Multiple Charge State Beam Acceleration at Atlas

A test of the acceleration of multiple charge-state uranium beams was performed at the ATLAS accelerator. A 238U+26 beam was accelerated in the ATLAS PII linac to 286 MeV (~1.2 MeV/u) and stripped in a carbon foil located 0.5 m from the entrance of the ATLAS Booster section. A 58Ni9+ 'guide' beam from the tandem injector was used to tune the Booster for 238U+38. All charge states from the stripping were injected into the booster and accelerated. Up to 94% of the beam was accelerated through the Booster linac, with losses mostly in the lower charge states. The measured beam properties of each charge state and a comparison to numerical simulations are reported in this paper.Comment: LINAC2000, MOD0

Composition of abyssal macrofauna along the Vema Fracture Zone and the hadal Puerto Rico Trench, northern tropical Atlantic

We analyzed composition and variations in benthic macrofaunal communities along a transect of the entire length of the Vema-Fracture Zone on board of RV Sonne (SO-237) between December 2014 and January 2015 in order to test whether the Mid-Atlantic Ridge serves as a barrier limiting benthic taxon distribution in the abyssal basins on both sides of the ridge or whether the fracture zone permits the migration of species between the western and eastern abyssal Atlantic basins. The Puerto Rico Trench, much deeper than the surrounding abyssal West Atlantic, was sampled to determine whether the biodiversity of its hadal macrofauna differs from that of the abyssal Atlantic. The composition of the macrofauna from the epibenthic sledge catches yielded a total of 21,332 invertebrates. Crustacea occurred most frequently (59%) with 12,538 individuals followed by Annelida (mostly Polychaeta) (26%) with 5,491 individuals, Mollusca (7%) with 1,458 individuals, Echinodermata (4%) with 778 individuals, Nematoda (2%) with 502 individuals and Chaetognatha (1%) with 152 and Porifera (1%) with 131 individuals. All other taxa occurred with overall less than ten individuals (Hemichordata, Phoronida, Priapulida, Brachiopoda, invertebrate Chordata, Echiurida, Foraminifera (here refereed to macrofaunal Komokiacea only), Chelicerata, Platyhelminthes). Within the Crustacea, Peracarida (62.6%) with 7,848 individuals and Copepoda (36.1%) with 44,526 individuals were the most abundant taxa. Along the abyssal Vema-Fracture Zone macrofaunal abundances (ind./1,000 m2) were generally higher on the eastern side, while the highest normalized abundance value was reported in the Puerto Rico Trench at abyssal station 14-1 2,313 individuals/1,000 m2. The lowest abundance was reported at station 11-4 with 120 ind./1,000 m2 located at the western side of the Vema-Fracture Zone. The number of major macrofaunal taxa (phylum, class) ranged between five (stations 12-5, 13-4 and 13-5 at hadal depths in the Puerto Rico Trench) and 14 (station 9-8) in the western abyssal basin of the Vema-Fracture Zone. Differences are seen in the distribution of Porifera at macrofaunal level between eastern and western sides of the Vema-Fracture Zone. Macrofaunal composition of the study area is compared with data from other expeditions in the Atlantic and the northwest Pacific Ocean

Studying X-ray burst nucleosynthesis in the laboratory

Type I X-ray bursts are the most common explosions in the Galaxy; however, the nucleosynthesis that occurs during the thermonuclear runaway and explosion is poorly understood. In this proceedings we discuss current experimental efforts and techniques that are being used to study X-ray burst nucleosynthesis in the laboratory. Specifically, radioactive ion beam techniques that have recently been developed have allowed the study of some of the most important (α, p) reactions in X-ray bursts for the first time. © Published under licence by IOP Publishing Ltd

COMMISSIONING OF THE 72 MHz QUARTER- WAVE CAVITY CRYOMODULE AT ATLAS*

Abstract A cryomodule of seven 72 MHz superconducting (SC) quarter-wave cavities optimized for ions with v/c=0.077 has been commissioned in the ATLAS heavy-ion accelerator at Argonne. The new module, with the new CW RFQ injecto

Simultaneous acceleration of multiply charged ions through a superconducting linac

The possibility of simultaneously accelerating particles with a range of charge-to-mass ratios (~20%) to the same energy is proposed and demonstrated for a superconducting linac. Uranium ions stripped in a foil with eight charge states have been accelerated through a portion of the ATLAS linac from 286 to 690 MeV, with 94% of the injected uranium in the accelerated beam. Emittance of the resultant beam has been measured and the energy spread was 1.3% compared to 0.4% for a single charge state. This development has immediate application to the high-intensity acceleration of heavy ions that are limited by ion-source intensities, such as the proposed rare isotope accelerator facility. (6 refs)

First measurement of the 33 Cl( p , α ) 30 S reaction

Physical Review C 84, 045802 (2011) /// The 30S(alpha; p)33Cl reaction may have a significant impact on final elemental abundances and energy output of type I X-ray bursts, as well as influencing observables such as double-peaked luminosity profiles, as it could bypass the 30S waiting point. This reaction has been studied experimentally for the first time in inverse kinematics via the time-inverse reaction p(33Cl,30S)alpha with a 33Cl radioactive ion beam produced at the ATLAS facility by the "in-flight" technique. This reaction was studied at three different beam energies. The experimental method used and the resulting data are discussed.Fil: Deibel, C. M.. Michigan State University; Estados Unidos. Argonne National Laboratory; Estados UnidosFil: Rehm, K. E.. Argonne National Laboratory; Estados UnidosFil: Figueira, Juan Manuel. Argonne National Laboratory; Estados Unidos. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigación y Aplicaciones No Nucleares. Gerencia Física (Centro Atómico Constituyentes). Proyecto Tandar; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Greene, J. P.. Argonne National Laboratory; Estados UnidosFil: Jiang, C. L.. Argonne National Laboratory; Estados UnidosFil: Kay, B. P.. Argonne National Laboratory; Estados UnidosFil: Lee, H. Y.. Argonne National Laboratory; Estados UnidosFil: Lighthall, J. C.. Argonne National Laboratory; Estados Unidos. Western Michigan University; Estados UnidosFil: Marley, S. T.. Argonne National Laboratory; Estados Unidos. Western Michigan University; Estados UnidosFil: Pardo, R. C.. Argonne National Laboratory; Estados UnidosFil: Patel, N.. Argonne National Laboratory; Estados Unidos. Colorado School of Mines; Estados UnidosFil: Paul, M.. The Hebrew University of Jerusalem; IsraelFil: Ugalde, C.. Argonne National Laboratory; Estados Unidos. University of Chicago; Estados UnidosFil: Woodard, A.. Argonne National Laboratory; Estados UnidosFil: Wuosmaa, A. H.. Western Michigan University; Estados UnidosFil: Zinkann, G.. Argonne National Laboratory; Estados Unido

Development and beam test of a continuous wave radio frequency quadrupole accelerator

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 0.75βλ 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^{5+} 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

Radioactive ion beam studies of α, p process waiting points in X-Ray Bursts

The nucleosynthetic flow in type I X-ray Bursts (XRBs) is driven by the triple-α, rp and α,p processes. Several intermediate mass nuclei, 22Mg, 26Si, 30S, and 34Ar, have been identified as possible candidates for waiting points in XRBs. When such a nucleus is reached, the flow stalls due to a (p, γ)-(γ, p) equilibrium and must await β decay unless the (α, p) reaction is fast enough to break out of the waiting point first. A method to study these αp-process reactions has been developed whereby the time-inverse reaction is studied in inverse kinematics using radioactive ion beams produced by the in-flight method at the Argonne National Laboratory ATLAS facility. These time-inverse reactions have been used to study all four of the α, p process waiting points via the p(25Al,22Mg)α, p(33Cl,30S)α, and p(37K, 34Ar)α reactions. The data from these studies have been used to determine rates for 22Mg(α, p)25Al, 26Si(α, p)29P, 30S(α, p) 33Cl, and 34Ar(α, p)37K and have also been compared with theoretical calculations. The results and possible implications for nucleosynthesis in XRBs will be discussed. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence