MARS MUONS RATE AND MUOGENIC NEUTRON PRODUCTION

Transcription

1 MARS MUONS RATE AND MUOGENIC NEUTRON PRODUCTION Belkis Cabrera-Palmer, For Jason Nattress. May 18, 2015 Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy s National Nuclear Security Administration under contract DE- AC04-94AL85000.

2 Taks 1: Muon rate vs overburden verification We have been assuming a given overburden for each of the KURF locations. But we have the ability of verifying the overburden based on the expected muon rate. For that, we can simulate the expected muon rate for this configuration of muon paddles, using the mine profile and David s muon generator, and compare the simulation results with the measured muon rates.

3 Muon rate vs overburden verification For our 7 muons paddles, comparing the rate of coincident events for all (or some): muon paddles pairs: R[i][j] : 21 combinations, 42 permutations (permutations identify angular direction, if timing allows) muon paddles triplets R[i][j][k]: 35 combinations, 210 permutations muon paddle quartets R[i][j][k][l]: 35 combinations. 840 permutations

4 Muon rate vs overburden verification So, look for events with N coincident muon paddles, N=(2,3,4), within a muon time window of about 10ns (~3m/3E8m/s). As suggested by Pete, it will be interesting to extract also the detector spectra due to the energy deposition of the traversing muons. This can provide another detector calibration. The traversing muon would deposit energy in the scintillator detector mainly by de/dx ionization, but muon spallation and muon-initiated cascades in the lead and the scintillator are also possible. For the case of muon de/dx ionization only, the signal is: N coincident vetoes (10ns window) and one large coincident prompt signal (~200MeV at 2MeV/cm if horizontally traversing the scintillator). These type of events can be easily simulated with the existing G4 code. The case of muon spallation or muon-initiated cascades also depositing energies will be studied next.

5 Task 2: Muogenic neutron production Muogenic neutron production in lead and scintillator from muon tagged events. The overlap in the muon veto system allows horizontal through-going muons to be tagged for the lead and scintillator separately. At the deeper depths there probably aren t a lot of these events, but we plan on running above ground for several weeks. We will analyze data and run simulations corresponding to KURF level 2 and above ground locations. Above ground runs started on April 23, with one week interruption on April 28, and currently still running.

6 Muogenic neutron production μ - Traversing muon produces one or several fast neutrons in the lead via: Muon spallation (μ->n,n) Muon elastic scattering Photo-nuclear reactions (γ-> N,n) associated with electromagnetic showers Spallation of muon-initiated cascade particles (π -, π, π +, p, n) We will only study muons traversing the lead, and thus coincident in all four side horizontal veto paddles.

7 Muons interacting in lead: μ - Those fast neutrons can interact in the lead via (n,kn), producing a multiplicity of ~1MeV neutrons (checked by previous simulations). time Look for events with: The 4 indicated vetoes coincident within a 10ns window Followed by 3 or more detector capture events, with time of each detector event to its second previous < 65us A background for these type of events is a muon traversing the detector in coincidence with its own fast neutrons previously produced in the rock.

8 Muons interacting in lead: μ - A muon-induced fast neutron can also interact the scintillator producing a prompt large signal in one detector, thermalize, and produce the Gd capture signal (in the same detector?) Look for events with: The 4 indicated vetoes coincident within a 10ns window and a coincident prompt detector signal Followed by 1 detector capture event time A background for these type of events is a muon traversing the detector in coincidence with its own fast neutrons previously produced in the rock.

9 Muogenic neutron production The rate of all of the above cases will be directly extracted from simulation and compared to the data. Simulation will illustrate which kind of events are more significant, or which events we have missed. For example, one muon could frequently create more than one fast neutron, affecting our estimates of neutron yield per muon. Muons traversing only the scintillator can also be studied. We will start with the existing Geant 4 code. A simpler detector configuration could be built in both FLUKA and Geant4 to compare their prediction of neutron production for these detector at the studied depths.

10 Where to start? -1 You will interact a lot with Caleb, who wrote most of the analysis and the simulation: For level 2, 6 and probably 14, Caleb has already calculated several corrections that have to be applied to the data. Gain correction in particular might change with time, so it has to be computed for aboveground data. Caleb will probably do it since he needs that for his own analysis. We need to check if Caleb s pre-processed data (with all corrections applied) contains the type of events we are interested in. If yes, we just need to get those pre-processed files from Caleb. If no, then we have to adapt the code to extract those events.

11 Where to start? - 2 In parallel, we should run G4 simulations of muon spectral flux at the various KURF levels 2, 6,14, and above ground. The various model components already exist: Detector model KURF sectional profile Generator for the muon input spectrum given a sectional profile Simulation might need to be adapted according to quantity of interest. Also, detector response features will have to be included in the simulation analysis, like energy calibration. Caleb has done this.

12 Where to start? - 3 Analysis of pre-processed and simulation data to compare the quantities of interest: Task 1: muon rate of all veto groups Task 1: detector spectra of events in coincidence with veto events of each veto groups Task 2: muon rate and detector spectra for the selected event types and side horizontal veto paddles Task 2: estimate the average neutron production in lead