Measurement of the 18Ne(a,p_0)21Na reaction cross section in the burning energy region for X-ray bursts

The 18Ne(a,p)21Na reaction provides one of the main HCNO-breakout routes into the rp-process in X-ray bursts. The 18Ne(a,p_0)21Na reaction cross section has been determined for the first time in the Gamow energy region for peak temperatures T=2GK by measuring its time-reversal reaction 21Na(p,a)18Ne in inverse kinematics. The astrophysical rate for ground-state to ground-state transitions was found to be a factor of 2 lower than Hauser-Feshbach theoretical predictions. Our reduced rate will affect the physical conditions under which breakout from the HCNO cycles occurs via the 18Ne(a,p)21Na reaction.Comment: 5 pages, 3 figures, accepted for publication on Physical Review Letter

Initial operation of the recoil mass spectrometer EMMA at the ISAC-II facility of TRIUMF

The Electromagnetic Mass Analyser (EMMA) is a new vacuum-mode recoil mass spectrometer currently undergoing the final stages of commissioning at the ISAC-II facility of TRIUMF. EMMA employs a symmetric configuration of electrostatic and magnetic deflectors to separate the products of nuclear reactions from the beam, focus them in both energy and angle, and disperse them in a focal plane according to their mass/charge (m∕q) ratios. The spectrometer was designed to accommodate the γ-ray detector array TIGRESS around the target position in order to provide spectroscopic information from electromagnetic transitions. EMMA is intended to be used in the measurement of fusion evaporation, radiative capture, and transfer reactions for the study of nuclear structure and astrophysics. Its complement of focal plane detectors facilitates the identification of recoiling nuclei and subsequent recoil decay spectroscopy. Here we describe the facility and report on commissioning efforts

Fighting post-COVID and ME/CFS - development of curative therapies

The sequela of COVID-19 include a broad spectrum of symptoms that fall under the umbrella term post-COVID-19 condition or syndrome (PCS). Immune dysregulation, autoimmunity, endothelial dysfunction, viral persistence, and viral reactivation have been identified as potential mechanisms. However, there is heterogeneity in expression of biomarkers, and it is unknown yet whether these distinguish different clinical subgroups of PCS. There is an overlap of symptoms and pathomechanisms of PCS with postinfectious myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). No curative therapies are available for ME/CFS or PCS. The mechanisms identified so far provide targets for therapeutic interventions. To accelerate the development of therapies, we propose evaluating drugs targeting different mechanisms in clinical trial networks using harmonized diagnostic and outcome criteria and subgrouping patients based on a thorough clinical profiling including a comprehensive diagnostic and biomarker phenotyping

Radiative Capture on Nuclear Isomers: Direct Measurement of the ²⁶ᵐAl (p, γ) ²⁷Si Reaction

We present the first direct measurement of an astrophysical reaction using a radioactive beam of isomeric nuclei. In particular, we have measured the strength of the key 447-keV resonance in the ²⁶ᵐAl (p, γ) ²⁷Si reaction to be 432 +146-226 meV and find that this resonance dominates the thermally averaged reaction rate for temperatures between 0.3 and 2.5 GK. This work represents a critical development in resolving one of the longest standing issues in nuclear astrophysics research, relating to the measurement of proton capture reactions on excited quantum levels, and offers unique insight into the destruction of isomeric ²⁶Al in astrophysical plasmas

Measurement of the 18Ne(α,p0) 21Na reaction cross section in the burning energy region for x-ray bursts.

The 18Ne(α,p) 21Na reaction provides one of the main HCNO-breakout routes into the rp process in x-ray bursts. The 18Ne(α,p0) 21Na reaction cross section has been determined for the first time in the Gamow energy region for peak temperatures T∼2  GK by measuring its time-reversal reaction 21Na(p,α) 18Ne in inverse kinematics. The astrophysical rate for ground-state to ground-state transitions was found to be a factor of 2 lower than Hauser-Feshbach theoretical predictions. Our reduced rate will affect the physical conditions under which breakout from the HCNO cycles occurs via the 18Ne(α,p) 21Na reaction

Fusion using radio active ion beams

The fusion excitation function for 9 Li + 70 Zn [1] and 9 Li + 208 Pb [2] systems were measured for near barrier energies using ISAC1 and ISAC2 facilities at TRIUMF. The α emitting evaporation residues ( 211−214 At) were stopped in the 208 Pb target and their decay was measured. The isotopic yields are in good agreements with the statistical model prediction using HIVAP code. The measured excitation function shows evidence for large enhancements in the sub-barrier energies, which is not accounted by current theoretical models. Also, suppression of the above barrier cross section with respect to these theoretical models have been seen. The implication of these measurement for studying the fusion of 11 Li with 208 Pb will be discussed. . This study was able to give insight into fusion enhancement and hindrance in the systems involving neutron rich nuclei. The coupled channel calculations were able to describe the data if the surface diffuseness is allowed to be 1.10 fm instead of 0.6 fm. The dinuclear system model (DNS) calculations were able to describe the excitation function reasonably well and if we use this barrier heights predicted by this model we can conclude that fusion hindrance (represented by extra push energy) is greater for the more neutron rich systems. This work is performed in collaboration with Prof