Inputs (table below display portion of the spreadsheet):
lambda wavelength, nm (controlled by on-screen slider)
Phi radiant flux, watts (controlled by on-screen slider)
flicfac flicker factor (0-1) (controlled by on-screen slider)
Kmax Max. Klam
LamMax Max. wavelength
block 1=on 0=off
k number of stages
V total applied voltage, volts (controlled by
on-screen slider)
Klam quantum efficiency at lambda
Ec cathode work function, Joule
eta collection efficiency
excess excess noise current, amps
RL Load resistance, ohms (controlled by on-screen
pop-up menu)
t integration time, sec (controlled by on-screen
pop-up menu)
Tr Temperature (K) of load resistor
Tc Temperature (K) of photocathode (controlled by
on-screen slider)
Ac Area of photocathode, cm2
C thermionic constant
Calculated quantities:
freq =(2.998E+17)/lambda Hz
E =(6.6261E-34)*freq Joule
Flux =Phi/E electrons/sec
Klam =Kmax*exp(-((lambda-LamMax)/thresh*3.5)^2) quantum efficiency at lambda
Vd =V/k voltage per dynode, volts
m =g^k multiplication factor
rcp =Klam*Flux*block photoelectron emission rate
rt =ict/1.602E-19 cathode thermionic emission rate
Rlam =(Klam*1.602E-19)/E radiant cathode responsivity (amps/watt)
g =0.17*Vd^0.7 gain per stage
ic =rcp*1.602E-19*block cathode photocurrent
ia =eta*m*Rlam*Phi*block anode photocurrent
ict =C*Ac*Tc*Tc*exp(-Ec/(Tc*1.3805E-23)) cathode thermionic current
iat =ict*m*eta anode thermionic (dark) current
Es =RL*(ia+iat) signal voltage
alpha =1/(g-1)~ secondary emission factor
deltaf =1/(2*t)~ noise bandwidth, Hz
sigmai =sqrt(2*1.602E-19*(1+alpha)*m*ia*deltaf) photosignal shot noise current
sigmat =sqrt(2*1.602E-19*(1+alpha)*m*iat*deltaf) thermionic shot noise current
sigmad =sqrt(sigmat^2+excess^2) total dark noise current
sigma =sqrt(sigmad^2+sigmai^2) total shot noise current
sigmaJ =sqrt(4*1.38E-23*Tr*RL*deltaf) Johnson noise voltage
sigman =sqrt((RL*sigma)^2+sigmaJ^2+sigmaf^2) total noise voltage
sigmav =RL*sigma total shot noise voltage
sigmaf =flicfac*(Es-iat*RL) flicker noise voltage (displayed)
SNR =ia*RL/sigman signal-to-noise ratio (displayed)
sigmadt =sqrt((RL*sigmad)^2+sigmaJ^2) total dark noise voltage (displayed)
thresh =6.626E-34*29980000000*10000000/Ec long wavelength threshold, nm
Display script (DC System):
Signal Voltage=Es+sigman*2*(rand()-rand()+rand()-rand()+rand()-rand())
Noise Voltage = sigman
SNR = SNR
flicker noise = sigmaf
photon noise = sigmai*RL
dark noise = sigmadt
Sheet script:
on recalc
if ia > .001
put "Anode current exceeds 1 mA maximum;
phototube may be damaged by excessive current." into B1
else put " " into B1
end if
if ic > .000001
put "Cathode current exceeds 1 ľA maximum;
phototube may exhibit fatigue." into B2
else put " " into B2
end if
if lambda > thresh
put 0 into block
else put 1 into block
end if
end recalc
on idle
put count+2 into count
if count = 10
recalc range H2
if signal > 10
put 10 into H4
else put signal into H4
end if
put 0 into count
end if
end idle