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Powdered TPB vs TPB Embedded in Plastic Matrix. Takeyasu Ito Los Alamos National Laboratory EDM Collaboration Meeting Pasadena, Feb 14-15. Light Guides and PMT’s. Requirements—20 p.e. per event (for particle ID). Schematic of light collection / detection.  conv : conversion efficiency.

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Powdered tpb vs tpb embedded in plastic matrix

Powdered TPBvsTPB Embedded in Plastic Matrix

Takeyasu Ito

Los Alamos National Laboratory

EDM Collaboration Meeting

Pasadena, Feb 14-15


Light guides and pmt s
Light Guides and PMT’s

  • Requirements—20 p.e. per event (for particle ID)

Schematic of light collection / detection

conv: conversion efficiency

Atrap: trapping efficiency

pmt: quantum efficiency

trans: transport efficiency

PMT

One or more thermal break(s)

Neuv

TPB coating

tpb:Solid angle subtended

by the TPB coating at the

location of the 3He+n reaction

LHe


Number of photoelectrons
Number of Photoelectrons

  • Npe: number of photoelectrons

  • Neuv: number of extreme ultraviolet photons

    • Neuv = Edeposit fprompt / eeuv

    • Edeposit = 760keV; eeuv = 16 eV

    • fprompt = 35% for , 9% for when E=0 kV/cm p, t should be somewhere in between

    • Using fprompt=9% gives Neuv = 4.3x103 euv photons

  • tpb: solid angle subtended by the TPB coating at the location of the n+3He capture event

  • conv: conversion efficiency of TPB (~0.3 for TPB in plastic matrix)

  • Atrap: fraction of the visible photons that meet the condition for the transmission by total internal reflection in the light guide (~0.34-0.50 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 )


A possible geometry current baseline
A Possible Geometry (current baseline)

  • 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)


Powder tpb vs tpb embedded in plastic matrix
Powder TPB vs TPB embedded in plastic matrix

Neuv

Neuv

LHe

LHe

conv ~ 1

conv ~ 0.3

Note: Powder TPB only possible for the top and bottom walls.


Trapping fraction readout from the ends
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.)



Trapping fraction light source outside the light guide
Trapping fraction — light source outside the light guide

c

c=41.5˚

(n=1.508)

T()



Powder tpb vs tpb in plastic matrix
Powder TPB vs TPB in Plastic Matrix

  • 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.



Trapping fraction x transmission efficiency
Trapping fraction x transmission efficiency

3 in.

.5 in.

Light source

1.25 m

Assuming 1% loss per bounce


Trapping fraction x transmission efficiency1
Trapping fraction x transmission efficiency

1 cm

1 cm

Light source

1.25 m

Assuming 1% loss per bounce


Trapping fraction x transmission efficiency2
Trapping fraction x transmission efficiency

0.3 cm

0.3 cm

Light source

1.25 m

Assuming 1% loss per bounce


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