Since the original detection of core-collapse supernova neutrinos in 1987, all large neutrino experiments seek to detect the neutrinos from the next nearby supernova. Among them, liquid argon time ...projection chambers (LArTPCs) offer a unique sensitivity to the electron neutrino flux of a supernova. However, the low energy of these events (scale of MeVs), and the fact that all large (multi-tonne) LArTPCs operating at the moment are located near the Earth's surface, and are therefore subject to an intense cosmic ray flux, makes triggering on the supernova neutrinos very challenging. Instead, MicroBooNE has pioneered a novel approach for detecting supernova neutrinos based on a continuous readout stream and a delayed trigger generated by other neutrino detectors (the Supernova Early Warning System, or SNEWS). MicroBooNE's data is stored temporarily for a few days, awaiting a SNEWS alert to prompt the permanent recording of the data. In order to cope with the large data rates produced by the continuous readout of the TPC and the PMT systems of MicroBooNE, FPGA-based zero-suppression algorithms have been developed.
This paper describes a procedure for the validation of alpha-particle sources (exempt unsealed sources) to be used in experimental setups with liquefied gases at cryogenic temperatures (down to ...−196 °C) and high vacuum. These setups are of interest for the development and characterization of neutrino and dark matter detectors based on liquid argon, among others. Due to the high purity requirements, the sources have to withstand high vacuum and cryogenic temperatures for extended periods. The validation procedure has been applied to 241Am sources produced by electrodeposition.
•A method to validate electrodeposited 241Am alpha-particle sources for use under high vacuum and cryogenic temperatures has been developed.•Electrodeposited alpha-particle sources from aqueous electrolytes containing sulphate ions were validated for use at cryogenic temperatures.•Electrodeposited alpha-particle sources from aqueous electrolytes containing sulphate ions were validated for use at high vacuum.
Abstract
The next core-collapse supernova in the Milky Way or its satellites will represent a once-in-a-generation opportunity to obtain detailed information about the explosion of a star and provide ...significant scientific insight for a variety of fields because of the extreme conditions found within. Supernovae in our galaxy are not only rare on a human timescale but also happen at unscheduled times, so it is crucial to be ready and use all available instruments to capture all possible information from the event. The first indication of a potential stellar explosion will be the arrival of a bright burst of neutrinos. Its observation by multiple detectors worldwide can provide an early warning for the subsequent electromagnetic fireworks, as well as signal to other detectors with significant backgrounds so they can store their recent data. The supernova early warning system (SNEWS) has been operating as a simple coincidence between neutrino experiments in automated mode since 2005. In the current era of multi-messenger astronomy there are new opportunities for SNEWS to optimize sensitivity to science from the next galactic supernova beyond the simple early alert. This document is the product of a workshop in June 2019 towards design of SNEWS 2.0, an upgraded SNEWS with enhanced capabilities exploiting the unique advantages of prompt neutrino detection to maximize the science gained from such a valuable event.
A
bstract
The Double Chooz experiment presents improved measurements of the neutrino mixing angle
θ
13
using the data collected in 467.90 live days from a detector positioned at an average distance ...of 1050 m from two reactor cores at the Chooz nuclear power plant. Several novel techniques have been developed to achieve significant reductions of the backgrounds and systematic uncertainties with respect to previous publications, whereas the efficiency of the
ν
¯
e
signal has increased. The value of
θ
13
is measured to be sin
2
2
θ
13
= 0.090
− 0.029
+ 0.032
from a fit to the observed energy spectrum. Deviations from the reactor
ν
¯
e
prediction observed above a prompt signal energy of 4 MeV and possible explanations are also reported. A consistent value of
θ
13
is obtained from a fit to the observed rate as a function of the reactor power independently of the spectrum shape and background estimation, demonstrating the robustness of the
θ
13
measurement despite the observed distortion.
The latest results from the Double Chooz experiment on the neutrino mixing angle θ13 are presented. A detector located at an average distance of 1050 m from the two reactor cores of the Chooz nuclear ...power plant has accumulated a live time of 467.90 days, corresponding to an exposure of 66.5 GW-ton-year (reactor power × detector mass × live time). A revised analysis has boosted the signal efficiency and reduced the backgrounds and systematic uncertainties compared to previous publications, paving the way for the two detector phase. The measured sin22θ13=0.090−0.029+0.032 is extracted from a fit to the energy spectrum. A deviation from the prediction above a visible energy of 4 MeV is found, being consistent with an unaccounted reactor flux effect, which does not affect the θ13 result. A consistent value of θ13 is measured in a rate-only fit to the number of observed candidates as a function of the reactor power, confirming the robustness of the result.
Liquid argon time projection chambers (TPC) are widely used in neutrino oscillation and dark matter experiments. Detection of scintillation light in liquid argon TPC’s is challenging because of its ...short wavelength, in the VUV range, and the cryogenic temperatures (∼86 K) at which the sensors must operate. Wavelength shifters (WLS) are typically needed to take advantage of the high Photon Detection Efficiency (PDE) in the visible range of most of photondetectors. The Hamamatsu VUV4 S13370–6075CN SiPMs can directly detect VUV light without the use of WLS, which main benefit is an improved PDE at these short wavelengths, but also the visible light from WLS. The manufacturer (Hamamatsu Photonics K.K.) provides a complete characterization of these devices at room temperature; however, previous studies have indicated a decrease of the PDE at cryogenic temperature for VUV light. In this work, we present the measurement of the PDE of VUV4 SiPMs at cryogenic temperature for different wavelengths in the range 270, 570 nm. A dedicated measurement at 127 nm is also shown.
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