803 research outputs found
X-ray analog pixel array detector for single synchrotron bunch time-resolved imaging
Dynamic x-ray studies may reach temporal resolutions limited by only the
x-ray pulse duration if the detector is fast enough to segregate synchrotron
pulses. An analog integrating pixel array detector with in-pixel storage and
temporal resolution of around 150 ns, sufficient to isolate pulses, is
presented. Analog integration minimizes count-rate limitations and in-pixel
storage captures successive pulses. Fundamental tests of noise and linearity as
well as high-speed laser measurements are shown. The detector resolved
individual bunch trains at the Cornell High Energy Synchrotron Source (CHESS)
at levels of up to 3.7x10^3 x-rays/pixel/train. When applied to turn-by-turn
x-ray beam characterization single-shot intensity measurements were made with a
repeatability of 0.4% and horizontal oscillations of the positron cloud were
detected. This device is appropriate for time-resolved Bragg spot single
crystal experiments.Comment: 9 pages, 11 figure
Photo-induced pyridine substitution in cis-[Ru(bpy)(2)(py)(2)]Cl-2 : a snapshot by time-resolved X-ray solution scattering
Determination of transient structures in light-induced processes is a challenging goal for time-resolved techniques. Such techniques are becoming successful in detecting ultrafast structural changes in molecules and do not require the presence of probe-like groups. Here, we demonstrate that TR-WAXS (Time-Resolved Wide Angle X-ray Scattering) can be successfully employed to study the photochemistry of cis-[Ru(bpy)(2)(py)(2)]Cl-2, a mononuclear ruthenium complex of interest in the field of photoactivatable anticancer agents. TR-WAXS is able to detect the release of a pyridine ligand and the coordination of a solvent molecule on a faster timescale than 800 ns of laser excitation. The direct measurement of the photodissociation of pyridine is a major advance in the field of time-resolved techniques allowing detection, for the first time, of the release of a multiatomic ligand formed by low Z atoms. These data demonstrate that TR-WAXS is a powerful technique for studying rapid ligand substitution processes involving photoactive metal complexes of biological interest
Novel technique to extract experimental symmetry free energy information of nuclear matter
A new method of accessing information on the symmetry free energy from yields
of fragments produced in Fermi-energy heavy-ion collisions is proposed.
Furthermore, by means of quantum fluctuation analysis techniques, correlations
between extracted symmetry free-energy coefficients with temperature and
density were studied. The obtained results are consistent with those of
commonly used isoscaling techniques.Comment: 6 pages, 3 figures Heavy-ion nuclear reactions at Fermi energies,
Nuclear equation of State, Fragmentatio
Experimental determination of the quasi-projectile mass with measured neutrons
The investigation of the isospin dependence of multifragmentation reactions
relies on precise reconstruction of the fragmenting source. The criteria used
to assign free emitted neutrons, detected with the TAMU Neutron Ball, to the
quasi-projectile source are investigated in the framework of two different
simulation codes. Overall and source-specific detection efficiencies for
multifragmentation events are found to be model independent. The equivalence of
the two different methods used to assign experimentally detected charged
particles and neutrons to the emitting source is shown. The method used
experimentally to determine quasi-projectile emitted free neutron multiplicity
is found to be reasonably accurate and sufficiently precise as to allow for the
study of well-defined quasi-projectile sources.Comment: 10 pages, 8 figures. To be submitted to Nucl. Instr. and Meth.
Feeding habits of Padogobius bonelli (Osteichthyes: Gobiidae) in the Curone Creek (Northwest Italy): territoriality influences diet?
Leaf litter decomposition (and invertebrate colonization) in alpine environments above the tree line: an experimental study
Using Light Charged Particles to Probe the Asymmetry Dependence of the Nuclear Caloric Curve
Recently, we observed a clear dependence of the nuclear caloric curve on
neutron-proton asymmetry through examination of fully
reconstructed equilibrated quasi-projectile sources produced in heavy ion
collisions at E/A = 35 MeV. In the present work, we extend our analysis using
multiple light charged particle probes of the temperature. Temperatures are
extracted with five distinct probes using a kinetic thermometer approach.
Additionally, temperatures are extracted using two probes within a chemical
thermometer approach (Albergo method). All seven measurements show a
significant linear dependence of the source temperature on the source
asymmetry. For the kinetic thermometer, the strength of the asymmetry
dependence varies with the probe particle species in a way which is consistent
with an average emission-time ordering.Comment: 7 pages, 4 figure
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