Drift distance survey in direct plasma injection scheme for high current beam production.
In a laser ion source, plasma drift distance is one of the most important design parameters. Ion current density and beam pulse width are defined by plasma drift distance between a laser target and beam extraction position. In direct plasma injection scheme, which uses a laser ion source and a radio frequency quadrupole linac, we can apply relatively higher electric field at beam extraction due to the unique shape of a positively biased electrode. However, when we aim at very high current acceleration such as several tens of milliamperes, we observed mismatched beam extraction conditions. We tested three different ion current at ion extraction region by changing plasma drift distance to study better extraction condition. In this experiment, C(6+) beam was accelerated. We confirmed that matching condition can be improved by controlling plasma drift distance.
Laser ion source activities at Brookhaven National Laboratory
In Brookhaven National Laboratory (BNL), we have been developing laser ion sources for diverse accelerators. Tabletop Nd:YAG lasers with up to several Joules of energy are mainly used to create ablation plasmas for stable operations. The obtained charge states depend on laser power density and target species. Two types of ion extraction schemes, direct plasma injection scheme (DPIS) and conventional static extraction, are used depending on the application. We optimized and selected a suitable laser irradiation condition and a beam extraction scheme to meet the requirement of the following accelerator system. We have demonstrated to accelerate more than 5 × 1010 of C6+ ions using the DPIS. We successfully commissioned a low-charge ion beam provider to the user facilities in BNL. To achieve higher current, higher charge state and lower emittance, further studies will continue.
Design and synthesis of water-soluble prodrugs of rifabutin for intraveneous administration.
Acinetobacter baumannii is a gram-negative bacterium causing severe hospital-acquired infections such as bloodstream infections or pneumonia. Moreover, multidrug resistant A. baumannii becomes prevalent in many hospitals. Consequently, the World Health Organization made this bacterium a critical priority for the research and development of new antibiotics. Rifabutin, a semisynthetic product from the rifamycin class, was recently found to be very active in nutrient-limited eukaryotic cell culture medium against various A. baumannii strains, including extremely drug-resistant strains, with minimal inhibitory concentrations as low as 0.008 μg/mL. Moreover, this in vitro potency translates into in vivo efficacy. Thus, rifabutin appears to be an attractive novel antibiotic against A. baumannii. In this work, our objective was to design and synthetize rifabutin prodrugs with increased aqueous solubility to allow intraveneous use. Synthetic methodologies were developed to selectively functionalize the hydroxyl group in position 21 and to afford 17 prodrugs. We measured the water solubility of the prodrugs, the stability in human and mouse plasma and their antimicrobial activity against A. baumannii after incubation in human serum. Finally, a pharmacokinetic release study of rifabutin was performed in CD1 mice with three selected prodrugs as a proof of concept.