SU1443051A1 - Method of determining gain factor of diode system of photoelectronic multiplier - Google Patents

Abstract

The invention relates to electronic methods of nuclear physics, in particular to experiments requiring the registration of weak light fluxes. The method for determining the gain of the dynode photomultiplier system (PMT) is as follows. The photocathode is illuminated with a pulsed light source, for example, a light emitting diode with a light pulse of a duration of --./10 not. After each flash of light, the charge of the pulse at the PM output is measured. Then, the gain factor of the dynodic system is found according to the formula given in the specification. The method allows to simplify the measurement process and the processing of the measurement results of S pulses at the output of the photomultiplier. 2 ill., 1 tab. (L

Description

4; ii 4

WITH

The invention relates to electronic methods of nuclear physics and can be used in scientific studies using photomultipliers (PMT), including in space physics, accelerator technology, in experiments requiring registration of weak light fluxes.

The aim of the invention is to simplify the method for measuring the gain of a dynode system by first introducing an additional parameter for this type of PMT.

FIG. 1 shows a histogram of the number of photomultiplier on the parameter cG for the PMT-49 in FIG. 2 - plot of the parameter cc | from the voltage supply of the PMT

(.

 The number of photons entering the photocathode N is described by the Poisson distribution:

p (m) e - fViN; e j.

(one)

RP N

(2)

and the process of knocking out p electrons from the photocathode and their focusing on the 1st diode are described by the binomial distribution

P (p) de P KI, q 1-P;

- the focusing coefficient of photoelectrons in the dynode system. Taking into account (1) and (2), P (n, N) is defined as the probability of n photop HqN-.

electrons on the 1st diode when the photocathode is irradiated with an average of N photons

R (n, Yu

(K (1-K) -

Nth

- Fri

(3)

0

five

0

five

0

Thus, the P (n, N) distribution is a Poisson distribution with mean fi N K.

Since the photomultiplier tube (PMT) is a linear transform. the number of photons in charge, then the following effects are valid:

Q n.Q; (4) Q- ii.Q ,. (5) About „n-D, (6)

where D h and D 1 are the dispersions of the distributions of the charges of the pulses Q and Q, measured at the output of the photomultiplier when they enter the dynode system, respectively, n, and one photoelectron.

The distribution of Q is the sum of the distributions of Q t with the weights P (n, N). Therefore, according to the dispersion theorem, the sum of distributions with different. mean values

(n, n) ED, + (n-fi) 2 Q

 IW, + Q (n - n) n (D, + Q,). (7)

Dividing expression (7) by (5) and learning that the gain

Q

e

X

m

we come to the formula M

D

pTr-

dl

Significantly, the magnitude of the same type of photomultipliers varies from photomultiplier to photomultiplier in the insignificant limits (Fig, 1) and is weakly dependent on the voltage of the photomultiplier (Fig. 2). The values of ti, for various types of photomultipliers are given in the table for dividers.

The FEU type of FEU-49 FEU-125 FEU-139 FEU-110 FEU-143-3 di, 0.80 0.82 0.76 0.76 0.74

Since the ratio does not depend

depending on the intensity of the photocathode illumination, the choice of intensity is regulated only by the range of recorded electronics and the need to control the stability of the radiation source is removed. In addition, when working with multi-electron illumination, there is no problem of measuring and identifying small charges, initiated by

controlled by a single photoelectron, which significantly simplifies the procedure of information processing and complies with the level of requirements for electronics.

An example of a method for measuring the gain of the PMT-49B.

The photocathode is illuminated using a pulsed light source, for example, a light emitting diode with a light pulse of approximately 10 ns

and the number of photons N 7 - (where K K,

average quantum yield of the photocathode). After each flash of light, the charge of the pulse at the PM output is measured. Thus, m measurements are repeated, for example, m 10. Then the average charge and the variance of the measured spectrum are calculated, for example, Q 5.0 -10 C;

D 1.0-10 Cl.

These values and the value of c / ,, taken from a table, for example, "0.80, are substituted into a formula to calculate the force factor:

D

one

one

 7,6-10

The proposed method simplifies the process of measuring and processing the results of measuring pulses at the output of the photomultiplier and can be most effectively used to calibrate and control the stability of photomultipliers operating in multi-channel spectrometric installations with a large number of photomultipliers.

Claims (1)

1.B If. Pete -four- 2 kV