RU1784931C - Recording method for ionizing radiation threshold - Google Patents

Description

may be, but may not be. If the average pulse frequency at the output of the detector is large and is 4-5 pulses per interval, then the probability of the absence of at least one pulse is small. Pulse registration processes obey the laws of random events. In our case, the calculation of the probability of detecting the threshold of ionizing radiation is defined as the probability of an event during repeated irreplacements

The probability of the detection of the threshold Pt is determined by the binomial distribution formula, as the product of the probability that xi / g would be one detector pulse during a given interval and this state would last for a given number of intervals

Pt (1 - e fiot) K,

where Po is the average pulse flux at the detector output during the interval;

K is the number of intervals.

Consider a specific case. Let us set an example when 32 pulses are present at the output of the detector for a time equal to 4 s. We divide the given analysis time, for example, into 5 intervals, the duration of each of which will be 0.8 s. The average pulse repetition rate will be equal to 6 pulses per 1 interval.

The probability that no pulse will arrive from the detector output during one interval is defined as: 1

RTL

L-48-0.008

The probability that at least one impulse arrives

about

RT 1-0.008 0.992 -

The probability that during five intervals in each of them there will be at least one impulse is defined as:

P 0.992K - 0.9925 0.96

It can be seen from the above example that if there are more intervals, the probability of false positives is less. It is also easy to verify that the reliability of event registration in this way is not worse than the known one (passport value is 0.95).

Thus, it is clear that, in order to register the threshold of ionizing radiation, it is not necessary to count the pulses. It is enough to make sure that they are, and only

fifty

5

0

fifty

5

40

45

50 55

(few or many) does not matter, because a threshold is recorded, and no values are measured.

In accordance with the law of mathematical statistics, it is unlikely that, for several successive intervals, each of them would have at least one impulse. This is only possible if the average number of pulses during the interval is large, then you can be sure that there will be at least one pulse. If, however, there is no pulse in one of the intervals, the counting of intervals will start again. Thus , in the proposed method, the threshold value is determined by the number of intervals, each of which has at least one detector pulse. This eliminates a significant drawback of the known method - the bulkiness of the electronic circuit and the need to count the number of pulses. It is very simple with the proposed method to change the accuracy of registering a threshold1 it is enough to increase or decrease the number of intervals and the reliability of registration will increase or fall accordingly.

On Fig, 1 presents a functional diagram of a radiometer that implements this method; figure 2, a-e - timing diagrams illustrating its operation,

The radiometer contains (Fig. 1) a series-connected detector 1, trigger 2. A counter 3 of the number of intervals and an indicator 4, as well as a pulse generator 5, connected by an input to the output of counter 3 and an output to the second inputs of trigger 2 and counter 3.

From the output of detector 1 (e.g., a Geiger-Muller counter, type SBM-20), short pulses are transmitted to the first input of trigger 2. At the same time, pulses from the output of the quartz generator 5 pulses are sent to the second input of trigger 2 (e.g., second pulses of an electronic clock). The pulses from the output of the generator 5 are simultaneously supplied to the counter 3 intervals, calculated for a certain number (5-6 or more, depending on the required reliability of registration).

The radiometer works as follows.

The pulses from the output of detector 1 (Fig. 2,6) are fed to the first input of trigger 2, the pulses from the output of which go to the first input of counter 3. If during the analysis period T from the output of generator 5 of Fig. 2, the first input of trigger 2 will come at least one pulse from the output of detector 1, the radiometer will be ready to calculate the next pulse from the output of generator 5 and the next pulse from the output of detector 1 will go to counter 4 and fill it by one. The trigger 2 from the output of the generator 5 will be prepared for the passage of new information from the output of the detector 1. If during the next analysis period there are no T pulses at the output of the detector 1 (as is the case between 2 and 3 pulses of the generator in Fig. 2a), then the pulse from the output of the generator 5, the counter 3 will be reset to zero, and the collection of information in it will begin again. In Fig.2, c shows the pulses arriving at the first input of the counter 3. The pulse from the output of the counter 3, arriving at the input of the indicator 4, is shown in Fig.2d. The counter 3 is filled with the next pulse from the output of the detector and thereby reduces the threshold registration time. The indicator signals are shown in fig.2d. To reduce the recording time, the threshold is triggered not by the pulses of the generator, but by the pulses of the detector. Due to this, the registration time can be reduced to one interval.

0

5

0

The use of the invention reduces the analysis time and simplifies the device implementing this method, since it is not the number of pulses from the output of the detector that is calculated, but the number of intervals, 6 of which there was at least one pulse at the output of the detector

Claims (1)

The formula from obobret and A method for detecting an ionizing radiation threshold, which consists in generating an analysis time period and counting the number of pulses from the detector output during the analysis period, characterized in that, in order to reduce the registration time and simplify the implementing equipment, the analysis period is divided into equal intervals, and the threshold of ionizing radiation is judged by the number of intervals during which at least one pulse arrives from the detector output.