Holographic techniques significantly extend the capabilities of laser tweezing, making possible extended trapping patterns for manipulating large numbers of particles and volumes of soft matter. We describe practical methods for creating arbitrary configurations of optical tweezers using computergenerated diffractive optical elements. While the discussion focuses on ways to create planar arrays of identical tweezers, the approach can be generalized to three-dimensional arrangements of heterogeneous tweezers and extended trapping patterns.

The Precision Reactor Oscillation and Spectrum Experiment, PROSPECT, is designed to make a precise measurement of the antineutrino spectrum from a highly-enriched uranium reactor and probe eV-scale sterile neutrinos by searching for neutrino oscillations over meter-long distances. PROSPECT is conceived as a 2-phase experiment utilizing segmented 6 Li-doped liquid scintillator detectors for both efficient detection of reactor antineutrinos through the inverse beta decay reaction and excellent background discrimination. PROSPECT Phase I consists of a movable 3-ton antineutrino detector at distances of 7-12 m from the reactor core. It will probe the best-fit point of the ν e disappearance experiments at 4σ in 1 year and the favored region of the sterile neutrino parameter space at >3σ in 3 years. With a second antineutrino detector at 15-19 m from the reactor, Phase II of PROSPECT can probe the entire allowed parameter space below 10 eV 2 at 5σ in 3 additional years. The measurement of the reactor antineutrino spectrum and the search for short-baseline oscillations with PROSPECT will test the origin of the spectral deviations observed in recent θ 13 experiments, search for sterile neutrinos, and conclusively address the hypothesis of sterile neutrinos as an explanation of the reactor anomaly.

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has performed a set of absolute Fission Product Yield (FPY) measurements. Using monoenergetic neutron at energies between 0.5 and 14.8 MeV, the excitation functions of a number of fission products from 235 U, 238 U and 239 Pu have begun to be mapped out. This work has practical applications for the determination of weapon yields and the rate of burn-up in nuclear reactors, while also providing important insight into the fission process. Combining the use of a dual-fission ionization chamber and-ray spectroscopy, absolute FPYs have been determined for approximately 15 di↵erent fission products. The dual-fission chamber is a back-to-back ionization chamber system with a 'thin' actinide foil in each chamber as a monitor or reference foil. The chamber holds a 'thick' target in the center of the system such that the target and reference foils are of the same actinide isotope. This allows for simple mass scaling between the recorded number of fissions in the individual chambers and the number of fissions in the center thick target, eliminating the need for the knowledge of the absolute fission cross section and its uncertainty. The 'thick' target was removed after activation and-rays counted with well shielded High Purity Germanium (HPGe) detectors for a period of 1.5-2 months.

We evaluate two dominant nuclear reaction rates and their uncertainties that affect 44 Ti production in explosive nucleosynthesis. Experimentally we develop thick-target yields for the 40 Ca(α,γ) 44 Ti reaction at E α = 4.13, 4.54, and 5.36 MeV using γ-ray spectroscopy. At the highest beam energy, we also performed an activation measurement which agrees with the thick target result. From the measured yields a stellar reaction rate was developed that is smaller than current statistical-model calculations and recent experimental results, which would suggest lower 44 Ti production in scenarios for the α−rich freeze out. Special attention has been paid to assessing realistic uncertainties of stellar reaction rates produced from a combination of experimental and theoretical cross sections. With such methods, we also develop a re-evaluation of the 44 Ti(α,p) 47 V reaction rate. Using these two rates we carry out a sensitivity survey of 44 Ti synthesis in eight expansions representing peak temperature and density conditions drawn from a suite of recent supernova explosion models. Our results suggest that the current uncertainty in these two reaction rates could lead to as large an uncertainty in 44 Ti synthesis as that produced by different treatments of stellar physics.

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The surrogate nuclear reaction method is being applied in many efforts to indirectly determine neutron-induced reaction cross sections on short-lived isotopes. This technique aims to extract accurate (n,γ) cross sections from measured decay properties of the compound nucleus of interest (created using a different reaction). The advantages and limitations of a method that identifies the γ-ray decay channel by detecting any high-energy ("statistical") γ ray emitted during the relaxation of the compound nucleus were investigated. Data collected using the STARS/LiBerACE silicon and germanium detector arrays were used to study the decay of excited gadolinium nuclei following inelastic proton scattering. In many cases, this method of identifying the γ-ray decay channel can simplify the experimental data collection and greatly improve the detection efficiency for γ-ray cascades. The results show sensitivity to angular-momentum differences between the surrogate reaction and the desired (n,γ) reaction similar to an analysis performed using low-lying discrete transitions even when ratios of cross sections are considered.

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