TOPICAL WORKSHOP ON LOW RADIOACTIVITY TECHNIQUES: LRT-2010
1338(2011); http://dx.doi.org/10.1063/1.3579554View Description Hide Description
Deep underground laboratories are the only places where the extremely low background radiation level required for most experiments looking for rare events in physics and astroparticle physics can be achieved. Underground sites are also the most suitable location for very low background γ‐ray spectrometers, able to assay trace radioactive contaminants. Many operational infrastructures are already available worldwide for science, differing for depth, dimension and rock characteristics. Other underground sites are emerging as potential new laboratories.
In this paper the European underground sites are reviewed, giving a particular emphasis on their relative strength and complementarity. A coordination and integration effort among the European Union underground infrastructures was initiated by the EU‐funded ILIAS project and proved to be very effective.
1338(2011); http://dx.doi.org/10.1063/1.3579555View Description Hide Description
Asian underground facilities are reviewed. The YangYang underground Laboratory in Korea and the Kamioka observatory in Japan are operational and several astrophysical experiments are running. Indian Neutrino Observatory(INO) and China JinPing Underground Laboratory (CJPL) are under construction and underground experiments are being prepared. Current activities and future prospects at those underground sites are described.
1338(2011); http://dx.doi.org/10.1063/1.3579556View Description Hide Description
The role of neutron activation analysis in low‐energy low‐background experimentsis discussed in terms of comparible methods. Radiochemical neutron activation analysis is introduce. The procedure of instrumental neutron activation analysis is detailed especially with respect to the measurement of trace amounts of natural radioactivity. The determination of reactor neutron spectrum parameters required for neutron activation analysis is also presented.
1338(2011); http://dx.doi.org/10.1063/1.3579557View Description Hide Description
Copper, thanks to its low content in radioactive contaminations, is a material widely used for shielding, holders and other objects close to the sensitive parts of the detectors in many experiments in rare event physics. This implies that tools able to reach sensitivity of the order of gram of contaminants per gram of copper are of crucial importance. A methodology based in Neutron Activation Analysis (NAA) has been developed to obtain an extremely high sensitivity in the analysis of in copper samples. A detection limit of Cu has been achieved through the irradiation of 200 g of copper sample which subsequently was radio‐chemically concentrated using nitric acid and then actinide resin from Eichrom Inc. Several elutions were performed with various inorganic acids to concentrate the activation product from the copper matrix and to also eliminate the radioactive background induced by the neutron bombardment to reach higher sensitivity.
1338(2011); http://dx.doi.org/10.1063/1.3579558View Description Hide Description
By surrounding a dark matter detector with a layer of boron‐loaded liquid scintillator, a highly efficient neutron veto can be produced. In Monte Carlo studies, a one meter thick layer of scintillator has a veto efficiency greater than 99.5% for nuclear recoil events induced by radiogenic neutrons, and a veto efficiency of more than 95% for nuclear recoil events produced by cosmogenic neutrons. The use of boron‐loaded scintillator both reduces the veto‐induced dead time by decreasing the neutron capture time and allows high neutron detection efficiency to be achieved in a relatively compact geometry.
1338(2011); http://dx.doi.org/10.1063/1.3579559View Description Hide Description
The development of BiPo detectors is dedicated to the measurement of extremely high radiopurity in and for the SuperNEMO double beta decay source foils. A modular prototype called BiPo‐1 with of sensitive surface area has been running in the Modane Underground Laboratory since February 2008. The goal of BiPo‐1 is to measure the different components of the background and in particular the surface radiopurity of the plastic scintillators that make up the detector. The first phase of data collection has been dedicated to the measurement of the radiopurity in After more than one year of background measurement a surface activity of the scintillators of is reported here.
Given this level of background, a larger BiPo3 detector having of active surface area, will able to qualify the radiopurity of the SuperNEMO selenium double beta decay foils with the required sensitivity of (90% C.L.) with a six month measurement. This detector is actually under construction and will be installed in the Canfranc Underground Laboratory mid 2011.
1338(2011); http://dx.doi.org/10.1063/1.3579560View Description Hide Description
FAARM is an acronym for a low background counting facility at the proposed DUSEL laboratory at the Homestake mine in South Dakota. Detailed plans for the 4850′ level facility are presented, as well as plans for associated technologies and integration activities.
1338(2011); http://dx.doi.org/10.1063/1.3579561View Description Hide Description
It is a continuous and ongoing effort to maintain radioactivity in materials and in the environment surrounding most underground experiments at very low levels. These low levels are required so that experiments can achieve the required detection sensitivities for the detection of low‐energy neutrinos, searches for dark matter and neutrinoless double‐beta decay. SNOLAB has several facilities which are used to determine these low background levels in the materials and the underground environment. This proceedings will describe the SNOLAB High Purity Germanium Detector which has been in continuous use for the past five years and give results of many of the items that have been counted over that period. Brief descriptions of SNOLAB’s alpha‐beta and electrostatic counters will be given, and the radon levels at SNOLAB will be discussed.
1338(2011); http://dx.doi.org/10.1063/1.3579562View Description Hide Description
The Kimballton Underground Research Facility (KURF) is home to several experiments. One consists to two HPGe detectors designed to screen candidate materials to be used in low‐background experiments for radioactivity. Analysis techniques, including our efficiency calculations will be presented. We have also deployed a customized BEGe (Broad Energy Germanium) detector in a low‐background cryostat. This paper will focus on the shield design, detector characteristics and measurements that can be performed with such a detector in a low‐background environment.
1338(2011); http://dx.doi.org/10.1063/1.3579563View Description Hide Description
Radon detectors have been deployed underground at the Sanford Underground Laboratory at the site of the former Homestake Mine in Lead, SD. Currently, no radon mitigation measures are in place in the underground environment, and the continuing evolution of the facility ventilation systems has led to significant variations in early airborne radon concentrations. The average radon concentration measured near the primary ventilation intake for the 4850‐ft level (Yates shaft) is based on approximately 146 days of data. The corresponding average radon concentration near the other main ventilation intake for the 4850‐ft level (Ross shaft) is based on approximately 350 days of data. Measurements have also been collected near the 1250‐ft level Ross shaft, with average radon concentrations at Secondary factors that may increase the baseline radon level underground include the presence of iron oxide and moisture, which are known to enhance radon emanation. The results of the current radon monitoring program will be used for the planning of future measurements and any potential optimization of ventilation parameters for the reduction of radon in relevant areas underground.
1338(2011); http://dx.doi.org/10.1063/1.3579564View Description Hide Description
BetaCage, a gaseous neon time‐projection chamber, has been proposed as a viable screener for emitters of low‐energy alphas and electrons to which commercial radioactivity counting techniques are insensitive. Using radiopure materials for construction, active and passive shielding from extrinsic backgrounds, large counting area and minimal detector mass, BetaCage will be able to achieve sensitivities of in a few days of running time. We report on progress in prototype development work since the last meeting of this workshop.
1338(2011); http://dx.doi.org/10.1063/1.3579565View Description Hide Description
The next generation low‐background detectors operating underground aim for unprecedented low levels of radioactive backgrounds. Although the radioactive decays of airborne radon (particularly ) and its subsequent progeny present in an experiment are potential backgrounds, also problematic is the deposition of radon progeny on detector materials. Exposure to radon at any stage of assembly of an experiment can result in surface contamination by progeny supported by the long half life (22 y) of on sensitive locations of a detector. An understanding of the potential surface contamination from deposition will enable requirements of radon‐reduced air and clean room environments for the assembly of low background experiments. It is known that there are a number of environmental factors that govern the deposition of progeny onto surfaces. However, existing models have not explored the impact of some environmental factors important for low background experiments. A test stand has been constructed to deposit radon progeny on various surfaces under a controlled environment in order to develop a deposition model. Results from this test stand and the resulting deposition model are presented.
1338(2011); http://dx.doi.org/10.1063/1.3579566View Description Hide Description
Radon (Rn) and its decay daughters are a well‐known source of background in direct WIMP detection experiments, as either a Rn decay daughter or an alpha particle emitted from a thin inner surface layer of a detector could produce a WIMP‐like signal. Different surface treatment and cleaning techniques have been employed in the past to remove this type of contamination. A new method of dealing with the problem has been proposed and used for a prototype acrylic DEAP‐1 detector. Inner surfaces of the detector were coated with a layer of ultra pure acrylic, meant to shield the active volume from alphas and recoiling nuclei. An acrylic purification technique and two coating techniques are described: a solvent‐borne (tested on DEAP‐1) and solvent‐less (being developed for the full scale DEAP‐3600 detector).
1338(2011); http://dx.doi.org/10.1063/1.3579567View Description Hide Description
The production of crystals needed for rare events physics represent a relatively new, exciting challenge in the field of materials science and engineering. Extremely low concentration of radioactive impurities and very high crystal perfection is required for the crystals to be used in experiments in which the main concerns are the reduction of the background and the use of high sensitivity detectors. A further complication is the fact that for an experiment with a significant discovery potential, relatively large quantities of crystals are needed. The present work makes a review of the general problems related to the production of crystals for rare events physics and gives details related to the production of the crystals needed for the major experiment in this field using bolometric technique, namely the CUORE experiment. The potential use of crystals for future double beta decay experiments is also discussed.
1338(2011); http://dx.doi.org/10.1063/1.3579568View Description Hide Description
CANDLES is the project to search for neutrinoless double beta (0νββ) decay of by using scintillators. The observation of 0νββ decay will prove the existence of massive Majorana neutrinos. Expected performances and current status of the CANDLES system are described.
1338(2011); http://dx.doi.org/10.1063/1.3579569View Description Hide Description
The XMASS project aims to detect pp and solar neutrinos, neutrino‐less double beta decay, and dark matter searches using ultra‐pure liquid xenon. The first stage of XMASS project is concentrated on dark matter searches using 800 kg liquid xenon detector which requires low background and low threshold. Several techniques applied to XMASS detector for low background will be presented.
1338(2011); http://dx.doi.org/10.1063/1.3579570View Description Hide Description
A search for WIMP dark matter has been undertaken with new‐generation germanium heat‐and‐ionization cryogenic detectors in the EDELWEISS‐II experiment. The InterDigit bolometers, with an interleaved electrode design, have proven excellent rejection performance against gamma‐ray and surface event backgrounds which are limiting germanium bolometer dark matter searches. One year of continuous operation at the Laboratoire Souterrain de Modane has been achieved with an array of ten 400 g detectors. Preliminary resultats for WIMP search are presented with an effective exposure of 322 kg.days, which corresponds to a sensitivity to the spin independant WIMP‐nucleon cross‐section at 90% C.L. for a WIMP mass of