16 research outputs found
Four methods for determining the composition of trace radioactive surface contamination of low-radioactivity metal
Four methods for determining the composition of low-level uranium- and
thorium-chain surface contamination are presented. One method is the
observation of Cherenkov light production in water. In two additional methods a
position-sensitive proportional counter surrounding the surface is used to make
both a measurement of the energy spectrum of alpha particle emissions and also
coincidence measurements to derive the thorium-chain content based on the
presence of short-lived isotopes in that decay chain. The fourth method is a
radiochemical technique in which the surface is eluted with a weak acid, the
eluate is concentrated, added to liquid scintillator and assayed by recording
beta-alpha coincidences. These methods were used to characterize two `hotspots'
on the outer surface of one of the He-3 proportional counters in the Neutral
Current Detection array of the Sudbury Neutrino Observatory experiment. The
methods have similar sensitivities, of order tens of ng, to both thorium- and
uranium-chain contamination.Comment: 22 pages, 19 figure
Astroparticle Physics with a Customized Low-Background Broad Energy Germanium Detector
The MAJORANA Collaboration is building the MAJORANA DEMONSTRATOR, a 60 kg
array of high purity germanium detectors housed in an ultra-low background
shield at the Sanford Underground Laboratory in Lead, SD. The MAJORANA
DEMONSTRATOR will search for neutrinoless double-beta decay of 76Ge while
demonstrating the feasibility of a tonne-scale experiment. It may also carry
out a dark matter search in the 1-10 GeV/c^2 mass range. We have found that
customized Broad Energy Germanium (BEGe) detectors produced by Canberra have
several desirable features for a neutrinoless double-beta decay experiment,
including low electronic noise, excellent pulse shape analysis capabilities,
and simple fabrication. We have deployed a customized BEGe, the MAJORANA
Low-Background BEGe at Kimballton (MALBEK), in a low-background cryostat and
shield at the Kimballton Underground Research Facility in Virginia. This paper
will focus on the detector characteristics and measurements that can be
performed with such a radiation detector in a low-background environment.Comment: Submitted to NIMA Proceedings, SORMA XII. 9 pages, 4 figure
Dead layer on silicon p–i–n diode charged-particle detectors
Semiconductor detectors in general have a dead layer at their surfaces that is either a result of natural or induced passivation, or is formed during the process of making a contact. Charged particles passing through this region produce ionization that is incompletely collected and recorded, which leads to departures from the ideal in both energy deposition and resolution. The silicon p-i-n diode used in the KATRIN neutrinomass experiment has such a dead layer. We have constructed a detailed Monte Carlo model for the passage of electrons from vacuum into a silicon detector, and compared the measured energy spectra to the predicted ones for a range of energies from 12 to 20 keV. The comparison provides experimental evidence that a substantial fraction of the ionization produced in the "dead" layer evidently escapes by diffusion, with 46% being collected in the depletion zone and the balance being neutralized at the contact or by bulk recombination. The most elementary model of a thinner dead layer from which no charge is collected is strongly disfavored
The design, construction, and commissioning of the KATRIN experiment
The KArlsruhe TRItium Neutrino (KATRIN) experiment, which aims to make a direct and model-independent determination of the absolute neutrino mass scale, is a complex experiment with many components. More than 15 years ago, we published a technical design report (TDR) [1] to describe the hardware design and requirements to achieve our sensitivity goal of 0.2 eV at 90% C.L. on the neutrino mass. Since then there has been considerable progress, culminating in the publication of first neutrino mass results with the entire beamline operating [2]. In this paper, we document the current state of all completed beamline components (as of the first neutrino mass measurement campaign), demonstrate our ability to reliably and stably control them over long times, and present details on their respective commissioning campaigns
Focal-plane detector system for the KATRIN experiment
The focal-plane detector system for the KArlsruhe TRItium Neutrino (KATRIN)
experiment consists of a multi-pixel silicon p-i-n-diode array, custom readout
electronics, two superconducting solenoid magnets, an ultra high-vacuum system,
a high-vacuum system, calibration and monitoring devices, a scintillating veto,
and a custom data-acquisition system. It is designed to detect the low-energy
electrons selected by the KATRIN main spectrometer. We describe the system and
summarize its performance after its final installation.Comment: 28 pages. Two figures revised for clarity. Final version published in
Nucl. Inst. Meth.
The Majorana Demonstrator readout electronics system
The Majorana Demonstrator comprises two arrays of high-purity germanium detectors constructed to search for neutrinoless double-beta decay in 76Ge and other physics beyond the Standard Model. Its readout electronics were designed to have low electronic noise, and radioactive backgrounds were minimized by using low-mass components and low-radioactivity materials near the detectors. This paper provides a description of all components of the Majorana Demonstrator readout electronics, spanning the front-end electronics and internal cabling, back-end electronics, digitizer, and power supplies, along with the grounding scheme. The spectroscopic performance achieved with these readout electronics is also demonstrated
The Majorana project
Building a 0νβ β experiment with the ability to probe neutrino mass in the inverted hierarchy region requires the combination of a large detector mass sensitive to 0νβ β, on the order of 1-tonne, and unprecedented background levels, on the order of or less than 1 count per year in the 0νβ β signal region. The Majorana Collaboration proposes a design based on using high-purity enriched 76Ge crystals deployed in ultra- low background electroformed Cu cryostats and using modern analysis techniques that should be capable of reaching the required sensitivity while also being scalable to a 1- tonne size. To demonstrate feasibility, the collaboration plans to construct a prototype system, the Majorana Demonstrator, consisting of 30 kg of 86% enriched 76Ge detectors and 30 kg of natural or isotope-76-depleted Ge detectors. We plan to deploy and evaluate two different Ge detector technologies, one based on a p-type configuration and the other on n-type
Measurement of the νe and total 8B solar neutrino fluxes with the Sudbury Neutrino Observatory phase-III data set
This paper details the solar neutrino analysis of the 385.17-day phase-III data set acquired by the Sudbury Neutrino Observatory (SNO). An array of 3He proportional counters was installed in the heavy-water target to measure precisely the rate of neutrino-deuteron neutral-current interactions. This technique to determine the total active 8B solar neutrino flux was largely independent of the methods employed in previous phases. The total flux of active neutrinos was measured to be 5.54-0.31+0.33(stat.)-0.34+0.36(syst.)×106 cm-2 s-1, consistent with previous measurements and standard solar models. A global analysis of solar and reactor neutrino mixing parameters yielded the best-fit values of Δm2=7.59-0.21+0.19×10 -5eV2 and θ=34.4-1.2+1.3degrees
The calorimeter system of the new muon g-2 experiment at Fermilab
The electromagnetic calorimeter for the new muon (g 122) experiment at Fermilab will consist of arrays of PbF2 \u10cerenkov crystals read out by large-area silicon photo-multiplier (SiPM) sensors. We report here the requirements for this system, the achieved solution and the results obtained from a test beam using 2.0\u20134.5 GeV electrons with a 28-element prototype array