Proof of principle of a high-spatial-resolution, resonant-response gamma-ray detector for Gamma Resonance Absorption in 14N

The development of a mm-spatial-resolution, resonant-response detector based on a micrometric glass capillary array filled with liquid scintillator is described. This detector was developed for Gamma Resonance Absorption (GRA) in 14N. GRA is an automatic-decision radiographic screening technique that combines high radiation penetration (the probe is a 9.17 MeV gamma ray) with very good sensitivity and specificity to nitrogenous explosives. Detailed simulation of the detector response to electrons and protons generated by the 9.17 MeV gamma-rays was followed by a proof-of-principle experiment, using a mixed gamma-ray and neutron source. Towards this, a prototype capillary detector was assembled, including the associated filling and readout systems. Simulations and experimental results indeed show that proton tracks are distinguishable from electron tracks at relevant energies, on the basis of a criterion that combines track length and light intensity per unit length.Comment: 18 pages, 16 figure

Pulse Shape Analysis with scintillating bolometers

Among the detectors used for rare event searches, such as neutrinoless Double Beta Decay (0$\nu$DBD) and Dark Matter experiments, bolometers are very promising because of their favorable properties (excellent energy resolution, high detector efficiency, a wide choice of different materials used as absorber, ...). However, up to now, the actual interesting possibility to identify the interacting particle, and thus to greatly reduce the background, can be fulfilled only with a double read-out (i.e. the simultaneous and independent read out of heat and scintillation light or heat and ionization). This double read-out could greatly complicate the assembly of a huge, multi-detector array, such as CUORE and EURECA. The possibility to recognize the interacting particle through the shape of the thermal pulse is then clearly a very interesting opportunity. While detailed analyses of the signal time development in purely thermal detectors have not produced so far interesting results, similar analyses on macro-bolometers ($\sim$10-500 g) built with scintillating crystals showed that it is possible to distinguish between an electron or $\gamma$-ray and an $\alpha$ particle interaction (i.e. the main source of background for 0$\nu$DBD experiments based on the bolometric technique). Results on pulse shape analysis of a CaMoO$_4$ crystal operated as bolometer is reported as an example. An explanation of this behavior, based on the energy partition in the heat and scintillation channels, is also presented.Comment: Presented at the 14th International Workshop on Low Temperature Detectors, proceedings to be published in the Journal of Low Temperature Physic

Diffusion with rearranging traps

A model for diffusion on a cubic lattice with a random distribution of traps is developed. The traps are redistributed at certain time intervals. Such models are useful for describing systems showing dynamic disorder, such as ion-conducting polymers. In the present model the traps are infinite, unlike an earlier version with finite traps, this model has a percolation threshold. For the infinite trap version a simple analytical calculation is possible and the results agree qualitatively with simulation.Comment: Latex, five figure

Optical nanofibers and spectroscopy

We review our recent progress in the production and characterization of tapered optical fibers with a sub-wavelength diameter waist. Such fibers exhibit a pronounced evanescent field and are therefore a useful tool for highly sensitive evanescent wave spectroscopy of adsorbates on the fiber waist or of the medium surrounding. We use a carefully designed flame pulling process that allows us to realize preset fiber diameter profiles. In order to determine the waist diameter and to verify the fiber profile, we employ scanning electron microscope measurements and a novel accurate in situ optical method based on harmonic generation. We use our fibers for linear and non-linear absorption and fluorescence spectroscopy of surface-adsorbed organic molecules and investigate their agglomeration dynamics. Furthermore, we apply our spectroscopic method to quantum dots on the surface of the fiber waist and to caesium vapor surrounding the fiber. Finally, towards dispersive measurements, we present our first results on building and testing a single-fiber bi-modal interferometer.Comment: 13 pages, 18 figures. Accepted for publication in Applied Physics B. Changes according to referee suggestions: changed title, clarification of some points in the text, added references, replacement of Figure 13

NEST: A Comprehensive Model for Scintillation Yield in Liquid Xenon

A comprehensive model for explaining scintillation yield in liquid xenon is introduced. We unify various definitions of work function which abound in the literature and incorporate all available data on electron recoil scintillation yield. This results in a better understanding of electron recoil, and facilitates an improved description of nuclear recoil. An incident gamma energy range of O(1 keV) to O(1 MeV) and electric fields between 0 and O(10 kV/cm) are incorporated into this heuristic model. We show results from a Geant4 implementation, but because the model has a few free parameters, implementation in any simulation package should be simple. We use a quasi-empirical approach, with an objective of improving detector calibrations and performance verification. The model will aid in the design and optimization of future detectors. This model is also easy to extend to other noble elements. In this paper we lay the foundation for an exhaustive simulation code which we call NEST (Noble Element Simulation Technique).Comment: 24 pages, 9 figures, 3 table

Borexino calibrations: Hardware, Methods, and Results

Borexino was the first experiment to detect solar neutrinos in real-time in the sub-MeV region. In order to achieve high precision in the determination of neutrino rates, the detector design includes an internal and an external calibration system. This paper describes both calibration systems and the calibration campaigns that were carried out in the period between 2008 and 2011. We discuss some of the results and show that the calibration procedures preserved the radiopurity of the scintillator. The calibrations provided a detailed understanding of the detector response and led to a significant reduction of the systematic uncertainties in the Borexino measurements

Climatic significance of the marginalization of Scots pine (Pinus sylvestris L.) c. 2500 BC at White Moss, south Cheshire, UK

Subfossil wood from White Moss, south Cheshire, has become the focus of palaeoenvironmental research employing not only conventional coring, pollen analysis, radiocarbon dating and dendrochronology on pine and oak, but also the exhumation of in situ peat areas and dendroecology of the pine ring-width records. Initial dendrochronological research at the site yielded five pine chronologies dating from 3520 to 2462 cal. BC. These and other data indicate three episodes of pine colonization of the mire in the period between 3643 and 1740 cal. BC. Comparison of the pollen and spore records suggest that pine became marginalized at the site c. 2500 cal. BC after successive episodes of increased wetness, and this may represent a staged response to climatic deterioration. Two oak chronologies were dated by reference to the Belfast and to English oak master chronologies to 3228-2898 BC and 2190-1891 BC, respectively, showing the possible co-existence of pine and oak on the mire for part of the time. Further dendrochronological work on subfossil pine at the site resulted in a chronology (WM4) that was cross-matched with pine from elsewhere in England, and subsequently dated absolutely to 2881-2559 BC. Detailed dendroecological information, such as fire episodes and periods of environmental stress indicated in the tree-ring records, have been assigned, precisely and accurately, to calendar years in prehistory. The detailed data show the potential for both dendroecological and wider palaeoclimatic and palaeoenvironmental information that may become available from prehistoric bog-pine chronologies, which might then permit precise correlation and comparisons of proxy-climate data between sites

Design and construction of the MicroBooNE detector

This paper describes the design and construction of the MicroBooNE liquid argon time projection chamber and associated systems. MicroBooNE is the first phase of the Short Baseline Neutrino program, located at Fermilab, and will utilize the capabilities of liquid argon detectors to examine a rich assortment of physics topics. In this document details of design specifications, assembly procedures, and acceptance tests are reported