Status of the light signal simulation for ProtoDUNE-DP Anne CHAPPUIS – Isabelle DE BONIS Dual-Phase Photon Detection System Consortium Meeting September 21th 2017 1/23
Introduction 6x6x6m 3 (fjducial) DLAr TPC @CERN The light signal simulation can be divided in 2 distinct parts: Scintillation (production of the photons) Light propagation in the detector This talk focuses on the light propagation simulation: Using pre-calculated maps For 6x6x6m 3 and 3x1x1m 3 detectors 36 PMT s Outline: Light signal in ProtoDUNE-DP 3x1x1m 3 (fjducial) Light map production procedure DLAr TPC @CERN Light map characteristics Examples of map utilization Simulations performed using the LightSim software based on GEANT4 5 PMT s Anne CHAPPUIS, September 21th 2017 ProtoDUNE-DP 2/23
Light Signal in ProtoDUNE-DP Anne CHAPPUIS, September 21th 2017 ProtoDUNE-DP 3/23
Light production in Liquid Argon Charge particle crossing LAr GAr Ionisation Direct excitation e- / ion pair creation e- LAr S1 recombination scintillation photon electron drifted (S1 Signal) toward the anode S1 Signal [ph/5ns] ProtoDUNE-DP Scintillation (S1) photon characteristics: 60 λ = 128nm (E = 9.69eV) 50 S1 signal induced by a 10-GeV muon Isotropic emission Fast contribution to S1 40 Slow contribution to S1 2 contributions with difgerent lifetimes: τ F ast = 6ns 30 τ Slow = 1600ns 20 Simulation based on the NEST approach 10 (arXiv:1106.1613v1) 0 Not detailed here 0 50 100 150 200 250 300 350 400 450 500 Time [ns] Anne CHAPPUIS, September 21th 2017 ProtoDUNE-DP 4/23
Light production in Argon Gas Not recombined electrons are drifted toward the top of the detector. S2 GAr Dual-Phase technology : e - travel through Ar gas. → Production of S2 photons: λ = 128nm (E = 9.69eV) Lifetimes: e- LAr τ F ast = 7ns S1 τ Slow = 3200ns Need to estimate the number of photons emitted toward the PMT array S2 photon production by electroluminescence: Anode From the LEMs during e - amplifj fjcation: 1 3 Main contribution LEMs 1 Need additional work and simulations to be precisely (e - amplifj fjcation) determined 2 2 Between LAr surface and LEMs e - Extraction 3 Between LEMs and anode Grid Simulation: the 3 productions are taken into account via an electroluminescence gain G G = Number of photons produced in GAr / drifted electron For the time being, G is estimated ~300ph/e → Has to be determined more precisely Anne CHAPPUIS, September 21th 2017 ProtoDUNE-DP 5/23
Light propagation simulation : light maps Anne CHAPPUIS, September 21th 2017 ProtoDUNE-DP 6/23
Implementation of the detailed geometry Implementation of all the components that have an impact on the photon trajectories Visualization from LightSim LEM Plates Extraction grid Z Y Field cage X Cathode pipes + supporting structure Ground grid Light collection: 36 TPB-coated PMT s 2 options for the PMT positioning: Non-uniformly spaced (to cover the full fjducial area) Uniformly spaced (more dense confjguration) Anne CHAPPUIS, 18 May 2017 ProtoDUNE-DP 7/23
Light Propagation in ProtoDUNE-DP Propagation of scintillation photons (128nm): Absorption in LAr Rayleigh scattering on LAr molecules Absorption on difgerent detector components (fjeld cage, cathode supporting structure, tank…) λ Rayleigh =200m λ Rayleigh = 55cm (arXiv:1502.04213v2) Problematic: Very large amount of photons (ex: for a 5-GeV muon track, production of 65.10 6 scintillation photons) T racking each scintillation photon takes a lot of time Less than 1% of photons fjnally reach the PMT s The exact knowledge of all the photon tracks is not needed Solution: simulate the tracks only once, and store the useful information in Light Maps Note: these maps describe the photon propagation → Independent from the scintillation parameters Anne CHAPPUIS, 18 May 2017 ProtoDUNE-DP 8/23
Light map production procedure Solution: simulate the tracks only once, and store the useful information in Light Maps For each photon production point in the detector, and each PMT, the map gives: Probability to reach the PMT T ravel time distribution Anne CHAPPUIS, September 21th 2017 ProtoDUNE-DP 9/23
Light map production procedure Solution: simulate the tracks only once, and store the useful information in Light Maps For each photon production point in the detector, and each PMT, the map gives: Probability to reach the PMT T ravel time distribution LAr and GAr volumes are split in voxels voxel Production point Anne CHAPPUIS, September 21th 2017 ProtoDUNE-DP 10/23
Light map production procedure Solution: simulate the tracks only once, and store the useful information in Light Maps For each photon production point in the detector, and each PMT, the map gives: Probability to reach the PMT T ravel time distribution LAr and GAr volumes Generation of N photons in Photons are tracked are split in voxels each voxel across the detector voxel Production point T racking Anne CHAPPUIS, September 21th 2017 ProtoDUNE-DP 11/23
Light map production procedure Solution: simulate the tracks only once, and store the useful information in Light Maps For each photon production point in the detector, and each PMT, the map gives: Probability to reach the PMT T ravel time distribution LAr and GAr volumes Generation of N photons in Photons are tracked are split in voxels each voxel across the detector T ravel time distribution obtained for each PMT Photons reaching PMT21 240 220 200 Entries 1566 Entries 1566 180 160 Mean Mean 40.98 40.98 140 120 100 80 60 40 voxel 20 0 0 50 100 150 200 250 300 350 400 Production point Travel time [ns] T racking T ravel time distribution Anne CHAPPUIS, September 21th 2017 ProtoDUNE-DP 12/23
Light map production procedure Solution: simulate the tracks only once, and store the useful information in Light Maps For each photon production point in the detector, and each PMT, the map gives: Probability to reach the PMT T ravel time distribution LAr and GAr volumes Generation of N photons in Photons are tracked are split in voxels each voxel across the detector T ravel time distribution Extraction of time Light Maps obtained for each PMT distribution parameters Photons reaching PMT21 240 220 200 Entries 1566 Entries 1566 180 160 Mean Mean 40.98 40.98 140 120 100 80 60 40 voxel 20 0 0 50 100 150 200 250 300 350 400 Production point Travel time [ns] T racking T ravel time distribution Anne CHAPPUIS, September 21th 2017 ProtoDUNE-DP 13/23
Light map characteristics Anne CHAPPUIS, September 21th 2017 ProtoDUNE-DP 14/23
ProtoDUNE-DP light map characteristics LAr maps: Large voxels defjnition: 250mmx250mmx250mm Y Z Number of generated photons per voxel: 10 7 over 4π X X GAr maps: Voxel defjnition: 250mmx250mmx5mm Only 1 voxel in Z Number of generated photons per voxel: 5.10 8 over 4π ✔ T o save time, photons are generated in ~1/8 of the detector, then we use the X-Y symmetry of the detector to reconstruct the whole map. → Gain of a factor 8 in the execution time. Propagation parameters in LAr LAr absorption process is not included in the map generation → Will be parametrized when using the maps Anne CHAPPUIS, September 21th 2017 ProtoDUNE-DP 15/23
T ravel time distribution characteristics weight = w 0 = Number of photons reaching the PMT Probability to reach the PMT : Number of generated photons T ravel time distribution shape: strongly depends on the distance to the PMT PMT Grid Z 8 18 24 32 4 12 28 36 7 17 23 31 Photons hitting PMT14 ProtoDUNE-DP 3 11 16 22 27 35 2 10 2 10 15 21 26 34 Photons produced: production ~1m above the cathode pipes 6 14 20 30 point ~2.5m above the cathode pipes 1 9 25 33 5 13 19 29 10 P h otons produced 1m Photons hitting the PMT ProtoDUNE-DP above the cathode pipes 2 10 1 PMT14 PMT17 0 50 100 150 200 250 300 Travel time [ns] 10 → Find a general parametrisation with the minimum number of parameters 1 0 50 100 150 200 250 300 Travel time [ns] Anne CHAPPUIS, September 21th 2017 ProtoDUNE-DP 16/23
T ravel time distribution characteristics The time distribution is reconstructed using a landau fj fjt and 3 parameters: t 0 (the fjrst bin N entries > 0) The MPV and σ of the landau fj fjt Voxels with N entries <50 are not taken into account LAr light maps (ProtoDUNE-DP) Reconstruction for Photons hitting PMT14 100 ProtoDUNE-DP 1200 b) photons generated at ProtoDUNE-DP (-1125, -1375, -2080)mm 1000 80 Mean 0.9387 Mean 0.9387 800 RMS 0.9731 RMS 0.9731 LightSim simulation 60 Reconstructed with Laundau fit χ 2 distribution 600 χ 2 =1.08 40 400 20 200 0 0 0 50 100 150 200 250 0 1 2 3 4 5 6 7 8 9 10 Travel time [ns] χ 2 /DoF 6.2% of voxels with χ 2 > 2.5: Peak at χ 2 <0.4: voxels with a small number of collected photons voxels close to the PMT → Satisfactory in most cases → Finally, 4 parameters are stored in the maps (ROOT TH3 objects) Anne CHAPPUIS, September 21th 2017 ProtoDUNE-DP 17/23
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