University of São Paulo Physics Institute Electroluminescence pulse shape of ReD TPC Argel Sosa Máximo Ave Ivone Albuquerque Nikolas Kemmerich
"Electroluminescence pulse shape and electron diffusion in liquid argon measured in a dual-phase TPC" (Nuclear Inst. and Methods in Physics Research, A 904 (2018) 23–34) The idealized form of the S2 pulse shape assumes that all electrons are extracted out of the liquid at the same time: y ideal ( t ; τ 1 , τ 2 , p , T ) = p · y ′ ideal ( t ; τ 1 , T )+( 1 − p ) · y ′ ideal ( t ; τ 2 , T ) where 0 , if t < 0 ideal ( t ; τ, T ) = 1 y ′ 1 − e − t /τ , if 0 ≤ t ≤ T T e − ( t − T ) /τ − e − t /τ , if t > T
τ 1 and τ 2 are the fast and slow component lifetimes respectively, p is the fast component fraction and T is the transit time of the electrons across the gas pocket. More realistic equation including the diffusion of the cloud of electrons: y ( t ; τ 1 , τ 2 , p , T , σ ) = y ideal ∗ gauss ( 0 , σ ) p · y ′ ( t ; τ 1 , T , σ ) + ( 1 − p ) · y ′ ( t ; τ 2 , T , σ ) = where 1 y ′ ( t ; τ, T , σ ) 2 T ( y ′′ ( t ; τ, σ ) − y ′′ ( t − T ; τ, σ )) = � σ 2 − t τ � � � t − e − t /τ e σ 2 / 2 τ 2 erfc y ′′ ( t ; τ, σ ) = erf √ √ 2 σ 2 στ
Model developed to DS–50 TPC 0.30 DS-50 data amp (arb) DS50 S2 Model 0.25 0.20 0.15 0.10 0.05 0.00 0.0 2.5 5.0 7.5 10.0 12.5 15.0 17.5 20.0 t ( s) Effect of the SiPM single photoelectron response (SPE) on the S2 pulse shape?
0.30 amp (arb) amp (arb) DS-50 data DS-50 data DS50 S2 Model DS50 S2 Model 0.25 SPE Model included SPE Model included 10 1 0.20 0.15 0.10 0.05 10 2 0 2 4 6 8 10 12 14 0 2 4 6 8 10 12 14 t ( s) t ( s) 0.30 amp (arb) amp (arb) ReD data ReD data DS50 S2 Model DS50 S2 Model 0.25 SPE Model included SPE Model included 10 1 0.20 0.15 0.10 0.05 10 2 0 2 4 6 8 10 12 14 0 2 4 6 8 10 12 14 t ( s) t ( s)
The analytical model is complicated by SPE. The fit event by event is computationally expensive. We fixed the parameters [ τ 1 =11 ns, τ 2 =3.45 µ s, p=0.08, σ =0.2] except the transit time (T): amp (arb) ReD data SPE Model T=0.50 s SPE Model T=1.00 s SPE Model T=1.25 s 1 SPE Model T=1.50 s 10 SPE Model T=2.00 s 10 2 0 2 4 6 8 10 12 14 t ( s)
Estimator based on the rise time of the pulse to get the transit time. CDF s] 1.7 1 µ Rise Time [ 1%-20% 1.6 0.8 1.5 0.6 1.4 1.3 0.4 T=0.50 [ µ s] 1.2 µ T=1.00 [ s] T=1.50 [ µ s] 0.2 µ 1.1 T=2.00 [ s] 1 0 0 5 10 0.5 1 1.5 2 2.5 µ µ t [ s] T [ s]
Rise time distribution for run 978 taken the inner and outer channels of the TPC:
Next steps: See dependence between transit time and electroluminiscence field. See dependence between transit time and gas pocket height. Other options? Maybe deconvolution of SPE + DS50 Model fit
DD–Gun + MCP (run 1039) Ch0 - MCP (MCP_Global) Ch1 - MCP (MCP_Xp) Ch2 - MCP (MCP_Xm) ADC ADC ADC 2000 2000 100 0 80 1000 − 60 2000 0 40 − 4000 − 1000 20 − 6000 − 2000 0 − 8000 − − 3000 20 0 200 400 600 800 1000 0 200 400 600 800 1000 0 200 400 600 800 1000 Sa Sa Sa Ch3 - MCP (MCP_Yp) Ch4 - MCP (MCP_Ym) Ch9 - MCP (LSci9) ADC 2000 ADC ADC 2000 8 1000 6 1000 0 4 0 − 1000 2 − 1000 − 2000 0 − 2000 − 3000 − 2 − 3000 − 4000 − 4 − 4000 − 5000 − 6 − − 5000 6000 − 8 0 200 400 600 800 1000 0 200 400 600 800 1000 0 200 400 600 800 1000 Sa Sa Sa
60 2 1 Charge(X+ X- Y+ Y-)/Norm Y 1.8 0.8 50 1.6 0.6 10 2 1.4 0.4 40 1.2 0.2 1 0 30 10 − 0.8 0.2 20 − 0.6 0.4 − 0.4 0.6 10 − 0.2 1 0.8 − 0 1 0 − − 0 0.5 1 1.5 2 1 0.5 0 0.5 1 Charge (Sum)/Norm X
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