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تسجيل مستخدم جديدDirect measurement of neutrons induced in lead by cosmic muons at a shallow underground site
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Qiang Du
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Neutron production in lead by cosmic muons has been studied with a Gadolinium doped liquid scintillator detector. The detector was installed next to the Muon-Induced Neutron Indirect Detection EXperiment (MINIDEX), permanently located in the Tubingen shallow underground laboratory where the mean muon energy is approximately 7 GeV. The MINIDEX plastic scintillators were used to tag muons; the neutrons were detected through neutron capture and neutron-induced nuclear recoil signals in the liquid scintillator detector. Results on the rates of observed neutron captures and nuclear recoils are presented and compared to predictions from GEANT4-9.6 and GEANT4-10.3. The predicted rates are significantly too low for bo
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We have measured the muon flux and production rate of muon-induced neutrons at a depth of 611 m water equivalent. Our apparatus comprises three layers of crossed plastic scintillator hodoscopes for tracking the incident cosmic-ray muons and 760 L of
gadolinium-doped liquid scintillator for producing and detecting neutrons. The vertical muon intensity was measured to be $I_{mu} = (5.7 pm 0.6) times 10^{-6}$ cm$^{-2}$s$^{-1}$sr$^{-1}$. The yield of muon-induced neutrons in the liquid scintillator was determined to be $Y_{n} = (1.19 pm 0.08 (stat) pm 0.21 (syst)) times 10^{-4}$ neutrons/($mucdot$g$cdot$cm$^{-2}$). A fit to the recently measured neutron yields at different depths gave a mean muon energy dependence of $leftlangle E_{mu} rightrangle^{0.76 pm 0.03}$ for liquid-scintillator targets.
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ts with MINIDEX (Muon-Induced Neutron Indirect Detection EXperiment) of the production of neutrons by cosmogenic muons in high-Z materials are reported. The setup is located at the T{u}bingen Shallow Underground Laboratory, which provides a vertical shielding depth of (13.2,$pm$,0.8) meter water equivalent at the setup location. Muon-induced neutrons are identified by the detection of 2.2,MeV gammas from their capture on hydrogen with high-purity germanium detectors. The experimental results were compared to Geant4 Monte Carlo predictions. The measured rate of 2.2,MeV neutron capture gammas for lead was found to be in good agreement with the Geant4 predicted rate. For copper the measured rate was found to be a factor of 0.72,$pm$,0.14 lower than the Geant4 predicted rate. An additional simulation was performed using the FLUKA Monte Carlo code. The FLUKA predicted rate of detected 2.2,MeV neutron capture gammas for lead was also found to be in good agreement with the experimental value. A detailed comparison of muon interactions and neutron production in lead for Geant4 and FLUKA revealed large discrepancies in the description of photo-nuclear and muon-nuclear inelastic scattering reactions for muon energies at shallow underground sites. These results suggest that Geant4, when used with Geant4 recommended or standard physics lists, underpredicts the neutron production in photo-nuclear inelastic scattering reactions while at the same time it overpredicts the neutron production in muon-nuclear inelastic scattering reactions.
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