ASU nEDM mtg, Feb 2008E. Beise, U Md 1 Light Guides and PMT’s (from T. Ito slides, Pasadena, Feb 2007) LHe N euv TPB coating  tpb :Solid angle subtended by the TPB coating at the location of the 3 He+n reaction  conv : conversion efficiency A trap : trapping efficiency  trans : transport efficiency  pmt : quantum efficiency PMT One or more thermal break(s) Requirements—20 p.e. per event (for particle ID)

ASU nEDM mtg, Feb 2008E. Beise, U Md 2 Light collection simulation From T. Ito’s slide 3 (Pasadena, Feb 2007) Summary of results from litrani (details to follow): (with 1 thermal break) (assumes perfect surfaces)

ASU nEDM mtg, Feb 2008E. Beise, U Md 3 Acceptance of UV light on Cell walls Where does the UV light go, as a function of (x,y,z) of generation point? For -15 cm < z < 15 cm, side walls see 90% of the light When opposite walls summed, light collection does not depend much on (x,y) location 50 cm 10 cm

ASU nEDM mtg, Feb 2008E. Beise, U Md 4 Adiabatic Guides attached to lucite cell downstreamupstream 100K photons (400 nm) generated into 2  from surface of sidewall downstream accepted = upstream accepted = total = 25% Josh Rehak, U Md 1/22/2008 if perfect optical coupling between guide and detector bend radius = 15 cm

ASU nEDM mtg, Feb 2008E. Beise, U Md 5 Adiabatic Guides attached to lucite cell downstreamupstream 100K photons (400 nm) generated into 2  from surface of sidewall downstream accepted = 8694 upstream accepted = 6832 total = 15.5% Josh Rehak, U Md /22/2008 with (1  m) air gap between detector and guide bend radius = 15 cm

ASU nEDM mtg, Feb 2008E. Beise, U Md 6 Rectangular Guides vs Adiabatic Guides >300 shapes per adiabatic guide Very complicated to rotate into place in simulation Use much simpler rectangular guides for majority of tests and then scale 100K photons generated (uniformly into 4  ) along a single wall no other side walls are in optical contact, no endcaps 100K thrownupstream (200 cm)downstream (100 cm) rectangular adiabatic (w/ air gap between guide & det) bend radius = 15 cmbulk absorption length = 450 cm

ASU nEDM mtg, Feb 2008E. Beise, U Md 7 How much is lost in endcaps? For side walls = 50 cm, (lucite) endcaps = 1.27 cm and optically coupled to side walls (but no emission from ends)  15% reduction in accepted light detector

ASU nEDM mtg, Feb 2008E. Beise, U Md 8 Where does the (blue) light go? 100K photons generated along each wall (400K total) (1) lucite side walls (1.27 cm) in optical contact, lucite endcaps optically connected to side walls. A single pair of (rectangular) guides sees (with air gap between guide and detectors) 7600 photons from own wall 2400 from each adjacent wall 1000 from opposite wall = 3.3% total (also, 3% lost into the two endcaps) (2) 8 lightguides,  total collected = 13.5%(3.3% per detector pair) (no losses/bounce or surface roughness yet included)

ASU nEDM mtg, Feb 2008E. Beise, U Md 9 Estimated Surface Losses (H.Breuer) Cast surface absorption:.. 0.2% Machined surface abs.: …. 2.0% Bulk attenuation length: 450 cm Reflections: cm: every 1.5 thickness cm: every 2.2 thickn. Light guides: - ¼ inch thick - 2 strips 2.5 cm wide - 4 strips 5.0 cm wide Coated wall: 10cm x 50 cm, one piece Reflection survival: 100 cm guide: cm guide: guide: 0.47 ( bulk attenuation: 0.60 already included in earlier slides) Components of attenuation: guide (cm): Cast surfaces: cm machined: cm machined:

ASU nEDM mtg, Feb 2008E. Beise, U Md 10 Losses: 1 vs. 2 light guides (H.Breuer) 2 light guides ( cm) survival: {0.231} 1 light guide (100 cm + reflector) survival: {0.328} … 15% overall improvement {42% for replaced 200cm} due to shorter path length much fewer surface reflections Using: -100 cm light guide + (100 cm +50 cm wall piece) -5% reflector loss -Assuming wavelength shifter coating acts like a cast surface (99.8 reflectivity, very iffy!) Needs MC and test verification.