More Like this

1. Separating $${^{39}\hbox {Ar}}$$ from $${^{40}\hbox {Ar}}$$ by cryogenic distillation with Aria for dark-matter searches

   https://doi.org/10.1140/epjc/s10052-021-09121-9  

   Agnes, P. ; Albergo, S. ; Albuquerque, I. F. M. ; Alexander, T. ; Alici, A. ; Alton, A. K. ; Amaudruz, P. ; Arba, M. ; Arpaia, P. ; Arcelli, S. ; et al ( April 2021 , The European Physical Journal C)

   Aria is a plant hosting a$${350}\,\hbox {m}$$$350\text{m}$cryogenic isotopic distillation column, the tallest ever built, which is being installed in a mine shaft at Carbosulcis S.p.A., Nuraxi-Figus (SU), Italy. Aria is one of the pillars of the argon dark-matter search experimental program, lead by the Global Argon Dark Matter Collaboration. It was designed to reduce the isotopic abundance of$${^{39}\hbox {Ar}}$$${}^{39}\text{Ar}$in argon extracted from underground sources, called Underground Argon (UAr), which is used for dark-matter searches. Indeed,$${^{39}\hbox {Ar}}$$${}^{39}\text{Ar}$is a$$\beta $$$\beta$-emitter of cosmogenic origin, whose activity poses background and pile-up concerns in the detectors. In this paper, we discuss the requirements, design, construction, tests, and projected performance of the plant for the isotopic cryogenic distillation of argon. We also present the successful results of the isotopic cryogenic distillation of nitrogen with a prototype plant.

    

   more » « less
2. A study of events with photoelectric emission in the DarkSide-50 liquid argon Time Projection Chamber

   The DarkSide-50 Collaboration) Agnes, P. ; Albuquerque, I. F. ; Alexander, T. ; Alton, A. K. ; Ave, M. ; Back, H. O. ; Batignani, G. ; Biery, K. ; Bocci, V. ; Bonivento, W. M. ; et al ( July 2021 , ArXivorg)

   null (Ed.)

   Finding unambiguous evidence of dark matter interactions in a particle detector is a main objective of physics research. The liquid argon time projection chamber technique for the detection of Weakly Interacting Massive Particles (WIMP) allows sensitivities down to the so-called neutrino floor for high and low WIMP masses. Based on the successful operation of the DarkSide-50 detector, a new and more sensitive experiment, DarkSide-20k, was designed and is now under construction. A thorough understanding of the DarkSide-50 detector response to events classified as dark matter as well as all other interactions is essential for an optimal design of the new experiment. In this paper, we report on a particular set of events, for which scintillation-ionization signals are observed in association with signals from single or few isolated electrons. We identified and provided an interpretation for two event types in which electrons are produced via photoelectric effect on the cathode electrode and in the bulk liquid. Events with photoelectric emissions are observed in association with most interactions with large energy depositions in the detector. From the measured rate of these events, we determine the photo-ionization probability, or photoelectric quantum efficiency, of tetraphenyl butadiene (TPB) at wavelengths around 128 nm. 

   more » « less
3. The fall, recovery, classification, and initial characterization of the Hamburg, Michigan H4 chondrite

   https://doi.org/10.1111/maps.13584  

   Heck, Philipp R. ; Greer, Jennika ; Boesenberg, Joseph S. ; Bouvier, Audrey ; Caffee, Marc W. ; Cassata, William S. ; Corrigan, Catherine ; Davis, Andrew M. ; Davis, Donald W. ; Fries, Marc ; et al ( October 2020 , Meteoritics & Planetary Science)

   The Hamburg meteorite fell on January 16, 2018, near Hamburg, Michigan, after a fireball event widely observed in the U.S. Midwest and in Ontario, Canada. Several fragments fell onto frozen surfaces of lakes and, thanks to weather radar data, were recovered days after the fall. The studied rock fragments show no or little signs of terrestrial weathering. Here, we present the initial results from an international consortium study to describe the fall, characterize the meteorite, and probe the collision history of Hamburg. About 1 kg of recovered meteorites was initially reported. Petrology, mineral chemistry, trace element and organic chemistry, and O and Cr isotopic compositions are characteristic of H4 chondrites. Cosmic ray exposure ages based on cosmogenic³He,²¹Ne, and³⁸Ar are ~12 Ma, and roughly agree with each other. Noble gas data as well as the cosmogenic¹⁰Be concentration point to a small 40–60 cm diameter meteoroid. An⁴⁰Ar‐³⁹Ar age of 4532 ± 24 Ma indicates no major impact event occurring later in its evolutionary history, consistent with data of other H4 chondrites. Microanalyses of phosphates with LA‐ICPMS give an average Pb‐Pb age of 4549 ± 36 Ma. This is in good agreement with the average SIMS Pb‐Pb phosphate age of 4535.3 ± 9.5 Ma and U‐Pb Concordia age of 4535 ± 10 Ma. The weighted average age of 4541.6 ± 9.5 Ma reflects the metamorphic phosphate crystallization age after parent body formation in the early solar system.

    

   more » « less
4. Modelling white mica pressure‐temperature‐time (P‐T‐t) paths using thermobarometric and 40 Ar/ 39 Ar thermochronologic data

   https://doi.org/10.1111/ter.12381  

   Gonzalez, Joseph P. ; Baldwin, Suzanne L. ( March 2019 , Terra Nova)

   White micas are major rock forming minerals in igneous and metamorphic rocks, and their chemical and isotopic variations can be used to determine pressure, temperature and time (P‐T‐t) histories. We apply⁴⁰Ar/³⁹Ar multi‐diffusion domain modelling to white micas from blueschists blocks in serpentinite matrix mélange from the exhumed Baja California subduction complex. Thermal history models yielded T‐t paths suggesting that⁴⁰Ar* resides within multiple diffusion domains with varying⁴⁰Ar* retentivity. Modelled white mica thermal histories and thermobarometric data were used to forward model continuous P‐T‐t paths. P‐T‐t paths are consistent with previous studies and are interpreted to constrain blueschist block exhumation paths within the Baja accretionary wedge. Our P‐T‐t models use temperature controlled⁴⁰Ar/³⁹Ar step heat data in which argon loss by volume diffusion can be demonstrated, and for which the white mica petrogenesis is known.

    

   more » « less
5. Argon constraints on the early growth of felsic continental crust

   https://doi.org/10.1126/sciadv.aaz6234  

   Guo, Meng ; Korenaga, Jun ( May 2020 , Science Advances)

   null (Ed.)

   The continental crust is a major geochemical reservoir, the evolution of which has shaped the surface environment of Earth. In this study, we present a new model of coupled crust-mantle-atmosphere evolution to constrain the growth of continental crust with atmospheric 40 Ar/ 36 Ar. Our model is the first to combine argon degassing with the thermal evolution of Earth in a self-consistent manner and to incorporate the effect of crustal recycling and reworking using the distributions of crustal formation and surface ages. Our results suggest that the history of argon degassing favors rapid crustal growth during the early Earth. The mass of continental crust, highly enriched in potassium, is estimated to have already reached >80% of the present-day level during the early Archean. The presence of such potassium-rich, likely felsic, crust has important implications for tectonics, surface environment, and the regime of mantle convection in the early Earth. 

   more » « less