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  • 1
    Electronic Resource
    Electronic Resource
    Low-threshold InGaAs/GaAs strained layer single quantum well lasers with simple ridge waveguide structure (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 7892-7894 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Double heterostructure InGaAs-GaAs strained-layer single quantum well ridge waveguide lasers grown by molecular beam epitaxy were fabricated by using in situ laser monitored reactive ion etching to form the ridges. Continuous-wave threshold current as low as 3.5 mA was obtained on a ridge laser diode of 3.3 μm wide and 215 μm long having cleaved mirrors. The lasing wavelength is at 0.988 μm and the measured differential external quantum efficiency is 61%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347473
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  • 2
    Electronic Resource
    Electronic Resource
    Recent progress in space- and time-resolved x-ray spectroscopy of laser-produced plasmas (abstract) : Eighth topical conference on high−temperature plasma diagnostics (1990)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 2813-2813 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: New diagnostic techniques have provided measurement of relatively gradient-free x-ray spectra from high-powered laser-produced plasmas. Simultaneously space- and time-resolved x-ray spectra were measured from a variety of microdot plasmas using an array of multiframe, imaging, electronically gated x-ray crystal spectrometers with 100 ps time resolution. A multiframed, multicolored gated x-ray pinhole camera provided measurement of the plasma uniformity. A four-frame holographic interferometer was used to measure the electron density profile. Conventional x-ray streaked crystal spectrographs, spatially resolved x-ray (film) spectrometer, and pinhole cameras supplemented these new diagnostics. The instruments allow detailed studies of both the population kinetics of highly charged ions in dense plasmas and the hydrodynamics of laser-produced plasmas for the first time. The new diagnostics are described including data from ongoing experiments. Work was performed in part under the auspices of the U.S. Dept. of Energy by LLNL under Contract No. W-7405-Eng-48.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1141840
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  • 3
    Electronic Resource
    Electronic Resource
    Measurement of Tc suppression in tungsten using magnetic impurities (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 6975-6978 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the effects of dilute magnetic-atom doping on the superconducting transition temperature of tungsten thin films. Our "Tc tuning" technique is accurate, precise, and simple. Experiments were performed using dc-magnetron-sputtered tungsten films with undoped values of Tc in the range of 70–150 mK. The magnetic-atom doping was achieved using ion implantation. Specific Tc suppressions of between 5% and 65% were targeted and observed in this study. The transition width of each undoped sample was (approximate)1 mK and the transition widths remained sharp after implantation with 56Fe+ ions. Our data are in good agreement with predictions of a linear dependence of Tc suppression with increasing magnetic-atom concentration, in the small concentration limit. At higher concentrations, antiferromagnetic coupling between the magnetic dopant atoms becomes important and the Tc-suppression effect is diminished. We use our Tc data to calculate the Abrikosov–Gor'kov (AG) and Ruderman–Kittel–Kasuya–Yosida (RKKY) spin–flip relaxation parameters τAG and τRKKY. We conclude with a brief discussion of applications of the Tc-tuning technique, and present our plans for future studies in this area. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.371781
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  • 4
    Electronic Resource
    Electronic Resource
    High-resolution x-ray spectrometer based on spherically bent crystals for investigations of femtosecond laser plasmas (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 4049-4053 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Ultrashort-pulse, laser-produced plasmas have become very interesting laboratory sources to study spectroscopically due to their very high densities and temperatures, and the high laser-induced electromagnetic fields present. Typically, these plasmas are of very small volume and very low emissivity. Thus, studying these near point source plasmas requires advanced experimental techniques. We present a new spectrometer design called the focusing spectrometer with spatial resolution (FSSR-2D) based on a spherically bent crystal which provides simultaneous high spectral (λ/Δλ(approximate)104) and spatial resolution ((approximate)10 μm) as well as high luminosity (high collection efficiency). We described in detail the FSSR-2D case in which a small, near point source plasma is investigated. An estimate for the spectral and spatial resolution for the spectrometer is outlined based on geometric considerations. Using the FSSR-2D instrument, experimental data measured from both a 100 fs and a nanosecond pulse laser-produced plasma are presented. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1149249
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  • 5
    Electronic Resource
    Electronic Resource
    A quasiparticle-trap-assisted transition-edge sensor for phonon-mediated particle detection (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 5322-5326 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have demonstrated the operation of composite superconducting tungsten and aluminum transition-edge sensors which take advantage of quasiparticle trapping and electrothermal feedback. We call these devices W/Al QETs (quasiparticle-trap-assisted electrothermal feedback transition-edge sensors). The quasiparticle trapping mechanism makes it possible to instrument large surface areas without increasing sensor heat capacity, thus allowing larger absorbers and reducing phonon collection times. The sensor consists of a 30-nm-thick superconducting tungsten thin film with Tc∼80 mK deposited on a high-purity silicon substrate. The W film is patterned into 200 parallel lines segments, each 2 μm wide and 800 μm long. Eight superconducting aluminum thin film pads are electrically connected to each segment, and cover a much larger surface area than the W. When phonons from particle interactions in the silicon crystal impinge on an aluminum pad, Cooper pairs are broken, forming quasiparticles which diffuse to the tungsten lines where they are rapidly thermalized. The W film is voltage biased, and self-regulates in temperature within its superconducting transition region by electrothermal feedback. Heat deposited in the film causes a current pulse of ∼100 μs duration, which is measured with a series array of dc superconducting quantum interference devices. We have demonstrated an energy resolution of 〈350 eV full width at half-maximum for 6 keV x rays incident on the backside of a 1 cm×1 cm×1 mm (0.25 g) silicon absorber, the highest resolution that has been reported for a fast (〈1 ms pulse duration) calorimetric detector with an absorber mass(approximately-greater-than)0.1 g. Applications of this technology include dark matter searches and neutrino detection. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146105
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  • 6
    Electronic Resource
    Electronic Resource
    Charge and mass resolved time of flight observations of 140 fs laser produced ions : Proceedings of the tenth topical conference on high temperature plasma diagnostics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 333-335 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Ions from this plasma are self-extracting with energies of 0.1 to 100 keV, the extraction potential being one of the desired observables. The charge/mass (z/μ, μ is mass in AMU) separation is provided by a static magnetic field (B⋅L=1280 G cm, FWHM=14 mm) located 5 cm from the linear (1−d) detector. Displacement along the detector axis is thus proportional to z/μ(1/v). The detector is a gold cathode MCP with a fast (sub-ns) phosphor. The phosphor output is coupled into a streak camera (typical sweep 8.5 or 24 μs total) through a coherent fiber bundle. Streak images are grabbed with a 14-bit CCD. The signature of any specific ion is a straight line of slope proportional to z/μ. Since there are usually more than one charge state of a given ion, integer multiple slopes appear. Thus z and m can be found. Absolute calibration is taken from the slope of the proton streak, which is always present with our plasmas. While providing the same information as a Thomson parabola, the straight line images are easier to extract information from and offer resolution with less energy dependence. By providing mass and time of flight information, the product of z⋅Te can be determined unambiguously during the hydrodynamic acceleration of the plasma. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146404
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  • 7
    Electronic Resource
    Electronic Resource
    Collection of athermal phonons into doped Ge thermistors using quasiparticle trapping (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 4887-4891 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have developed a low-temperature particle detector that uses a novel quasiparticle trapping mechanism to funnel athermal phonon energy from an 80 mg Ge absorber into a 1.6 mg doped Ge thermistor via a superconducting Al film. We report on pulse height spectra obtained at 320 mK by scanning a 241Am alpha source along the device, and show that up to 20% of the energy deposited in the Ge absorber by a 5.5 MeV alpha particle interaction can be collected into a thermistor via quasiparticle trapping. We show that this device is sensitive to the position of an alpha particle interaction in the Ge absorber for interaction distances of up to 5 mm from a quasiparticle trap. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359292
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  • 8
    Electronic Resource
    Electronic Resource
    Charge collection and trapping in low-temperature silicon detectors (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 8179-8186 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Charge collection efficiency measurements in silicon detectors at low temperature (T〈0.5 K) and low applied electric field (E=0.1–100 V/cm) were performed using a variety of high-purity, p-type silicon samples with room-temperature resistivity in the range 2–40 kΩ cm. Good charge collection under these conditions of low temperature and low electric field is necessary for background suppression, through the simultaneous measurement of phonons and ionization, in a very low event rate dark matter search or neutrino physics experiment. Charge loss due to trapping during drift is present in some samples, but the data suggest that another charge–loss mechanism is also important. We present results which indicate that, for 60 keV energy depositions, a significant fraction of the total charge loss by trapping occurs in the initial electron-hole cloud near the event location which may briefly act as a shielded, field-free region. In addition, measurements of the lateral size, transverse to the applied electric field, of the initial electron-hole cloud indicate large transverse diffusion lengths. At the lowest fields a lateral diameter on the order of 1 mm is found in a detector ∼5 mm thick. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.362552
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  • 9
    Electronic Resource
    Electronic Resource
    Ion-implanted charge collection contacts for high purity silicon detectors operated at 20 mK (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 2625-2630 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have developed a technique for fabricating high resolution, ohmic contacts for cryogenic silicon detectors operated at temperatures well below 1 K. In this paper, we give a detailed description of the techniques used to fabricate these boron-implanted contacts, and present characterization data obtained on 24 test samples studied during the design phase of our program. We then describe the fabrication and operation of a 23 g prototype silicon hybrid detector which simultaneously senses both the phonons and ionization produced by a single event, and which incorporates these new contacts into its design. Finally, we present data obtained using a radioactive source of 241Am and this detector operated at 20 mK, and conclude that the contacts are fully sufficient for applications in particle astrophysics as well as in many other areas of physics. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145599
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  • 10
    Electronic Resource
    Electronic Resource
    Experiment demonstration of a 100-ps microchannel plate framing camera (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 2729-2732 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We report on the construction and testing of a 100-ps framing camera based on a gated microchannel plate. The gating is obtained by applying a fast voltage pulse directly across the microchannel plate detector. An infinite ground-plane microstrip transmission-line configuration is used. We have measured the transit time for electrons through the microchannel plate to be 150±35 ps and the rise and fall times of the detector to be less than 100 ps. The time resolution computed using the experimentally measured edge response times is less than 100 ps.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139033
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