John Crane - Academia.edu (original) (raw)

Papers by John Crane

OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Apr 1, 1993

Proceedings of SPIE, Jul 23, 1999

PACS2001. Proceedings of the 2001 Particle Accelerator Conference (Cat. No.01CH37268), Nov 13, 2002

We describe recent results and developments in the preamplifier module (PAM) engineering prototyp... more We describe recent results and developments in the preamplifier module (PAM) engineering prototype located in NIF's front end or Optical Pulse Generation (OPG) system. This prototype uses the general laser design developed on a physics testbed ('3 ') and integrates NIP type packaging as well as controls and diagnostics. We will present laser, mechanical and electrical hardware designed and built to date as well as laser energetics measurements.

Proceedings of SPIE, Dec 8, 1997

Advanced Radiographic Capability (ARC) project at the National Ignition Facility (NIF) is designe... more Advanced Radiographic Capability (ARC) project at the National Ignition Facility (NIF) is designed to produce energetic, ultrafast x-rays in the range of 70-100 keV for backlighting NIF targets. The chirped pulse amplification (CPA) laser system will deliver kilo-Joule pulses at an adjustable pulse duration from 1 ps to 50 ps. System complexity requires sophisticated simulation and modeling tools for design, performance prediction, and comprehension of experimental results. We provide a brief overview of ARC, present our main modeling tools, and describe important performance predictions. The laser system (Fig. 1) consists of an all-fiber front end, including chirped-fiber Bragg grating (CFBG) stretchers. The beam after the final fiber amplifier is split into two apertures and spatially shaped. The split beam first seeds a regenerative amplifier and is then amplified in a multi-pass Nd:glass amplifier. Next, the preamplified chirped pulse is split in time into four identical replica...

Quantum Aspects of Beam Physics 2003, 2004

This is a preprint of a paper intended for publication in a journal or proceedings. Since changes... more This is a preprint of a paper intended for publication in a journal or proceedings. Since changes may be made before publication, this preprint is made available with the understanding that it will not be cited or reproduced without the permission of the author.

Review of Scientific Instruments

To study matter at extreme densities and pressures, we need mega laser facilities such as the Nat... more To study matter at extreme densities and pressures, we need mega laser facilities such as the National Ignition Facility as well as creative methods to make observations during timescales of a billionth of a second. To facilitate this, we developed a platform and diagnostic to characterize a new point-projection radiography configuration using two micro-wires irradiated by a short pulse laser system that provides a large field of view with up to 3.6 ns separation between images. We used tungsten-carbide solid spheres as reference objects and inferred characteristics of the back-lighter source using a forward-fitting algorithm. The resolution of the system is inferred to be 15 μm (using 12.5 μm diameter wires). The bremsstrahlung temperature of the source is 70–300 keV, depending on laser energy and coupling efficiency. By adding the images recorded on multiple stacked image plates, the signal-to-noise of the system is nearly doubled. The imaging characterization technique described ...

Physics of Plasmas

Compound parabolic concentrator (CPC) targets are utilized at the National Ignition Facility Adva... more Compound parabolic concentrator (CPC) targets are utilized at the National Ignition Facility Advanced Radiographic Capability (NIF-ARC) laser to enhance the acceleration of electrons and production of high energy photons, for laser durations of 10 ps and energies up to 2.4 kJ. A large enhancement of mean electron energy (>2 ×) and photon brightness (>10×) is found with CPC targets compared to flat targets. Using multiple diagnostic techniques at different spatial locations and scaling by gold activation spatial data, photon spectra are characterized for Ephoton=0.5–30 MeV. Beam width and pointing variations are given. The efficient production of MeV photons at Ilaser≈2×1018 W/cm2 with CPCs is observed, with doses of >10 rad in air at 1 m for Ephoton>0.5 MeV; these exceed those previously reported with laser-driven sources. Using this source, sub-mm resolution radiographs are generated through large areal density radiograph objects. These results are promising for the dev...

AIP Conference Proceedings, 2002

We report on the performance of an S-band RF photocathode electron gun and accelerator for operat... more We report on the performance of an S-band RF photocathode electron gun and accelerator for operation with the PLEIADES Thomson x-ray source at LLNL. Simulations of beam production, transport, and focus are presented. It is shown that a 1 ps, 500 pC electron bunch with a normalized emittance of less than 5 Tcmm-mrad can be delivered to the interaction point. Initial electron measurements are presented. Calculations of expected x-ray flux are also performed, demonstrating an expected peak spectral brightness of 10 20 photons/s/mm 2 /mrad 2 /0.1% bandwidth. Effects of RF phase jitter are also presented, and planned phase measurements and control methods are discussed.

Conference on Lasers and Electro-Optics 2012, 2012

Third International Conference on Solid State Lasers for Application to Inertial Confinement Fusion, 1999

SPIE Proceedings, 1999

We describe recent, energetics performance results on the engineering preamplifier module (PAM) p... more We describe recent, energetics performance results on the engineering preamplifier module (PAM) prototype located in the front end of the 1.8MJ National Ignition Facility (NIF) laser system. Three vertically mounted subsystem located in the PAM provide laser gain as well as spatial beam shaping. The first subsystem in the PAM prototype is a diode pumped, Nd:glass, linear, TEMoo , 4.5m long regenerative amplifier cavity. With a single diode pumped head, we amplify a lnJ, mode matched, temporally shaped (= 20ns) seed pulse by a factor of approximately 10 to 20mJ. The second subsystem in the PAM is the beam shaping module, which magnifies the gaussian output beam of the regenerative amplifier to provide a 30mm X 30mm square beam that is spatially shaped in two dimensions to pre-compensate for radial gain profiles in the main amplifiers. The final subsystem in the PAM is the 4-pass amplifier which relay images the 1mJ output of the beam shaper through four gain passes in a $5cm X 48cm flashlamp pumped rod amplifier, amplifying the energy to 175. The system gain of the PAM is 10". Each PAM provides 35 of injected energy to four separate main amplifier chains which in turn delivers 1.8MJ in 192 frequency converted laser beams to the target for a broad range of laser fusion experiments.

AIP Conference Proceedings, 2013

Lasers are of increasing interest to the accelerator community and include applications as divers... more Lasers are of increasing interest to the accelerator community and include applications as diverse as stripping electrons from hydrogen atoms, sources for Compton scattering, efficient high repetition rate lasers for dielectric laser acceleration, peta-watt peak power lasers for laser wake field and high energy, short pulse lasers for proton and ion beam therapy. The laser requirements for these applications are briefly surveyed. State of the art of laser technologies with the potential to eventually meet those requirements are reviewed. These technologies include diode pumped solid state lasers (including cryogenic), fiber lasers, OPCPA based lasers and Ti:Sapphire lasers. Strengths and weakness of the various technologies are discussed along with the most important issues to address to get from the current state of the art to the performance needed for the accelerator applications. Efficiency issues are considered in detail as in most cases the system efficiency is a valuable indicator of the actual ability of a given technology to deliver the application requirements.

We present the status of plans to commission a short-pulse, quad of beams on the National Ignitio... more We present the status of plans to commission a short-pulse, quad of beams on the National Ignition Facility (NIF), capable of generating > 10 kJ of energy in 10 ps. These beams will initially provide an advanced radiographic capability (ARC) to generate brilliant, x-ray back-lighters for diagnosing fuel density and symmetry during ignition experiments. A fiber, mode-locked oscillator generates the

Applications using high energy ''petawatt-class'' laser drivers operating at repe... more Applications using high energy ''petawatt-class'' laser drivers operating at repetition rates beyond 0.01 Hz are only now being envisioned. The Mercury laser system is designed to operate at 100 J/pulse at 10 Hz. We investigate the potential of configuring the Mercury laser to produce a rep-rated, ''petawatt-class'' source. The Mercury laser is a prototype of a high energy, high repetition

Physical Review Letters, 2000

Exploiting the energetic interaction of intense femtosecond laser pulses with deuterium clusters,... more Exploiting the energetic interaction of intense femtosecond laser pulses with deuterium clusters, it is possible to create conditions in which nuclear fusion results from explosions of these clusters. We have conducted high-resolution neutron time-of-flight spectroscopy on these plasmas and show that they yield fast bursts of nearly monochromatic fusion neutrons with temporal duration as short as a few hundred picoseconds. Such a short, nearly pointlike source now opens up the unique possibility of using these bright neutron pulses, either as a pump or a probe, to conduct ultrafast studies with neutrons.