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The Energy Spectrum of Neutrons produced by Cosmic Ray Muons in LVD.

The Energy Spectrum of Neutrons produced by Cosmic Ray Muons in LVD. Детектор большого объема. Гран Сассо, Италия. Assumptions:. The pulses at energy > 10 MeV in the temporal range 0 – 0.25 s after t-muon in counters of d-volume are the neutron energy releases.

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The Energy Spectrum of Neutrons produced by Cosmic Ray Muons in LVD.

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  1. The Energy Spectrum of Neutrons produced by Cosmic Ray Muons in LVD.

  2. Детектор большого объема Гран Сассо, Италия

  3. Assumptions: • The pulses at energy > 10 MeV in the temporal range 0 – 0.25 s after t-muon in counters of d-volume are the neutron energy releases. • These pulses are produced by a single neutron (in correspondence with data on neutron yield from muons a probability for 2 neutrons is 3%). • The neutrons come out from t-column and pass through d-volume are isotropic in 2. • Horizontal gaps between the d-volume counters weekly change the efficiency of a fast neutron detection. • The role of Fe at determination of the spectrum and the flux of fast neutrons is insignificant.

  4. L=7 L=6 L=5 L=4 L=3 L=2 L=1 1 2 3 4 5 6 7 8 9 10 C=1 C=2 C=3 C=4 C=5 d-volume Target column Geometry Вид сверху Вид сбоку Veto-system

  5. T- criterea L=7 L=6 L=5 L=4 L=3 L=2 L=1 1 2 3 4 5 6 7 8 9 10 C=1 C=2 C=3 C=4 C=5 Selection of vertical muons crossing target column а) E50 MeVin counters of L=1 andL=7; b) E>50 MeV L=3 & 4 or L=4 & 5 or L=3 & 5; c) Amount of triggering counterswith E50MeV Ntr 5 D- criterea Selection of neutron events а) Amount of counters in d–volume N4 b)  Ei350MeVin counters of d-volume c) Should be no events with E>100 MeV in counters on the same vertical – to exclude parallel muon crossing d-volume а) in veto counters should be no events withE>100 MeV;

  6. L=7 L=6 L=5 L=4 L=3 L=2 L=1 1 2 3 4 5 6 7 8 9 10 C=1 C=2 C=3 C=4 C=5 40ns Nn Ncount 151640 552

  7. 1 2 3 4 5 6 7 8 9 10

  8. Distribution of neutron stoppings over half column (hc) -a transmittance of the LVD matter for fast neutrons, =0.779 – best fit of the neutron stopping distribution. The half column containing neutron stop is a last one from t-column where a neutron pulse appears. In such a case, at the mean neutron range in LVD matter Ln=12m*0.59=7.1 m the average neutron pass length in hc is lhc=1.8 m.

  9. - the fast neutron detection efficiency The coefficient k2 takes into account the number of operating counters in target column (~54 from 60)

  10. t s 1d 2d 3d 4d 5d 6d 0 1 1.7 2.7 3.7 4.4 5.4 6.4 7.1 8.1 9.1 m Calculations using previous formula.

  11. The neutron flux from the target column surface producing by a vertical muon in target column - the area of the neutron emitting surface of target column = 151640– total amount of vertical muons crossing target column = 5400– total amount of neutrons - the neutron flux from the target column surface, producing by the total flux passing t-c - average number of counters in target column - average number of counters in target column crossing by vertical muons The neutron flux at energy 20< Tn< 450MeV

  12. - the neutron flux from the target column surface, producing by the total flux of muons passing t-c G =63 м2sr – the geometric factor of target column for the total muon flux.

  13. m L=7 L=6 L=5 L=4 L=3 L=2 L=1 L=7 L=6 L=5 L=4 L=3 L=2 L=1 1 2 3 4 5 6 7 8 9 10 C=1 C=2 C=3 C=4 C=5 1 2 3 4 5 6 7 8 9 10 C=1 C=2 C=3 C=4 C=5 n Configurations of data set (variants of choice of t-column)

  14. The spectrum of the detected energy releases

  15. The distributions of the neutron energy releases in SC at fixed Tn. Tn=20 MeV Tn=100 MeV Tn=180 MeV Tn=260 MeV Tn=300 MeV Tn=60 MeV Tn=140 MeV Tn=220 MeV The correspondence between Tn and a neutron energy En in scintillator; Black squares – MonteCarlo simulation at quenching, Red circles – without quenching, Green circles – calculations using the SHIELD code (Nikolay Sobolevskiy)

  16. The differential energy spectrum of neutrons Фn ( Tn ) Фn , m-2 s-1 (10MeV)-1

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