Direct measurement of neutrons induced in lead by cosmic muons at a shallow underground site

Du, Qikui; Abt, I.; Empl, A.; Gooch, C.; Kneißl, R.; Lin, Shou-De; Majorovits, B.; Palermo, M.; Schulz, O.; Wang, Liang; Yue, Qian; Zsigmond, Anna Julia

doi:10.1016/j.astropartphys.2018.04.005

Cited by 8 publications

(10 citation statements)

References 30 publications

(34 reference statements)

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“…The neutron yield predicted by GEANT4 for muon induced interactions in a low-A target, as organic liquid scintillator, was found to agree with the experimental results from KamLAND within 10% [22]. As for neutron production in high-A materials, the recent work of [23,24] reports that GEANT4 under-estimates it by a factor of 3-4 in Pb for cosmic muons at shallow depth ( E µ =7 GeV). However, [21] shows that GEANT4 slightly over-estimates the neutron production in Pb in a deep underground laboratory ( E µ = 260 GeV) by 25% and that the choice of the physics list has a < 5% impact.…”

Section: Monte Carlo Implementationsupporting

confidence: 56%

Virtual depth by active background suppression: revisiting the cosmic muon induced background of Gerda Phase II

2018

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In-situ production of radioisotopes by cosmic muon interactions may generate a non-negligible background for deep underground rare event searches. Previous Monte Carlo studies for the Gerda experiment at Lngs identified the delayed decays of 77 Ge and its metastable state 77m Ge as dominant cosmogenic background in the search for neutrinoless double beta decay of 76 Ge. This might limit the sensitivity of next generation experiments aiming for increased 76 Ge mass at background-free conditions and thereby define a minimum depth requirement. A re-evaluation of the 77(m) Ge background for the Gerda experiment has been carried out by a set of Monte Carlo simulations. The obtained 77(m) Ge production rate is (0.21±0.01) nuclei/(kg·year). After application of state-of-the-art active background suppression techniques and simple delayed coincidence cuts this corresponds to a background contribution of (2.7 ± 0.3) × 10 −6 cts/(keV·kg·year). The suppression achieved by this strategy equals an effective muon flux reduction of more than one order of magnitude. This virtual depth increase opens the way for next generation rare event searches.

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Section: Monte Carlo Implementationsupporting

confidence: 56%

Virtual depth by active background suppression: revisiting the cosmic muon induced background of Gerda Phase II

2018

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“…When considering the matching between simulation and underground neutron flux data, it is important to note that it was recently reported that GEANT4 simulations underpredicted the flux of (μ, n) neutrons [28] in a laboratory with just 13 m.w.e. rock overburden.…”

Section: B Comparison Of Data and Simulationmentioning

confidence: 99%

“…Other work, for example, concentrates on thermal neutrons [22,23], shows only one [24] to three energy bins [25] or a limited energy range [26], or does not present a deconvoluted neutron energy spectrum [27]. It was reported that the flux of muon-induced neutrons seems to be underpredicted by GEANT4 Monte Carlo simulations with the standard physics list [28], whereas FLUKA simulations seemed to fare better [29].…”

Section: Introductionmentioning

confidence: 99%

Neutron flux and spectrum in the Dresden Felsenkeller underground facility studied by moderated He3 counters

et al. 2020

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Ambient neutrons may cause significant background for underground experiments. Therefore, it is necessary to investigate their flux and energy spectrum in order to devise a proper shielding. Here, two sets of altogether ten moderated 3 He neutron counters are used for a detailed study of the ambient neutron background in tunnel IV of the Felsenkeller facility, underground below 45 m of rock in Dresden/Germany. One of the moderators is lined with lead and thus sensitive to neutrons of energies higher than 10 MeV. For each 3 He counter moderator assembly, the energy-dependent neutron sensitivity was calculated with the FLUKA code. The count rates of the ten detectors were then fitted with the MAXED and GRAVEL packages. As a result, both the neutron energy spectrum from 10 −9 to 300 MeV and the flux integrated over the same energy range were determined experimentally. The data show that at a given depth, both the flux and the spectrum vary significantly depending on local conditions. Energy-integrated fluxes of (0.61 AE 0.05), (1.96 AE 0.15), and ð4.6 AE 0.4Þ × 10 −4 cm −2 s −1 , respectively, are measured for three sites within Felsenkeller tunnel IV which have similar muon flux but different shielding wall configurations. The integrated neutron flux data and the obtained spectra for the three sites are matched reasonably well by FLUKA Monte Carlo calculations that are based on the known muon flux and composition of the measurement room walls.

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“…The muon data developed here will be used in forthcoming work [32] addressing the recent debate on muoninduced neutrons underground [33]. In addition, it will be instrumental for designing an active veto for underground nuclear astrophysics experiments planned in Felsenkeller tunnels VIII and IX [25].…”

Section: Introductionmentioning

confidence: 99%

The muon intensity in the Felsenkeller shallow underground laboratory

Ludwig

Wagner

Al-Abdullah

et al. 2019

Astroparticle Physics

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The muon intensity and angular distribution in the shallow-underground laboratory Felsenkeller in Dresden, Germany have been studied using a portable muon detector based on the close cathode chamber design. Data has been taken at four positions in Felsenkeller tunnels VIII and IX, where a new 5 MV underground ion accelerator is being installed, and in addition at four positions in Felsenkeller tunnel IV, which hosts a low-radioactivity counting facility. At each of the eight positions studied, seven different orientations of the detector were used to compile a map of the upper hemisphere with 0.85 • angular resolution. The muon intensity is found to be suppressed by a factor of 40 due to the 45 m thick rock overburden, corresponding to 140 meters water equivalent. The angular data are matched by two different simulations taking into account the known geodetic features of the terrain: First, simply by determining the cutoff energy using the projected slant depth in rock and the known muon energy spectrum, and second, in a Geant4 simulation propagating the muons through a column of rock equal to the known slant depth. The present data are instrumental for studying muon-induced effects at these depths and also in the planning of an active veto for accelerator-based underground nuclear astrophysics experiments. [34,35] that such a veto may reduce the observed background in γ-detectors typical for in-beam nuclear astrophysics experiments to a level that is close to the background in the same detectors deep underground, underlining the importance of a proper muon veto.This work is organized as follows. The underground site is described in sec. 2. Section 3 introduces the experimental setup, including the REGARD muon telescope used here, and experimental procedures. The data analysis and results are presented in sec. 4. The data are then matched, first, by a calculation based on the known rangeenergy relation, and second, by a Monte Carlo simulation using the Geant4 framework (sec. 5). A discussion is offered in sec. 6. The conclusions, a summary and an outlook are given in sec. 7. Description of the underground site studiedThe shallow-underground site Felsenkeller is located in the Plauenscher Grund district, inside the city of Dresden, Germany. The site extends along the Weißeritz river, a tributary of the Elbe, and was used as a quarry until the 18th century, then converted to a brewery, which in turn closed in 1991. The terrain is characterized by a steep cliff that runs from Northeast to Southwest, an approximately flat high plain at 200 m a.s.l. and a river floodplain at 140 m a.s.l. (Fig. 1).Nine horizontal storage tunnels were dug into the rock from 1856 to 1859. All nine tunnels have horizontal access and are interconnected in a comb-like structure (Fig. 2). The site is protected from cosmic rays by an overburden of 45 m of hornblende monzonite rock, part of the "Meißner Massiv" formation. The density of rock samples taken from the tunnels VIII and IX was here found to be (2.69±0.06) g/cm 3 . The hornblende mon...

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Direct measurement of neutrons induced in lead by cosmic muons at a shallow underground site

Cited by 8 publications

References 30 publications

Virtual depth by active background suppression: revisiting the cosmic muon induced background of Gerda Phase II

Virtual depth by active background suppression: revisiting the cosmic muon induced background of Gerda Phase II

Neutron flux and spectrum in the Dresden Felsenkeller underground facility studied by moderated He3 counters

The muon intensity in the Felsenkeller shallow underground laboratory

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