22 research outputs found
Control of virtual environments for young people with learning difficulties
Purpose: The objective of this research is to identify the requirements for the selection or development of usable virtual environment (VE) interface devices for young people with learning disabilities. Method: a user-centred design methodology was employed, to produce a design specification for usable VE interface devices. Details of the users' cognitive, physical and perceptual abilities were obtained through observation and normative assessment tests. Conclusions : A review of computer interface technology, including virtual reality and assistive devices, was conducted. As there were no devices identified that met all the requirements of the design specification, it was concluded that there is a need for the design and development of new concepts. Future research will involve concept and prototype development and user-based evaluation of the prototypes
Constraints on the decay of Ta
Ta is a rare nuclear isomer whose decay has never been observed. Its
remarkably long lifetime surpasses the half-lives of all other known
and electron capture decays due to the large K-spin differences and small
energy differences between the isomeric and lower energy states. Detecting its
decay presents a significant experimental challenge but could shed light on
neutrino-induced nucleosynthesis mechanisms, the nature of dark matter and
K-spin violation. For this study, we repurposed the MAJORANA DEMONSTRATOR, an
experimental search for the neutrinoless double-beta decay of Ge using
an array of high-purity germanium detectors, to search for the decay of
Ta. More than 17 kilograms, the largest amount of tantalum metal ever
used for such a search was installed within the ultra-low background detector
array. In this paper we present results from the first year of Ta data taking
and provide an updated limit for the Ta half-life on the different
decay channels. With new limits up to 1.5 x years, we improved
existing limits by one to two orders of magnitude. This result is the most
sensitive search for a single and electron capture decay ever achieved
Interpretable Boosted Decision Tree Analysis for the Majorana Demonstrator
The Majorana Demonstrator is a leading experiment searching for neutrinoless
double-beta decay with high purity germanium detectors (HPGe). Machine learning
provides a new way to maximize the amount of information provided by these
detectors, but the data-driven nature makes it less interpretable compared to
traditional analysis. An interpretability study reveals the machine's
decision-making logic, allowing us to learn from the machine to feedback to the
traditional analysis. In this work, we have presented the first machine
learning analysis of the data from the Majorana Demonstrator; this is also the
first interpretable machine learning analysis of any germanium detector
experiment. Two gradient boosted decision tree models are trained to learn from
the data, and a game-theory-based model interpretability study is conducted to
understand the origin of the classification power. By learning from data, this
analysis recognizes the correlations among reconstruction parameters to further
enhance the background rejection performance. By learning from the machine,
this analysis reveals the importance of new background categories to
reciprocally benefit the standard Majorana analysis. This model is highly
compatible with next-generation germanium detector experiments like LEGEND
since it can be simultaneously trained on a large number of detectors.Comment: 13 pages, 9 figure
Modeling Backgrounds for the MAJORANA DEMONSTRATOR
The MAJORANA DEMONSTRATOR is a neutrinoless double-beta decay
() experiment containing 30 kg of p-type point contact
germanium detectors enriched to 88% in 76Ge and 14 kg of natural
germanium detectors. The detectors are housed in two electroformed copper
cryostats and surrounded by a graded passive shield with active muon veto. An
extensive radioassay campaign was performed prior to installation to insure the
use of ultra-clean materials. The DEMONSTRATOR achieved one of the lowest
background rates in the region of the Q-value, 15.7 1.4
cts/(FWHM t y) from the low-background configuration spanning most of the 64.5
kg-yr active exposure. Nevertheless this background rate is a factor of five
higher than the projected background rate. This discrepancy arises from an
excess of events from the 232Th decay chain. Background model fits aim to
understand this deviation from assay-based projections, potentially determine
the source(s) of observed backgrounds, and allow a precision measurement of the
two-neutrino double-beta decay half-life. The fits agree with earlier
simulation studies, which indicate the origin of the 232Th excess is not from a
near-detector component and have informed design decisions for the
next-generation LEGEND experiment. Recent findings have narrowed the suspected
locations for the excess activity, motivating a final simulation and assay
campaign to complete the background model.Comment: 8 pages, 6 figures, Proceedings from the Low Radioactivity Techniques
Workshop 2022 in Rapid City, SD, US
Majorana Demonstrator Data Release for AI/ML Applications
The enclosed data release consists of a subset of the calibration data from
the Majorana Demonstrator experiment. Each Majorana event is accompanied by raw
Germanium detector waveforms, pulse shape discrimination cuts, and calibrated
final energies, all shared in an HDF5 file format along with relevant metadata.
This release is specifically designed to support the training and testing of
Artificial Intelligence (AI) and Machine Learning (ML) algorithms upon our
data. This document is structured as follows. Section I provides an overview of
the dataset's content and format; Section II outlines the location of this
dataset and the method for accessing it; Section III presents the NPML Machine
Learning Challenge associated with this dataset; Section IV contains a
disclaimer from the Majorana collaboration regarding the use of this dataset;
Appendix A contains technical details of this data release. Please direct
questions about the material provided within this release to [email protected]
(A. Li).Comment: Zenodo DOI: https://doi.org/10.5281/zenodo.825702
Final Result of the MAJORANA DEMONSTRATOR's Search for Neutrinoless Double- Decay in Ge
The MAJORANA DEMONSTRATOR searched for neutrinoless double- decay
() of Ge using modular arrays of high-purity Ge
detectors operated in vacuum cryostats in a low-background shield. The arrays
operated with up to 40.4 kg of detectors (27.2 kg enriched to 88\% in
Ge). From these measurements, the DEMONSTRATOR has accumulated 64.5 kg
yr of enriched active exposure. With a world-leading energy resolution of 2.52
keV FWHM at the 2039 keV (0.12\%), we set a half-life limit of
in Ge at yr (90\% C.L.).
This provides a range of upper limits on of meV
(90\% C.L.), depending on the choice of nuclear matrix elements.Comment: 8 pages, 2 figure
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