Low pressure gaseous Time Projection Chambers (TPCs) are aviable technology for directional Dark Matter (DM) searches and havethe potential for exploring the parameter space below the neutrinofog ...1,2. Gases like CF4 are advantageousbecause they contain flourine which is predicted to have heightenedelastic scattering rates with a possible Weakly Interacting MassiveParticle (WIMP) DM candidate 3,4,5. Thelow pressure of CF4 must be maintained, ideally lower than100 Torr, in order to elongate potential Nuclear Recoil (NR) trackswhich allows for improved directional sensitivity and NR/ElectronRecoil (ER) discrimination 6. Recent evidence suggeststhat He can be added to heavier gases, like CF4, withoutsignificantly affecting the length of 12C and 19F recoilsdue to its lower mass. Such addition of He has the advantage ofimproving sensitivity to lower massWIMPs 1. Simulations can not reliably predictoperational stability in these low pressure gas mixtures and thusmust be demonstrated experimentally. In this paper we investigatehow the addition of He to low pressure CF4 affects the gas gainand energy resolution achieved with a single Thick Gaseous ElectronMultiplier (ThGEM).
Type 5 Å molecular sieves (MS) have been demonstrated to remove radon from SF6 gas. This is important for ultra-sensitive SF6 gas-based directional dark matter and related rare-event physics ...experiments, as radon can provide a source of unwanted background events. Unfortunately, commercially available sieves intrinsically emanate radon at levels not suitable for ultra-sensitive physics experiments. A method to produce a low radioactive MS has been developed in Nihon University (NU). In this work, we explore the feasibility of the NU-developed 5 Å type MS for use in such experiments. A comparison with a commercially available Sigma-Aldrich 5 Å type MS was made. The comparison was done by calculating a parameter indicating the amount of radon intrinsically emanated by the MS per unit radon captured from SF6 gas. The measurements were made using a specially adapted DURRIDGE RAD7 radon detector. The NU-developed 5 Å MS emanated radon up to 61 ± 9% less per radon captured (2.1 ± 0.1) × 10−3, compared to the commercial Sigma-Aldrich MS (5.4 ± 0.4) × 10−3, making it a better candidate for use in a radon filtration setup for future ultra-sensitive SF6 gas based experiments.
Abstract
Photomultiplier tubes (PMTs) are traditionally an integral part of large underground experiments as they measure the light emission from particle interactions within the enclosed detection ...media. The BUTTON experiment will utilise around 100 PMTs to measure the response of different media suitable for rare event searches. A subset of low-radioactivity 10-inch Hamamatsu R7081 PMTs were tested, characterised, and compared to manufacture certification. This manuscript describes the laboratory tests and analysis of gain, peak-to-valley ratio and dark rate of the PMTs to give an understanding of the charge response, signal-to-noise ratio and dark noise background as an acceptance test of the suitability of these PMTs for water-based detectors. Following the evaluation of these tests, the PMT performance agreed with the manufacturer specifications. These results are imperative for modeling the PMT response in detector simulations and providing confidence in the performance of the devices once installed in the detector underground.
Abstract
The COSINE-100 experiment is designed to test the DAMA
experiment which claimed an observation of a dark matter signal from
an annual modulation in their residual event rate. To measure the
...1 %-level signal amplitude, it is crucial to control and monitor
nearly all environmental quantities that might systematically mimic
the signal. The environmental monitoring also helps ensure a stable
operation of the experiment. Here, we describe the design and
performance of the centralized environmental monitoring system for
the COSINE-100 experiment.
Abstract
We demonstrate a new type of analysis for the DRIFT-IId
directional dark matter detector using a machine learning algorithm
called a Random Forest Classifier. The analysis labels events as
...signal or background based on a series of selection parameters,
rather than solely applying hard cuts. The analysis efficiency is
shown to be comparable to our previous result at high energy but
with increased efficiency at lower energies. This leads to a
projected sensitivity enhancement of one order of magnitude below a
WIMP mass of 15 GeV c
-2
and a projected sensitivity limit that
reaches down to a WIMP mass of 9 GeV c
-2
, which is a first for
a directionally sensitive dark matter detector.
COSINE-100 is a dark matter detection experiment that uses NaI(Tl) crystal detectors operating at the Yangyang underground laboratory in Korea since September 2016. Its main goal is to test the ...annual modulation observed by the DAMA/LIBRA experiment with the same target medium. Recently DAMA/LIBRA has released data with an energy threshold lowered to 1 keV, and the persistent annual modulation behavior is still observed at 9.5σ. By lowering the energy threshold for electron recoils to 1 keV, COSINE-100 annual modulation results can be compared to those of DAMA/LIBRA in a model-independent way. Additionally, the event selection methods provide an access to a few to sub-GeV dark matter particles using constant rate studies. In this article, we discuss the COSINE-100 event selection algorithm, its validation, and efficiencies near the threshold.
The gas SF6 has become of interest as a negative ion drift gas for use in directional dark matter searches. However, as for other targets in such searches, it is important that radon contamination ...can be removed as this provides a source of unwanted background events. In this work we demonstrate for the first time filtration of radon from SF6 gas by using a molecular sieve. Four types of sieves from Sigma-Aldrich were investigated, namely 3Å, 4Å, 5Å and 13X. A manufactured radon source was used for the tests. This was attached to a closed loop system in which gas was flowed through the filters and a specially adapted Durridge RAD7 radon detector. In these measurements, it was found that only the 5Å type was able to significantly reduce the radon concentration without absorbing the SF6 gas. The sieve was able to reduce the initial radon concentration of 3875 ± 13 Bqm−3 in SF6 gas by 87% when cooled with dry ice. The ability of the cooled 5Å molecular sieve filter to significantly reduce radon concentration from SF6 provides a promising foundation for the construction of a radon filtration setup for future ultra-sensitive SF6 gas rare-event physics experiments.
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