The Jiangmen Underground Neutrino Observatory is building the world’s largest liquid scintillator (LS) detector, and the radiopurity in LS should reach 0.01-1 ppq (10$^{-17}$-10$^{-15}$ g/g) $^{238}$U/$^{232}$Th. The 20 kt LS is filled in the acrylic sphere with 35.4 m diameter, and both the acrylic bulk (<1 ppt $^{238}$U/$^{232}$Th) and the surface (<5 ppt $^{238}$U/$^{232}$Th in the first 50...
To measure low surface and bulk specific activities of alpha emitters a low-background, large-surface alpha spectrometer is needed. In our studies we use the XIA UltraLo-1800 instrument, in which the low background is achieved by using radio-pure construction materials and by application of Pulse Shape Analysis (PSA). The PSA is based on inspection of amplitudes, shapes and rise times of the...
NEWS-G (New Experiments With Spheres-Gas) is a project searching for sub-GeV dark matter with a Spherical Proportional Counter (SPC) filled with low-Z gases (H, He, Ne). A 140cm-diameter sphere has been commissioned at the Laboratoire Souterrain de Modane (France) and is now installed at SNOLAB (Canada). Presented here are the techniques used to reduce the backgrounds, external but more...
DarkSide-20k, a direct dark matter search experiment, is located at the Gran Sasso National Laboratory (LNGS), Italy. It is designed to achieve groundbreaking 200-tonne-year exposure, nearly free from instrumental backgrounds. The core of the detector is a dual-phase Time Projection Chamber (TPC) containing 50 tonnes (20 tonnes fiducial) of underground liquid argon (UAr) with low levels of...
Neutrinoless double beta decay ($0\nu\beta\beta$) is a lepton-number-violating nuclear transition beyond the Standard Model. If detected, it would unequivocally demonstrate that neutrinos are Majorana particles. This process is expected to be extremely rare, therefore very low background tonne-scale experiments are necessary for its observation. The Cryogenic Underground Observatory for Rare...
Future liquid xenon (LXe) dark matter detectors require the detector background event rate to be significantly lower non-shieldable solar neutrino background yielding the request that each radioactive background rate should be 10-times smaller than that from solar neutrinos. To achieve this ambitious goal for 222Rn, a reduction of the intrinsic 222Rn concentration to less than <0.1 µBq/kg in...
The Jiangmen Underground Neutrino Observatory (JUNO) is a state-of-the-art liquid-scintillator-based neutrino physics experiment under construction in South China. Thanks to 20 ktons of the ultra-pure liquid scintillator (LS), JUNO can perform innovative and groundbreaking measurements like determining neutrino mass ordering. To mitigate the impact of radioactivity emanating from the...
Ultra-low-background (ULB) high purity germanium (HPGe) detectors are essential tools for measurements of materials with extremely low levels of radioactivity. Such detectors support research areas ranging from fundamental physics of rare events like dark matter and neutrinoless double beta decay, to nuclear safeguards and treaty verification.
A common shortcoming specific to ULB HPGe...
A novel system for ultra-sensitive Radon emanation studies has been developed. It is based on a cryogenic
Radon detector coupled to two large-volume chambers, able to accommodate samples up to 250 L in volume. Due to the unique properties of the detector it is possible, for the first time, to study simultaneously emanation of two Radon isotopes, namely 222Rn and the short-lived 220Rn. Special...
Gamma-spectrometry has been a crucial technique for the analysis of natural and anthropogenic radionuclides in nuclear, astrophysical, and environmental investigations, although recently mass spectrometry techniques such as ICPMS (Inductively Coupled Plasma Mass Spectrometry) and AMS (Accelerator Mass Spectrometry) have reached the lowest detection limits. The great advantage of...
Radon emanation from materials presents a major background to dark matter searches. Presenting the dual-detector radon emanation system operating at Boulby Underground Laboratory, which uses two 80L electrostatic alpha detectors. By incorporating a radon concentration line, this will enhance its sensitivity of 222Rn to below 0.1 mBq, providing more accuracy at characterising radioactive...
Książ Castle is located in the Lower Silesian Voivodeship in the south-western Poland. During the Second World War several tunnels were excavated in the castle hill. They are located 50 m below the courtyard of the castle and 350 m above sea level.
In 1968 the Geophysical Observatory of the Institute of Geophysics of the Polish Academy of Sciences was established in the tunnels. At the end...
About two tons of ultra pure copper has been produced as a material for construction of an internal shield of a low-background gamma spectrometer. Aurubis A.G. (Germany) has prepared a dedicated casting mould, selected the best possible raw material and cast the 2-ton block. In order to minimize the cosmic exposure the block was immediately transported and stored underground, 150 m below the...
GEM-like charge amplification structures, including FAT GEMs, can find applications in TPCs for dark matter, neutrino and generally rare event search experiments.
A new concept of GEM-like structures was recently proposed. In this concept a double-stack of GEM-like structures is used to optically decouple LAr and GAr regions from a dual-phase TPC. Its core element is a type of GEM...
One of the main challenges in rare event searches is interference from background radiation. We can travel deep underground where we experience a reduction of a factor 1 million in cosmic rays, but that still leaves background from radioactivity intrinsic to the materials we use to build these detectors. A solution to this problem, is to create a radioactive background model for these...
Lead is the most popular material to shield the external gamma-ray. The radioactivity of the lead shielding is important for the rare event search experiments, such as neutrinoless double beta decay and weakly interacting massive particle searches. In the rare event searches, the radioactivity of the lead shielding itself may contribute significant background signals. We cannot measure the...
The AMoRE-II is searching for neutrinoless double beta-decay (0νDBD) of 100Mo using cryogenic calorimeters with 360 lithium molybdate ultra-pure scintillation crystals. Experiments seeking rare nuclear processes, like 0νDBD, are propelled by pursuing ever-diminishing levels of radioactive backgrounds and the techniques that can extract a weak signal from this background. Among these...
Many particle physics experiments utilize gadolinium (Gd), a rare earth element with the most significant neutron capture cross-section among all elements, to detect anti-neutrinos via inverse beta decays or to remove neutron-induced background events.
For example, to load Gd into water Cherenkov detectors, Gd sulfate is dissolved and rare event search experiments are required to screen for...
The hardware upgrades and third fill of DEAP-3600 are designed to produce a zero-background dark-matter measurement. DEAP-3600 is a single-phase liquid-argon detector containing 3300kg of liquid argon in a ultra-pure transparent acrylic sphere. TPB, on the inner surface of the acrylic, is used to wavelength shift argon scintillation light into the visible, this allowing its detection by an...
