Liquid Argon Detector Calibration R&D for Dark Matter and Neutrino Physics

Lead Research Organisation: University of Sussex
Department Name: Sch of Mathematical & Physical Sciences


This proposal is for R&D to improve the performance of experiments testing the fundamental symmetries of nature using neutrinos and searching for interactions of the mysterious dark matter that makes up most of the matter in the universe.
Particle physics seeks to understand the nature of matter at the smallest scales and relate that knowledge to the behaviour of the universe at the largest scales. One of the main questions being addressed by experiments today is why the universe is made of matter and not antimatter. The standard model of particle physics links conservation laws with fundamental symmetries: the missing antimatter is connected to the violation of charge-parity (CP) symmetry---which says that the laws of nature should be the same for matter and for antimatter seen through a parity inversion, equivalent to looking at something upside down in a mirror. All known instances of CP violation are too small to account for the lack of antimatter, so experimenters are now searching for the origin of this using the elusive neutrino.
Astronomical observations have shown us definitively that the matter we see makes up only a small fraction of the universe---just 5%! A significant fraction, 25%, is made up of enigmatic dark matter: massive particles that do not interact with light but do influence the world around us. The standard models of particle physics and cosmology predict that these dark matter particles obey the same laws of nature that normal matter does and so we can devise laboratory experiments to detect evidence of their presence. The leading theory is that dark matter is made up of heavy particles that interact via the weak nuclear force, just like neutrinos do. If so, then it should leave characteristic traces in terrestrial matter: atomic nuclei struck by dark matter particles will recoil with tiny amounts of energy. To test this hypothesis we build experiments designed to observe these tiny recoil energies. Because the rate of these interactions is small, and the recoil energy is tiny, we must build experiments at the cutting edge of particle detection technology to search for this weak signal.
Many dark matter and neutrino experiments use cryogenic (very cold) noble liquids, such as liquid neon, argon or xenon, because of their stable atoms and excellent optical properties. In particular, these liquids emit large amounts of light when the dark matter particles cause nuclear recoils, and that light can be collected and interpreted readily to identify the type of particle that created it: nuclear recoil signal or an interaction of background radiation. Cryogenic noble liquid detector development is pushing the boundaries of particle detection, in a world-wide technology race to study the fundamental questions of the nature of neutrinos and dark matter. However the properties of light in these liquids is not very well understood, and therefore experiments must develop systems to initiate controlled "signals" inside the detectors that test the ability of the experiment to observe the signal, distinguish it from backgrounds and measure its energy correctly. This process is called detector calibration and it is where experimenters spend much of their effort.
This proposal is to develop new technology for detector calibration and to make measurements of the optical properties of cold liquid argon, neon and xenon. Specifically, we will measure the attenuation lengths of light in these liquids; we will measure the angles that light is scattered into from the wavelength shifting films that must be used in cold liquids; and we will test the mechanical utility of certain designs for calibration devices. Once these measurements are made, the calibration of large, liquid noble detectors will be significantly improved, and we will be one step closer to identifying the nature of the puzzling dark matter that accounts for 25% of the universe, and understanding the mystery of the missing antimatter.

Planned Impact

Refer to lead proposal by Royal Holloway


10 25 50
Description The absolute light production and exact angular distributionn of TPB wavelength shifter. This is used in single phase, liquid noble gas direct dark matter detectors, such as DEAP-3600 and CLEAN.
Exploitation Route These findings will be used in the calibration of the DEAP-3600 (and subsequent) direct dark matter dectector using liquid argon and TPB wavelength shifters (currently the default technology).
Sectors Aerospace, Defence and Marine

Description Junior Research Associateship (HW)
Amount £2,400 (GBP)
Organisation University of Sussex 
Sector Academic/University
Country United Kingdom
Start 06/2011 
End 08/2011
Description Junior Research Associateship (TB)
Amount £2,400 (GBP)
Funding ID Talitha Bromwich 
Organisation University of Sussex 
Sector Academic/University
Country United Kingdom
Start 06/2013 
End 08/2013
Description RSE/STFC Enterprise Fellowship 2017
Amount £44,303 (GBP)
Organisation Royal Society of Edinburgh (RSE) 
Sector Charity/Non Profit
Country United Kingdom
Start 07/2017 
End 06/2018
Title Light Pulse Generating Circuits and Systems 
Description In this patent, we protect the novel technology developed for the SNO+ experiment and successfully used in the DEAP0-3600 experiment. 
IP Reference GB1707768.6 
Protection Patent granted
Year Protection Granted 2017
Licensed No
Impact We are in the process of spinning out a company,
Description DEAP, The future of Dark Matter in the UK, 2012 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? Yes
Type Of Presentation Keynote/Invited Speaker
Geographic Reach National
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact 30 peers attended the workshop

Led to the foundation of the DMUK institute, which is a peer organisation determining the focus of the Dark Matter programme in the UK
Year(s) Of Engagement Activity 2012
Description DEAP-3600, Dark Attack 2012 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Type Of Presentation Keynote/Invited Speaker
Geographic Reach International
Primary Audience Other academic audiences (collaborators, peers etc.)
Results and Impact DEAP-3600 presented to an international audience of 60 experts in the fieds

Increased awareness of the single phase liquid scintillator approach to direct dark matter searches
Year(s) Of Engagement Activity 2012
Description Research-based Outreach 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Type Of Presentation Keynote/Invited Speaker
Geographic Reach Local
Primary Audience Schools
Results and Impact At the University of Sussex, we run a major outreach programme within the department of physics and astronomy, originally set up as part of the SEPnet initiative. The program involves members of the department at all levels, from taught undergraduate and postgraduate students, research students, post doctorial researchers and faculty. We have a wide range of practical activities available to take out to local schools, which are boxed up with a detailed lesson plan for department members to take to take out or use on site. The majority of our outreach activities are linked to our research.
Our annual reach is to 5,000 students per year, working with approximately 800 primary school students, 3500 secondary student, and 700 A-level students, in addition to the 2,000 members of the general public that experience our events. We currently run 130 events per year, reaching school and college students at 60 different schools. We have both schools visiting the University of Sussex campus in Brighton, and we also go out to schools.
Around half of our events involve communicating the research carried out at the University direct to schools, colleges and the public.

25% of our events involve describing our particle physics research, usually consisting of a research talk (about the Large Hadron Collider, SNO+, etc) which is reinforced by practical activities (such as building cloud chambers, or visiting our research labs).

Every week during the school terms, we run a School's Lab day, where a group of students visit the University for as full day of experiments specifically designed for the GCSE, AS and A2 level syllabus. During those days, the students visit a research lab, and get the opportunity to talk with our research students about their work. In addition, visiting A-level students also have a research lecture, and get to here the latest research being done here at Sussex.

Every year, we offer masterclasses in particle physics, with one day aimed at GCSE students, and another at A-level. These days involve research-level talks, visits to labs, as well as hands on experimental experience.

We have developed links with local schools and colleges. Teachers frequently approach us to request research related outreach activities (talks, lab tours, practical activities), ask for advice or to borrow equipment for teaching. In 2013, we ran the Institute of Physics sponsored Physic Update weekend conference for teachers.

Since we began our outreach program, undergraduate numbers has risen significantly within the department, from an intake of 40 students in 2009, up to the current (and sustained) 140 students per year.
Year(s) Of Engagement Activity 2009,2010,2011,2012,2013,2014