26 research outputs found
Searching for ER and/or NR-like dark matter signals with the especially low background liquid helium TPCs
In the Dark Matter (DM) direct detection community, the absence of convincing
signals has become a ``new normal'' for decades. Among other possibilities, the
``new normal'' might indicate that DM-matter interactions could generate not
only the hypothetical NR (Nuclear Recoil) events but also the ER (Electron
Recoil) ones, which have often been tagged as backgrounds historically.
Further, we argue that ER and NR-like DM signals could co-exist in a DM
detector's same dataset. So in total, there would be three scenarios we can
search for DM signals: (i) ER excess only, (ii) NR excess only, and (iii) ER
and NR excesses combined. To effectively identify any possible DM signal under
the three scenarios, a DM detector should (a) have the minimum ER and NR
backgrounds and (b) be capable of discriminating ER events from NR ones.
Accordingly, we introduce the newly established project, ALETHEIA, which
implements liquid helium-filled TPCs (Time Projection Chamber) in hunting for
DM. Thanks to the nearly single-digit number of ER and NR backgrounds on 1
ton*yr exposure, presumably, the ALETHEIA detectors should be able to identify
any form of DM-induced excess in its ROI (Research Of Interest). As far as we
know, ALETHEIA is the first DM direct detection experiment claiming such an
inclusive search; conventional detectors search DM mainly on the ``ER excess
only'' and/or the ``NR excess only'' channel, not the ``ER and NR excesses
combined'' channel. In addition, we introduce a preliminary scheme to one of
the most challenging R\&D tasks, transmitting 500+ kV into a 4 K LHe detector
Conceptual design and progress of transmitting MV DC HV into 4 K LHe detectors
A dual-phase TPC (Time Projection Chamber) is more advanced in characterizing
an event than a single-phase one because it can, in principle, reconstruct the
3D (X-Y-Z) image of the event, while a single-phase detector can only show a 2D
(X-Y) picture. As a result, more enriched physics is expected for a dual-phase
detector than a single-phase one. However, to build such a detector, DC HV
(High Voltage) must be delivered into the chamber (to have a static electric
field), which is a challenging task, especially for an LHe detector due to the
extremely low temperature, 4 K, and the very high voltage, MV
(Million Volts). This article introduces a convincing design for transmitting
MV DC into a 4 K LHe detector. We also report the progress of
manufacturing a 100 kV DC feedthrough capable of working at 4 K. Surprisingly,
we realized that the technology we developed here might be a valuable reference
to the scientists and engineers aiming to build residential bases on the Moon
or Mars
Expression, purification and characterization of the Lily symptomless virus coat protein from Lanzhou Isolate
Background: Lily symptomless virus (LSV) is widespread in many countries where lily are grown or planted, and causes severe economic losses in terms of quantity and quality of flower and bulb production. To study the structure-function relationship of coat protein (CP) of LSV, to investigate antigenic relationships between coat protein subunits or intact virons, and to prepare specific antibodies against LSV, substantial amounts of CP protein are needed. Results: Thus, full-length cDNA of LSV coat protein was synthesized and amplified by RT-PCR from RNA isolated from LSV Lanzhou isolate. The extended 33.6 kDa CP was cloned and expressed prokaryoticly and then purified by Ni-ion affinity chromatography. Its identity and antigenicity of recombinant CP were identified on Western-blotting by using the prepared anti-LSV antibodies. Conclusions: The results indicate that fusion CP maintains its native antigenicity and specificity, providing a good source of antigen in preparation of LSV related antibodies. Detailed structural analysis of a pure recombinant CP should allow a better understanding of its role in cell attachment and LSV tropism. This investigation to LSV should provide some specific antibodies and aid to development a detection system for LSV diagnostics and epidemiologic surveys
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TAO Conceptual Design Report: A Precision Measurement of the Reactor Antineutrino Spectrum with Sub-percent Energy Resolution
The Taishan Antineutrino Observatory (TAO, also known as JUNO-TAO) is a
satellite experiment of the Jiangmen Underground Neutrino Observatory (JUNO). A
ton-level liquid scintillator detector will be placed at about 30 m from a core
of the Taishan Nuclear Power Plant. The reactor antineutrino spectrum will be
measured with sub-percent energy resolution, to provide a reference spectrum
for future reactor neutrino experiments, and to provide a benchmark measurement
to test nuclear databases. A spherical acrylic vessel containing 2.8 ton
gadolinium-doped liquid scintillator will be viewed by 10 m^2 Silicon
Photomultipliers (SiPMs) of >50% photon detection efficiency with almost full
coverage. The photoelectron yield is about 4500 per MeV, an order higher than
any existing large-scale liquid scintillator detectors. The detector operates
at -50 degree C to lower the dark noise of SiPMs to an acceptable level. The
detector will measure about 2000 reactor antineutrinos per day, and is designed
to be well shielded from cosmogenic backgrounds and ambient radioactivities to
have about 10% background-to-signal ratio. The experiment is expected to start
operation in 2022
Neutrino Physics with JUNO
The Jiangmen Underground Neutrino Observatory (JUNO), a 20 kton multi-purposeunderground liquid scintillator detector, was proposed with the determinationof the neutrino mass hierarchy as a primary physics goal. It is also capable ofobserving neutrinos from terrestrial and extra-terrestrial sources, includingsupernova burst neutrinos, diffuse supernova neutrino background, geoneutrinos,atmospheric neutrinos, solar neutrinos, as well as exotic searches such asnucleon decays, dark matter, sterile neutrinos, etc. We present the physicsmotivations and the anticipated performance of the JUNO detector for variousproposed measurements. By detecting reactor antineutrinos from two power plantsat 53-km distance, JUNO will determine the neutrino mass hierarchy at a 3-4sigma significance with six years of running. The measurement of antineutrinospectrum will also lead to the precise determination of three out of the sixoscillation parameters to an accuracy of better than 1\%. Neutrino burst from atypical core-collapse supernova at 10 kpc would lead to ~5000inverse-beta-decay events and ~2000 all-flavor neutrino-proton elasticscattering events in JUNO. Detection of DSNB would provide valuable informationon the cosmic star-formation rate and the average core-collapsed neutrinoenergy spectrum. Geo-neutrinos can be detected in JUNO with a rate of ~400events per year, significantly improving the statistics of existing geoneutrinosamples. The JUNO detector is sensitive to several exotic searches, e.g. protondecay via the decay channel. The JUNO detector will providea unique facility to address many outstanding crucial questions in particle andastrophysics. It holds the great potential for further advancing our quest tounderstanding the fundamental properties of neutrinos, one of the buildingblocks of our Universe
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TAO Conceptual Design Report: A Precision Measurement of the Reactor Antineutrino Spectrum with Sub-percent Energy Resolution
The Taishan Antineutrino Observatory (TAO, also known as JUNO-TAO) is a
satellite experiment of the Jiangmen Underground Neutrino Observatory (JUNO). A
ton-level liquid scintillator detector will be placed at about 30 m from a core
of the Taishan Nuclear Power Plant. The reactor antineutrino spectrum will be
measured with sub-percent energy resolution, to provide a reference spectrum
for future reactor neutrino experiments, and to provide a benchmark measurement
to test nuclear databases. A spherical acrylic vessel containing 2.8 ton
gadolinium-doped liquid scintillator will be viewed by 10 m^2 Silicon
Photomultipliers (SiPMs) of >50% photon detection efficiency with almost full
coverage. The photoelectron yield is about 4500 per MeV, an order higher than
any existing large-scale liquid scintillator detectors. The detector operates
at -50 degree C to lower the dark noise of SiPMs to an acceptable level. The
detector will measure about 2000 reactor antineutrinos per day, and is designed
to be well shielded from cosmogenic backgrounds and ambient radioactivities to
have about 10% background-to-signal ratio. The experiment is expected to start
operation in 2022
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The Design and Sensitivity of JUNO's scintillator radiopurity pre-detector OSIRIS
The OSIRIS detector is a subsystem of the liquid scintillator fillling chain
of the JUNO reactor neutrino experiment. Its purpose is to validate the
radiopurity of the scintillator to assure that all components of the JUNO
scintillator system work to specifications and only neutrino-grade scintillator
is filled into the JUNO Central Detector. The aspired sensitivity level of
g/g of U and Th requires a large (20 m)
detection volume and ultralow background levels. The present paper reports on
the design and major components of the OSIRIS detector, the detector simulation
as well as the measuring strategies foreseen and the sensitivity levels to U/Th
that can be reached in this setup
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JUNO Physics and Detector
The Jiangmen Underground Neutrino Observatory (JUNO) is a 20 kton LS detector
at 700-m underground. An excellent energy resolution and a large fiducial
volume offer exciting opportunities for addressing many important topics in
neutrino and astro-particle physics. With 6 years of data, the neutrino mass
ordering can be determined at 3-4 sigma and three oscillation parameters can be
measured to a precision of 0.6% or better by detecting reactor antineutrinos.
With 10 years of data, DSNB could be observed at 3-sigma; a lower limit of the
proton lifetime of 8.34e33 years (90% C.L.) can be set by searching for
p->nu_bar K^+; detection of solar neutrinos would shed new light on the solar
metallicity problem and examine the vacuum-matter transition region. A
core-collapse supernova at 10 kpc would lead to ~5000 IBD and ~2000 (300)
all-flavor neutrino-proton (electron) scattering events. Geo-neutrinos can be
detected with a rate of ~400 events/year. We also summarize the final design of
the JUNO detector and the key R&D achievements. All 20-inch PMTs have been
tested. The average photon detection efficiency is 28.9% for the 15,000 MCP
PMTs and 28.1% for the 5,000 dynode PMTs, higher than the JUNO requirement of
27%. Together with the >20 m attenuation length of LS, we expect a yield of
1345 p.e. per MeV and an effective energy resolution of 3.02%/\sqrt{E (MeV)}$
in simulations. The underwater electronics is designed to have a loss rate
<0.5% in 6 years. With degassing membranes and a micro-bubble system, the radon
concentration in the 35-kton water pool could be lowered to <10 mBq/m^3.
Acrylic panels of radiopurity <0.5 ppt U/Th are produced. The 20-kton LS will
be purified onsite. Singles in the fiducial volume can be controlled to ~10 Hz.
The JUNO experiment also features a double calorimeter system with 25,600
3-inch PMTs, a LS testing facility OSIRIS, and a near detector TAO