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"Gales, S"
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GANIL-SPIRAL2: a new era
2011
GANIL presently offers unique opportunities in nuclear physics and in many other fields that arise from not only the provision of low-energy stable beams, fragmentation beams and re-accelerated radioactive species, but also from the availability of a wide range of state-of-the-art spectrometers and instrumentation. A few examples of recent highlights are presented. With the construction of SPIRAL2 over the next few years, GANIL is in a good position to retain its world-leading capability. As selected by the ESFRI committee, the next generation of ISOL facility in Europe is represented by the SPIRAL2 project to be built at GANIL (Caen, France). SPIRAL 2 is based on a high power, CW, superconducting LINAC, delivering 5 mA of deuteron beams at 40MeV (200KW) directed on a C converter+ Uranium target and producing therefore more 1013 fissions/s. The expected radioactive beams intensities in the mass range from A=60 to A=140, will surpass by two order of magnitude any existing facilities in the world. These unstable atoms will be available at energies between few KeV/n to 15 MeV/n. The same driver will accelerate high intensity (10μA to 1 mA), heavier ions (Ar up to Xe) at maximum energy of 14 MeV/n. Under the 7FP program of European Union called *Preparatory phase*, the SPIRAL2 project has been granted a budget of about 4M to build up an international consortium around this new venture. The scientific pillars of the future facility, the status of the construction of SPIRAL2 accelerator and associated physics instruments in collaboration with EU and International partners will be presented.
Journal Article
A demonstration of ultra-high time resolution with a pulse-dilation photo-multiplier
2016
A novel microchannel plate (MCP) intensified high-speed photo-multiplier tube making use of pulse-dilation[1] has been tested. A ramped photo-cathode voltage followed by a relatively long drift region results in a transit time which is dependent on the photo-electron birth time. This leads to temporal magnification or dilation, so providing an enhancement in time resolution of the optical signal with respect to the electrical signal at the output anode. By this means a time resolution on the order of picoseconds may be realized with a substantially slower oscilloscope. The photo-electron signal is guided from a photo-cathode to an MCP by an axial magnetic field and a short input record length is stretched by a factor up to 40X to yield significantly improved time resolution at the photo-cathode. Results of the first measurements are presented.
Journal Article
Gamma Ray Measurements at OMEGA with the Newest Gas Cherenkov Detector \GCD-3\
by
Young, C S
,
Gales, S
,
Leatherland, A
in
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
,
Cerenkov counters
,
Gamma rays
2016
Initial results from the newest Gas Cherenkov Detector (GCD-3) are reported demonstrating improved performance over previous GCD iterations. Increased shielding and lengthening of the Cherenkov photon optical path have resulted in a diminished precursor signal with increased temporal separation between the precursor and the primary DT Cherenkov signal. Design changes resulted in a measured GCD-3 sensitivity comparable to GCD-1 at identical 100 psia CO2 operation. All metal gasket seals and pressure vessel certification to 400 psia operation allow for a GCD-3 lower Cherenkov threshold of 1.8 MeV using the fluorinated gas C2F6 as compared to the 6.3 MeV lower limit of GCD-1 and GCD-2. Calibration data will be used to benchmark GEANT4 and ACCEPT detector models. The GCD-3 acts as a prototype for the Super GCD being fielded at the National Ignition Facility (NIF) as part of the National Diagnostics Plan and will be installed at NIF in early 2016.
Journal Article
The first capsule implosion experiments on Orion
by
Leatherland, A E
,
Woolhead, V E
,
Horsfield, C J
in
Design optimization
,
Experiments
,
Implosions
2016
Direct drive capsule implosions are being developed on the Orion laser at AWE as a platform for ICF and HED physics experiments. The Orion facility combines both long pulse and short-pulse beams, making it well suited for studying the physics of alternative ignition approaches. Orion implosions also provide the opportunity to study aspects of polar direct drive. Limitations on drive symmetry from the relatively small number of laser beams makes predictive modelling of the implosions challenging, resulting in some uncertainty in the expected capsule performance. Initial experiments have been fielded to evaluate baseline capsule performance and inform future design optimization. Highly promising DD fusion neutron yields in excess of 109 have been recorded. Results from the experiments are presented alongside radiation-hydrocode modelling.
Journal Article
Direct-drive DT implosions with Knudsen number variations
by
Hoffman, N M
,
Schmitt, M J
,
Gales, S
in
CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
,
Filled plastics
,
Implosions
2016
Direct-drive implosions of DT-filled plastic-shells have been conducted at the Omega laser facility, measuring nuclear yields while varying Knudsen numbers (i.e., the ratio of mean free path of fusing ions to the length of fuel region) by adjusting both shell thickness (e.g., 7.5, 15, 20, 30 μm) and fill pressure (e.g., 2, 5, 15 atm). The fusion reactivity reduction model showed a stronger effect on yield as the Knudsen number increases (or the shell thickness decreases). The Reduced-Ion-Kinetic (RIK) simulation which includes both fusion reactivity reduction and mix model was necessary to provide a better match between the observed neutron yields and those simulated.
Journal Article
Using HT and DT gamma rays to diagnose mix in Omega capsule implosions
2016
Experimental evidence [1] indicates that shell material can be driven into the core of Omega capsule implosions on the same time scale as the initial convergent shock. It has been hypothesized that shock-generated temperatures at the fuel shell interface in thin exploding pusher capsules diffusively drives shell material into the gas core between the time of shock passage and bang time. We propose a method to temporally resolve and observe the evolution of shell material into the capsule core as a function of fuel shell interface temperature (which can be varied by varying the capsule shell thickness). Our proposed method uses a CD plastic capsule filled with 50 50 HT gas and diagnosed using gas Cherenkov detection (GCD) to temporally resolve both the HT \"clean\" and DT \"mix\" gamma ray burn histories. Simulations using Hydra [2] for an Omega CD-lined capsule with a sub-micron layer of the inside surface of the shell pre-mixed into a fraction of the gas region produce gamma reaction history profiles that are sensitive to the depth to which this material is mixed. An experiment to observe these differences as a function of capsule shell thickness is proposed to determine if interface mixing is consistent with thermal diffusion λii∼T2 Z2ρ at the gas shell interface. Since hydrodynamic mixing from shell perturbations, such as the mounting stalk and glue, could complicate these types of capsule-averaged temporal measurements, simulations including their effects also have been performed showing minimal perturbation of the hot spot geometry.
Journal Article
Laser-based acceleration for nuclear physics experiments at ELI-NP
2016
As part of the Extreme Light pan-European research infrastructure, Extreme Light Infrastructure − Nuclear Physics (ELI-NP) in Romania will focus on topics in Nuclear Physics, fundamental Physics and applications, based on very intense photon beams. Laser-based acceleration of electrons, protons and heavy ions is a prerequisite for a multitude of laser-driven nuclear physics experiments already proposed by the international research community. A total of six outputs of the dual-amplification chain laser system, two of 100TW, two of 1PW and two of 10PW will be employed in 5 experimental areas, with the possibility to use long and short focal lengths, gas and solid targets, reaching the whole range of laser acceleration processes. We describe the main techniques and expectations regarding the acceleration of electrons, protons and heavy nuclei at ELI-NP, and some physics cases for which these techniques play an important role in the experiments.
Journal Article
Childhood asthma in the emergency department: Trends, challenges, and opportunities
by
Walsh-Kelly, Christine M.
,
Drendel, Amy L.
,
Kelly, Kevin J.
in
Acute Disease
,
Asthma
,
Asthma - drug therapy
2006
Acute exacerbations of childhood asthma are frequently managed in the emergency department (ED). ED-based surveillance and intervention projects highlight the limitations and challenges of acute and chronic childhood asthma management. Because a significant number of asthmatic children currently receive and will likely continue to seek acute asthma care in the ED, provision of asthma education and initiation of controller medication therapy during the ED visit, although controversial, may contribute to improving asthma outcomes and eventually to reducing the burden of asthma on our overcrowded EDs.
Journal Article
Diets With Either Beef or Plant Proteins Reduce Risk of Calcium Oxalate Precipitation in Patients With a History of Calcium Kidney Stones
2001
Objective To determine the effect of substituting equal amounts of dietary protein as animal protein (beef) for plant protein (legumes, seeds, nuts, and grains) on urinary components associated with calcium oxalate precipitability risk.
Design Randomized crossover trial.
Subjects Twenty-three normocalciuric patients with a history of calcium kidney stones (8 women and 15 men, mean age 50.7±14.6 years) with 24-hour urinary calcium ≤10.3μmol, 24 hour urinary oxalate excretion between 228 and 963μmol, and a urinary calcium increase of ≤1.0μmol in 4 hours after a 25μmol oral calcium load.
Setting Four-day, free-living adaptation period, followed by 2-day metabolic unit study.
Intervention The study compared consumption of 2 servings of beef (43g protein for women and 50g for men) daily with an equal amount of protein from plant foods including legumes, nuts, and grains.
Main outcome measures Tiselius risk index (TRI) for calcium oxalate precipitability calculated from urinary calcium, oxalate, magnesium, citrate, and volume.
Statistical analyses Paired t tests.
Results Urinary calcium, oxalate, magnesium, citrate, phosphorus, volume, and TRI did not differ between diets. Urinary sodium and potassium were higher for patients on the plant protein diet. After correcting for variations in urinary sodium and potassium between diets, the difference in urinary calcium remained insignificant. TRI was lower on both beef- and plant-protein diets compared with self-selected prestudy diets for all participants.
Conclusion/Applications Balanced diets containing moderate amounts of either beef or plant protein are equally effective in reducing calcium oxalate kidney stone risk based on changes in urinary composition. J Am Diet Asoc. 2001; 101:326-331.
Journal Article