Results from the CACTI experiment: Air-Cerenkov and particle measurements of PeV air showers at Los Alamos

An array of six wide angle Cerenkov detectors was constructed amongst the scintillator and muon detectors of the CYGNUS II array at Los Alamos National Laboratory to investigate cosmic ray composition in the PeV region through measurements of the shape of Cerenkov lateral distributions. Data were collected during clear, moonless nights over three observing periods in 1995. Estimates of depths of shower maxima determined from the recorded Cerenkov lateral distributions align well with existing results at higher energies and suggest a mixed to heavy composition in the PeV region with no significant variation observed around the knee. The accuracy of composition determination is limited by uncertainties in the expected levels of depth of maximum predicted using different Monte-Carlo shower simulation models

Quantitative beta autoradiography of a heterogeneous granulite sample and implications for luminescence dating

Beta dose rate heterogeneity is a known source of scatter in OSL measurement and equivalent dose distributions. Without proper methods to describe and account for it, it can contribute significantly to the uncertainties in OSL ages. For this reason, investigating the beta dose rate (β Dr) distribution is necessary to improve the dating of heterogeneous samples. Here we present a method for quantitative and high sensitivity autoradiographic imaging of beta dose rates. It is demonstrated using highly heterogeneous granulite rock samples. The accuracy and sensitivity of this method is improved using pulsed laser stimulation, and by underground exposure of samples in an ultra-low background environment. Results are calibrated using gamma (γ)irradiation and Monte Carlo simulation and have been validated using homogeneous dose rate standards. Combining analysis of autoradiography results and SEM backscattered images of the same samples allows determination of the dose rate distributions in the different mineral phases. A significant difference between the dose rate of K-feldspar grains obtained from the imaging and the dose rates calculated using methods commonly used in OSL dating is noted because of the clustering of grains in the sample. This represents a risk of bias in age determination in coarse grained rock samples which can be analysed using dose rate imaging methods. The beta Dr spatial distributions result in a significant dose scattering received by single grains, even compared to the total dose rate. The effect of such beta dose rate distributions on OSL dating of coarse-grained crystalline materials is discussed

First measurement of the Head-Tail directional nuclear recoil signature at energies relevant to WIMP dark matter searches

We present first evidence for the so-called Head-Tail asymmetry signature of neutron-induced nuclear recoil tracks at energies down to 1.5 keV/amu using the 1m^3 DRIFT-IIc dark matter detector. This regime is appropriate for recoils induced by Weakly Interacting Massive Particle (WIMPs) but one where the differential ionization is poorly understood. We show that the distribution of recoil energies and directions induced here by Cf-252 neutrons matches well that expected from massive WIMPs. The results open a powerful new means of searching for a galactic signature from WIMPs.Comment: 4 pages, 6 figures, 1 tabl

Subsurface robotic exploration for geomorphology, astrobiology and mining during MINAR6 campaign, Boulby Mine, UK : part I (Rover development)

Acknowledgement. The authors of this paper would like to thank Kempe Foundation for its generous funding support to develop KORE, the workshop at the Teknikens Hus, Luleå, for their invaluable and unconditional support in helping with the fabrication of the Rover components and the organizers of the MINAR campaign comprising the UK Centre of Astrobiology, Dark Matter Research Facility and the Israel Chemicals Limited (ICL), UK.Peer reviewedPublisher PD

From site-focused intervention towards landscape-scale surface water management using Synthetic Stream Networks and Rapid Scenario Screening

This is the final version. Available on open access from IWA Publishing via the DOI in this recordData availability statement: All relevant data are included in the paper or its Supplementary InformationThis research addresses the need to transform success in technical understanding and practical implementation of surface water management (SWM) interventions at a site-scale towards integrated landscape-scale management. We achieve this through targeting the informative preliminary stages of strategic design, where broad, early and effective exploration of opportunities can enhance and direct a regional SWM perspective. We present a new method, ‘Synthetic Stream Networks’ (SSN), capable of meeting these requirements by taking advantage of easily accessible data, likely to be available during regional screening. We find that results from the SSN are validated by existing, ‘downstream’ focused data (90% of the river network is within 30 m of an associated SSN flow path), with the added advantage of extending understanding of surface water exceedance flow paths and watersheds into the upper catchment, thus establishing a foundational and physically based sub-catchment management unit exploring surface water connectivity at a catchment and landscape scale. We also demonstrate collaborative advantages of twinning the new SSN method with ‘Rapid Scenario Screening’ (RSS) to develop a novel approach for identifying, exploring and evaluating SWM interventions. Overall, we find that this approach addresses challenges of integrating understanding from sub-catchment, catchment and landscape perspectives within surface water management.Engineering and Physical Sciences Research Council (EPSRC)Natural Environment Research Council (NERC

Low Energy Electron and Nuclear Recoil Thresholds in the DRIFT-II Negative Ion TPC for Dark Matter Searches

Understanding the ability to measure and discriminate particle events at the lowest possible energy is an essential requirement in developing new experiments to search for weakly interacting massive particle (WIMP) dark matter. In this paper we detail an assessment of the potential sensitivity below 10 keV in the 1 m^3 DRIFT-II directionally sensitive, low pressure, negative ion time projection chamber (NITPC), based on event-by-event track reconstruction and calorimetry in the multiwire proportional chamber (MWPC) readout. By application of a digital smoothing polynomial it is shown that the detector is sensitive to sulfur and carbon recoils down to 2.9 and 1.9 keV respectively, and 1.2 keV for electron induced events. The energy sensitivity is demonstrated through the 5.9 keV gamma spectrum of 55Fe, where the energy resolution is sufficient to identify the escape peak. The effect a lower energy sensitivity on the WIMP exclusion limit is demonstrated. In addition to recoil direction reconstruction for WIMP searches this sensitivity suggests new prospects for applications also in KK axion searches