The front end of any modern ion accelerator includes a radio frequency quadrupole (RFQ). While many pulsed ion linacs successfully operate RFQs, several ion accelerators worldwide have significant difficulties operating continuous wave (CW) RFQs to design specifications. In this paper we describe the development and results of the beam commissioning of a CW RFQ designed and built for the National User Facility: Argonne Tandem Linac Accelerator System (ATLAS). Several innovative ideas were implemented in this CW RFQ. By selecting a multisegment split-coaxial structure, we reached moderate transverse dimensions for a 60.625-MHz resonator and provided a highly stabilized electromagnetic field distribution. The accelerating section of the RFQ occupies approximately 50% of the total length and is based on a trapezoidal vane tip modulation that increased the resonator shunt impedance by 60% in this section as compared to conventional sinusoidal modulation. To form an axially symmetric beam exiting the RFQ, a very short output radial matcher with a length of 0:75 was developed. The RFQ is designed as a 100% oxygen-free electronic (OFE) copper structure and fabricated with a two-step furnace brazing process. The radio frequency (rf) measurements show excellent rf properties for the resonator, with a measured intrinsic Q equal to 94% of the simulated value for OFE copper. An O 5þ ion beam extracted from an electron cyclotron resonance ion source was used for the RFQ commissioning. In off-line beam testing, we found excellent coincidence of the measured beam parameters with the results of beam dynamics simulations performed using the beam dynamics code TRACK, which was developed at Argonne. These results demonstrate the great success of the RFQ design and fabrication technology developed here, which can be applied to future CW RFQs.

Generation of quasistationary flows of multicharged ions with a current density of up to 1 A/cm2 from a dense electron cyclotron resonance plasma confined in a magnetic trap under the quasi-gas-dynamic regime has been achieved [Golubev et al., Trans. Fusion Sci. Technol. 47, 345 (2005)]. This technique provides opportunities for extracting high current multicharged ion beams. The present research is concerned with experimental and theoretical investigations of two ion extraction systems for the gas-dynamic ion sources. (1) Single-aperture system. In this case, there is a principal possibility to obtain ion beams with low emittance by using a small-diameter aperture for extraction. Here we describe investigations aimed at creating nitrogen ion beams (the main ion in the spectrum is N2+) with currents of up to 6.5 mA through a 1.5 mm aperture in the plasma electrode. (2) Multiaperture system. Such systems provide significantly higher beam currents. First results of testing an extractor with five apertures are presented in this article

Absolutely calibrated vacuum ultraviolet spectra in the 150 -250 -nm range from plasmas generated by the NIKE KrF laser Phys. Plasmas 12, 062701 (2005); 10.1063/1.1920328 Generation of intense streams of metallic ions with a charge state up to 10+ in a laser ion source Rev. Sci. Instrum. 75, 1575 (2004);Charge state and energy distributions of ions generated by a 3 J / 30 ns Nd-glass laser were measured at a distance of 3.7 m from the target for seven different elements of the Periodic Table and for two different laser power densities ͑of the order of 10 11 and 10 12 W/cm 2 ͒. Two groups of elements were found: highly charged ions with ionization potentials in the range of 500-1000 eV were registered for all elements between 12 C and 56 Fe; at the same time, ions with about-one-order-less ionization potentials were registered for elements between 74 Ge and 181 Ta. The most probable reason for such a big difference is the recombination losses of ions during laser-produced plasma expansion into vacuum. Verification of recombination losses in the case of 181 Ta target has shown no losses at distances longer than 32.5 cm from the target, so recombination processes should take place at shorter distances. Current densities, pulse durations, energy ranges, and numbers of ions with different charge states were found for all elements by normalizing charge state distributions to total ion currents. Two different ion groups exist for all elements and laser power densities used in experiments: the faster group has a very weak dependence of energy on ion charge state, and the energies of the slower group are proportional to the charge states with high accuracy.

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The idea of direct plasma injection scheme (DPIS) was proposed in 2000. This new technique has been studied and proven to accelerate intense ion beams. To provide medium mass ions with highly charged states, small tabletop solid lasers were used for plasma production. Based on the measured plasma properties, aluminum and carbon ions were accelerated with more than 60 mA of current. The next experiments will use an radio frequency quadrupole designed for q/m=1/6 and explore beam productions using targets up to silver, and future work will explore production up to uranium. The DPIS has been established and is ready to be used with various accelerators which require pulsed high current, high charge state ion beams.