Neutrinoless double-beta decay searches seek to determine the nature of neutrinos, the existence of a lepton violating process, and the effective Majorana neutrino mass. The Majorana Collaboration is ...assembling an array of high purity Ge detectors to search for neutrinoless double-beta decay in 76Ge. The Majorana Demonstrator is composed of 44.8 kg (29.7 kg enriched in 76Ge) of Ge detectors in total, split between two modules contained in a low background shield at the Sanford Underground Research Facility in Lead, South Dakota. The initial goals of the Demonstrator are to establish the required background and scalability of a Ge-based, next-generation, tonne-scale experiment. Following a commissioning run that began in 2015, the first detector module started physics data production in early 2016. We will discuss initial results of the Module 1 commissioning and first physics run, as well as the status and potential physics reach of the full Majorana Demonstrator experiment. The collaboration plans to complete the assembly of the second detector module by mid-2016 to begin full data production with the entire array.
We present measurement results of airborne fission products in Chapel Hill, NC, USA, from 62 d following the March 11, 2011, accident at the Fukushima Dai-ichi nuclear power plant. Airborne particle ...samples were collected daily in air filters and radio-assayed with two high-purity germanium (HPGe) detectors. The fission products 131I and 137Cs were measured with maximum activity concentrations of 4.2 ± 0.6 mBq/m3 and 0.42 ± 0.07 mBq/m3 respectively. Additional activity from 131,132I, 134,136,137Cs and 132Te were measured in the same air filters using a low-background HPGe detector at the Kimballton Underground Research Facility (KURF).
► We measured airborne fission products following the Fukushima nuclear accident. ► A sensitive HPGe detector was used to search for more exotic fission products. ► We measured a maximum of 4.2 mBq/m3 I-131 and 0.42 mBq/m3 Cs-137. ► Measured radioactivity is below government limits for iodine and cesium.
The vegetational development of two neighbouring farm sites at the Arctic cereal limit was investigated by pollen analysis and 14C-dates. One farm was small and one larger and both had a long ...habitation history according to archaeological data. Temporary cereal growing at the minor farm may have been introduced about 3100 cal B.P. and was discontinued before 2550 cal B.P. From 1700—1600 cal B.P. Hordeum was cultivated at both farms. At the larger farm there was continuous settlement from c. 2250 cal B.P., but no evidence of cereal growing during the first c. 600 years after the establishment of the farm. It is suggested that changes in the natural conditions, especially paludification, caused a low-activity/abandonment phase at the smaller farm from c. 2550 to c. 1700 cal B.P. A regional abandonment period about 1250 cal B.P. (in the 7th century A.D.) affected the smaller farm in particular.
The observation of neutrino less double-beta decay would show that neutrinos are Majorana particles and provide information on neutrino mass. Attaining sensitivities for neutrino masses in the ...inverted hierarchy region requires large, tonne scale detectors with extremely low backgrounds, at the level of 10−3 counts keV−1 t−1 y−1 or lower in the region of the signal. The MAJORANA collaboration is constructing the DEMONSTRATOR, an array consisting of 40 kg of p-type point contact germanium detectors, at least half of which will be enriched to 86% in 76Ge. The primary aim is to show the feasibility for a future tonne scale measurement. With a sub-keV energy threshold, the array should also be able to search for light WIMP dark matter. This paper presents a brief update on the status of constructing the DEMONSTRATOR including an electroforming facility that is now operating underground at the Sanford Underground Research Facility.
Pollen monitoring at the north-western fringe of the European boreal forest by means of modified Tauber traps, was carried out during the years 1996–2004 along a coast-inland gradient, including two ...altitudinal transects inland. The relationship between annual pollen deposition and local flora and vegetation was investigated. Pinus sylvestris stands in the open coastal lowland and mixed birch-pine forest inland are reflected by a mean pollen accumulation rate (PAR) of 200–400 grains cm−2 yr−1, and dense pine-dominated forest inland by ≥2000 grains cm−2 yr−1. The deposition of Betula pubescens-type pollen in the coastal birch woodland is 80–350 grains cm−2 yr−1. During the same time interval, the sub-alpine birch forest inland has a PAR of 240–720 grains cm−2 yr−1. This figure increases to c. 2000 when the two high-productive years 1998 and 1999 are included in the mean. The alpine forest-line ecotone is reflected in the pollen deposition by a decrease in Betula pubescens-type, meadow and heath herbs, and an increase in Salix and alpine herbs with altitude. This floristic change starts in the upper part of the sub-alpine belt and continues gradually into the open alpine belts. The presence of phytophagous insects in the pollen traps is found to influence the pollen record by overrepresentation of insect-dispersed herb taxa, but does not obscure the recognition of local vegetation types. PAR and percentages show the same main trends along the geographical gradients.
The M
ajorana
Collaboration is using an array of high-purity Ge detectors to search for neutrinoless double-beta decay in
76
Ge. Searches for neutrinoless double-beta decay are understood to be the ...only viable experimental method for testing the Majorana nature of the neutrino. Observation of this decay would imply violation of lepton number, that neutrinos are Majorana in nature, and provide information on the neutrino mass. The M
ajorana
D
emonstrator
comprises 44.1 kg of p-type point-contact Ge detectors (29.7 kg enriched in
76
Ge) surrounded by a low-background shield system. The experiment achieved a high efficiency of converting raw Ge material to detectors and an unprecedented detector energy resolution of 2.5 keV FWHM at Q
ββ
. The M
ajorana
collaboration began taking physics data in 2016. This paper summarizes key construction aspects of the Demonstrator and shows preliminary results from initial data.
The goal of the Majorana Demonstrator project is to search for 0νββ decay in 76Ge. Of all candidate isotopes for 0νββ, 76Ge has some of the most favorable characteristics. Germanium detectors are a ...well established technology, and in searches for 0νββ, the high purity germanium crystal acts simultaneously as source and detector. Furthermore, p-type germanium detectors provide excellent energy resolution and a specially designed point contact geometry allows for sensitive pulse shape discrimination. This paper will summarize the experiences the MAJORANA collaboration made with enriched germanium detectors manufactured by ORTEC®®. The process from production, to characterization and integration in MAJORANA mounting structure will be described. A summary of the performance of all enriched germanium detectors will be given.
The Majorana Demonstrator is a planned 40 kg array of Germanium detectors intended to demonstrate the feasibility of constructing a tonne-scale experiment that will seek neutrinoless double beta ...decay (0νββ) in 76Ge. Such an experiment would require backgrounds of less than 1 count tonne-year in the 4 keV region of interest around the 2039 keV Q-value of the ββ decay. Designing low-noise electronics, which must be placed in close proximity to the detectors, presents a challenge to reaching this background target. This paper will discuss the Majorana collaboration's solutions to some of these challenges.
PDF
