SU1783456A1 - Radiometer - Google Patents

Description

The invention relates to radiation technology, and in particular to devices for recording ionizing radiation, its threshold radiation. .

Known threshold device for recording ionizing radiation (ed. St., No. 713281, CL G 01 T 1/02. 1978).

The disadvantage of this device is the complexity of the electronic circuit, the high power consumed to generate packs of sinusoidal pulses, the instability of operation depending on the power source.

A device for determining the dose of ionizing radiation containing the element., Forming a time interval; the number of pulses from the detector output is calculated for the analysis interval. The disadvantage of this device is the complexity of the device and the significant time spent on registration.

Closest to the invention in technical essence is a device for determining the dose of ionizing radiation, with the help of which they form a time-varying analysis time interval and count the number of pulses from the output of the detector for the analysis interval. .

The disadvantage of this device is the significant time spent on registration, and the complexity of the device.

The purpose of the invention is to increase the speed of measurements.

An analysis time period is formed in the device and the number of successive periods is calculated when at least one impulse has arrived from the detector during the analysis period. Thus, the entire analysis time period is divided into equal intervals and the achievement of the threshold level of ionizing radiation is judged by the number of intervals during which at least one pulse was received from the detector output.

1783456 A1

The predetermined analysis period is divided with the help of a stabilized generator into equal intervals during which pulses may or may not come from the output of the detector. If the average number of pulses at the detector’s output is large and is 4-5 pulses per interval. then the probability of the absence of at least one impulse is small. Pulse registration processes obey the laws of Random Events. In this case, the calculation of the probability of detecting the threshold of ionizing radiation is defined as the probability of an event during repeated independent tests.

The probability of detecting the threshold Pt is determined by the binomial distribution formula as the product of the probabilities that at least one detector impulse will arrive during the specified’s interval and this state will last for a specified number of intervals: ’’. ”·

Pt = (1st ^ntk ), where η is the average pulse flux at the detector output during the interval:.

k is the number of intervals.

Suppose that over a period of 4 s there are an average of 32 pulses at the detector output ’. They divide a given analysis time, for example, into 5 intervals, each of which’s duration will be 0.8 s. The average pulse repetition rate will be 6 pulses per 1 interval.

The probability that during one interval will not come from the output of the detector, not a single pulse, is defined as

RT ₀ -.-And ..- ag008. ·. /

The probability that at least one impulse arrives is how

RT-1-0.008 0.992. /

The probability that there will be at least one “•” impulse in each of them over 5 intervals is defined as' - / .Pt - 0.992 ^k = 0.992 ⁵ = 0.96.

From the above example, it can be seen that if there are more intervals, the probability of false positives is less. It is also easy to verify that the reliability of detecting the threshold level of radioactive radiation by this device will be no worse than the known one (the rating value for the device. Type ДРС-01 is 0.95).

Thus, it is clear that it is not necessary to count pulses for recording the threshold of ionizing radiation, it is enough to make sure that they are, and how many of them - few or many - does not matter. If on average there are more than 5 pulses. Then after registering this threshold, the duration of the interval between the generator pulses should decrease, for example, by 2 times. If in this case the threshold is registered, the totem will confirm the dose rate in excess of 2 times the originally recorded. Further, the process of reducing the duration of the intervals continues until the circuit is triggered. The process will stop at the dose rate limit value recorded by the radiometer.

In accordance with the law of mathematical statistics, it is unlikely that for several successive intervals in each of them there would be at least one impulse if the average number of impulses is small. This is possible only in the 8th case, if the average number of pulses during the interval is large (5 or more), then you can be sure that at least one pulse will be. If in one of the intervals the pulse does not follow, the calculation of the intervals will start again. Thus, in the proposed device, the threshold value is determined by the number of intervals, each of which had at least one detector pulse. The scheme works on the principle of "Yes-No." This eliminates a significant drawback of the known solution - the bulkiness of the electronic circuit and the need to count the number of pulses. It is very simple in the proposed device to change the accuracy of the threshold registration, it is enough to increase or decrease the number of intervals, and the reliability of the registration will increase or decrease accordingly.

Figure 1 presents the functional diagram of the radiometer; figure 2, is a timing chart explaining its operation.

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

From the output of detector 1 (for example, a Geiger-Muller counter, type SBM-21), short pulses are fed to the first input of trigger 2. Simultaneously, pulses from the output of the quartz generator 5 are fed to the second input of trigger 2 (for example, second pulses of an electronic clock). The pulses from the output of the generator 5 are simultaneously fed to the counter 3 counting intervals. ' calculated for a certain number (5-6 or more, depending on the required accuracy of registration).

The radiometer works as follows. The pulses from the output of detector 1 (Fig. 2a) 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 the generator (Fig. 26) to the first input of trigger 2 at least one 5 impulse arrives from the output of detector 1, the radiometer will be ready to calculate the next impulse from the output of generator 5, trigger 2 will be prepared to pass a new impulse from the output of detector 1. If during the next analysis period there are no T pulses at the output of detector 1 (as is the case between the second and the third pulses of the generator in figa). then the pulse from the output of the generator 5, the counter 3 will be reset to zero and the set of information in it will start again. On figv shows the pulses arriving at the first input of the counter 3. The pulse at the input of the counter 3 is shown on fig.2g, and the pulse received at the input of the indicator 4. shown in fig.2d. The counter 3 is filled with the next pulse from the output of the detector, and thereby reduces the time of registration of the threshold.

To reduce the recording time, the threshold is triggered not by the generator pulses, but by the detector pulses. Due to this, the registration time can be reduced by up to one interval T.

The use of the invention provides a simplification of the device for detecting the threshold of ionizing radiation and reducing analysis time.

Claims (1)

Claim A radiometer comprising a detector, a pulse generator, a counter and an indicator, characterized in that. what. in order to increase the measurement performance, a trigger is inserted into it, connected by the first input to the detector output, the second input to the output of the pulse generator and to the zeroing input of the counter and the output to the counter input of the counter, the output of which is connected to the inputs of the indicator and the pulse generator. Legend: 3 * L 5* Detenter Trigger Interval counter Indicator Pulse generator •? Ig. .1