C. Mileham
University of Rochester
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Featured researches published by C. Mileham.
Physics of Plasmas | 2006
W. Theobald; K. U. Akli; R. J. Clarke; J. A. Delettrez; R. R. Freeman; S. H. Glenzer; J. S. Green; G. Gregori; R. Heathcote; N. Izumi; J. King; J. A. Koch; Jaroslav Kuba; K. L. Lancaster; A. J. Mackinnon; M.H. Key; C. Mileham; J. F. Myatt; D. Neely; P.A. Norreys; H.-S. Park; J. Pasley; P. K. Patel; S. P. Regan; H. Sawada; R. Shepherd; Richard Adolph Snavely; R. Stephens; C. Stoeckl; M. Storm
A hot, T{sub e} {approx} 2- to 3-keV surface plasma was observed in the interaction of a 0.7-ps petawatt laser beam with solid copper-foil targets at intensities >10{sup 20} W/cm{sup 2}. Copper K-shell spectra were measured in the range of 8 to 9 keV using a single-photon-counting x-ray CCD camera. In addition to K{sub {alpha}} and K{sub {beta}} inner-shell lines, the emission contained the Cu He{sub {alpha}} and Ly{sub {alpha}} lines, allowing the temperature to be inferred. These lines have not been observed previously with ultrafast laser pulses. For intensities less than 3 x 10{sup 18} W/cm{sup 2}, only the K{sub {alpha}} and K{sub {beta}} inner-shell emissions are detected. Measurements of the absolute K{sub {alpha}} yield as a function of the laser intensity are in agreement with a model that includes refluxing and confinement of the suprathermal electrons in the target volume.
Review of Scientific Instruments | 2012
C. Stoeckl; G. Fiksel; D. Guy; C. Mileham; P.M. Nilson; T. C. Sangster; M. J. Shoup; W. Theobald
A narrowband x ray imager for the Cu K(α) line at ~8 keV using a spherically bent quartz crystal has been implemented on the OMEGA EP laser at the University of Rochester. The quartz crystal is cut along the 2131 (211) planes for a 2d spacing of 0.3082 nm, resulting in a Bragg angle of 88.7°, very close to normal incidence. An optical system is used to remotely align the spherical crystal without breaking the vacuum of the target chamber. The images show a high signal-to-background ratio of typically >100:1 with laser energies ≥1 kJ at a 10-ps pulse duration and a spatial resolution of less than 10 μm.
Review of Scientific Instruments | 2011
C. G. Freeman; G. Fiksel; C. Stoeckl; N. Sinenian; M. J. Canfield; G. B. Graeper; A. T. Lombardo; C. R. Stillman; S. J. Padalino; C. Mileham; T. C. Sangster; J. A. Frenje
A Thomson parabola ion spectrometer has been designed for use at the Multiterawatt (MTW) laser facility at the Laboratory for Laser Energetics (LLE) at the University of Rochester. This device uses parallel electric and magnetic fields to deflect particles of a given mass-to-charge ratio onto parabolic curves on the detector plane. Once calibrated, the position of the ions on the detector plane can be used to determine the particle energy. The position dispersion of both the electric and magnetic fields of the Thomson parabola was measured using monoenergetic proton and alpha particle beams from the SUNY Geneseo 1.7 MV tandem Pelletron accelerator. The sensitivity of Fujifilm BAS-TR imaging plates, used as a detector in the Thomson parabola, was also measured as a function of the incident particle energy over the range from 0.6 MeV to 3.4 MeV for protons and deuterons and from 0.9 MeV to 5.4 MeV for alpha particles. The device was used to measure the energy spectrum of laser-produced protons at MTW.
Nature Communications | 2014
W. Theobald; A. A. Solodov; C. Stoeckl; Karen S. Anderson; F. N. Beg; R. Epstein; G. Fiksel; E. Giraldez; V. Yu. Glebov; H. Habara; S. Ivancic; L. C. Jarrott; F. J. Marshall; G. McKiernan; H.S. McLean; C. Mileham; P.M. Nilson; P. K. Patel; F. Pérez; T. C. Sangster; J. J. Santos; H. Sawada; A. Shvydky; R. Stephens; M. S. Wei
The advent of high-intensity lasers enables us to recreate and study the behaviour of matter under the extreme densities and pressures that exist in many astrophysical objects. It may also enable us to develop a power source based on laser-driven nuclear fusion. Achieving such conditions usually requires a target that is highly uniform and spherically symmetric. Here we show that it is possible to generate high densities in a so-called fast-ignition target that consists of a thin shell whose spherical symmetry is interrupted by the inclusion of a metal cone. Using picosecond-time-resolved X-ray radiography, we show that we can achieve areal densities in excess of 300 mg cm(-2) with a nanosecond-duration compression pulse--the highest areal density ever reported for a cone-in-shell target. Such densities are high enough to stop MeV electrons, which is necessary for igniting the fuel with a subsequent picosecond pulse focused into the resulting plasma.
Review of Scientific Instruments | 2010
C. Stoeckl; M. Cruz; V. Yu. Glebov; J. P. Knauer; R. Lauck; K. L. Marshall; C. Mileham; T. C. Sangster; W. Theobald
The detection of neutrons in fast-ignitor experiments or down-scattered neutrons in inertial fusion experiments is very challenging since it requires the neutron detection system to recover within 10-100 ns from a high background orders of magnitude stronger than the signal of interest. The background is either the hard x-ray emission from short-pulse laser target interactions for the fast-ignitor experiments or the primary neutron signal for the down-scattered neutrons. A liquid-scintillator detector has been developed using a gated photomultiplier that suppresses the background signal and eliminates the afterglow present in conventional plastic scintillators.
Review of Scientific Instruments | 2014
C. Stoeckl; M. Bedzyk; G. Brent; R. Epstein; G. Fiksel; D. Guy; V.N. Goncharov; S. X. Hu; S. Ingraham; D. Jacobs-Perkins; R. Jungquist; F. J. Marshall; C. Mileham; P.M. Nilson; T. C. Sangster; M. J. Shoup; W. Theobald
A high-performance cryogenic DT inertial confinement fusion implosion experiment is an especially challenging backlighting configuration because of the high self-emission of the core at stagnation and the low opacity of the DT shell. High-energy petawatt lasers such as OMEGA EP promise significantly improved backlighting capabilities by generating high x-ray intensities and short emission times. A narrowband x-ray imager with an astigmatism-corrected bent quartz crystal for the Si Heα line at ∼1.86 keV was developed to record backlit images of cryogenic direct-drive implosions. A time-gated recording system minimized the self-emission of the imploding target. A fast target-insertion system capable of moving the backlighter target ∼7 cm in ∼100 ms was developed to avoid interference with the cryogenic shroud system. With backlighter laser energies of ∼1.25 kJ at a 10-ps pulse duration, the radiographic images show a high signal-to-background ratio of >100:1 and a spatial resolution of the order of 10 μm. The backlit images can be used to assess the symmetry of the implosions close to stagnation and the mix of ablator material into the dense shell.
Review of Scientific Instruments | 2012
G. Fiksel; F. J. Marshall; C. Mileham; C. Stoeckl
The spatial resolution of two types of imaging plates, Fuji BAS-TR and Fuji BAS-SR, has been measured using a knife-edge x-ray source of 8-keV Cu K(α) radiation. The values for the spatial resolution, defined as the distance between 10% and 90% levels of the edge spread function, are 94 μm and 109 μm, respectively. The resolution values are important for quantitative analysis of x-ray and particle imaging and spectroscopic diagnostics.
Physics of Plasmas | 2011
P.M. Nilson; W. Theobald; C. Mileham; C. Stoeckl; J. F. Myatt; J. A. Delettrez; J. MacFarlane; I. A. Begishev; Jonathan D. Zuegel; R. Betti; T. C. Sangster; D. D. Meyerhofer
Target-heating effects on the Kα1,2-emission spectrum from small-mass Cu targets irradiated with 1-ps pulses focused to intensities >1018 W/cm2 have been observed. A collisional-radiative atomic physics model is unable to reproduce the time-integrated Kα1,2-emission spectrum from the smallest-mass targets when calculated with a single, time-independent thermal-electron temperature. When time-dependent heating to several hundred electron volts is included in the model, the synthetic spectra better reproduce the main observed spectral features.
Review of Scientific Instruments | 2006
V. Yu. Glebov; C. Stoeckl; T. C. Sangster; C. Mileham; S. Roberts; R. A. Lerche
A simple, low-cost, high-yield neutron bang time (HYNBT) detector has been developed and implemented on the 60-beam, 30kJ OMEGA Laser Facility at the University of Rochester’s Laboratory for Laser Energetics. The HYNBT consists of three chemical-vapor deposition diamond detectors of different sizes and sensitivities placed in a lead-shielded housing. The HYNBT is located in a reentrant tube 50cm from the center of the target chamber. The HYNBT has been temporally cross calibrated against the streak-camera-based neutron temporal diagnostic (NTD) for both D2 and DT implosions. The HYNBT has an internal time resolution better than 20ps and is able to measure bang time for yields above 1010 for DT and 5×1010 for D2 implosions. The implementation of the HYNBT on the National Ignition Facility will be discussed.
Review of Scientific Instruments | 2012
C. Stoeckl; J. A. Delettrez; R. Epstein; G. Fiksel; D. Guy; M. Hohenberger; R. Jungquist; C. Mileham; P.M. Nilson; T. C. Sangster; M. J. Shoup; W. Theobald
Using a spherically bent quartz crystal for the Si He(α) line at ~1.865 keV, a narrowband x-ray imager has been deployed at the Omega Laser Facility to record backlit images of direct-drive laser implosions. The crystal was cut along the 1011 planes for a 2d spacing of 0.687 nm, resulting in a Bragg angle of 83.9°. Apertures in front of the crystal were used to control the astigmatism of the imaging system. The backlit images show a high signal-to-background ratio of >10:1 with backlighter laser energies ≥1.5 kJ at a 10-ps pulse duration and a spatial resolution of better than 20 μm.