SU900347A1 - Method of measuring postpulses of photomultiplier tube - Google Patents

Description

(54) METHOD OF MEASUREMENT OF POSTELETUMES OF A PHOTO-ELECTRON MULTIPLE

This invention relates to methods for measuring parameters of photomultipliers.

There is a known method for measuring afterpulses of a photomultiplier using sensitive broadband oscilloscopes 1.

However, in the linear mode of the photomultiplier, the measurement of the afterpulses is difficult, since their amplitude may lie at the limit of sensitivity of modern measuring equipment.

The closest technical solution to this invention is a method for measuring the afterpulses of a photomultiplier, including measuring the amplitude of the main signal at voltages at the photomultiplier corresponding to a given anodic sensitivity 2.

The disadvantage of the known method is that the measurements do not carry quantitative information about the amplitude of the post-pulses, since there is no energy calibration attached to the anode sensitivity or dynamic range that objectively characterizes this amplitude.

The purpose of the invention is to measure the afterpulses of a photomultiplier by eliminating the overload of the measuring channel by the main signal.

It should also be noted that the amplitude of the main signal may differ significantly from the amplitude of the post-pulses.

The goal is achieved by the method of measuring the afterpulses of a photomultiplier, which includes measuring the amplitude of the main signal at voltages on the photomultiplier corresponding to a given anodic sensitivity, is measured by the amplitude of the amplitude characteristic and compared with the amplitude of the main signal the light impulse by neutral absorbers and the amplitude of post-pulses are estimated from the multiplicity of attenuation of which.

The drawing shows a schematic diagram of an installation for measuring the afterpulses of a photomultiplier tube by the proposed method.

The installation contains a photomultiplier 1, a pulsed source of 2 light of picosecond duration, a set of neutral absorbers 3, a load resistance 4 and a broadband oscilloscope 5. The afterpulses of the photomultiplier are measured by the proposed method as follows.

The measured PMT is supplied with a supply voltage corresponding to a predetermined anode sensitivity. The photocathode of the measured photomultiplier 1 is irradiated with pulses of a powerful light source of picosecond duration, such as a quantum generator 2. For example, the power of the light pulse incident on the photocathode can be monitored by observing the light absorbers 3 using a broadband oscilloscope 5. PM afterimpulses separated from the main signal by a certain interval. In this case, the amplitude of the afterpulses should be in the near-linear mode, i.e., be proportional to the multiplicity of the neutral light absorber to control the linearity, while the amplitude of the main Uumaii signal can be in the saturation mode or in the near-saturation mode After the impulse is in a nonlinear region, its change may differ from the multiplicity entered to test the neutral light absorber by a factor of K).

Thus, a PMT mode of operation is created when the amplitude of UH after impulses is sufficient for reliable detection by modern measuring devices, such as a wideband oscilloscope, and the overload of the measuring equipment of signal pulses is eliminated due to a slight difference between the amplitude of the main signal in the saturation mode and after the pulses not yet reached saturation mode. Then the neutral absorbers of light begin to weaken the amplitude of the main signal of the UtahDO UQ Up values. The obtained value of the optical attenuation of the signal, calculated from the known multiplicity of the used neutral light absorbers, is the numerical value characterizing the multiplicity of the amplitude of the signal after the amplitude of the post-pulse. Since a photomultiplier can have several afterpulses that are separated from the main signal at different time intervals, the characteristics of each afterpulse can be expressed by a fractional number, where in the numerator the relative value of the afterpulse characteristic is indicated by the proposed method, and in the denominator, the maximum afterpulse from the front of the main signal is picoseconds or nanoseconds.

The proposed method for assessing the post-pulses of a photomultiplier allows one to organize the control of this parameter in serial photomultipliers, thus eliminating the need for the supply of serial products with the subsequent selection of products.

The technique allows new developments of PMT with the control of this parameter and to conduct objective comparisons of different

PMT among themselves.

Claims (2)

Invention Formula 25 Method for measuring afterpulses of a photoelectric multiplier; including the measurement of the amplitude of the main signal at voltages on a photomultiplier tube corresponding to a given anodic sensitivity, characterized in that 30 in order to quantify the afterpulses of the photomultiplier by eliminating the overload of the measuring channel with the main signal, the afterpulses of the photomultiplier are measured in the linearity mode of the amplitude response and compared with. by the amplitude of the main signal, weakened by a light pulse by neutral absorbers, and by the multiplicity of attenuation of which the amplitude is estimated by the pulse. 40 Sources of Information taken into account during the examination 1. Ronkin g. M. et al. Investigation of the PMT overload mode by the power of light pulses. Sat “Pulsed photometry, 1975, no. 4, s. 185-211.  2. Ronkin J.M. and others. On the occurrence of afterpulses in a photomultiplier. Sat “Impulse photometry, 1978, vol. 5, s. 207-211 (prototype).