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  • 1
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recently, a novel optical modulator heterostructure has been introduced based on voltage controlled electron transfer from a reservoir to a closely spaced quantum well. It has proven to exhibit large absorptive and refractive modulation at high speed and low power dissipation. In order to achieve monolithic integration with the existing high quality InGaAsP/InP lasers for high bit-rate systems, it is crucial to implement such devices within the same material system. In this letter, we demonstrate for the first time, InGaAsP/InP electron-transfer modulators grown using metalorganic vapor phase epitaxy.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 2475-2477 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The fine-focusing capability of a current-carrying, "active" plasma lens has been demonstracted for the first time. A cylindrically symmetric argon discharge plasma pulsed with an oscillating current of over 20 kA in amplitude served as a current conducting medium. With this plasma lens has been demonstrated for the first time. A cylindrically symmetric argon discharge plasma pulsed with an oscillating current of over 20 kA in amplitude served as a current conducting medium. With this plasma lens the diameter of an incident 2.2-GeV gold ion beam from the linear accelerator UNILAC at GSI-Darmstadt was focused from initially 10 to about 0.25 mm, at a focal length of only 140 mm. The gradient of the azimuthal magnetic field exceeded 120 T/m. The striking features of this first-order and strong-focusing plasma lens favor its use as a precise high-gradient focusing device for high-energy charged particles.
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  • 3
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High current discharge channels can neutralize both current and space charge of very intense ion beams. Therefore, they are considered an interesting solution for final focus and beam transport in a heavy ion beam fusion reactor. At the Gesellschaft fuer Schwerionenforschung accelerator facility, 50 cm long, free-standing discharge channels were created in a 60 cm diameter metallic chamber. Discharges with currents of 45 kA in 2 to 25 mbar ammonia (NH3) gas are initiated by a CO2 laser pulse along the channel axis before the capacitor bank is triggered. Resonant absorption of the laser, tuned to the v2 vibration of the ammonia molecule, causes strong gas heating. Subsequent expansion and rarefaction of the gas prepare the conditions for a stable discharge to fulfill the requirements for ion beam transport. The influence of an electric prepulse on the high current discharge was investigated. This article describes the laser–gas interaction and the discharge initiation mechanism. We found that channels are magnetohydrodynamic stable up to currents of 45 kA, measured by fast shutter and streak imaging techniques. The rarefaction of the laser heated gas is studied by means of a one-dimensional Lagrangian fluid code (CYCLOPS) and is identified as the dominant initiation mechanism of the discharge. © 2002 American Institute of Physics.
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  • 4
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A semiautomated pulse injection and data analysis system utilizing 200 MHz surface acoustic wave resonators has been constructed. A cell consisting of a separate sample splitting chamber, sample transfer lines, and sensor device areas has been constructed to allow individual temperature control over the regions. Experiments involving injections of hexane, trichlorobenzene, and 1% (w/v) of biphenyl in hexane show that all three temperatures play an important role in the magnitude and time dependency of the SAW response. Flow rate is also shown to be an important factor. The capabilities of the system have been demonstrated with uncoated and poly(isobutylene) coated devices. © 1995 American Institute of Physics.
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  • 5
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In a series of experiments a laser plasma ion source for TA ions has been investigated. The main components were a 3-J CO2 laser, the laser ion source, a 3.2-m beamline, a 90° analyzing magnet, and an ion detector. The FWHM of the CO2 laser pulse was approximately 100 ns, the full duration was about 1 μs. The spot diameter was about 0.2 mm. The charge state distribution has been measured up to 10+. The plasma temperature has been calculated; recombination has been observed. The results will be shown and discussed in detail.
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  • 6
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The new Schwerionen-Synchrotron (SIS)/Experimenteller Speicher-Ring (ESR) heavy ion accelerator facility [Nucl. Instrum. Methods A 278, 7, 19 (1989)], built for basic atomic and nuclear physics at Darmstadt (Federal Republic of Germany), also provides unique possibilities to study rf accelerator and beam/target interaction physics for inertial confinement fusion driven with heavy ion beams. It is the first machine that offers this opportunity. Beam parameters and experiments planned over the next five years are discussed.
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  • 7
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper presents one- and two-dimensional computer simulations of the hydrodynamic response of solid cylindrical targets made of different materials that are irradiated by intense beams of energetic ions. The beam parameters considered in this study correspond to the design parameters of the heavy ion beam that will be produced at the Gesellschaft für Schwerionenforschung (GSI), Darmstadt heavy ion synchrotron facility (SIS) in 1999. A few calculations, however, were also done using the beam parameters that are currently available at the SIS. Different values for specific energy deposition including 1, 10, 50, and 100 kJ/g, respectively, have been considered, whereas a number of different pulse lengths, namely, 10, 50, 100, and 200 ns, have been assumed. Various target materials, for example, solid lead, solid neon, and solid hydrogen, have been used. It is expected that this simulation study will be very helpful in the design of efficient targets for the future experiments at the GSI. These experiments will hopefully provide very useful information about many important basic physics phenomena, such as enhanced energy loss of heavy ions in hot dense plasmas, equation-of state (EOS) of matter under extreme conditions, material opacity and shock wave propagation. Another very interesting experiment with important practical implications that could be done at this facility may be the creation of metallic hydrogen by imploding appropriately designed multilayered targets containing a layer of frozen hydrogen. This paper presents the design of such a target, together with implosion simulations of this target using a hydrodynamic simulation model. These simulations show that it may be possible to compress the frozen hydrogen to achieve the theoretically predicted physical conditions necessary for hydrogen metallization (a density of the order of 1 to 2 g/cm3, a temperature of a few 0.1 eV and a pressure of about 2–5 megabar). In some cases, compression of frozen deuterium was also studied. © 1998 American Institute of Physics.
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  • 8
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 4242-4250 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Nanocapsule dispersions are investigated by 1H–13C cross polarization experiments. The capsule walls, made up from polybutylcyanoacrylate, are detectable merely as a solid state signal, whereas the triglyceride forming the liquid core and the surfactant on the outside of the capsules give rise to narrow resonance lines in the cp-spectrum indicating their mobility. In order to clarify the mechanism of cross polarization for the mobile components, the time-resolved polarization of the corresponding 13C-signals is investigated. Further, the spin-lattice relaxation times for the proton magnetization in the rotating frame are studied under direct excitation as well as under cross polarization conditions. Based on the results, we propose a special mechanism of cross polarization which is initiated by a temporary adsorption of mobile molecules to the more rigid capsule surface. During this short period of immobilization, the polarization is transferred from 1H to 13C nuclei. After desorption, the freshly generated 13C-signal is essentially conserved, now being motionally averaged by a high molecular mobility and detectable as a narrow line in the corresponding spectrum. © 2000 American Institute of Physics.
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  • 9
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Beams of high-energy heavy ions (Ar and U) from the UNILAC accelerator have been used to excite rare gases at pressures near 1 bar. The dominant spectroscopic feature observed in Ar, Kr, and Xe gases was molecular excimer emission at the second excimer continuum at 130, 150, and 170 nm, respectively. The excimer radiation was studied as a function of time (with respect to the excitation pulse), ion-beam current, pressure, and excitation density. The efficiency of excimer production from heavy-ion-beam energy was found to be several percent. Details of spectral shape, especially the ratio of first-to-second continuum emission, were found to depend on pressure and exciting beam type.
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  • 10
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An all-optical sampling technique that allows the simultaneous measurement of optical pulse intensities and wavelengths with a temporal resolution of about 1 ps is introduced. Using four-wave mixing (FWM) in a semiconductor optical amplifier, the optical signal under test is cross correlated with nearly transform-limited 1.4 ps optical sampling pulses. While the intensity of the generated FWM signal is used to determine the temporal shape of the signal intensity, the wavelength of the FWM signal yields time-resolved information about the signal wavelength (i.e., the frequency chirp). Using this technique, the correlation of intensity and wavelength dynamics of pulses generated by a self-Q-switched distributed-feedback laser is determined directly. © 1998 American Institute of Physics.
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