Ion-Ion Interaction Induced Nondispersive Dynamics in an Electrostatic Ion Beam Trap.

We demonstrate both experimentally and using a numerical simulation that, under special conditions, the repulsive Coulomb interaction helps to suppress the emittance growth of an rf-driven bunch of ions in an electrostatic ion beam trap. The underlying mechanisms can be explained by the synchronization of ion motion when nonlinear interactions are present. The surprising effect can help in improving the phase space manipulation of ions and the beam control in storage rings and accelerators and may be applied to other systems with many-body interactions in a periodic potential.

Time-dependent dynamics of radio-frequency-bunched ions in an electrostatic ion beam trap.

The dynamics of ions in an electrostatic ion beam trap in the presence of an external time-dependent field is studied with a recently developed particle-in-cell simulation technique. The simulation technique, capable of accounting for space-charge effects, has reproduced all the experimental results on the bunch dynamics in the radio frequency mode. With simulation, the motion of ions is visualized in phase space and it is shown that the ion-ion interaction strongly affects the distribution of ions in phase space in the presence of an rf driving voltage.

Particle-in-cell techniques for the study of space charge effects in an electrostatic ion beam trap.

We developed a simulation technique to study the effect of space charge interaction between trapped ions in the electrostatic ion beam trap (EIBT). The importance of space charge is demonstrated in both the dispersive and the self-bunching regime of the ion trap. The simulation results provide an estimate for the space charge effect on the trapping efficiency. They also allow for a better understanding of the enhanced diffusion and the self-bunching effect and provide a better characterization of the EIBT as a mass spectrometer, where peak coalescence is important. The numerical results reproduce all experimental data, demonstrating the critical importance of including space charge effects, even at low ion density, to understand the ion trap dynamics.

A Fully Automated High-Throughput Zebrafish Behavioral Ototoxicity Assay.

Zebrafish animal models lend themselves to behavioral assays that can facilitate rapid screening of ototoxic, otoprotective, and otoregenerative drugs. Structurally similar to human inner ear hair cells, the mechanosensory hair cells on their lateral line allow the zebrafish to sense water flow and orient head-to-current in a behavior called rheotaxis. This rheotaxis behavior deteriorates in a dose-dependent manner with increased exposure to the ototoxin cisplatin, thereby establishing itself as an excellent biomarker for anatomic damage to lateral line hair cells. Building on work by our group and others, we have built a new, fully automated high-throughput behavioral assay system that uses automated image analysis techniques to quantify rheotaxis behavior. This novel system consists of a custom-designed swimming apparatus and imaging system consisting of network-controlled Raspberry Pi microcomputers capturing infrared video. Automated analysis techniques detect individual zebrafish, compute their orientation, and quantify the rheotaxis behavior of a zebrafish test population, producing a powerful, high-throughput behavioral assay. Using our fully automated biological assay to test a standardized ototoxic dose of cisplatin against varying doses of compounds that protect or regenerate hair cells may facilitate rapid translation of candidate drugs into preclinical mammalian models of hearing loss.

First direct double-ß decay Q-value measurement of 82Se in support of understanding the nature of the neutrino.

In anticipation of results from current and future double-ß decay studies, we report a measurement resulting in a (82)Se double-ß decay Q value of 2997.9(3) keV, an order of magnitude more precise than the currently accepted value. We also present preliminary results of a calculation of the (82)Se neutrinoless double-ß decay nuclear matrix element that corrects in part for the small size of the shell model single-particle space. The results of this work are important for designing next generation double-ß decay experiments and for the theoretical interpretations of their observations.