Transistor Simulator of a Betatron
Abstract Generated abstract
A transistorized simulator is described for testing and adjusting optimizers of betatron gamma-radiation intensity without using the accelerator itself. The device reproduces the dependence of radiation intensity on the electron injection phase by deriving timed pulses from the line-voltage waveform, shaping them with one-shot multivibrators, integrating and differentiating circuits, an adder, and a transistor gate synchronized with the simulated electron dumping pulse. The resulting artificial radiation pulse has an amplitude corresponding to the modeled operating point on the intensity characteristic, allowing oscilloscope observation of the curve, marking of the operating point, and examination of optimizer search and stabilization behavior, including with added instability to imitate changes in the real system.
Full Text
TRANSISTOR SIMULATOR OF A BETATRON
V. M. RAZIN, V. P. SHERSTOBITOV
(Presented by the scientific seminar of the Faculty of Automation and Computer Engineering)
For adjusting optimizers of the gamma-radiation intensity of a betatron, it is convenient to use a device simulating its operation. The radiation occurs in the form of short pulses of 2–3 μsec. The dependence of the gamma-radiation intensity \(J\) on the phase (the time of injection of electrons into the accelerating chamber) has the form shown in Fig. 1.
The radiation pulses follow the injection pulses with a delay equal to the amount necessary for accelerating the electrons.
Below, one version of a simulator built with transistors is described.
The operating principle of the simulator is explained by the block diagram in Fig. 2.
The line voltage, coinciding in shape with the variation of the field in the electromagnet of the betatron, is applied to the step-down transformer Tr and then to the limiting amplifier LO. By the leading edge of a positive rectangular voltage, the one-shot multivibrator \(M_1\) is triggered, which forms a pulse with a duration equal to the time interval between the injection pulse and the radiation pulse (the pulse for dumping the accelerated electrons from the orbit). By the trailing edge of this pulse, the one-shot multivibrator \(M_2\) is triggered, which forms
Fig. 1. Dependence of the gamma-radiation intensity on the phase of injection of electrons into the accelerating chamber of the betatron.
Fig. 2. Block diagram of the betatron simulator.
a pulse with a duration equal to the width of the characteristic \(J=f(T)\). Then the positive pulse from \(M_2\) is fed to the integrating circuit IC, and the negative pulse to the differentiating circuit DC. The resulting positive pulses from the outputs of these circuits are added by the adder \(\Sigma\). The summed curve has a form similar to the dependence in Fig. 1.
The voltage from the adder is fed to the transistor gate \(K\), which is opened by a short pulse from the blocking oscillator BO, coinciding in phase with the pulse by which the electrons are dumped from the equilibrium orbit in the betatron. This pulse can be formed in the circuit of the gamma-radiation intensity optimizer.
At the output of the gate there appears a pulse with a duration equal to the duration of the pulse from the BO and with an amplitude corresponding to the voltage at that instant at the adder. The gate pulse is then amplified by the amplifier \(U\) and is fed as a radiation pulse to the optimizer.
The formation of the dependence \(J=f(T)\) is explained by Fig. 3. Here the negative pulse from the differentiating circuit can be used as a sync pulse for starting the sweep of the oscilloscope. The voltage from the adder is applied to the vertical plates of this oscilloscope, which makes it possible to observe the indicated curve. In addition, one can obtain a mark of the position of the operating point on the curve and trace the nature of the search for, and maintenance of, the maximum of the function by the optimizer. It is also possible to introduce elements of instability imitating changes in the real dependence \(J=f(T)\). The circuit for generating an artificial radiation pulse is shown in Fig. 4.
Fig. 3. Formation of the curve \(J=f(T)\).
Fig. 4. Circuit for obtaining artificial radiation pulses.
Transistor \(T_1\), in the normal state in the absence of an input signal, is in the open state (the operating point is set at the boundary between the active region and the saturation region). A voltage from the adder is applied to the base of the transistor through the resistance \(R_1\). The negative pulse from the differentiating circuit in this case practically does not change the voltage at the collector of \(T_1\), while the positive summed voltage is repeated with opposite polarity. The elements of the stage on \(T_1\) must be calculated so that the operating point is not displaced into the cutoff region. The voltage at \(T_1\) is used as the source of collector voltage for the stage on transistor \(T_2\), which is in the normally closed state and performs the role of a gate. At the appropriate instant of time \(T_2\) is opened when a negative pulse is applied to the base, and the voltage at its collector decreases to zero. The resistance \(R_4\) is made sufficiently large so that ...
place the attenuation of the effect of the opening of \(T_2\) on the stage with transistor \(T_1\). At the collector of \(T_2\) a voltage is formed in the shape of the curve \(J=f(T)\), with a notch that can be observed on the oscilloscope screen as a mark of the position of the operating point. The resulting short positive pulse with an amplitude equal to the notch is filtered by means of the circuit \(C R_6\) and diode \(D\) and is fed to the power amplifier and into the optimizer circuit. The circuit \(C R_6\) and the diode make it possible to close the simulator output for the voltage simulating the dependence of the intensity of the betatron gamma radiation on the injection phase. The simulator is convenient when setting up optimizers and observing their operation, since during this time it eliminates the need for contact directly with the object being regulated—the betatron.