Unique particle detector array built
A collaboration of nuclear physicists from the Universities of Edinburgh and Liverpool, and mechanical engineers from the Science and Technology Facilities Council (STFC) have designed a vacuum chamber for use in nuclear and atomic physics experiments.
The camber, known as CARME (CRYRING Array for Reaction Measurements), is unique in that it can work in extremely high vacuum conditions. The camber has been produced for CRYRING – a heavy ion storage ring at the Facility for Antiproton Research (FAIR) in Germany.
Experiments with CARME
CARME will initially be used for detecting charged particles for nuclear astrophysics experiments. Elements heavier than helium are created by nuclear reactions taking place in stars. Nuclear astrophysics aims to study these key nuclear reactions to understand the origin of the elements.
In stellar explosions such as novae and supernovae, nuclear reactions involving short-lived radioactive isotopes play a key role in the synthesis of new elements. Producing these radioisotopes in Earth-based laboratories is a major challenge. CRYRING at FAIR offers the unique possibility to recreate the conditions in which nuclear reactions occur in stellar explosions, such as novae and supernovae, using pure beams of radioisotopes inaccessible elsewhere in the world.
The first experiment approved for CARME will be led by Dr Carlo Bruno from the School’s Nuclear Physics research group, and will aim at improving our understanding of the expected composition of cosmic dust formed in nova explosions.
Whilst the initial focus will be on detecting charged particles, CARME is special in that it will also be able to detect gamma rays and X-rays, making it very flexible. In the longer term this will be advantageous because to mount/unmount a system like this is very time consuming, not least because when you break the vacuum it can take weeks or months to recover those specific conditions.
In order to create CARME, the scientists and engineers had to calculate the number of pumps required to reach extremely high vacuum (XHV) and find the necessary space inside the chamber to make it pump at the required speed. They then created a complete set of construction specifications, from mechanical requirements to what material to weld CARME.
When it came to building CARME’s vessels, they were manufactured in the UK and delivered back to the lab. Each element had to be dismounted, cleaned, fired to high temperatures, rebuilt and then checked for leaks. Finally, before being carefully packaged for delivery to Germany, CARME was re-assembled and tested.