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Mar 2000

Volume 71, Issue 3, pp. 1243-1570

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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

Method of processing ion energy distributions using a Thomson parabola ion spectrograph with a microchannelplate image converter camera

W. Mróz, P. Norek, A. Prokopiuk, P. Parys, M. Pfeifer, L. Laska, M. P. Stöckli, D. Fry, and K. Kasuya

Rev. Sci. Instrum. 71, 1417 (2000); http://dx.doi.org/10.1063/1.1150472 (4 pages) | Cited 4 times

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A Thomson parabola ion spectrograph (TP) is a very useful tool for the investigation of pulsed laser ablation. Measurements performed with the TP give useful information about physical processes, ion species and their energy distributions, as well as charge states. For ions with the lower charge states, q<20, complete information about energy distributions of all ionization states of ions can be obtained from a single laser shot. For ions with higher ionization states, parabolas generated in the TP interfere and it is impossible to get energy distributions for all the ion species. In this situation, the registered ions are composed of a few groups with different charge states and different energies. The TP enables the charge states and energetic ranges of different ion groups to be estimated. This presentation describes a method of processing experimental results, obtained from a TP, using a microchannelplate (MCP) image converter. Ion energy distributions for C1+–C6+ and Ta1+–Ta12+ are shown, and the effects of correcting the obtained ion energy distributions for the detection efficiency of the MCP are illustrated. © 2000 American Institute of Physics.
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52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
07.77.Ka Charged-particle beam sources and detectors
52.70.Nc Particle measurements
07.81.+a Electron and ion spectrometers
07.75.+h Mass spectrometers

Measurement of angular divergence and ion species ratios of an rf-driven multicusp ion source for diagnostic neutral beam by Doppler shift spectroscopy

S. J. Yoo, H. L. Yang, and S. M. Hwang

Rev. Sci. Instrum. 71, 1421 (2000); http://dx.doi.org/10.1063/1.1150473 (4 pages) | Cited 9 times

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The ion species ratios as well as the angular divergences are measured by using a Doppler shift spectroscopy of Hα spectral lines, which originate from several different ions, such as H2+ and H3+ as well as H+, and are spectrally well resolvable from each other on the measured spectral window of detection system. The angular divergences of the ion beam components are determined from the linewidths of the measured emission lines, and the ratio of mixed species is deduced from the intensity ratio of each peak. The ion species ratios measured by the Doppler shift spectroscopy are cross checked by a mass analyzing magnet. The measurements are performed varying the input rf power and the operating source pressure. © 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

Quantitative measurements of the chemical composition of unprepared samples, using a reflectron mass analyzer with a microchannelplate detector assembly

W. Mróz, A. Prokopiuk, B. Kozlov, T. Czujko, S. Józwiak, J. Krzywiński, M. P. Stöckli, and C. Fehrenbach

Rev. Sci. Instrum. 71, 1425 (2000); http://dx.doi.org/10.1063/1.1150474 (4 pages) | Cited 1 time

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This article presents measurements of the chemical composition of Al–Li samples using a reflectron mass analyzer and laser ionization of the sample. The measurements were taken of as-received samples with rough surfaces to ascertain if useful results could be obtained from samples that had not been cleaned or prepared in any way. The power density of the laser used (Nd:yttrium–aluminum–garnet λ = 1.06 μm, E ≅ 6 mJ, τ = 5 ns) was I ∼ 3×109 W/cm2. We have described the quantitative processing of our results using the measured analog particle gains of the Galileo microchannelplates. The problems associated with quantitative measurements of ion pulses using a microchannelplate detector assembly are also discussed. © 2000 American Institute of Physics.
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82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
07.75.+h Mass spectrometers
42.62.Eh Metrological applications; optical frequency synthesizers for precision spectroscopy
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