D. Gigliotti

The DRAGON facility for nuclear astrophysics at TRIUMF-ISAC: design, construction and operation

A facility for measuring cross-sections (resonance strengths) for reactions of astrophysical importance involving short-lived, radioactive reactants has been designed, built and installed at the new TRIUMF-ISAC Radioactive Beams Laboratory in Canada. Named DRAGON (Detector of Recoils And Gamma-rays of Nuclear reactions), it has been successfully commissioned with stable and radioactive heavy ion beams from ISAC. This report presents the main components of the facility, namely, the windowless gas target, the surrounding g detector array, the subsequent electromagnetic recoil mass separator, the focal plane detectors for recoils, the detection system for elastics, and the modular electronics and computer software used for the data acquisition. Examples of the operation of the facility for both stable beam reactions and the first radioactive beam reaction study, 21 Naðp;gÞ 22 Mg are also presented, along with future plans for the program. r 2003 Elsevier Science B.V. All rights reserved. PACS: 29.0

21Na(p,gamma)22Mg reaction and oxygen-neon novae.

The 21Na(p,gamma)22Mg reaction is expected to play an important role in the nucleosynthesis of 22Na in oxygen-neon novae. The decay of 22Na leads to the emission of a characteristic 1.275 MeV gamma-ray line. This report provides the first direct measurement of the rate of this reaction using a radioactive 21Na beam, and discusses its astrophysical implications. The energy of the important state was measured to be E(c.m.)=205.7+/-0.5 keV with a resonance strength omegagamma=1.03+/-0.16(stat)+/-0.14(sys) meV.

The DRAGON facility for nuclear astrophysics at TRIUMF-ISAC

A facility for measuring cross-sections (resonance strengths) for reactions of astrophysical importance involving short-lived, radioactive reactants has been designed, built and installed at the new TRIUMF-ISAC Radioactive Beams Laboratory in Canada. Named DRAGON (Detector of Recoils And Gamma-rays of Nuclear reactions), it has been successfully commissioned with stable and radioactive heavy ion beams from ISAC. This report presents the main components of the facility, namely, the windowless gas target, the surrounding g detector array, the subsequent electromagnetic recoil mass separator, the focal plane detectors for recoils, the detection system for elastics, and the modular electronics and computer software used for the data acquisition. Examples of the operation of the facility for both stable beam reactions and the first radioactive beam reaction study, Naðp; gÞMg are also presented, along with future plans for the program. r 2003 Elsevier Science B.V. All rights reserved.

Calibration and simulation of a gamma array for DRAGON at ISAC

Abstract A γ ray detector has been built for the DRAGON facility at TRIUMF to detect the γ ray emitted in astrophysically important proton and α radiative capture reactions. The γ detector was designed to balance cost with maximum solid angle coverage and efficiency. To study the properties of the current design, GEANT simulations are being carried out and compared with prototype measurements using calibration sources and radioactive beams supplied by ISAC. Simulations will be compared with data allowing a realistic simulation to be produced. This modified simulation will then be used to provide efficiency predictions of the γ array when an actual experiment’s parameters are inputted. Using the simulated efficiency of the array, cross sections for radiative capture can be calculated from the measured γ ray yields, for the individual reactions. The following will outline some initial results of background suppression of beam related experiments. Also shown, are some preliminary comparison of point source data and GEANT simulations.

Results of 21Na+p experiments at ISAC

Abstract Several resonances in 22 Mg have been observed with a radioactive beam of 21 Na impinging on a hydrogen target at ISAC. Both elastic scattering as well as radiative capture have been investigated. Some results together with the experimental methods used will be reported.

Measurements with DRAGON on resonances in the 21Na(p, γ)22Mg reaction with a radioactive ion beam

Abstract In the modelling of nucleosynthesis in nova explosions, temperature and density are important parameters to describe the hydrodynamics. Those parameters are not easy to observe, but specific gamma-ray emitters produced in the explosion provide constrains on the models, such as 22 Na, produced via 21 Na ( p , γ ) 22 Mg ( β + ) 22 Na . The new DRAGON recoil separator facility, designed and built to measure directly the rates of radiative proton and alpha capture reactions, important for nuclear astrophysics, is now operational. Experiments have been conducted on the 21 Na(p , γ) 22 Mg reaction using a radioactive 21 Na beam incident onto a windowless hydrogen gas target. Yield measurements have been performed detecting the prompt gamma and the reaction recoils at E cm ≈ 821 keV and 204 keV.

Testing the ISAC radioactive ion accelerator beam specifications using the H(15N,αγ)12C reaction

Important ion beam parameters like energy spread and stability of the new isotope separator and accelerator accelerator at TRIUMF were determined during the first beamtime with the detector of recoils and gammas of nuclear gas target and BGO array. For this purpose a variation of the nuclear resonance method, using a geometrical scan over the resonance as placed in an extended gas target cell, as well as time-of-flight correlations were employed.

Measurement of the 21Na(p,γ)22Mg Reaction with the Dragon Facility at TRIUMF-ISAC

The DRAGON recoil separator facility, designed to measure the rates of radiative proton and alpha capture reactions important for nuclear astrophysics, is now operational at the TRIUMF‐ISAC radioactive beam facility in Vancouver, Canada. We report on first measurements of the 21Na(p,γ)22Mg reaction rate with radioactive beams of 21Na.

Na21(p,γ)Mg22Reaction and Oxygen-Neon Novae

The 21Na(p,gamma)22Mg reaction is expected to play an important role in the nucleosynthesis of 22Na in oxygen-neon novae. The decay of 22Na leads to the emission of a characteristic 1.275 MeV gamma-ray line. This report provides the first direct measurement of the rate of this reaction using a radioactive 21Na beam, and discusses its astrophysical implications. The energy of the important state was measured to be E(c.m.)=205.7+/-0.5 keV with a resonance strength omegagamma=1.03+/-0.16(stat)+/-0.14(sys) meV.

The 21Na(p,gamma)22Mg Reaction and Oxygen-Neon Novae

The 21Na(p,gamma)22Mg reaction is expected to play an important role in the nucleosynthesis of 22Na in oxygen-neon novae. The decay of 22Na leads to the emission of a characteristic 1.275 MeV gamma-ray line. This report provides the first direct measurement of the rate of this reaction using a radioactive 21Na beam, and discusses its astrophysical implications. The energy of the important state was measured to be E(c.m.)=205.7+/-0.5 keV with a resonance strength omegagamma=1.03+/-0.16(stat)+/-0.14(sys) meV.