SU809021A1 - Device for scintillation detector circuit stabilization - Google Patents

Description

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I The invention relates to experimental nuclear physics and radioisotope instrumentation and may be used primarily in radioisotope instruments to control materials and products.

A device is known for stabilizing the transmission coefficient of a differential type scintillation detector, in which a characteristic peak (photo peak) in the spectrum of the detected radiation is used as a reference signal.

The device contains a scintillation detector, crystal and Photomultiplier (), amplifier, dual channel analyzer, differential intensity meter, count rate meter, rectifier.

The principle of operation of the known device is based on the invariance of the instrumental spectrum in the measurement process 13.

It contains no elements that would take into account or correct the deformation of the instrumental spectrum with a change in ambient temperature. When the temperature changes, the shape and parameters of the output pulses of the photomultiplier change, which in turn changes the number of overlaps and leads to deformation and shift of the spectral lines.

Consequently, the disadvantage of the known. the device is the error arising due to the distortion of the instrumental spectrum when the temperature of the surrounding medium changes, i.e. the temperature instability of the path.

Closest to the proposed device is to stabilize the transfer coefficient of an integral type of the collation detector, in which a characteristic peak is used as the information base.

The known device contains a sci-tillade detector consisting of a SCINTILLATION crystal and a photoelectron multiplier (LeU), a linear amplifier, an integral discriminator, an intensimeter and a control high-voltage source, connected to the PMI divider G23.

The disadvantage of the device is the error arising from the distortion of the instrumental spectrum under the action of temperature.

Claims (1)

The object of the invention is to increase the temperature stability of a scintillation detector. The goal is achieved by the fact that the device for stabilizing the path of the unifunction of the field detector, consisting of a scintillation crystal and a photoelectron multiplier (PMT), contains a linear amplifier integral discriminator, an intensifier and a controlled source of high voltage, connected with an PMT divider, connected with an PMT divider, connected with an PMT divider, and an element that provides a high voltage source connected with an EEE divider, which is controlled by a high-voltage voltage divider. with an adjustable time constant, a control circuit of a constant time and load, and an integrator, with the output of the photomultiplier connected to the adjustable load and through a linear device Integral with the input divisor diskriglinatora whose output is connected through a ratemeter with controllable high voltage source and via an integrator to the input of the control circuit time constant photomultiplier load. FIG. 1 shows a block diagram of the proposed device; in fig. 2 epures of currents and voltages. The device contains a PMT scintillation crystal 1, a load 3 with an adjustable time constant, an amplifier 4, an integral discriminator 5, an intensimeter 6, an integrator 7, a load time constant control circuit 8, a control unit of the PMT power 9. The device works as follows. The PMT 2 current pulses are converted to an adjustable load 3 into voltage pulses, the nominal load time constant being chosen longer than the constant scintillation crystal emitting time (lig. 2a) .- After amplification by the linear amplifier 4, the voltage pulses go to the registration channel, as well as the input of the integral stabilizer of the 5 cxeh-M stabilizer, the response threshold of which is set in the photopeak region of the instrumental spectrum. The integral discriminator 5 generates pulses of standard amplitude and a width equal to the width of that portion of the pulses that the co-ora exceeds the trigger threshold of the discriminator Edlfig. 2b). The pulses are then fed to an intensimeter b, the output voltage of which is proportional to the number of pulses at the output of the discriminator 5. This voltage is compared with the reference in the photomultiplier of the PMT 9, and the difference of these voltages is the voltage of the PMT 2 This circuit of the stabilization system is reduced to maintaining a constant number of pulses in the stabilization channel. From the output of the integral discriminator 5, the voltage pulses also go to the input of the integrator 7, the output voltage of which is proportional to the area of the input pulses. This voltage enters the constant load time control circuit 8, where it is compared with the reference one, and the difference of these voltages is a signal for adjusting the constant load time constant 3 of the PMT. This control loop contour maintains a constant pulse width at the output of the PMT. So, for example, if the width of the pulses generated at the output of the photomultiplier is increased (Fig. 2), this will increase the width of the pulses at the output of the integral discriminator 5, and since the first control loop (intensity meter 6, the photomultiplier power supply 9) supports the number of pulses the stabilization channel is constant, then the output voltage of the integrator 7 increases. The difference between the output voltage of the integrator 7 and the reference voltage is converted in the control circuit of a constant load time 8 to a signal that reduces the load time constant C RC (by decreasing R or c). The generated pulses become narrower and the circuit equilibrium is restored. In this case, the number of superimposed pulses does not change, and therefore, the spectrum will not deform. The system works in the same way with a decrease in the width of the output pulses of the photomultiplier, with the only difference that the constant load time increases. The described device reduces the temperature error of the path of the scintillation detector due to the stabilization of the shape of the instrumental spectrum and allows an increase in the operating temperature range by 20-30 ° C without decreasing the Accuracy. Apparatus of the Invention A device for stabilizing a scintillator detector path consisting of a scintillating crystal and a photomultiplier tube (PMT) containing a linear amplifier, an integral discriminator, an intensity meter and a controlled high voltage source connected to a PMT divider, which is connected in order to increase temperature stability, it additionally introduces: a load with an adjustable constant time, a control circuit of a constant load time and an integrator, with output F The EC is connected to a controlled load and through a linear amplifier to the input of an integral discriminator, the output of which is connected to a controlled high-voltage source and through an integrator to the input of a photomultiplier. 58090216. taken into account in the examination of the new-measurable radio radiommuna 1, scintillation methods of the param- eter parameters. M., Ltomizdat, 1963. with 12 rii. Under the editorship of B.V. Rybakova.M., 1961, p. 367. (prototype).