-of-flight mass spectrometer

Ansgar Brock, Nestor Rodriguez, and Richard N. Zare

Rev. Sci. Instrum. 71, 1306 (2000); http://dx.doi.org/10.1063/1.1150456 (13 pages) | Cited 22 times

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A pseudorandom time-of-flight method (also called the cross-correlation method) has been used to perform time-of-flight mass spectrometry with a duty cycle of 50%. Modulation of an ion beam is accomplished by deflecting the ion beam with an interleaved comb of oppositely charged elements. Maximum-length pseudorandom sequences based on Hadamard-type difference sets are produced by feedback shift register circuitry and used for ion beam modulation. The inverse transformation of the recorded signal is carried out speedily with the help of the fast Hadamard transform, which allows real-time monitoring of the mass spectrum. The components of the instrument are described, and its performance is characterized. Trajectory simulations are found to be in good agreement with experimental findings, which aids in understanding the modulation dynamics. It is found that the wire comb modulator can be modeled as a set of ideal deflection plates of length 0.875 l, where l is the spacing between oppositely charged wires. © 2000 American Institute of Physics.
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07.75.+h Mass spectrometers
41.85.-p Beam optics
07.05.Hd Data acquisition: hardware and software

A pump-probe photoionization mass spectrometer utilizing tunable extreme ultraviolet laser-produced-plasma radiation

R. Flesch, M. C. Schürmann, M. Hunnekuhl, H. Meiss, J. Plenge, and E. Rühl

Rev. Sci. Instrum. 71, 1319 (2000); http://dx.doi.org/10.1063/1.1150457 (6 pages) | Cited 9 times

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An experimental device is reported that utilizes time-correlated nanosecond light pulses in combination with photoionization mass spectrometry. A primary light pulse is generated by a tunable dye laser in the ultraviolet regime, which photolyzes neutral gas targets under collision free conditions. Subsequently, a time-correlated extreme ultraviolet-light pulse comes from a laser-produced plasma that is monochromatized in the 10–25 eV regime. The photolysis products are ionized by one-photon absorption, so that the cations are finally detected by time-of-flight mass spectrometry. The performance of this experimental approach is characterized by investigating the primary photolysis products of chlorine dioxide. Finally, possible applications of this approach are briefly discussed. © 2000 American Institute of Physics.
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07.75.+h Mass spectrometers
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
07.60.-j Optical instruments and equipment
82.50.Bc Processes caused by infrared radiation
82.50.Hp Processes caused by visible and UV light
42.55.Vc X- and γ-ray lasers

Pulsed field ionization-photoion spectroscopy using two-bunch synchrotron radiation: Time-of-flight selection scheme

G. K. Jarvis, R. C. Shiell, J. W. Hepburn, Y. Song, and C. Y. Ng

Rev. Sci. Instrum. 71, 1325 (2000); http://dx.doi.org/10.1063/1.1150458 (7 pages) | Cited 8 times

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We have demonstrated that the time-of-flight (TOF) selection method for pulsed field ionization (PFI) photoelectron detection [Jarvis et al., Rev. Sci. Instrum. 70, 2615 (1999)] can also be applied for the detection of PFI-photoions (PFI-PIs) using the two-bunch synchrotron radiation at the Advanced Light Source. By employing the supersonic beam technique to lower the translational temperature of the sample gas, we show that background prompt ions formed in direct and spontaneous autoionization processes arrive at the ion detector in a pattern similar to that of the vacuum ultraviolet light bunches. The PFI-PIs formed at dark gaps can be designed to arrive at the detector in between adjacent prompt ion peaks, enabling the gating of the PFI-PI signal with only minor contamination from background prompt ions. This experiment has revealed important considerations for the design of a general TOF selection scheme for PFI-PI detection using synchrotron radiation. © 2000 American Institute of Physics.
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07.81.+a Electron and ion spectrometers
07.75.+h Mass spectrometers
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
07.60.-j Optical instruments and equipment

Development of a high precision quadrupole mass filter using the zero-method control circuit

O. Tsukakoshi, T. Hayashi, K. Yamamuro, and M. Nakamura

Rev. Sci. Instrum. 71, 1332 (2000); http://dx.doi.org/10.1063/1.1150459 (5 pages)

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A high precision quadrupole mass filter has been developed using the zero-method control circuit. With this method, peak values of a control voltage are compared with a high-precision reference voltage and detected by a diode and signal-producing resistance connected in series. The dc component of the signal is selectively amplified and fed back to a module in the amplifying system of the rf voltage so as to minimize the voltage in excess of the reference voltage. An instrument has been constructed and the doublet of 4He+–D2+ has been successfully separated. © 2000 American Institute of Physics.
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07.75.+h Mass spectrometers
84.30.Jc Power electronics; power supply circuits

Velocity imaging photoionization coincidence apparatus for the study of angular correlations between electrons and fragment ions

M. Takahashi, J. P. Cave, and J. H. D. Eland

Rev. Sci. Instrum. 71, 1337 (2000); http://dx.doi.org/10.1063/1.1150460 (8 pages) | Cited 50 times

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A new apparatus has been developed to detect and measure angular correlations between energy-selected photoelectrons and coincident mass-analyzed fragment ions from photoionization at selected wavelengths. It achieves velocity imaging for electrons and ions simultaneously and has high collection efficiency for both particles, with moderate mass and energy resolution. Angular and energy correlations between the two particles are measured, as are the angular distributions of each particle independently relative to the light polarization direction. Fixed-molecule electron angular distributions are deduced in cases of pure axial recoil. Examples of angular distributions from photoionization of diatomic molecules are reported. © 2000 American Institute of Physics.
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07.81.+a Electron and ion spectrometers
07.57.-c Infrared, submillimeter wave, microwave and radiowave instruments and equipment
07.60.-j Optical instruments and equipment
07.75.+h Mass spectrometers

Measurement of mechanical vibrations excited in aluminum resonators by 0.6 GeV electrons

G. D. van Albada, E. Coccia, V. Fafone, H. van der Graaf, G. Heijboer, J. W. van Holten, W. J. Kasdorp, J. B. van der Laan, L. Lapikás, G. Mazzitelli, G. J. L. Nooren, C. W. J. Noteboom, J. E. J. Oberski, G. Pallottino, H. Z. Peek, et al.

Rev. Sci. Instrum. 71, 1345 (2000); http://dx.doi.org/10.1063/1.1150461 (10 pages) | Cited 6 times

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We present measurements of mechanical vibrations induced by 0.6 GeV electrons impinging on cylindrical and spherical aluminum resonators. To monitor the amplitude of the resonator’s vibrational modes we used piezoelectric ceramic sensors calibrated by standard accelerometers. Calculations using the thermo-acoustic conversion model agree well with the experimental data, as demonstrated by specific variations of the excitation strengths with the absorbed energy, and with the traversing particles’ track positions. For the first longitudinal mode of the cylindrical resonator we measured a conversion factor of 7.4±1.4 nm/J, confirming the model value of 10 nm/J. Also, for the spherical resonator, we found the model values for the L = 2 and L = 1 mode amplitudes to be consistent with our measurement. We thus have confirmed the applicability of the model, and we note that calculations based on the model have shown that next generation resonant mass gravitational wave detectors can only be expected to reach their intended ultrahigh sensitivity if they are shielded by an appreciable amount of rock, where a veto detector can reduce the background of remaining impinging cosmic rays effectively. © 2000 American Institute of Physics.
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04.80.Nn Gravitational wave detectors and experiments
95.55.Ym Gravitational radiation detectors; mass spectrometers; and other instrumentation and techniques
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
06.20.F- Units and standards

Absolute calibration of a multichannel plate detector for low energy O, O−, and O+

T. M. Stephen and B. L. Peko

Rev. Sci. Instrum. 71, 1355 (2000); http://dx.doi.org/10.1063/1.1150462 (5 pages) | Cited 19 times

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Absolute detection efficiencies of a commercial multichannel plate detector have been measured for O, O+, and O−, impacting at normal incidence for energies ranging from 30–1000 eV. In addition, the detection efficiencies for O relative to its ions are presented, as they may have a more universal application. The absolute detection efficiencies are strongly energy dependent and significant differences are observed for the various charge states at lower energies. The detection efficiencies for the different charge states appear to converge at higher energies. The strongest energy dependence is for O+; the detection efficiency varies by three orders of magnitude across the energy range studied. The weakest dependence is for O−, which varies less than one order of magnitude. © 2000 American Institute of Physics.
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07.75.+h Mass spectrometers
06.20.F- Units and standards
29.40.Gx Tracking and position-sensitive detectors
back to top NUCLEAR PHYSICS, FUSION and PLASMAS

Solid-state pulsed power for driving a high-power dense plasma focus x-ray source

R. Petr, D. Reilly, J. Freshman, N. Orozco, D. Pham, L. Ngo, and J. Mangano

Rev. Sci. Instrum. 71, 1360 (2000); http://dx.doi.org/10.1063/1.1150463 (3 pages) | Cited 2 times

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Solid-state pulsed power technology has been successfully applied to a high average power dense plasma focus (DPF) x-ray point source. In the past, electrode erosion and the associated insulator lifetime have been the primary limiting factors for implementing a DPF x-ray source in a practical x-ray lithographic tool. The solid-state pulsed power supply described here uses fast-switching thyristors, diodes, and saturable magnetics to eliminate current reversal through the DPF electrodes. This has improved the DPF system performance and lifetime by reducing the electrode and insulator vaporization rates more than 20× compared to conventional sparkgap-switched drivers. Erosion measurements indicate that an electrode set can last more than 5 million shots before refurbishment. The DPF source produces an average energy of 7.3 J pulse into 4π Sr at a 1.1 keV effective wavelength in ∼1 Torr of neon gas at repetition rates up to 60 Hz. The x-ray yield efficiency is nominally 0.6%. © 2000 American Institute of Physics.
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07.85.Fv X- and γ-ray sources, mirrors, gratings, and detectors
52.55.Ez Theta pinch
84.70.+p High-current and high-voltage technology: power systems; power transmission lines and cables

Plasma and ion barrier for electron beam spot stability

Thomas J. T. Kwan and Charles M. Snell

Rev. Sci. Instrum. 71, 1363 (2000); http://dx.doi.org/10.1063/1.1150464 (4 pages) | Cited 3 times

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High-current electron beams of small spot size are used for high-resolution x-ray radiography of dense objects. Intense energy deposition in the bremsstrahlung target causes generation of ions which can propagate upstream and disrupt the electron beam. We have investigated the use of a thin beryllium foil placed 1–2 cm in front of the target, which serves as a barrier for the ions but is essentially transparent to the incoming electron beam. Analysis and computer simulations confirm that this confinement method will halt ion propagation and preserve the spot size stability of the electron beam. © 2000 American Institute of Physics.
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41.85.Ja Particle beam transport
41.75.Fr Electron and positron beams
07.85.-m X- and γ-ray instruments
07.77.Ka Charged-particle beam sources and detectors

A probe for measurements of electrostatic fluctuations in a low-temperature magnetized plasma

S. V. Ratynskaia, V. I. Demidov, and K. Rypdal

Rev. Sci. Instrum. 71, 1367 (2000); http://dx.doi.org/10.1063/1.1150465 (3 pages) | Cited 12 times

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A cylindrical probe with insulating end plugs for investigations of fluctuations of electron temperature and plasma potential is proposed. The radii of the metallic rod and plugs are chosen to optimize the ratio of ion saturation current to electron saturation current (>1) for the probe oriented parallel to the magnetic field. This probe is applicable when the electron temperature is much larger than the ion temperature. © 2000 American Institute of Physics.
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52.70.Ds Electric and magnetic measurements
52.25.Gj Fluctuation and chaos phenomena
52.25.Fi Transport properties

Characterization of geometrical detection-system properties for two-dimensional tomography

L. C. Ingesson, C. F. Maggi, and R. Reichle

Rev. Sci. Instrum. 71, 1370 (2000); http://dx.doi.org/10.1063/1.1150466 (9 pages) | Cited 4 times

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Quantities that characterize the three-dimensional geometrical properties of detection systems for two-dimensional tomography are reviewed and compared. It is discussed how the quantities can be calculated and how they can be measured, including a measuring technique that uses a parallel laser beam. In many detection systems the finite detector size and the finite sizes of bounding apertures are not negligible, and these result in instrument functions with finite widths. Line-integral measurements are referred to as ideal measurements, whereas measurements by systems with instrument functions with finite width are nonideal. The quantities discussed make it possible to take into account these finite sizes in several tomography algorithms. If the spacing between adjacent lines of sight is much smaller than the widths of the instrument functions, the ideal measurements can be approximately reconstructed from the nonideal measurements. Such a reconstruction has been applied to bolometer measurements in a high plasma-density discharge in the Joint European Torus tokamak by sweeping the plasma in front of the bolometer detectors. The sweeping creates many extra virtual lines of sight and thus increases the resolution of the measurements close to the X point, where in high-density plasmas a peak in the radiation is found. © 2000 American Institute of Physics.
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42.30.Wb Image reconstruction; tomography
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Optimization of Cs deposition in the 1/3 scale hydrogen negative ion source for the large helical device-neutral beam injection system

Y. Oka, Y. Takeiri, Yu. I. Belchenko, M. Hamabe, O. Kaneko, K. Tsumori, M. Osakabe, E. Asano, T. Kawamoto, and R. Akiyama

Rev. Sci. Instrum. 71, 1379 (2000); http://dx.doi.org/10.1063/1.1150449 (6 pages) | Cited 7 times

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A compact cesium deposition system was used for direct deposition of cesium atoms and ions onto the inner surface of the 1/3 scale hydrogen negative ion source for the large helical device-neutral beam injection (LHD-NBI), system. A small, well defined amount of cesium deposition in the range of 3–200 mg was tested. Negative ion extraction and acceleration were carried out both in the pure hydrogen operation mode and in the cesium mode. Single Cs deposition of 3–30 mg to the plasma chamber has produced temporary 2–5 times increases of H− yield, but the yield was decreased within several discharge pulses to the previous steady-state value. Two consecutive 30 mg depositions done within a 3–5 h/60 shot interval, produced a similar temporary increase of H− beam, but reached a large H− yield steady-state value. Deposition of larger 0.1–0.2 g Cs portions with a 20–120 h/150–270 shot interval improved the H− yield for a long (2–5 days) period of operation. Directed depositions of Cs to the various walls of the plasma chamber showed approximately the same H− increase. Deposition of 0.13 g Cs to a surface polluted by a water leak, produced a temporary increase, and a H− steady-state level similar to that from a single 30 mg cesium deposition. Deposition of 0.1 g with a cesium plasma produced one half the H− yield obtained by deposition of the same amount of cesium atoms. A higher steady-state H− current value and a smaller rate of H− yield decrease was recorded during the eight filament discharge operation, as compared to the 12 filament operation at the same discharge power. © 2000 American Institute of Physics.
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29.25.Ni Ion sources: positive and negative
52.50.Gj Plasma heating by particle beams
29.27.Ac Beam injection and extraction

Ion-beam characteristics of novel helicon ion sources for different plasma parameters

I. S. Hong, Y. S. Hwang, G. H. Lee, D. Y. Kim, H. Y. Won, G. S. Eom, and W. Choe

Rev. Sci. Instrum. 71, 1385 (2000); http://dx.doi.org/10.1063/1.1150467 (4 pages) | Cited 10 times

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A high-current ion source requires a high-density plasma source to provide sufficient ions to be accelerated. For a continuous high-power ion source, a new concept ion source using a helicon plasma source has been developed. A compact high-density helicon plasma is generated with very high-power efficiency, and ion beams are extracted from the plasma source. With various plasma parameters, extracted ion-beam characteristics are studied in a helicon ion source for the first time. Plasma parameters, especially plasma density, are shown to be strongly correlated with the extracted beam characteristics. © 2000 American Institute of Physics.
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29.25.Ni Ion sources: positive and negative
07.77.Ka Charged-particle beam sources and detectors
41.75.Ak Positive-ion beams
41.85.Ar Particle beam extraction, beam injection

NSTAR Xenon Ion Thruster on Deep Space 1: Ground and flight tests (invited)

M. G. Marcucci and J. E. Polk

Rev. Sci. Instrum. 71, 1389 (2000); http://dx.doi.org/10.1063/1.1150468 (12 pages) | Cited 2 times

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After having been in development for many years at the Glenn Research Center (formerly the Lewis Research Center), the national aeronautics and space administration-designed, 30 cm, ring-cusp, xenon ion engine was launched on the Deep Space 1 (DS1) spacecraft on 24 Oct. 1998 from the Kennedy Space Center in Florida. It has since accumulated 2200 h of in-space thrusting at input power levels ranging from 0.52 to 1.96 kW, has successfully enabled the spacecraft to fly by the asteroid Braille in July 1999, and is now thrusting DS1 along a trajectory towards its comet destinations in 2001. The design, assembly, test, integration, and operation of this thruster comprise a unique path of technical determination, artful design choices, persistent engineering and analysis, and mastery of vacuum chamber operations. The testing program over the development years, the assembly and integration periods, and the flight operational period thus far have shown that the project test philosophy of segregating effects against unique causes proved itself most useful. The 8000 h life test, the culmination of the pre-launch ground test plan, not only met its goals but surpassed them with margin. This article will explain the thruster test program from beginning to end, illustrating the technical and programmatic decision making along the way. It will justify the use of engineering models as an inexpensive method of determining answers to key design questions and will explain why testing of the thruster alone only solved a portion of the system operations task. The highlight of the test program proved to be the vacuum firing of the ion engine during the spacecraft’s solar thermal vacuum test. A comparison of the preflight data with postflight data shows that high confidence was warranted for executing a successful flight to the asteroid and beyond. © 2000 American Institute of Physics.  
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89.40.-a Transportation
95.55.Pe Lunar, planetary, and deep-space probes

Development of a high-current plasma lens for focusing broad beams of heavy metal ions

A. Goncharov, I. Protsenko, G. Yushkov, and I. G. Brown

Rev. Sci. Instrum. 71, 1401 (2000); http://dx.doi.org/10.1063/1.1150469 (4 pages) | Cited 3 times

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We describe the results of investigations of the manipulation of moderate energy, large area beams of heavy metal ions by a high-current electrostatic plasma lens. Electrostatic plasma lenses are essential for the focusing of high-current heavy ion beams with moderate energies of 10–100 keV. In our experiments, beams of carbon, copper, zinc, and tantalum (separately) were formed by a repetitively pulsed vacuum arc ion source with energy in the range 10–50 keV, beam current up to 0.5 A, and initial diameter 10 cm. The characteristics of the focusing of the ion beam passing through the lens were measured by a radially movable, magnetically suppressed Faraday cup. The plasma lens focusing properties were determined for a number of different distributions of the lens ring-electrode potentials. We have shown that by changing the lens electrode potential distribution we can control the lens focusing, in both the convergent and divergent regimes. Some features of heavy metal ion beam focusing under these conditions are discussed. The experiments demonstrate the versatile possibilities of the plasma lens for use with moderate-energy, high-current, heavy ion beams. © 2000 American Institute of Physics.
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41.85.Ne Electrostatic lenses, septa
07.77.Ka Charged-particle beam sources and detectors
41.75.Ak Positive-ion beams

Novel laser ion sources

P. Fournier, H. Haseroth, H. Kugler, N. Lisi, R. Scrivens, F. Varela Rodriguez, P. Di Lazzaro, F. Flora, S. Duesterer, R. Sauerbrey, H. Schillinger, W. Theobald, L. Veisz, J. W. G. Tisch, and R. A. Smith

Rev. Sci. Instrum. 71, 1405 (2000); http://dx.doi.org/10.1063/1.1150470 (4 pages) | Cited 6 times

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Development in the field of high-power laser systems with repetition rates of several Hz and energies of few joules is highly active and opening, giving new possibilities for the design of laser ions sources. Preliminary investigations on the use of four different laser and target configurations are presented: (1) A small CO2 laser (100 mJ, 10.6 μm) focused onto a polyethylene target to produce C ions at 1 Hz repetition rate (CERN). (2) An excimer XeCl laser (6 J, 308 nm) focused onto solid targets (Frascati). (3) A femtosecond Ti: sapphire laser (250 mJ, 800 nm) directed onto a solid targets (Jena). (4) A picosecond Nd: yttrium–aluminum–garnet (0.3 J, 532 nm) focused into a dense medium of atomic clusters and onto solid targets (London). The preliminary experimental results and the most promising schemes will be discussed with respect to the scaling of the production of high numbers of highly charged ions. Different lasers are compared in terms of current density at 1 m distance for each charge state. © 2000 American Institute of Physics.
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29.25.Ni Ion sources: positive and negative
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
07.77.Ka Charged-particle beam sources and detectors

Production of He-like light and medium mass ions in laser ion source

S. Kondrashev, N. Mescheryakov, B. Sharkov, A. Shumshurov, S. Khomenko, K. Makarov, Yu. Satov, and Yu. Smakovskii

Rev. Sci. Instrum. 71, 1409 (2000); http://dx.doi.org/10.1063/1.1150471 (4 pages) | Cited 7 times

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Operation of the laser ion source of He-like light ions designed for the first stage of the ITEP Terra Watt Accumulator (TWAC) project is discussed. A 5 J/0.5 Hz rep-rate CO2 laser was used for generation of highly charged light ions. The absolute number of ions with different charge states for carbon and aluminum ion beams has been measured. The obtained number of C+4 ions ( ∼ 1011ions/pulse) is sufficient to start the experimental proof of the accelerator scheme of the TWAC project. The investigation of shot to shot stability indicates significant increasing (∼2–3 times) of highly charged ion yield for the first shot onto the fresh target surface with respect to the next shots onto the same spot of aluminum target. This effect was not observed for the carbon target. Experimental results for highly charged light and medium mass (F, Mg, Al, Ca, Ti) ions produced by of 75 J single pulse CO2 laser consisting of a master oscillator and power amplifier are also presented. © 2000 American Institute of Physics.
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29.25.Ni Ion sources: positive and negative
07.77.Ka Charged-particle beam sources and detectors
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
29.20.dk Synchrotrons

Emittance improvement of the electron cyclotron resonance high intensity light ion source proton beam by gas injection in the low energy beam transport

P-Y. Beauvais, R. Ferdinand, R. Gobin, J. M. Lagniel, P.-A. Leroy, L. Celona, G. Ciavola, S. Gammino, B. Pottin, and J. Sherman

Rev. Sci. Instrum. 71, 1413 (2000); http://dx.doi.org/10.1063/1.1150448 (4 pages) | Cited 9 times

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SILHI is the ECR high intensity light ion source studied in France at C.E.A. Saclay. This is the source for the injector of the high intensity proton injector prototype developed by a CNRS-IN2P3 collaboration. 80 mA at 95 keV beams with a rms normalized r–r′ emittance lower than 0.3 π mm mrad and a proton fraction better than 85% are currently produced. Recently, it has been found that the injection in the low energy beam transport of a buffer gas had a strong effect on the emittance measured 1 m downstream of the focusing solenoid. By adding several gases (H2, N2, Ar, Kr), improvements as great as a factor of 3 have been observed. The emittance has been measured by means of an r–r′ emittance measurement unit equipped with a sampling hole and a wire profile monitor, both moving across the beam. Simultaneously, the space charge compensation factor is measured using a four-grid analyzer unit. In this article all results of these experiments are presented and discussed. A first explanation of the emittance reduction phenomenon and possible consequences on the injector operation is given. © 2000 American Institute of Physics.
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29.25.Ni Ion sources: positive and negative
29.27.Fh Beam characteristics
29.27.Ac Beam injection and extraction
29.27.Eg Beam handling; beam transport
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