arXiv subjects

Lorraine Hanlon

Publications and source records attributed to Lorraine Hanlon.

23 records · Page 2Linked to original sources

arXiv2017

Localisation of gamma-ray interaction points in thick monolithic CeBr3 and LaBr3:Ce scintillators

Localisation of gamma-ray interaction points in monolithic scintillator crystals can simplify the design and improve the performance of a future Compton telescope for gamma-ray astronomy. In this paper we compare the position resolution of three monolithic scintillators: a 28x28x20 mm3 (length x breadth x thickness) LaBr3:Ce crystal, a 25x25x20 mm3 CeBr3 crystal and a 25x25x10 mm3 CeBr3 crystal. Each crystal was encapsulated and coupled to an array of 4x4 silicon photomultipliers through an optical window. The measurements were conducted using 81 keV and 356 keV gamma-rays from a collimated 133Ba source. The 3D position reconstruction of interaction points was performed using artificial neural networks trained with experimental data. Although the position resolution was significantly better for the thinner crystal, the 20 mm thick CeBr3 crystal showed an acceptable resolution of about 5.4 mm FWHM for the x and y coordinates, and 7.8 mm FWHM for the z-coordinate (crystal depth) at 356 keV. These values were obtained from the full position scans of the crystal sides. The position resolution of the LaBr3:Ce crystal was found to be considerably worse, presumably due to the highly diffusive optical in- terface between the crystal and the optical window of the enclosure. The energy resolution (FWHM) measured for 662 keV gamma-rays was 4.0% for LaBr3:Ce and 5.5% for CeBr3. The same crystals equipped with a PMT (Hamamatsu R6322-100) gave an energy resolution of 3.0% and 4.7%, respectively.

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arXiv2016

GAVIP: A Platform for Gaia Data Analysis

Gaia is a major European Space Agency (ESA) astrophysics mission designed to map and analyse 10$^9$ stars, ultimately generating more than 1 PetaByte of data products. As Gaia data becomes publicly available and reaches a wider audience, there is an increasing need to facilitate the further use of Gaia products without needing to download large datasets. The Gaia Added Value Interface Platform (GAVIP) is designed to address this challenge by providing an innovative platform within which scientists can submit and deploy code, packaged as "Added Value Interfaces" (AVIs), which will be executed close to the data. Deployed AVIs and associated outputs may also be made available to other GAVIP platform users, thus providing a mechanism for scientific experiment reproducibility. This paper describes the capabilities and features of GAVIP.

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arXiv2013

Developing a method for soft gamma-ray Laue lens assembly and calibration

Laue lenses constitute a promising option for concentrating soft gamma rays with a large collection area and reasonable focal lengths. In astronomy they could lead to increased telescope sensitivity by one to two orders of magnitude, in particular for faint nuclear gamma-ray lines, but also for continua like hard X-ray tails from a variety of compact objects. Other fields like Homeland security and nuclear medicine share the same need for more sensitive gamma-ray detection systems and could find applications for gamma-ray focusing optics. There are two primary challenges for developing Laue lenses: the search for high-reflectivity and reproducible crystals, and the development of a method to accurately orient and fix the thousands of crystals constituting a lens. In this paper we focus on the second topic. We used our dedicated X-ray beamline and Laue lens assembly station to build a breadboard lens made of 15 crystals. This allowed us to test our tools and methods, as well as our simulation code and calibration procedure. Although some critical points were identified, the results are very encouraging, with a crystal orientation distribution lower than $10''$, as required to build a Laue lens telescope dedicated to the study of Type Ia supernovae (30-m focal length). This breadboard lens represents an important step towards raising the technology readiness level of Laue lenses.

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arXiv2013

Study of silicon photomultipliers for the readout of scintillator crystals in the proposed GRIPS γ-ray astronomy mission

Among the top priorities for high-energy astronomy in the coming decade are sensitive surveys in the hard X-ray/soft γ-ray (10-600 keV) and medium-energy γ-ray (0.2-80 MeV) bands. Historically, observations in the soft and medium energy γ-ray bands have been conducted using detectors based on inorganic scintillators read out by photo-multiplier tubes (PMTs). These observations were limited by the modest energy and time resolution of traditional scintillator materials (e.g. NaI and CsI), and by the demands on mission resources imposed by the bulky, fragile, high-voltage PMTs. Recent technological advances in the development of both new scintillator materials (e.g. LaBr3:Ce, L(Y)SO) and new scintillation light readout devices (e.g. Silicon Photo-Multipliers) promise to greatly improve the observational capabilities of future scintillator-based γ--ray telescopes, while retaining the relative simplicity, reliability, large collection volumes, and low-cost of scintillator instruments. We present initial results of a study on the use of silicon photomultipliers in the calorimeter module design of the proposed GRIPS astrophysics mission.

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arXiv1998

Wavelet Analysis and Lognormal Distributions in GRBs

A wavelet analysis has been performed on 80 intense gamma-ray bursts GRBs) from the BATSE 3B catalog with durations longer than 2 seconds. The wavelet analysis applied novel features developed for edge detection in image processing and this filtering process was used to extract a fit to the irregular GRB profile from the background. A straightforward algorithm was subsequently used to identify statistically significant peaks in this profile. The areas and FWHM of 270 peaks that were characterised as isolated were found to be consistent with lognormal distributions. The distribution of time intervals between peak maxima for all 963 identified peaks in the GRBs is also presented.

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