NeuLAND - FAIR

More documents

Recommendations

Info

Figure 4.12.: Displayed is a side view of NeuLAND together with the interaction of one incoming neutron at 1000 MeV. In blue we see the track of the incoming neutron from the left hand side. After interaction in one of the first layers, one fast proton is traversing part of the detector (red), while the neutron is scattered. Several other neutrons with short tracks and gammas (in green) are visible. The display was created using GEANT4. 4.5.1. One-Neutron Response Regarding first the key quantity, the detection efficiency, the advantage of a fully-active detector over a converter-based one, manifests itself predominantly at lower neutron energies, see section 4.2 and table 4.3 as well. For the final detector design, simulated here, we find a value of 90% efficiency of 200 MeV neutrons, 94% at 600 and 96% at 1000 MeV, respectively 2 . The submodule multiplicity for 200 MeV neutrons amounts to about 4, for 600 MeV neutrons on average about 14 paddles have a valid entry, and for 1000 MeV per neutron, 25 paddles are involved. 4.5.2. Multi-Neutron Response The following criteria are used in order to identify and resolve multi-neutron events: 1. The number of incident neutrons. It has to be determined as unambiguous as possible. 2. The momentum of each identified neutron. It has to be resolved with good resolution. 2 These values comprise the loss of neutrons due to interactions in air for the distance of 15.5 m between 52 target and detector, an effect of 1 to 2%
Since, as discussed above, several hits in the detector occur per neutron, it is essential to find not only the correct number of neutrons but also to reconstruct their momentum from the first interaction point. In the following we describe the methods developed for the NeuLAND neutron reconstruction, as of today. It turns out that a generalized tracking mechanism alone does not lead to satisfactory results with respect to the multi-neutron identification. Instead, we use a method which combines tracking with calorimetric information in order to resolve multi-neutron events. We first introduce the definition of a valid cluster in Neu- LAND, then detail the calorimetric resolving power and finally, by a combination of both, determine the number of neutrons and their momentum. Clusters Within one event a hit in NeuLAND is defined as a coincident observation of a signal, above threshold, at both ends of a NeuLAND submodule. The hits are sorted time-wise, and then, in a first step, neighbouring hits are identified, starting from the first hit in time. Hits belonging to a cluster are thus defined by certain distance in space (≤ 7.5 cm in x, y and z each) and a certain time difference (≤ 1 ns) to at least one other member of the cluster. After all hits have been assigned to clusters, for each cluster only the first and last hit in time are stored. 3 Again, the clusters are sorted according to their time of the first hit. The first cluster is treated as occurring from a first interaction of an incident neutron. For all following clusters a procedure with kinematical conditions is applied in order to check whether these clusters could stem from elastically scattered neutrons from a prior incident point with an earlier cluster. That takes into account the scattering angle of the particle of the earlier cluster (most likely a proton), which we define from the first and last hits of the cluster. If one of the later clusters fulfills the criteria of an elastic scattering process of the incident neutron, this cluster is eliminated from the further analysis. This procedure is iterated for all clusters until no more correlated secondary clusters can be found. The number of remaining clusters still is substantially higher than the number of incident neutrons and depends on the energy of impinging neutrons. Exemplarily, for 200 MeV neutrons, a mean value of about 2.7 clusters is observed for one-neutron events, at 600 MeV the value increases to about 6.3 and for 1000 MeV we observe on average 10.5 clusters per neutron. In figure 4.13 the number of clusters is displayed for one- to six-neutron events at 600 MeV. The overlap of the number of clusters for the different neutron channels is large. Therefore, in the following we detail the use of the calorimetric properties of NeuLAND for the assignment of proper neutron multiplicities. 3 As special case hits without any neighbour are defined as clusters by themselves. 53
Page 1 and 2: FAIR/NUSTAR/R 3 B/TDR NeuLAND Techn
Page 3 and 4: Germany EMMI and FIAS: Enrico Fiori
Page 5 and 6: INR Moscow: Alexander Botvina Russi
Page 7 and 8: Contents Executive Summary 11 1. In
Page 9: B.7. MRPC Solution using Glass as C
Page 12 and 13: Apart from the excellent energy res
Page 14 and 15: processes in the universe, such as
Page 16 and 17: decaying into 24 O plus 4 neutrons
Page 19 and 20: 2. Physics Scenarios: Requirements
Page 21 and 22: e studied at R 3 B at FAIR include
Page 23 and 24: all theoretical calculations predic
Page 25 and 26: at the surface of the nucleus. The
Page 27 and 28: the evolution of fission channels (
Page 29 and 30: 3. Summary of NeuLAND Prototype Res
Page 31 and 32: 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: Counts 600 500 400 300 200 100 with
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
Page 65 and 66: 5. Technical Specifications and Des
Page 67 and 68: construction, or for subsequent rep
Page 69 and 70: positioning of 50 submodules mounti
Page 71 and 72: Figure 5.6.: Detector frame with fi
Page 73 and 74: 5.4. Peripheral Systems 5.4.1. Read
Page 75 and 76: Figure 5.12.: The photo shows the T
Page 77: 6. Radiation Environment and Safety
Page 81 and 82: 8. Calibration 8.1. Calibration wit
Page 83 and 84: Figure 8.3.: ToF distribution in 10
Page 85: Figure 8.4.: Event display for seve
Page 89 and 90: 10. Installation procedure, its Tim
Page 91: 11. Cost and Funding 11.1. Cost Est
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 %
Page 112 and 113:
B.7. MRPC Solution using Glass as C
Page 114 and 115:
114
Page 116 and 117:
[Bot-04] S. Botvina andI.N. Mishust
Page 118 and 119:
[Lip-03] C. Lippmann, PhD Thesis, U
show all

NeuLAND - FAIR

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?