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Equation of state of dense argon; a comparison of shock and static studies. [R]

Description: In the present paper we report new diamond anvil cell (DAC) measurements for room temperature solid argon to 800 kbars. This isotherm is in excellent agreement with one predicted from a theoretical analysis of shockwave data. These results are important for several reasons. First they demonstrate agreement between shock and static techniques even in cases where shock temperatures are extremely high and a large thermal correction is required to reduce the Hugoniot to an isotherm. Secondly the results suggest that solid argon may provide a useful pressure standard up to 3 Mbar. 12 refs., 3 figs.
Date: July 1, 1985
Creator: Ross, M.; Mao, H.K.; Bell, P.M. & Xu, J.A.
Partner: UNT Libraries Government Documents Department

Development and characterization of a CCD camera system for use on six-inch manipulator systems

Description: The Lawrence Livermore National Laboratory has designed, constructed, and fielded a compact CCD camera system for use on the Six Inch Manipulator (SIM) at the Nova laser facility. The camera system has been designed to directly replace the 35 mm film packages on all active SIM-based diagnostics. The unit`s electronic package is constructed for small size and high thermal conductivity using proprietary printed circuit board technology, thus reducing the size of the overall camera and improving its performance when operated within the vacuum environment of the Nova laser target chamber. The camera has been calibrated and found to yield a linear response, with superior dynamic range and signal-to-noise levels as compared to T-Max 3200 optic film, while providing real-time access to the data. Limiting factors related to fielding such devices on Nova will be discussed, in addition to planned improvements of the current design.
Date: May 3, 1996
Creator: Logory, L.M.; Bell, P.M.; Conder, A.D. & Lee, F.D.
Partner: UNT Libraries Government Documents Department

Engineering the Petawatt Laser into Nova

Description: The engineering process of integrating the Petawatt (10{sup 15} watts) laser system into the existing 30 kJ (UV) Nova laser at Lawrence Livermore National Laboratory (LLNL) is described in detail. The nanosecond-long, chirped Petawatt laser pulse is initially generated in a separate master oscillator room and then injected into one of Nova`s 10 beamlines. There, the pulse is further amplified and enlarged to {approximately}{phi}60 cm, temporally compressed under vacuum to <500 fs using large diameter diffraction gratings, and then finally focused onto targets using a parabolic mirror. The major Petawatt components are physically large which created many significant engineering challenges in design, installation and implementation. These include the diffraction gratings and mirrors, vacuum compressor chamber, target chamber, and parabolic focusing mirror. Other Petawatt system components were also technically challenging and include: an injection beamline, transport spatial filters, laser diagnostics, alignment components, motor controls, interlocks, timing and synchronization systems, support structures, and vacuum systems. The entire Petawatt laser system was designed, fabricated, installed, and activated while the Nova laser continued its normal two-shift operation. This process required careful engineering and detailed planning to prevent experimental downtime and to complete the project on schedule.
Date: December 23, 1997
Creator: Tietbohl, G.L.; Bell, P.M. & Hamilton, R.M.
Partner: UNT Libraries Government Documents Department

X-ray framing cameras for > 5 keV imaging

Description: Recent and proposed improvements in spatial resolution, temporal resolution, contrast, and detection efficiency for x-ray framing cameras are discussed in light of present and future laser-plasma diagnostic needs. In particular, improvements in image contrast above hard x-ray background levels is demonstrated by using high aspect ratio tapered pinholes.
Date: July 20, 1995
Creator: Landen, O.L.; Bell, P.M.; Costa, R.; Kalantar, D.H. & Bradley, D.K.
Partner: UNT Libraries Government Documents Department

Detailed measurements and shaping of gate profiles for microchannel-plate-based X-ray framing cameras

Description: Gated, microchannel-plate-based (MCP) framing cameras are increasingly used worldwide for x-ray imaging of subnanosecond laser-plasma phenomena. Large dynamic range (> 1,000) measurements of gain profiles for gated microchannel plates (MCP) are presented. Temporal profiles are reconstructed for any point on the microstrip transmission line from data acquired over many shots with variable delay. No evidence for significant pulse distortion by voltage reflections at the ends of the microstrip is observed. The measured profiles compare well to predictions by a time-dependent discrete dynode model down to the 1% level. The calculations do overestimate the contrast further into the temporal wings. The role of electron transit time dispersion in limiting the minimum achievable gate duration is then investigated by using variable duration flattop gating pulses. A minimum gate duration of 50 ps is achieved with flattop gating, consistent with a fractional transit time spread of {approx} 15%.
Date: October 3, 1994
Creator: Landen, O.L.; Hammel, B.A.; Bell, P.M.; Abare, A. & Bradley, D.K.
Partner: UNT Libraries Government Documents Department

Characterization of X-ray streak cameras for use on Nova

Description: There are many different types of measurements that require a continuous time history of x-ray emission that can be provided with an x-ray streak camera. In order to properly analyze the images that are recorded with the x-ray streak cameras operated on Nova, it is important to account for the streak characterization of each camera. We have performed a number of calibrations of the streak cameras both on the bench as well as with Nova disk target shots where we use a time modulated laser intensity profile (self-beating of the laser) an the target to generate an x-ray comb. We have measured the streak camera sweep direction and spatial offset, curvature of the electron optics, sweep rate, and magnification and resolution of the electron optics.
Date: October 1, 1996
Creator: Kalantar, D.H.; Bell, P.M.; Costa, R.L.; Hammel, B.A.; Landen, O.L.; Orzechowski, T.J. et al.
Partner: UNT Libraries Government Documents Department