Research & Development
Facilities: Noble gas purification system Laminar flow cabinet Fully functioning Xenon based detector prototype consisting of a 200ml target, 3 separate readout technologies, 5kV supply, data acquisition system including software, a cryostat and all associated vacuum generators.
Research: The Particle Astrophysics group is dedicated to the discovery of WIMPs - a candidate for Dark Matter, the missing mass in the universe. This laboratory is intended for the development of liquid Xenon based Dark Matter detectors. Xenon is the target i.e. the material with which the background particles including Dark Matter interact. This produces ionisation (electric currents) and scintillation (light pulses) which can be recorded using a readout system and subsequently analysed using data acquisition software. The standard readout system used to record events is an array of photomultiplier tubes (PMTs). These convert light into electrical pulses. Although PMTs have been used in Dark Matter searches for many years, their relatively high levels of radioactive contamination increase the background of events seen by the detector, obscuring a potential Dark Matter signal.
An alternative to PMTs is a charge readout system such as Micromegas which simply amplifies the tiny currents produced within the target by accelerating them within a huge field established between a solid copper anode and a mesh separated by 1/20mm from one another. Although charge readout potentially offers an improvement in detector performance, a reduction of the costs and a lowering of the radioactive background, the technology still requires development.
We are currently evaluating the performance of a detector consisting of gaseous Xenon held above 200ml of liquid Xenon at over twice atmospheric pressure and below -100 degrees Celsius. This "double phase" system improves our ability to discriminate between events recorded in the target, enabling us to separate background noise from nuclear recoils. The emphasis of our research centres on the evaluation of double phase Xenon based detector prototypes prior to their evolution into full size >100Kg future detectors.
Noble Liquids Simulations
Facilities: Under construction.
Research: As the current generation of liquid noble gas non-baryonic dark matter detectors are being commissioned, active research and development is taking place to determine the feasibility of using a larger target mass. Larger target mass should allow greater the sensitivity to WIMP-nucleon interactions, provided low energy threshold and background rejection can be maintained. Argon is an attractive detector medium due to its relatively low cost, high light yield, good sensitivity to low mass WIMPs and excellent recoil discrimination. A suitable chamber is currently being designed to liquefy argon gas. There are plans to investigate the electric breakdown, pulse shape discrimination and quenching factor of liquid argon in a region relevant to dark matter search experiments.MICROMEGAS Noble Liquids Simulations
Research: There are several simulation efforts for different projects. Simulation of particle physics experiments is an important part of understanding the behaviour of detectors and analysing the data produced by the experiment. For the dark matter experiments it is vital that particle backgrounds that may effect the detector's sensitivity are simulated. It is also useful, when calculating a detector's efficiency, to simulate calibration data runs using radioactive sources to compare the actual detection rate of the experiment with the expected rate from the source. Full detector simulations, including electric fields and charge readout, are also performed to assess the detector's performance.
MICROMEGAS Noble Liquids Simulations