NeuLAND - FAIR

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8.1.2. Characterization of Neutron Interactions with the Full-Size Detector After the installation of the fully-equipped NeuLAND, again, a calibration experiment will be performed. The above-mentioned technique of quasi-free scattering of deuteron beams will be applied. Time resolution and efficiency of the full system will be determined, the latter as a function of neutron energy. Using the full detector volume, it allows in addition a detailed study of the event patterns for real one-neutron events. This is an important input for the development of tracking algorithms in order to optimize the recognition capabilities. The measured one-neutron response can be used in order to simulate the response of NeuLAND to multiple neutron events by overlaying several one-neutron hit-patterns, taken from experimental data. This method relies on the superposition principle for hit patterns on the NeuLAND detector. Moreover, NeuLAND will be exposed to real and clearly characterized two-neutron events, using the breakup of tritons as detailed in the following. Tritons provide a clean source of correlated two neutron events, where the intrinsic wave function is known with high precision. Quasifree proton knockout on the tritons with coincident detection of the two protons from the (p,2p) reaction enables us to put strict cuts on the reaction kinematics, in particular the transferred momentum to the removed proton. By requiring a momentum transfer considerable larger than the proton’s Fermi momentum inside the tritons we enhance events where the two neutrons act as spectators in the reaction, and thus keep their original correlations. Using the known n-n scattering length, also finalstate interaction can be taken into account precisely. The n-n relative-energy spectrum can thus be calculated reliably and compared to the observed spectrum. The response of the detector to 2n events is particularly important for low relative energy between the two neutrons, En−n, for which the efficiency drops rapidly. In addition, the incident CM angle of the two neutrons can be determined by the measurement of the angles of the two protons. This measurement will, thus, allow for a detailed check of the simulation procedure for the two neutron response. 8.2. Cosmic Ray Tracking in NeuLAND for Adjustment and Calibration For the internal calibration of NeuLAND before, during and after experiments, tracks from cosmic rays will be used. The hard component of the cosmic ray flux at sea level, mainly muons (97%), has sufficiently high energy (mean energy is 2 GeV) to penetrate the concrete ceiling of the Cave C or the R 3 B Cave, respectively, and to traverse NeuLAND with approximately the speed of light. The expected rates of incident cosmic rays amount to about 1.5 kHz. That enables a full scan of the detector within reasonable time scales. The tracks of muons, as displayed in a GEANT4 simulation in figure 8.4, serve as a good time reference between the traversed submodules. 84
Figure 8.4.: Event display for several muons (cyan lines) traversing NeuLAND. The detector is presented in a side view, simulated using GEANT4. Secondary gamma rays (green) and electrons/positrons (yellow lines) can be seen as well. Within the calibration procedure, the distance of the two hits belonging to one muon track is determined and their relative time difference has to satisfy the condition of a particle traversing with speed of light. A minimization procedure can be applied to match all 3000 submodules of NeuLAND. At the same time, this calibration also allows an energy gain matching. This procedure has been developed for LAND [Lei-93b], and proven very successful. A more detailed description, can be found, e.g., in [Aks-09b] . 85
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FAIR/NUSTAR/R 3 B/TDR NeuLAND Techn
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Germany EMMI and FIAS: Enrico Fiori
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INR Moscow: Alexander Botvina Russi
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Contents Executive Summary 11 1. In
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B.7. MRPC Solution using Glass as C
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Apart from the excellent energy res
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processes in the universe, such as
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decaying into 24 O plus 4 neutrons
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2. Physics Scenarios: Requirements
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e studied at R 3 B at FAIR include
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all theoretical calculations predic
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at the surface of the nucleus. The
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the evolution of fission channels (
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3. Summary of NeuLAND Prototype Res
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counts 70 60 50 40 30 20 10 0 15 15
Page 33 and 34: Figure 3.4.: Shown is the time reso
Page 35 and 36: 4. Monte Carlo Simulations Within t
Page 37 and 38: normalized counts normalized counts
Page 39 and 40: GEANT3 interface. Here, we compare
Page 41 and 42: Counts 1000 900 800 700 600 500 400
Page 43 and 44: counts 5 10 4 10 3 10 2 10 10 LAND
Page 45 and 46: incident neutron fully active detec
Page 47 and 48: investigated. Three values for the
Page 49 and 50: spectrum, absorption length, refrac
Page 51 and 52: Counts 600 500 400 300 200 100 with
Page 53 and 54: Since, as discussed above, several
Page 55 and 56: events 800 600 400 200 0 0 200 400
Page 57 and 58: clusters N 100 50 0 0 500 1000 1500
Page 59 and 60: In the following section we discuss
Page 61 and 62: events 15000 10000 5000 input outpu
Page 63 and 64: events 2000 1500 1000 500 σ = 15 k
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Page 69 and 70: positioning of 50 submodules mounti
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Page 75 and 76: Figure 5.12.: The photo shows the T
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Page 89 and 90: 10. Installation procedure, its Tim
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Page 94 and 95: The timeline for milestone 1 includ
Page 96 and 97: 96 2. Sample Tests Random samples o
Page 98 and 99: PNPI St. Petersburg: G.D. Alkhazov,
Page 100 and 101: HV 1.$ mm 2$ mm 0+$1-2)-2'.%/ 5%4'.
Page 102 and 103: Beamline Be exit window P 6 P 3 P 4
Page 104 and 105: B.3. Design Issues Addressed with 4
Page 106 and 107: Time [ns] Counts 41 40 39 2200 2000
Page 108 and 109: Efficiency 100 80 60 40 20 0 7.5 8
Page 110 and 111: 200 AMeV, Erel = 100 keV emitted %
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Page 116 and 117: [Bot-04] S. Botvina andI.N. Mishust
Page 118 and 119: [Lip-03] C. Lippmann, PhD Thesis, U
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