Charge state studies of low energy heavy ions passing through hydrogen and helium gas


Studies of the charge state distribution of low energy (<1.5 MeV/u), low Z (<13) heavy ions passing through hydrogen and helium gas of varying target pressure have been performed using separate windowless gas target systems at TRIUMF and the University of Naples. Semi-empirical relationships have been deduced to estimate the equilibrium charge state distributions as a function of beam energy. From these distributions, cross-sections for the relevant charge changing reactions have been deduced.

Author: Liu, W. et al.
Journal: Nuclear Instruments and Methods in Physics Research A

21Na(ρ,ϒ)22Mg Reaction and Oxygen-Neon Novae

Sodium 21

The 21Na(ρ,ϒ)22Mg recation is expected to play in 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 Ec.m.= 205.7 keV with a resonance strength ωϒ= 1.03 ± 0.16stat ± 0.14sys meV.

Author: Bishop, L. et al.
Journal: Physical Review Letters

A double sided silicon strip detector as a DRAGON end detector


The new DRAGON facility (detector of recoils and gammas of nuclear reactions), located at the TRIUMF-ISAC Radioactive Beams facility in Vancouver, Canada, is now operational. This facility is used to study radiative proton capture reactions in inverse kinematics (heavy ion beam onta a light gaseous target) with both stable beams and radioactive beams of mass A=13-26 in the energy range 0.15-1.5 MeV/u. A double sided silicon strip detector (DSSSD) has been used to detect recoil ions. Tests have been performed to determine the performance of this DSSSD.

Author: Wrede, C.; Hussein, A; Rogers, J. G.; D'Auria, J
Journal: Nuclear Instruments and Methods in Physics Research B

Energy loss around the stopping power maximum of Ne, Mg, and Na ions in hydrogen gas


The DRAGON (detector of recoils and gamma-rays of nuclear reactions) setup at the ISAC radioactive ion beam facility of TRIUMF, Vancouver, was used to measure the energy loss of stable neon and magnesium as well as of radioactive sodium ions (energy range 200-1150 keV/u) in hydrogen gas. Stopping power values were determined and (as no previous experimental data around the stopping power maximum existed) compared to the available semi-empirical codes SRIM 2003, ATIMA and MSTRAR. The experimental data seems to favor the new SRIM 2003 approach and will hopefully provide input to a further improvement of the parameter set.

Author: Greife, U. et al.
Journal: Nuclear Instruments and Methods in Physics Research B

The 40Ca(α,ϒ)44Ti reaction at DRAGON

Calcium 40

Nuclear reactions play a key role in understanding nucleosynthesis in stars. Recoil mass spectrometers such as DRAGON are well suited to study reactions with respect to astrophysical production because of direct detection of reaction products. Here we present the first stage of an experiment running at the recoil mass spectrometer DRAGON at the ISAC/TRIUMF facility in Vancouver, Canada, to study the reaction 40Ca(α,ϒ)44Ti at astrophysically relevant energies. This reaction is one of the key reactions for production of 44Ti, which has been identified in younf supernova remnants by space based ϒ-ray telescopes onboard COMPTEL and INTEGRAL. In this paper, we focus on technical upgrade of DRAGON for 40Ca(α,ϒ)44Ti and preliminary results at resonances at Ex~9.2 MeV.

Author: Vockenhuber, A. et al.
Journal: Nuclear Instruments and Methods in Physics Research B

Charge-State Distributions After Radiative Capture


We present new measurements of the charge-state distributions (CSD) of a 1.068 MeV/u C beam in He, and of the 6+ : 5+ charge-state population ratio in the recoils of the 12C(α,ϒ)16O reaction, noth measured at the DRAGON recoil mass spectrometer. A computer simulation to model the CSD of both beam and recoil particles in inverse-kinematics experiments is compared to data from this work and from previous work at ERNA. The simulation provides good agreement with both data sets. The results suggest that, for this fusion reaction on the Jπ=4+ resonance at Ebeam=1.064 MeV/u, immediately after fusion, the recoil ions contain only the nucleons and not the electrons of the target He atom.

Author: Zylberberg, J. et al.
Journal: Elsevier Preprint

Measurement of the Ec.m.=184 keV Resonance Strength in the 26gAl(ρ,ϒ)27Si Reaction

Aluminium 26

The strength of the Ec.m.=184 keV resonance in the 26gAl(ρ,ϒ)27Si reaction has been measured in inverse kinematics using the DRAGON recoil separator at TRIUMF's ISAC facility. We measure a value of ωϒ=35 ±7 µeV and a resonance energy of Ec.m.=184±1 keV, consistent with p-wave proton capture into the 7652(3) keV state in 27Si, and discuss the implications of these values for 26gAl nucleosynthesisin typical oxygen-neon white-dwarf novae.

Author: Ruiz, C. et al.

Commissioning the DRAGON facility at ISAC


The performance of the DRAGON recoil spectrometer at TRIUMF-ISAC has been studied using the radiative capture reactions with stable beams of 12C, 20Ne, 21Ne, 23Na, 24Mg, and 26Mg. Calibration of the deflection magnet measuring the beam energy was established and the beam suppression factors of the separator were investigated. Yields from six narrow resonances were measured and compared with previous results. For the 1112.6 keV resonance in 20Ne(ρ,ϒ)21Na, our result is in disagreement with the NACRE database assignment but agrees with one other previous result.

Author: Engel, S. et al.

Direct Measurement of the 21Na(ρ,ϒ)22Mg Reaction: Resonance Strengths and Gamma-Gamma Analysis

Sodium 21

A series of astrophysical measurements was recently completed at TRIUMF, related to the unknown total rate of the 21Na(ρ,ϒ)22Mg reaction. With a high intensity 21Na beam from the ISAC facility, the DRAGON recoil mass spectrometer was used to directly measure seven resonances at center of mass energies from Ec.m.=200 to 1135 keV and determine their respective contributions to the 21(ρ,ϒ)22Mg reaction rate in novae and x-ray bursts, as well as their impact on 22Na production in novae. This study also allowed the investigation of different excited states in 22Mg; proposed decays and spin assignments are given for the 6246, 6329, 6609 keV levels.

Author: Trinczek, M. et al.