Argon Resonance Transmission Interaction Experiment (ARTIE) Luca - - PowerPoint PPT Presentation
Argon Resonance Transmission Interaction Experiment (ARTIE) Luca Pagani 2 nd Dec. 2019 Bay Area DUNE Meeting ARTIE Collaboration UC Davis : R. Svoboda, M. Mulhearn, E. Pantic, J. Wang, L. Pagani, L. J. Pickard, V. Fischer, J. Huang, Y.
2nd Dec. 2019 Bay Area DUNE Meeting
▪ UC Davis: R. Svoboda, M. Mulhearn, E. Pantic, J. Wang, L. Pagani,
▪ Boston University: C. Grant ▪ LIP (Portugal): S. Andringa ▪ LANL: J. Ullmann, M. Mocko
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2 −
10 × 2
2 −
10 × 3
1 −
10 (eV)
n
E 200 400 600 800 1000 1200 1400 (mb) σ
ENDF/B-VIII.0
R.L.D. French et al. (1965)
This work Total error
▪ Leon’s talk: showed we solved discrepancies between measurements from 60s and theoretical prediction ▪ What about at 57 keV?
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▪ ARTIE’s goal is to measure the 57 keV neutron anti-resonance using a liquid argon target. Important for:
– Calibration via a Pulsed Neutron Source which relies on the 57 keV anti-resonance – Energy reconstruction, if neutrons don’t travel far from the vertex – Supernova and solar neutrino physics
▪ One previous experiment did not see the anti-resonance at 57 keV, but may not have been sensitive enough
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Winters et al., 1991
▪ ENDF predictions: ▪ Previous measurements (Winters et al.):
▪ 37 atm target 2.216 m long to give ~0.2 atoms/b ▪ Measured a total cross-section ~0.08 barn @ 57 keV ▪ Difference in transmission coefficients between Winters’ data and ENDF prediction, given T(E) = exp[ -nσ ] is: ▪ T(E,σ=0.0116 b) = exp[-0.211*0.0116] ≃ 99.8% vs. T(E,σ=0.08 b) = exp[-0.211*0.08] ≃ 98.3%
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▪ Uses a 1.68 m long x 1” diameter (≫ beam size) liquid argon (99.99% pure) target with a column density of 3.5 atoms/b: ▪ Kapton windows ends (allows neutron to go thought) flushed with dry gas (avoid ice formation due to air moisture)
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Liquid argon fill & buffer volume Gas argon vent Gas collar Foam insulation Target pipe
▪ Given a column density of 3.5 atoms/b, the target is ~15 times thicker than Winter’s and: ▪ T(E,σ=0.0116 b) = exp[-3.5*0.0116] ≃ 96.0% vs. T(E,σ=0.08 b) = exp[-3.5*0.08] ≃ 75.6% ▪ Difference in the transmission coefficient will be ~19% (very sensitive)
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▪ Optimized tungsten spallation target provides a high peak flux with a broad wavelength bandwidth ▪ Typical beam pulse width is ~125 ns (FWHM). E.g. at 60 meters a 1 keV energy difference is about 150 ns, so about 150 µs across the 10 keV wide resonance – GOOD ENOUGH to see the ”dip” ▪ Typical beam pulse spacing is 50 ms (~20 Hz trigger rate) ▪ 800 MeV proton beam on a cold target viewed by long TOF lines in Flight Path 13 should give adequate flux
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▪ FP-13 configured for making total cross section measurements: uses an evacuated neutron guide (8” pipe ~70m long) + collimator (6mm) ▪ Brass target before target ▪
6Li glass detector
coupled to 2 PMTs as neutron tagging detector to measure TOF
▪ Energy-time correlation: ▪ where: ▪ mc2 is the rest mass of the neutron ▪ T is time of flight ▪ L is the flight path ▪ ΔT is time offset (ideally is 0) ▪ Obtained using Cd (Cd filter present to reduce thermal neutrons), Al (inserted in the beam pipe both for background estimation and energy calibration) and Ar itself resonances
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▪ Moderator adds a time delay that is energy dependent ▪ 2D moderator function is simulated for 10 m flight path using MCNP. It can be scaled to any particular length of flight path. Thanks to LANL folks! ▪ It is an asymmetric function: the median of the moderator response distribution was subtracted from the measured TOF. Then the well-known resonance energies (Cd, Ar, Al) were used to calibrate TOF
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Preliminary
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Ar+Al resonances Preliminary
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Cd resonances Preliminary
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Preliminary Not “perfect” … More work needed!
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▪ If neutron reaction on compensator is negligible, Texp is near exact ▪ Texp coefficient is always smaller than the real value, which means we always measure a higher cross-section ▪ Need to minimize the contributions from non-argon materials (Kapton window, gas flushing collar, air…), or apply a small systematic correction with the help of reference materials
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▪ Black notch resonance method: “place material in the neutron beam that have resonances with large cross sections at specific neutron energies. This allows to remove all the neutrons in the beam at that energy, leaving only the off-energy neutrons and gamma rays to interact with the detector”
http://accapp17.org/wp-content/2017/data/pdfs/158-22827.pdf, (2012)
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▪ Inserted 2” Al but …
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▪ Maybe Ar itself
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NUCLEAR SCIENCE AND ENGINEERING: 172, 268–277, (2012)
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▪ Finalization of energy calibration and relative systematics ▪ Determination of the golden data set ▪ Better understanding of effective columnar density in the target: it is mostly liquid but insulation is not perfect so LAr is boiling off ▪ Precise measurement of boiling off rate and its systematic ▪ Determination of the cross section at 57 keV ▪ Analysis is ongoing … so … stay tuned!