RU2228580C1 - Switch-mode power system for betatron incorporating magnetic circuit demagnetization provision - Google Patents

Abstract

FIELD: acceleration engineering; generation of high-energy electron beams. SUBSTANCE: betatron power system characterized in that demagnetizing current is independent of radiation pulse repetition frequency has storage capacitor 4 connected through branch circuits of thyristors 5 and 6 using current inverter circuit arrangement to windings 2 and 3 interconnected in series opposition; compensating winding 3 incorporates diode 7 in its circuit. High-voltage dc power supply 8 is parallel-connected through diode 9 and switching choke coil 10 to capacitor 11. The latter is connected through thyristor 12 to diode 7 and winding 3, the latter and diode 7 being shorted out by diode 13. Low-voltage dc power supply 14 is parallel-connected to choke coil 15 and field winding 2. One plate of correcting capacitor 16 is connected through correcting-circuit thyristor 17 to common point of diodes 7, 13. Same plate is connected through variable resistor 18 to common point of high-voltage dc power supply 8 and diode 9. Other plate of capacitor 16 is connected through resistor 19 to common point of field winding 2, compensating winding 3, and low-voltage power supply 14. Same winding is connected to common point of high-voltage dc power supply 8 and choke coil 10. EFFECT: reduced size and mass, simplified design, enhanced reliability of system. 1 cl, 4 dwg

Description

The invention relates to the field of accelerator technology and is intended to generate high-energy electron beams for the subsequent use of accelerated electron energy for defectoscopy, cancer treatment, etc.

Known pulse power supply system of a betatron with demagnetization of the magnetic circuit (BRM) [Kasyanov V.A., Furman E.G., Chakhlov V.L., Chertov A.S. Pulse power supply system of an induction accelerator. RF patent for the invention No. 2187912], selected as a prototype, containing an electromagnet with a magnetic circuit, with an excitation winding and with a compensation winding laid on a solid central core of the magnetic circuit, a high-voltage DC power supply, a correction capacitor, a correction circuit thyristor, a capacitive storage device connected according to the current inverter circuit to excitation and compensation windings connected in series and counterclockwise, in the circuit of which a diode is connected, a low-voltage constant power supply a current connected in parallel to the inductor and the field winding, a switching inductor, a capacitor that is connected via a thyristor to the diode and the compensation winding, which is additionally shunted by the diode with the diode.

This pulsed power system uses three power sources: the first is a high-voltage DC power supply that provides the charge of a correction capacitor; the second is a low-voltage direct current power supply providing demagnetization of the magnetic circuit of the electromagnet BRM; the third is a power source that provides a capacitor charge in the energy input circuit and demagnetization of the magnetic circuit of the BRM electromagnet.

The use of three power sources leads to an increase in weight and size parameters and complicates the design of the pulse power supply system BRM.

In addition, in this pulse BRM power supply system, the demagnetization of the magnetic circuit of the BRM electromagnet is carried out by the sum of the demagnetization currents. The first demagnetization current I _p1 flows through the circuit: the power supply 8 - switching inductor 9 - field winding 2 - capacitor 10. The second demagnetization current I _p2 flows through the circuit: low voltage DC 15 power supply - inductor 16 - field winding [Kasyanov V. A., Furman E.G., Chakhlov V.L., Chertov A.S. Pulse power system of induction accelerator. RF patent for the invention No. 2187912].

The value of the first demagnetization current can be approximately determined from the expression

where C ₁₀ is the capacitance of the capacitor 10 [F]; T is the pulse repetition period [s], U _C10 is the voltage to which the capacitor 10 [V] is charged beyond T; f is the pulse repetition rate [Hz].

As can be seen from (1), the current value I _p1 depends on the pulse repetition rate f.

For the purposes of intraoperative radiation therapy, a repeated-short-term mode of operation of the betatron is required [Chakhlov V.L., Chertov A.S. Betatron with magnetization and with the extraction of an electron beam // Proceedings of the VII International Scientific and Practical Conference of students, graduate students and young scientists "Modern Techniques and Technologies". Sat reports. Tomsk: TPU Publishing House, 2001 - S.206-209]. Windings of an electromagnet BRM, designed to operate in intermittent mode, to increase the technical and economic effect of the demagnetization of the magnetic circuit of an electromagnet [Chertov A.S. Betatron with demagnetization of the magnetic circuit. Abstract of dissertation for the degree of candidate of technical sciences, Tomsk, 2002], are calculated on the current density in copper more than 10 A / mm ² . At such current densities in copper, BRM, as practice shows, can work no more than 5 minutes, and the break should be more than 1 hour [Chertov A.S. The results of measuring the focal spot and thermal tests of a betatron with sequentially counter-switching the excitation and compensation windings // Transactions of the VIII International Scientific and Practical Conference of Students, Graduate Students and Young Scientists “Modern Techniques and Technologies”. Sat reports. Volume 1. Tomsk: Publishing house of TPU, 2002. - S.100-102]. 5 minutes is usually not enough to tune the BRM to maximum radiation. To increase the setup time of the BRM for maximum radiation, it will be necessary to reduce the frequency of the radiation pulses. From (1) it follows that with decreasing f, the current I _p1 will decrease, this circumstance will lead to a decrease in the total demagnetization current (I _p1 + I _p2 ) and, consequently, to a decrease in the kinetic energy of accelerated electrons. In order to compensate for the decrease in the value of the total demagnetization current, it is necessary to increase the current value I _p2 . Further, after tuning the BRM to the maximum radiation, when switching to the desired pulse repetition rate, the current values I _p2 will have to be changed again. From the foregoing, it follows that the dependence of the demagnetization current on the repetition rate of the radiation pulses f will lead to difficulties in tuning the BRM to the maximum radiation intended for operation in intermittent mode.

The objective of the invention is to eliminate the dependence of the demagnetization current on the repetition rate of the radiation pulses, reduce weight and size parameters, simplify the design and increase the reliability of the pulse power system of the betatron with the demagnetization of the magnetic circuit.

The task is achieved by the fact that in a pulse power supply system of a betatron with demagnetization of a magnetic circuit containing an electromagnet with a magnetic circuit, with an excitation winding and with a compensation winding laid on a solid central core of the magnetic circuit, a high-voltage DC power supply, correction capacitor, correction circuit thyristor, capacitive storage connected according to the current inverter circuit to excitation and compensation windings connected in series and counterclockwise, in the circuit of which a diode, a low-voltage DC power supply connected in parallel to the inductor and the field winding, a switching inductor, a capacitor that is connected via a thyristor to the diode and the compensation winding, which is additionally shunted by the diode with the diode, according to the invention, the high-voltage direct current power supply is connected in parallel to the capacitor through a diode and a switching inductor, and a correction capacitor is connected in parallel to the diode and the compensation winding through a resistor and a thyristor circuit correction, and the high-voltage DC power supply is connected in parallel to the correction capacitor and a variable resistor.

With this design of the BRM pulse power system, instead of three power sources, two will be used, which, accordingly, will lead to a decrease in weight and size parameters, to simplify the design and increase the reliability of the BRM pulse power system. In this case, there will be no dependence of the demagnetization current on the repetition rate of the radiation pulses, which will simplify the tuning of the BRM, designed to operate in intermittent mode, to maximum radiation.

Figure 1 shows the BRM electromagnetic system, where the dotted line shows the position of the vacuum accelerator chamber in the interpolar space.

Figure 2 shows a schematic diagram of a pulse power supply system BRM.

Figure 3 shows plots of changes in voltage, currents, magnetic induction, the radius of the equilibrium orbit in the working gap of the electromagnet and magnetomotive forces in the pulse power supply system BRM, where the numbers indicate:

20 - voltage change on the excitation winding 2;

21 - change in magnetic induction in the reverse magnetic circuit of the magnetic circuit 1 of the BRM electromagnet;

22 - voltage change on the correction capacitor 16;

23 - voltage change across the capacitor 11;

24 - change in magnetic induction in the equilibrium orbit of the electromagnet BRM;

25 - change in magnetic induction in the Central core of the magnetic circuit 1 of the electromagnet BRM;

26 - voltage change on the compensation winding 3;

27 - voltage change on the capacitive storage 4;

28 - change in current correction capacitor 16;

29 - change in the magnetomotive force of the field winding 2;

30 - change in the magnetomotive force of the compensation winding 3;

31 - change in the radius of the equilibrium orbit.

Figure 4 shows the limit hysteresis loop 32 of the ferromagnetic material of the central core of the magnetic core 1 of the BRM electromagnet.

The BRM electromagnetic system (Fig. 1) contains a BRM solenoid 1, an excitation winding 2, a compensation winding 3 laid on a continuous central core of the BRM solenoid 1.

The pulse power supply system BRM (figure 2), includes the magnetic circuit 1 of the BRM electromagnet, the excitation winding 2, the compensation winding 3, laid on the solid central core of the magnetic circuit 1 of the BRM electromagnet. Capacitive storage 4 through the branches of thyristors 5 and 6, assembled according to the current inverter circuit, is connected to windings 2 and 3 connected in series and opposite, and diode 7 is connected in the compensation winding circuit 3. High-voltage DC power supply 8 is connected in parallel through diode 9 and switching the inductor 10 to the capacitor 11. The capacitor 11 is connected through a thyristor 12 to the diode 7 and the winding 3, and the winding 3 and the diode 7 are shunted by the diode 13. A low-voltage DC power supply 14 is connected in parallel to the inductor 15 and the winding 2 in zbuzhdeniya. One plate of the correction capacitor 16 through the thyristor 17 of the correction circuit is connected to the common point of connection of the diodes 7, 13. The same plate through the variable resistor 18 is connected to the common point of the connection of the high-voltage DC power supply 8 and diode 9. Another plate of the capacitor 16 is connected through the resistor 19 to the common point of connection of the field winding 2, compensation winding 3 and low-voltage power supply 14. The same plate is connected to the common point of connection of the high-voltage power supply 8 constantly on the current and the switching inductor 10.

Consider the operation of the pulse power supply system BRM in figure 2.

In the initial state, the capacitive storage 4 is charged to a voltage of U ₁ (figure 3, curve 27). From a low-voltage DC power supply 14, a direct current I _p flows through the inductor 15 along the field winding 2, which sets the magnetic state of the magnetic circuit 1 of the BRM electromagnet.

By time t _{1, the} magnetic state of the magnetic circuit is determined by the magnetomotive force of the field winding 2 (Fig. 3, curve 29) and is characterized by the initial value of magnetic induction - B _{c max} (Fig. 4, curve 32, point 1) in the central core of the magnetic circuit 1 and the initial the value of magnetic induction - B _OM in the reverse magnetic circuit of the magnetic circuit 1, while the initial value of the magnetic induction in the equilibrium orbit is close to zero (figure 3, curves 21, 24, 25).

At time t ₁ with the arrival of control pulses to the thyristors 5 or 6, the capacitive storage 4 begins to discharge to the windings 2 and 3 connected in series and counterclockwise (Fig. 3, curve 27). Magnetic fluxes are created in the region of the equilibrium orbit, in the central core of the magnetic circuit 1 and in the reverse magnetic circuit of the magnetic circuit 1.

At time t _{1, the} thyristor 17 of the correction circuit and the correction capacitor 16, charged to the required voltage U ₀ (Fig. 3, curve 22) through the variable resistor 18 from the high-voltage DC power supply 8, are also turned on and begins to discharge to the winding 2 through the resistor 19 and capacitive storage 4. The discharge current of the capacitor 16 (Fig. 3, curve 28) is directed in accordance with the current of the winding 2, and its magnetomotive force increases, which causes the appearance of additional magnetic flux through the central core of the magnetic circuit 1 in the interval le time t ₁ -t _2, initial compression is compensated equilibrium orbit caused by the nonlinearity of the hysteresis loop at the initial stage of magnetization reversal (Figure 4, curve 32, section 1-2). The radius of the equilibrium orbit in this time interval is changed from the initial value to the design _he r r _op (Figure 3, curve 31). By changing the resistance of the resistor 18, it is possible to widely control the position of the radius of the equilibrium orbit at the moment of injection of t _i electrons into the vacuum accelerator chamber, thereby optimizing the capture of electrons in acceleration.

At time t ₂ , when the magnetization reversal of the ferromagnetic material of the central core of the magnetic circuit 1 begins along the linear section of the limit hysteresis loop (Fig. 4, curve 32, section 2-3), the discharge current of the correction capacitor 16 drops to zero (Fig. 3, curve 28 ), the thyristor 17 is turned off and in the future (up to time t ₃ ), the betatron ratio 2: 1 is fulfilled at the calculated radius of the equilibrium orbit r _op (Fig. 3, curve 32) is completely implemented due to the selected ratio of windings 2 and 3.

At time t _{3, the} thyristor 12 is turned on and connects the capacitor 11, charged to voltage U ₂ through the diode 9 and the inductor 10 from the high-voltage DC power supply 8, to the diode 7. The discharge current of the capacitor 11 is directed counter to the current of the compensation winding 3. Winding current 3 begins to decrease, and the current of the field winding 2 passes into the circuit of the capacitor 11 and the thyristor 12.

During the time interval t ₃ ÷ t ₅ , energy is introduced from the capacitor 11 into the oscillating circuit to compensate for the energy losses in it during the acceleration cycle t _y , and the current of the winding 3 drops to zero. When the winding 3 is de-energized (time interval t ₃ ÷ t ₅ ) due to an increase in the difference in the magnetomotive forces of the windings 2, 3 (Fig. 3, curves 29, 30), the magnetic flux in the central core of the magnetic circuit increases, the radius of the equilibrium orbit increases (Fig. 3 , curve 31). At time t ₄ , when the radius of the equilibrium orbit reaches the injector installation radius r _i , electrons are dumped onto an external target. Further de-energization of the winding 3 leads to saturation of the central core of the magnetic circuit (Fig. 4, curve 32, point 4). When the capacitor 11 is completely discharged (time t ₅ ), the diode 13 is turned on, the thyristor 12 is de-energized and turned off, and the capacitor 11 begins to be charged from the high-voltage DC power supply 8 through the diode 9 and the inductor 10.

By time t _{4, the} magnetic state of the magnetic circuit is characterized by a finite value of magnetic induction in the central core of the magnetic circuit + B _s.k. and a final value of magnetic induction in the reverse magnetic circuit + B _s.m.k (Fig. 3, curves 21, 25).

Magnetic induction in the region of the equilibrium orbit during the acceleration process t _y at the radius of the equilibrium orbit r _op varies from approximately 0 to the final value + V _o.r.k. (Fig. 3, curve 24).

By the time t ₆ , when the current of the winding 2 drops to the value of the saturation current, determined by the magnetomotive force of the field winding 2, the central core of the magnetic circuit goes out of saturation and in the time interval t ₆ ÷ t _{7 is} demagnetized again to its initial state - B _{c max} (Fig. 4, curve 32, section 4-5-6-1).

At time t _7, thyristors 5 or 6 are turned off and the magnetic state of the central core of the magnetic circuit is determined by the current I _p flowing through winding 2, and the cycle of operation of the pulse power supply system of the BRM has ended.

Thus, in the considered BRM pulse power system, instead of three power sources, only two are used, which makes the proposed BRM pulse power system simpler and more reliable and reduces its overall dimensions. In this case, the dependence of the demagnetization current on the repetition rate of the radiation pulses is excluded, which makes it possible to simplify the tuning of the BRM, designed to operate in intermittent mode, to maximum radiation. And the connection of the thyristor 17 of the correction circuit to the common point of connection of the diodes 13 and 7 allows you to reduce the reverse voltage on it by the value of the open circuit voltage of the compensation winding 3, which, accordingly, reduces the cost of the correction circuit of the radius of the equilibrium orbit in comparison with the correction circuit proposed in [Kasyanov V.A., Furman E.G., Chakhlov V.L., Chertov A.S. Pulse power system of induction accelerator. RF patent for the invention No. 2187912].

Claims (1)

A Betatron pulse power supply system with demagnetization of the magnetic circuit, containing an electromagnet with a magnetic circuit, with an excitation winding and with a compensation winding laid on the solid central core of the magnetic circuit, a high-voltage DC power supply, a correction capacitor, a correction circuit thyristor, and a capacitive storage connected to the current inverter circuit to the excitation and compensation windings connected in series and counterclockwise, in the circuit of which a diode is connected, a low-voltage power supply a constant current, parallel connected to the inductor and the field winding, a switching inductor, a capacitor that is connected through a thyristor to a diode and a compensation winding, which is additionally shunted by a diode with a diode, characterized in that the high-voltage DC power supply is connected in parallel to the capacitor through the diode and the switching the inductor, and the correction capacitor is connected in parallel to the diode and the compensation winding, through the resistor and thyristor of the correction circuit, and the high-voltage source DC power is connected in parallel to a correction capacitor and a variable resistor.

Images