Space Charge Effects at DUNE FD from Cosmics and Ar-39 Michael Mooney Colorado State University DUNE Calibration Task Force Meeting October 24 th , 2017 1
Introduction Introduction ♦ Space charge effects are big at ProtoDUNEs – up to 20 (60) cm spatial distortions for SP (DP), at 500 V/cm ♦ But what about for DUNE FD? Expect to be small, but how small? Present studies with simulation in these slides ♦ Topics like these discussed in ProtoDUNE DRA meetings • Thursdays at 8 am CT – please join the conversation! Toy MC Calibration (ProtoDUNE-SP): 10000 Isotropic Muons with no MCS 2
Some Numbers Some Numbers ♦ Start with some simple calculations ♦ Expected cosmic rate at DUNE FD (one 10 kt module): • If on surface: O(30000)/second (projection from μBooNE) • On 4850L: O(4000)/day → O(0.01)/second ♦ Space charge scales with cosmic rate, and is roughly three million times less bad than if on surface. Negligible! • Effect highly stochastic/local (unlikely to impact ν events) ♦ What about contribution from Ar-39? • Assume 1 Bq/kg → ten million decays/second in DUNE FD • Roughly 1.0 × 10 -12 C/m 3 /s vs. 2.0 × 10 -10 C/m 3 /s from cosmics on surface → small, but might not be negligible ♦ Study SCE sim. using prediction of space charge from Ar-39 3
SCE for DUNE SP FD SCE for DUNE SP FD ♦ DUNE SP FD – looking at one half of central Z slice • APA+CPA+APA ♦ E field distortions on order of 0.1% – very small! • Impact on dQ/dx from recombination ~ 0.03% 4
SCE for DUNE SP FD (cont.) SCE for DUNE SP FD (cont.) ♦ DUNE SP FD – looking at one half of central Z slice • APA+CPA+APA ♦ Spatial distortions on order of 1.0-1.5 mm – very small! • Total impact on dQ/dx (including recomb.) < 0.1% 5
SCE for DUNE DP FD SCE for DUNE DP FD ♦ DUNE DP FD – looking at full detector, central Z slice • Ionization drift is to the left (anode on left, cathode on right) ♦ E field distortions on order of 1% – larger than for SP case • Impact on dQ/dx from recombination ~ 0.3% 6
SCE for DUNE DP FD SCE for DUNE DP FD ♦ DUNE DP FD – looking at full detector, central Z slice • Ionization drift is to the left (anode on left, cathode on right) ♦ Spatial distortions on order of 5 cm – not negligible! • Total impact on dQ/dx (including recomb.) ~ 2-3% 7
Putting Ar-39 To Use? Putting Ar-39 To Use? ♦ While the main contributor for SCE, can use Ar-39 as calibration source at DUNE FD – O(100,000)/event • e.g. electron lifetime measurement (Ar-39 uniform in x direction) • CSU undergraduate, Alex Flesher, and Mike M. studying this with MicroBooNE data (preliminary report later this week) ♦ Ar-42 for higher energy calib.? ~100 μBq/kg, O(10)/event Ar-39 Ar-42 Ar-39 DUNE DP FD DUNE DUNE SP FD SP FD 8
Summary Summary ♦ Space charge at DUNE FDs dominated by Ar-39 decays ♦ SCE in SP DUNE FD negligible ♦ SCE in DP DUNE FD not negligible and likely needs calibration to pin down dQ/dx to 2% or below ♦ Can we use Ar-39 (and Ar-42) as a calibration source at the DUNE FDs? 9
BACKUP SLIDES 10 10 10 10
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