Powdered TPB vs TPB Embedded in Plastic Matrix Takeyasu Ito Los Alamos National Laboratory EDM Collaboration Meeting Pasadena, Feb 14-15

2 Light Guides and PMT’s 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) Schematic of light collection / detection Requirements—20 p.e. per event (for particle ID)

3 Number of Photoelectrons N pe : number of photoelectrons N euv : number of extreme ultraviolet photons – N euv = E deposit f prompt / e euv – E deposit = 760keV; e euv = 16 eV – f prompt = 35% for , 9% for  when E=0 kV/cm p, t should be somewhere in between – Using f prompt =9% gives N euv = 4.3x10 3 euv photons  tpb : solid angle subtended by the TPB coating at the location of the n+ 3 He capture event  conv : conversion efficiency of TPB (~0.3 for TPB in plastic matrix) A trap : fraction of the visible photons that meet the condition for the transmission by total internal reflection in the light guide (~ if readout from both edges )  trans : efficiency of the light transport in the light guide  pmt : quantum efficiency of the photocathode of the PMT (~0.15 )

4 Extracting light from both edges of the side walls Need  trans > 30% Operate PMTs at 4K to reduce loss due to thermal breaks (R&D underway) A Possible Geometry (current baseline)

5 Powder TPB vs TPB embedded in plastic matrix LHe N euv  conv ~ 1 LHe N euv  conv ~ 0.3 Note: Powder TPB only possible for the top and bottom walls.

6 Trapping fraction — readout from the ends Light source Light that emitted into these cones is lost (There are two more cones coming out to the side walls that are not shown.)

7 Trapping fraction — tube cc

8 Trapping fraction — light source outside the light guide  c =41.5˚ (n=1.508)  c T(  )

9 Fresnel’s equation

10 Powder TPB vs TPB in Plastic Matrix Powder TPBTPB in Plastic Matrix  conv 10.3 f trap 40%35-50% Area to be covered by PMTs (bottom and top only) 2032 cm cm 2 # of 2” PMT’s11418 # of P.E.s ~123 x  trans ~ 66 x  trans Remarks: TPB in plastic matrix might give us enough PE.s depending on  trans If that is the case, TPB in plastic matrix is more advantageous because of the smaller number of necessary PMTs Both should be tested in the mockup, and also both should be modeled/simulated.

11 Light guide test box

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13 Trapping fraction x transmission efficiency Light source 3 in..5 in m Assuming 1% loss per bounce

14 Trapping fraction x transmission efficiency Light source 1 cm 1.25 m Assuming 1% loss per bounce

15 Trapping fraction x transmission efficiency Light source 0.3 cm 1.25 m Assuming 1% loss per bounce