As part of the R2D2 (Rare Decays with Radial Detector) R &D, the use of a gas detector with a spherical or cylindrical cathode, equipped with a single anode and operating at high pressure, was ...studied for the search of rare phenomena such as neutrinoless double-beta decay. The presented measurements were obtained with a cylindrical detector, covering gas pressures ranging from 1 to 10 bar in argon and 1 to 6 bar in xenon, using both a point-like source of
210
Po (5.3 MeV
α
) and a diffuse source of
222
Rn (5.5 MeV
α
). Analysis and interpretation of the data were developed using the anodic current waveform. Similar detection performances were achieved with both gases, and comparable energy resolutions were measured with both sources. As long as the purity of the gas was sufficient, no significant degradation of the measured energy was observed by increasing the pressure. At the highest operating pressure, an energy resolution better than 1.5% full-width at half-maximum (FWHM) was obtained for both gaseous media, although optimal noise conditions were not reached.
The CODALEMA experiment aims to study the radio-detection of Ultra High Energy Cosmic Rays in the energy range of 1017eV. Spread over an area of 0.25km2, the original device hosted at Nançay (France) ...has mainly benefited of an array of short dipoles, connected by cables up to a centralized acquisition room. Since 2010, a major evolution has been initiated to add 60 autonomous radio-detection stations, covering a surface of 1.5km2. This enlarged configuration should help refine the studies and serve as a bench test for the mastery of autonomous detection. The main characteristics of this new mode of operation is presented in the light of recent results obtained by the original CODALEMA setup.
New Experiments with Spheres-Gas (NEWS-G) is a dark matter direct detection experiment that will operate at SNOLAB (Canada). Similar to other rare-event searches, the materials used in the detector ...construction are subject to stringent radiopurity requirements. The detector features a 140-cm diameter proportional counter comprising two hemispheres made from commercially sourced 99.99% pure copper. Such copper is widely used in rare-event searches because it is readily available, there are no long-lived Cu radioisotopes, and levels of non-Cu radiocontaminants are generally low. However, measurements performed with a dedicated 210Po alpha counting method using an XIA detector confirmed a problematic concentration of 210Pb in bulk of the copper. To shield the proportional counter’s active volume, a low-background electroforming method was adapted to the hemispherical shape to grow a 500-µm thick layer of ultra-radiopure copper to the detector’s inner surface. In this paper the process is described, which was prototyped at Pacific Northwest National Laboratory (PNNL), USA, and then conducted at full scale in the Laboratoire Souterrain de Modane in France. The radiopurity of the electroplated copper was assessed through Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Measurements of samples from the first (second) hemisphere give 68% confidence upper limits of <0.58µBq/kg (<0.24µBq/kg) and <0.26µBq/kg (<0.11µBq/kg) on the 232Th and 238U contamination levels, respectively. These results are comparable to previously reported measurements of electroformed copper produced for other rare-event searches, which were also found to have low concentration of 210Pb consistent with the background goals of the NEWS-G experiment.
An antenna array devoted to the autonomous radio-detection of high energy cosmic rays is being deployed on the site of the 21
cm array radio telescope in XinJiang, China. Thanks in particular to the ...very good electromagnetic environment of this remote experimental site, self-triggering on extensive air showers induced by cosmic rays has been achieved with a small scale prototype of the foreseen antenna array. We give here a detailed description of the detector and present the first detection of extensive air showers with this prototype.
The amount of energy released by a nuclear recoil ionizing the atoms of the active volume of detection appears “quenched” compared to an electron of the same kinetic energy. This different behavior ...in ionization between electrons and nuclei is described by the Ionization Quenching Factor (IQF) and it plays a crucial role in direct dark matter searches. For low kinetic energies (below
50
keV
), IQF measurements deviate significantly from common models used for theoretical predictions and simulations. We report measurements of the IQF for proton, an appropriate target for searches of Dark Matter candidates with a mass of approximately
1
GeV
, with kinetic energies in between
2
keV
and
13
keV
in
100
mbar
of methane. We used the Comimac facility in order to produce the motion of nuclei and electrons of controlled kinetic energy in the active volume, and a NEWS-G SPC to measure the deposited energy. The Comimac electrons are used as a reference to calibrate the detector with 7 energy points. A detailed study of systematic effects led to the final results well fitted by
IQF
(
E
K
)
=
E
K
α
/
(
β
+
E
K
α
)
with
α
=
0.70
±
0.08
and
β
=
1.32
±
0.17
. In agreement with some previous works in other gas mixtures, we measured less ionization energy than predicted from SRIM simulations, the difference reaching
33
%
at
2
keV
.
The new setup of the CODALEMA experiment installed at the Radio Observatory in Nançay, France, is described. It includes broadband active dipole antennas and an extended and upgraded particle ...detector array. The latter gives access to the air shower energy, allowing us to compute the efficiency of the radio array as a function of energy. We also observe a large asymmetry in counting rates between showers coming from the North and the South in spite of the symmetry of the detector. The observed asymmetry can be interpreted as a signature of the geomagnetic origin of the air shower radio emission. A simple linear dependence of the electric field with respect to
v
∧
B is used which reproduces the angular dependencies of the number of radio events and their electric polarity.
Taking advantage of recent technical progress which has overcome some of the difficulties encountered in the 1960s in the radio detection of extensive air showers induced by ultra-high-energy cosmic ...rays (UHECR), a new experimental apparatus (CODALEMA) has been built and operated. We will present the characteristics of this device and the analysis techniques that have been developed for observing electrical transients associated with cosmic rays. We find a collection of events for which both time and arrival direction coincidences between particle and radio signals are observed. The counting rate corresponds to shower energies
⩾
5
×
10
16
eV
. The performance level which has been reached considerably enlarges the perspectives for studying UHECR events using radio detection.
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