WATCHMAN - 6 Month bridging grant

The Advanced Instrumentation Testbed (AIT) is a new facility, to be sited in the Boulby Underground Laboratory, that aims to explore new technologies for the purposes of nuclear non-proliferation and particle physics. The first phase of AIT is the WATer CHerenkov Monitor for Anti-Neutrinos (WATCHMAN). WATCHMAN construction is primarily funded through the US National Nuclear Security Administration (NNSA). UK involvement is a partnership between our industrial partners in the Atomic Weapons Establishment (AWE), the STFC-Boulby laboratory, and the Universities of Sheffield, Edinburgh, Liverpool, and Warwick.

The WATCHMAN detector is a technology demonstrator, which will attempt the first monitoring of nuclear reactors from a standoff distance of tens of kilometres. The mechanism for this monitoring is anti-neutrino detection. Nuclear reactions all produce a large flux of anti-neutrinos, which cannot be shielded. The WATCHMAN detector combines the decades-old technology of water Cherenkov neutrino detectors with the new technique of gadolinium loading. Adding gadolinium to the detector makes it sensitive to the neutron that is produced in an anti-neutrino interaction, but not a low-energy neutrino interaction. As such, the coincident signature of positron plus neutron can be used to tag anti-neutrinos.

If successful, the techniques pioneered by WATCHMAN could be used to search for clandestine nuclear reactors as a means of non-proliferation and nuclear threat reduction.

An excellent 'side effect' of this work is that WATCHMAN will also be one of the world's most sensitive telescopes for supernova neutrinos. When a massive star exhausts all sources of nuclear fuel to power its fusion reaction, it dies in what is known as a 'core-collapse supernova'. In essence, the star collapses under its own gravity, leaving behind a neutron star or a black hole. An enormous number of neutrinos are produced at this time, which WATCHMAN would be sensitive to detecting. To date, humanity has only observed 25 neutrinos from supernovae, which arrived in 1987 and were generated by the explosion of a star in the Large Magellanic Cloud, a satellite galaxy of the Milky Way. Once WATCHMAN is operational, a galactic supernova would produce hundreds, or even thousands, of neutrino interactions in WATCHMAN, providing a unique window into the heart of a dying star.

The AIT also includes a significant component of research and development into new detection materials and technologies. For this purpose, AIT will be investigating fast photosensors such as the Large Area Picosecond Photo-Detectors (LAPPDs), and new detector materials, such as water-based liquid scintillator. These can be used in future phases of the project to enhance the reactor detection range, as well as to enable particle physics goals such as geoneutrino studies and searches for neutrinoless double-beta decay.

First and foremost, WATCHMAN is an impact project. The primary sponsor is the US National Nuclear Security Administration, which will be contributing most of the $65M USD required for the funding of WATCHMAN. The primary objective of WATCHMAN is nuclear non-proliferation. The main aims are to establish non-intrusive monitoring of nuclear reactor from a distance of tens of kilometers that is able to (a) confirm the existence of an operating reactor, and (b) determine the power plant operational status. An additional aim is to demonstrate scalability of this technology, as a field-deployment of the WATCHMAN technology would wish to detect clandestine reactors of smaller size over larger distances. Thus, the main goal of this project is impact, as WATCHMAN applies particle physics detection techniques developed over the past four decades to the aim of nuclear threat reduction, meeting the NNSA goal of developing 'novel remote sensing technologies for weaponization detection'.

The primary non-proliferation impact case will be fully realised on the timescale of six years, following the construction phase and the exploitation phase. In the interim, there is also a secondary impact case, which is knowledge transfer. UK involvement in WATCHMAN is a partnership between the STFC / Boulby Underground Laboratory, the universities, and the Atomic Weapons Establishment (AWE). We are engaged in knowledge exchange with our industrial partners at AWE, which is a valuable impact case taking place now, during the construction phase of WATCHMAN. Similarly, one of the mission goals from WATCHMAN is to 'provide next-generation US and UK scientists and nuclear policy experts with hands-on opportunities to develop, operate, and analyse results from non-proliferation policy deployments.' This is an additional source of impact, as we train the next generation of scientists for the non-proliferation sector.