# DHC 101 Introduction to scintillation detectors. How many PE/MIP should we expect? Scintillation & Fluorescence WSFWSF PMTPEs  (MIP)

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DHC 101 Introduction to scintillation detectors

How many PE/MIP should we expect? Scintillation & Fluorescence WSFWSF PMTPEs  (MIP)

Energy loss by heavy particles Moderately relativistic charged particles other than electrons lose energy in matter primarily by ionization and atomic excitation The mean rate of energy loss is given by the Bethe-Bloch equation:

Minimum ionizing particles There is a minor dependence on mass at the highest energies, but for all practical purposes in HEP, dE/dx in a material is only a function of . Most relativistic particles (e.g. cosmic ray muons) have mean energy loss rates close to the minimum and are called minimum ionizing particles, better known as MIPs. MIPs

Parameters required to calculate the number of PE/MIP dE/dx for the MIP Density, , of the material Distance particle will traverse Photon yield/energy deposited Transmission to WSF Transmission to PMT

dE/dx for MIP 2

Parameters required to calculate the number of PE/MIP dE/dx for the MIP = 2 Mev*cm 2 /g Density, , of the material Distance particle will traverse Photon yield/energy deposited Transmission to WSF Transmission to PMT

Density of scintillator Plastic scintillator densities range from 1.03 to 1.20 g/cm 3 (Physical Review D, Review of Particle Physics, p.207)

Parameters required to calculate the number of PE/MIP dE/dx for the mip = 2 Mev*cm 2 /g Density, , of the material = 1.11g/cm 3 Distance particle will traverse Photon yield/energy deposited Transmission to WSF Transmission to PMT

Path length in scintillator A particle that traverses perpendicular to the cell’s surface would travel 0.5 cm. So the minimum distance is 0.5 cm 0.5cm 

Parameters required to calculate the number of PE/MIP dE/dx for the mip = 2 Mev*cm 2 /g Density, , of the material = 1.11g/cm 3 Distance particle will traverse = 0.5 cm Photon yield/energy deposited Transmission to WSF Transmission to PMT

Photon yield Typical photon yields are about 1 photon per 100 eV of energy deposited. (Physical Review D, Review of Particle Physics, p.207)

Parameters required to calculate the number of PE/MIP dE/dx for the mip = 2 Mev*cm 2 /g Density, , of the material = 1.11g/cm 3 Distance particle will traverse = 0.5 cm Photon yield/energy deposited = 1 photon/100 eV Transmission to WSF Transmission to PMT

Transmission to WSF Typical transmission to WSF is about 5% Good to within a factor of 2 f(scintillation, fluorescence, reflection and refraction, …) How can we get a better estimate? GEANT?

Parameters required to calculate the number of PE/MIP dE/dx for the MIP = 2 Mev*cm 2 /g Density, , of the material = 1.11g/cm 3 Distance particle will traverse = 0.5 cm Photon yield/energy deposited = 1 photon/100 eV Transmission to WSF = 2.5%-10% Transmission to PMT

Quantum efficiency of PMT One factor that determines the transmission from the WSF to the PMT is the quantum efficiency of the PMT According to the Hamamatsu H6568 data sheet, the PMT’s quantum efficiency for green light (480nm-530nm) ranges from about 6%-18%.

Transmission to PMT Typical transmission through WSF and clear fiber to PMT cathode is about 5% Good to within a factor of 2 f(reflection and refraction, quantum efficiency of photo detector, …) How can we get a better estimate? GEANT?

Parameters required to calculate the number of PE/MIP dE/dx for the MIP = 2 Mev*cm 2 /g Density, , of the material = 1.11g/cm 3 Distance particle will traverse = 0.5 cm Photon yield/energy deposited = 1 photon/100 eV Transmission to WSF = 2.5%-10% Transmission to PMT = 2.5%-10%

Number of PE/MIP 2.5% 5% 10%

Kurt measured 8-19 PE/MIP!!!

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