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LENS - The Lattice Architecture Jeff Blackmon (ORNL) on behalf of LENS Collaboration

LENS - The Lattice Architecture Jeff Blackmon (ORNL) on behalf of LENS Collaboration. The Basic LENS Concept. 8% Indium-loaded liquid scintillator (pseudocumene) High light output >8000 h  /MeV Long attenuation length >8m. Crucial breakthrough See next talks. #1 prompt electron

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LENS - The Lattice Architecture Jeff Blackmon (ORNL) on behalf of LENS Collaboration

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  1. LENS - The Lattice ArchitectureJeff Blackmon (ORNL) on behalf of LENS Collaboration The Basic LENS Concept 8% Indium-loaded liquid scintillator (pseudocumene) High light output >8000 h/MeV Long attenuation length >8m Crucial breakthrough See next talks #1 prompt electron  e energy (-like) signal #1 signal #2 Buffer up to 10s Shower Time/space correlation discrimination (~6 m)3 fiducial volume  ~15 tons Indium ~ 500 pp events/yr (50% eff.)  3% measurement in a few years Critical issues: light collection & resolution (space/time)

  2. Longitudinal Design: Classic LENS Typically 3”x3” modules (~5m long) with PMTs on ends Extensive simulations: Russia, VaTech, ORNL End view tposition 30 cm localization along length Energy must be deposited in 2 of 8 neighbors for good discrimination Efficiency ~35%

  3. LENS: The Lattice Architecture Monolith segmented with double-pane nylon & trapped air Cartoon representation (2D) Fresnel reflections n=1.51.0 air In-loaded scintillator Laser demonstration at P~2atm Full 3D segmentation for LENS Nearly perfect “digital” event localization Antireflective coatings can reduce losses

  4. A Tale of Two Sims Two independent modeling efforts with somewhat different approaches (1) Track every optical photon Decouple optics from background studies (1) Study pe/MeV yield for each geometry (2) Compare pe/PMT distribution Like “real life” Study optical imperfections Reconstruction & trigger development (2) Background studies: E(x)  Fast

  5. Impose 2 very simple cuts 40.4% 7.8/ton/yr 0.24% Radius Cascade vs. 2 background (5”x6m)3 • Light output lower than expected • 708 pe/MeV (VaTech = 950 pe/MeV)  Cascade Cascade 

  6. LENS Design Figures of Merit Signal and Background in LENS Christian Grieb, Virginia Tech, October 2006 • Excellent agreement with efficiency & background rate (geometric) • Still looking at difference in light: 708 pe/MeV vs. 950 pe/MeV

  7. The “Hard Lattice” No trapped air Easier construction More robust Most photons “channeled” crit~60 Good event localization Less trapping Greater light output Solid Teflon Segmentation Challenges: How to deal with “spray”? Background rate Trigger logic

  8. Dark current Each  decay fires ~150 PMT’s (5”) Total decay rate ~4MHz (6m)3 1% of PMTs fire every ~250 ns ~20 decays between  and cascade Events All PMTs Must reject dark current Simple threshold? More elaborate solution? PMTs with > 2pe Events Number of PMTs firing

  9. Effect of threshold on cascade All pe’s • Total light output > 2x that w/ air gaps • Only 1 pe detected by ~276 PMT’s • Introduce threshold at varying levels Cascade  >2 pe/PMT Cascade  • Threshold hurts energy resolution • Light output still better than air gap

  10. Impose the same 2 cuts 52% 0.48% Double-foil 40% & 0.24% Hard lattice results

  11. 39% 0.35% Towards a better analysis • With the most simple cuts, hard lattice performance is worse … … but the jury is still out • We’re currently investigating a larger parameter space pe1/pesum pe1/pesum • More sophisticated approaches: • Maximum likelihood • Neural network algorithm

  12. Optical imperfections • Fine segmentation  treatment of optical properties is very important GEANT4 Optics 4 Types of reflection at boundary • Specular spike • About average surface normal • Specular lobe • About normal of micofacet • Diffuse lobe • Lambertian “diffuse” scattering • Backscatter spike • About average surface normal • Little data on optical properties for detector materials • Measurements needed • Parameterized simulations

  13. Lambertian scattering in “air gap” specular 1% diffuse 5% diffuse 10% diffuse • Total pe’s not significantly affected • Increasing diffuseness rapidly spreads the pe’s • Reconstruction difficult • “Dark current” problem similar to the “hard lattice” all pe’s >2pe/PMT

  14. Same results ~40% ~0.3% Cascade What if we impose >2pe/PMT threshold?  Similar results are possible Cascade  Low light yield is more problematic for single  5% Lambertian in “air gap” Same analysis assuming  all pe

  15. Scintillation Lattice Hard Lattice Double-layer nylon lattice Solid teflon segmentation Longitudinal Design Summary The LENS concept is robust 3 viable detector designs Modular approach Best potential performance Most straightforward construction Benchmarking simulations to lab data Prototyping Optical properties important

  16. (100 keV) 0.036 % (200 keV) 0.190 % (300 keV) 0.423 % Bremsstrahlung Beta decay rate = 19 kHz/m3 P(E>40keV) = 0.00270 51 Hz/m3 (BS) (400 keV) 0.71 % (450 keV) Fold with Pfeiffer E spectrum 0.88 %   (500 keV) 1.03 %

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