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Discussion: Open physics questions in the liquid nobles. T. Shutt Case Western Reserve University. Why we shouldn’t talk about “quenching”. Lindhard: nuclear recoils give less “electronic” excitation than electron recoils. Not a quenching process
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Discussion:Open physics questions in the liquid nobles. T. Shutt Case Western Reserve University T. Shutt, Fermilab, 5/11/07
Why we shouldn’t talk about “quenching” • Lindhard: nuclear recoils give less “electronic” excitation than electron recoils. • Not a quenching process • Recombination creates one photon from one electron • Also not a quenching • Quenching from exciton-exciton interactions may be present (Hitachi) • In organic liquid scintillators, is a quenching process that loses light for dense tracks (alphas, nuclear recoils). T. Shutt, Fermilab, 5/11/07
Charge and light yield phenomena (figure: N. Smith) zero field Wph-1 more zero recombination recombination less W-1 W0-1 • Recombined ionization gives light. • Most signal is initially ionization. • Nex/Ni - fraction directly into excitons: ~ 10 % Xe, 21% Ar • Recombination is not complete, even at zero field: “escape electrons” • Ni0/Ni - fraction of “escape electrons”: ~ 10% (Case) 0.43 (1 MeV -Doke) Xe, Ar: 26% • Doke: timescale of > ms. (excitons) (Doke - Jpn.J.Appl. Phys. 41 p1538 2002) T. Shutt, Fermilab, 5/11/07
Questions • What is the origin of PSD in noble liquids? • Is is independent of recombination, and if so, how? • Is PSD affected by recombination fluctuations? • What about the recombination timescale? • Is the direct exciton fraction (and escape electron fraction) the same for nuclear recoils and electron recoils? • Is this related to the (nearly complete) field-independence of the charge collection for nuclear recoils? • Do we have a complete energy picture - in Xe? in Ar? (and Ne?) • Is Lindhard correct? Is Hitachi quenching present? • Could the high light yield in Ar possible? • Is the escape electron fraction in zero-field nr measurements ~ 20% in Xe? In Ar? • What can we learn from the gas phase? T. Shutt, Fermilab, 5/11/07