Making tracks towards understanding exploding stars and the origin of the elements

The novel instrument, which will improve our understanding of some of the most spectacular explosions in space, has taken its first data at TRIUMF, Canada’s subatomic research facility.

The TACTIC detector is an active gas target time-projection chamber. It is similar to some of the large detectors used at CERN (the European Organisation for Nuclear Research) the world’s largest particle physics laboratory near Geneva.

But TACTIC is designed specially to study the much lower energy nuclear reactions that occur in supernovae and X-ray bursts, and this means that the detector is substantially smaller than its counterparts at CERN.

TACTIC was designed jointly by researchers at the University of York, led by Dr. Alison Laird, and at TRIUMF, led by Dr Lothar Buchmann, with technical support from Science and Technology Facilities Council (STFC) Daresbury Laboratory. The detector was constructed over 10 months in the University of York’s Department of Physics, by PhD student, Paul Mumby-Croft, working with the department’s specialist workshop team.

After assembly and initial testing at York, TACTIC was shipped to TRIUMF in British Columbia, where initial online data visualisation showed the tracks of boron and nitrogen nuclei being scattered through the device. TACTIC allows scientists to follow these atoms one at a time as they interact in the gas, leaving a trail behind them. Studying how such light atoms behave helps them to understand how elements are created in stars.

Dr Laird said: “TACTIC surpassed almost all performance expectations and the data collected has proved to be a goldmine of information. It will take us some time to extract all the information it contains. But once this analysis is complete, the performance of TACTIC will be optimised to study specific nuclear astrophysics reactions with radioactive beams at TRIUMF and other laboratories around the world.

“The initial tests have proved extremely exciting and the Nuclear Astrophysics group at the University of York and TRIUMF are enthusiastic about the many years of work ahead with this impressive new detector.”

Funding for the initial UK development was provided by the Royal Society, Engineering and Physical Sciences Research Council (EPSRC) and the University of York. A Science and Technology Facilities Council project grant will be submitted to enable the York Nuclear Astrophysics group to use TACTIC in a range of laboratories worldwide.