20 research outputs found
Erosion rate study at the Allchar deposit (Macedonia) based on radioactive and stable cosmogenic nuclides (26Al, 36Cl, 3He, and 21Ne)
This paper focuses on constraining the erosion rate in the area of the Allchar Sb-As-Tl-Au deposit (Macedonia). It contains the largest known reserves of lorandite (TlAsS2), which is essential for the LORanditeEXperiment (LOREX), aimed at determining the long-term solar neutrino flux. Because the erosion history of the Allchar area is crucial for the success of LOREX, we applied terrestrial in situ cosmogenic nuclides including both radioactive (26Al and 36Cl) and stable (3He and 21Ne) nuclides in quartz, dolomite/calcite, sanidine, and diopside. The obtained results suggest that there is accordance in the values obtained by applying 26Al, 36Cl, and 21Ne for around 85% of the entire sample collection, with resulting erosion rates varying from several tens of m/Ma to ∼165 m/Ma. The samples from four locations (L-8 CD, L1b/R, L1c/R, and L-4/ADR) give erosion rates between 300 and 400 m/Ma. Although these localities reveal remarkably higher values, which may be explained by burial events that occurred in part of Allchar, the erosion rate estimates mostly in the range between 50 and 100 m/Ma. This range further enables us to estimate the vertical erosion rate values for the two main ore bodies Crven Dol and Centralni Deo. We also estimate that the lower and upper limits of average paleo-depths for the ore body Centralni Deo from 4.3 Ma to the present are 250–290 and 750–790 m, respectively, whereas the upper limit of paleo-depth for the ore body Crven Dol over the same geological age is 860 m. The estimated paleo-depth values allow estimating the relative contributions of 205Pb derived from pp-neutrino and fast cosmic-ray muons, respectively, which is an important prerequisite for the LOREX experiment
Energy Resolution Performance of the CMS Electromagnetic Calorimeter
The energy resolution performance of the CMS lead tungstate crystal electromagnetic calorimeter is presented. Measurements were made with an electron beam using a fully equipped supermodule of the calorimeter barrel. Results are given both for electrons incident on the centre of crystals and for electrons distributed uniformly over the calorimeter surface. The electron energy is reconstructed in matrices of 3 times 3 or 5 times 5 crystals centred on the crystal containing the maximum energy. Corrections for variations in the shower containment are applied in the case of uniform incidence. The resolution measured is consistent with the design goals
Lorandite from Allchar, a long-term double detector for pp-neutrinos and fast myons
The Sb-As-Tl-Au deposit at Allchar, providing one of the world-wide largest concentrations of thallium and also numerous other Tl-bearing minerals, may open an outstanding scientific perspective. Allchar belongs to the Serbian –
Macedonian metallogenic province located near the border between Macedonia and Greece. By a long-lasting international research it has been shown that Lorandite from Allchar can serve, together with cogenetic monitor minerals, as a geochemical detector for both, the flux of solar pp-neutrinos, averaged over the geological age of Lorandite, and for the average flux of fast cosmic myons within the same period of time
Geochemical Determination of the Solar pp-Neutrino Flux with LOREX: A Progress Report
LOREX (LORandite EXperiment) is a geochemical experiment addressing the solar (pp) neutrino flux for the period of 4.3 Ma from the reaction 205Tl + ve → 205Pb + e- with an unprecedentedly low threshold (52 keV) for solar pp-neutrino capture. A decisive step for this purpose is getting the precise, background-corrected ratio of 205Pb/205Tl in lorandite (TlAsS2). This report presents the status of major challenges being addressed, in particular the determination of the paleo-depth of lorandite, including the eroded layer over 4.3 Ma, as well as the choice of appropriate techniques for extraction, separation and quantitative determination of the ultra-low 205Pb concentration in the extracted lorandite samples
Geochemical Determination of the pp-Neutrino Flux with 205Tl-LOREX: A Progress Report
Intensive research from the 1970's to 1990's towards geochemical detection of solar neutrinos using
205
Tl,
98
Mo
and
81
Br has left
205
Tl the only viable candidate. LOREX (LORandite EXperiment
) is based on determining the solar
(pp) neutrino flux for the period of 4.3 Ma from the reaction
205
Tl+v
e
→
205
Pb+e
-
,
the lowest threshold (52 keV) for
neutrino capture. The ratio of
205
Pb/
205
Tl in lorandite (TlAsS
2
) depends also on contributions from
fast muon cosmic
radiation. The latter is a function of paleo
-
depth, including the eroded layer over 4.3 Ma, determined using
cosmogenic nuclides (
26
Al,
36
Cl,
3
He and
21
Ne) in the ore body Crven Dol (Tl
-
As
-
Sb
-
S) in Allchar (Macedonia). The
results give a l
ower limit of paleo
-
depth of 490mwe and an upper limit of 2300mwe. From this the ratios
205
Pb
ve
/
205
Pb
tot
are estimated as 2:8 and 6:4, respectively.
Identification
of the
205
Pb nuclei in the lead sample extracted from the lorandite mineral requires 10
-
10
to 10
-
11
overall detection sensitivity for
205
Pb/Pb and comparable suppression of the
205
Tl isobar. This is proposed by full
stripping of
205
Pb at high energy (345MeV/u) at the RIKEN
-
RIBF ion
-
beam facility.
205
Tl isobar separation is already
largely achiev
ed by chemical Pb
-
Tl separation by the overall sample preparation. Samples with a higher
concentration (
205
Tl/natPb=1%)
are necessary
for a guide
-
beam and initial accelerator tuning. A sample with a
considerably lower level of about 10
-
8
is needed for cont
rol of the beam analysis system with
205
Tl ions,
in the
presence ultimately of a lighter guide beam, to limit the
in
-
beam production of
205
Pb by the (p,n) reaction on
205
Tl in
the energy
-
loss and ion
-
stripping steps in the accelerator and the subsequent Bi
gRIPS/Mass
-
Ring experimental
apparatus. The relative cross sections between full stripping of
205
Pb and (p,n) on
205
Tl is estimated as 10
5
. Test
experiments to verify the various aspects of the proposed approach at the RIBF are under preparation