RU2185041C1 - Linear induction accelerator - Google Patents

Abstract

FIELD: acceleration engineering. SUBSTANCE: accelerator used for generating electron and ion beams of nanosecond length with high pulse repetition rate has ferromagnetic induction system in the form of set of ferromagnetic cores with magnetizing turns around them. Electrodes of single shaping line are attached to ends of turns. Electrodes are connected on opposite end to magnetic pulse generator designed to charge shaping line. One of shaping-line electrodes is grounded and open. Magnetic switch in the form of single-turn saturable reactor is inserted in the open circuit. Magnetic pulse generator is, essentially, sequence of circuits set up of capacitors and saturable reactors. Load is proposed to be furnished with shaping line of capacitance lower by two-four times than that of last-circuit capacitor of magnetic pulse generator; magnetic switch characteristics are proposed to be in definite relationship with accelerator components. Charging voltage amplitude of single shaping line is maintained at charging voltage level of C_N. EFFECT: reduced discharge time of single shaping line through load. 1 cl, 1 dwg

Description

 The invention relates to accelerator technology and can be used to generate electron and ion beams of nanosecond duration with a high pulse repetition rate.

 A known device is a linear induction accelerator containing a ferromagnetic induction system in the form of a set of ferromagnetic cores covered by magnetization turns [Bakhrushin Yu.R., Anatsky AI Linear induction accelerators. M .: Atomizdat, 1978]. Electrodes of the forming line are connected to the magnetization coils.

A pulse of a charging voltage, usually of positive polarity, with an amplitude of 30-250 kV, depending on the installation class, is supplied to one of the electrodes of the forming line from the power source. The second electrode is grounded. After switching on the forming line switch installed in the gap of any of the electrodes, the single forming line starts to discharge to the turns of the induction system, forming a current along the magnetization turns of the ferromagnetic cores. This current causes an alternating magnetic flux, creating a vortex electric field that accelerates electrons. The electric field strength along the axis of the induction system is defined as
E (t) = - NU (t) / L,
where N is the number of cores; U (t) is the voltage applied to the magnetization coils (voltage of the forming line); L is the length of the induction system.

 As a switch for forming lines, gas spark gaps are used. Such switches have limitations in response frequency. In addition, during the operation of the arresters, erosion of the electrode material is observed, which makes it possible to reduce the amount of switched energy or to reduce the number of pulses between preventive work on cleaning the insulators of the arresters.

 The closest technical solution is the design of the accelerator [Vintisenko I. I., Furman E.G. Linear induction accelerators. University News. Physics. TSU Edition, 1998, 4, p. 111-119]. The main difference from the construction of a linear induction accelerator described above is the use of a magnetic energy switch of the forming line. Such a switch is capable of switching with an unlimited resource in the nanosecond range of durations with a frequency of units of kilohertz current of hundreds of kiloamperes. However, in this case, it is required to charge the forming line for hundreds of nanoseconds from magnetic pulse generators.Thus, such a linear induction accelerator contains a ferromagnetic induction system in the form of a set of ferromagnetic cores covered by magnetization turns, the ends of the electrodes of a single forming line are connected to the ends of them. The opposite ends of the electrodes of the forming line are connected to a magnetic pulse generator. The grounded electrode of the forming line is open, and a magnetic switch is included in the gap.

A magnetic pulse generator is a sequence of circuits with increasing natural frequency. Each circuit contains a lumped capacitor and a saturation choke. Capacitors of capacitors of circuits C ₁ , C ₂ ,. .C _N are equal to each other and equal to the capacitance C _{fl of the} single forming line. Each subsequent saturation inductor L _i , in comparison with the previous L _i-1 , has a smaller number of turns of the winding, i.e. 1) a smaller inductance of the winding when the core is saturated, 2) a lower flux linkage, defined as Ψ _i = W _i S _i ΔB where W _i , S _i is the number of turns and the steel section of the i-th saturation inductor, ΔB is the induction span in the steel of the inductor core.

где L_i-1 - индуктивность обмотки дросселя при насыщенном состоянии сердечника, ψ_i = W_i•S_iΔB; W_i,S_i - число витков и сечение стали дросселя насыщения, ΔB - размах индукции в материале сердечника.To reduce the steel cross section of the ferromagnetic cores of the saturation chokes of the magnetic pulse generator and the core of the magnetic switch, the discharge processes of the capacitor C _{i + 1 of the} previous circuit and the charge of the capacitor C _{i of the} next circuit are used (the recharging process has not been completed, and the throttle core has already been saturated). In this case, the condition

where L _i-1 is the inductance of the inductor winding in the saturated state of the core, ψ _i = W _i • S _i ΔB; W _i , S _i - the number of turns and the steel cross section of the saturation inductor, ΔB - the magnitude of the induction in the core material.

When using this effect for a magnetic pulsed generator, it is really possible to reduce the cross section of the steel cores of saturation chokes, therefore, the overall dimensions of the installation. However, the use of the discharge phase overlap leads to an incomplete charge of the capacitor of the subsequent circuit C _i compared to the previous C _{i + 1} , that is, a gradual decrease in the charge voltage level of the capacitors of the circuits, including the incomplete charge of a single forming line (U _N > U _fl ) where U _N , U _fl - the amplitude of the charging voltage on the capacitor and the forming line, respectively. This effect reduces the maximum accelerator power.

The task of the invention is to increase the maximum pulse power allocated to the load. The technical result is to maintain the amplitude of the charging voltage of a single forming line at the level of the charging voltage C _N and reducing the time of its discharge to the load.

To solve this problem, a linear induction accelerator is proposed, containing, like the prototype, a ferromagnetic induction system in the form of a set of ferromagnetic cores covered by magnetization coils. The ends of the magnetization turns are connected to the ends of the electrodes of a single forming line. The opposite ends of the electrodes are connected to a magnetic pulse generator. The grounded electrode is open and a magnetic switch is connected to the gap. A magnetic generator is a sequence of circuits with increasing natural frequency, each of which consists of a capacitor with lumped parameters C _i and a saturation inductor L _i .

где L_N - индуктивность дросселя насыщения последнего контура магнитного импульсного генератора, W_k, S_k, ΔB - число витков, сечение стали, размах индукции в стали магнитного коммутатора, <U>=U_фл/2=U_N/2 - действующее зарядное напряжение формирующей линии, U_фл, U_N - амплитуды зарядного напряжения формирующей линии и конденсатора последнего контура магнитного импульсного генератора.The difference from the known technical solution is that the single forming line is carried out with a capacity significantly less (2-4 times) than the capacitance of the capacitor C _N , and the parameters of the magnetic switch are in a certain ratio with the elements of the accelerator

where L _N is the inductance of the saturation inductor of the last loop of the magnetic pulse generator, W _k , S _k , ΔB is the number of turns, the cross section of the steel, the magnitude of the induction in the steel of the magnetic switch, <U> = U _fl / 2 = U _N / 2 is the current charger the voltage of the forming line, U _fl , U _N - the amplitude of the charging voltage of the forming line and the capacitor of the last loop of the magnetic pulse generator.

 A schematic diagram of the device is shown in the drawing, where it is indicated: 1 - ferromagnetic induction system, 2 - single forming line, 3 - magnetic switch, 4 - magnetic pulse generator, 5 - magnetization coils.

The device comprises a ferromagnetic induction system 1 of sequentially installed ferromagnetic cores. The ferromagnetic cores are covered by magnetization coils 5. The electrodes of a single forming line 2 are connected to the ends of the magnetizing coils 5. The opposite ends of the electrodes of the forming line 2 are connected to a magnetic pulse generator 4, consisting of series circuits С _i -L _i , where С _i is a capacitor with capacitance C _i , L _i - inductor saturation inductor L _i . One of the electrodes of the forming line 2 is connected to the capacitor C _N by the saturation inductor L _{N of the} last circuit. The other electrode is grounded and open. A magnetic switch L _k 4, which is a single-turn saturation choke, is installed at the gap.

 The forming line is a set of parallel-connected copper electrodes, and the line capacitance is determined by the number of electrodes, their length and width, and also depends on the thickness of the insulation between the electrodes. The forming line is made with a capacity significantly smaller (2-4 times) the capacitance of the capacitor of the last circuit. The parameters of the magnetic switch (the number of turns, the cross section of steel, the core material used, which determines the magnitude of the induction in steel) are selected in relation to the capacitance of the capacitor and the forming line in accordance with formula (2).

Этот интервал времени ограничен величиной потокосцепления Ψ₂ дросселя насыщения L₂. При заряде конденсатора C₂ к виткам дросселя насыщения L₂ начинает прикладываться разность потенциалов:

где

Среднее значение напряжения на витках дросселя насыщения в интервале времени [0,π] составит

Это напряжение вызывает перемагничивание дросселя насыщения L₂ и переход его в состояние с μ = 1. Поэтому

где ψ₂ = W₂S₂ΔB - потокосцепление дросселя насыщения L₂(W₂, S₂ - число витков и сечение стали сердечника дросселя насыщения L₂, ΔB - размах индукции в стали).The device operates as follows. Initially, demagnetization of the cores of saturation chokes L _i -L _{N of the} loops, magnetic pulse generator 4, magnetic switch 3, induction system 1 is demagnetized from an external power source (for example, a capacitor bank is discharged when the ignitron or thyristor switch is turned on) the capacitor C _{1 of the} first circuit of the magnetic pulse generator 4 is charged. When C _{1 is} charged, the potential difference U _C1 appears at the terminals of the saturation inductor L ₁ , causing leakage e magnetization current and the core of the saturation inductor L _{1 is} magnetized. The flux linkage of the saturation inductor L ₁ is ψ ₁ = W ₁ S ₁ ΔB, where W ₁ is the number of turns, S ₁ is the cross section of the inductor steel, ΔB is the induction span (for example, ΔB = 2.5 T for permalloy 50 NP) and is selected so that the core of the throttle is saturated at the end of the charge With ₁ . When the core is saturated, its magnetic permeability decreases from μ = 10 ⁵ to μ = 1 and the saturation inductor turns into a conventional air inductance. The discharge begins C ₁ and the charge C ₂ through the inductance of the turns of the inductor L ₁ in the time interval

This time interval is limited by the flux linkage Ψ _{2 of the} saturation inductor L ₂ . When the capacitor C _{2 is} charged, the potential difference begins to be applied to the turns of the saturation inductor L ₂ :

Where

The average value of the voltage at the turns of the saturation inductor in the time interval [0, π] will be

This voltage causes a magnetization reversal magnetization saturation L ₂ and its transition to a state with μ = 1. Therefore

where ψ ₂ = W ₂ S ₂ ΔB is the flux linkage of the saturation inductor L ₂ (W ₂ , S ₂ is the number of turns and the cross section of the core steel of the saturation inductor L ₂ , ΔB is the induction span in steel).

где

(W₃, S₃ - число витков и сечение стали сердечника дросселя насыщения L₃

Аналогично предыдущим рассуждениям

где W_k - число витков магнитного коммутатора 3, S_k - сечение стали сердечника магнитного коммутатора 3. Обычно W_k=1 для того, чтобы обеспечить минимальную индуктивность магнитного коммутатора в насыщенном состоянии, поскольку

где а - линейный размер магнитного коммутатора 3, D_n, D_в - наружный и внутренний диаметры витка. Используя соотношения (3-7), рассчитывают параметры линейного индукционного ускорителя. Обычно выбирают С₁=C₂=...=С_N=С_фл, и без использования эффекта перекрытия фаз получим
<U₂>=<U₃>=...=<U_N>=<U_фл>=1/2U_С2=1/2U_С3=1/2U_CN=1/2U_фл. (9)
U_C2, U_C1, U_CN - aмплитyда зарядного напряжения конденсаторов магнитного импульсного генератора. Если С_N>С_фл, то зарядное напряжение на одинарной формирующей линии 2 составит
U_фл=2С_NU_CN/(C_фл+C_N). (10)
Кроме того, что одинарная формирующая линия 2 заряжается до большего напряжения, она разряжается на нагрузку за более короткое время (емкость меньше). Это позволяет увеличить импульсную мощность на нагрузке. Причем, чем меньше емкость формирующей линии, тем больше мощность, отдаваемая ей в нагрузку.When the inductor L _{2 is} saturated, the discharge of the capacitor begins, C ₂ and the charge of the capacitor C ₃ through the inductance of the turns of the saturation inductor L ₂ . The time interval of this process is limited by the magnitude of the flux linkage of the saturation inductor L ₃ , i.e.

Where

(W ₃ , S ₃ - the number of turns and the cross section of the steel core of the saturation inductor L ₃

Similar to the previous reasoning

where W _k is the number of turns of the magnetic switch 3, S _k is the cross section of the steel of the core of the magnetic switch 3. Usually, W _k = 1 in order to ensure the minimum inductance of the magnetic switch in a saturated state, since

where a is the linear size of the magnetic switch 3, D _n , D _in - the outer and inner diameters of the coil. Using relations (3-7), the parameters of the linear induction accelerator are calculated. Usually choose C ₁ = C ₂ = ... = C _N = C _fl , and without using the effect of phase overlap we get
<U ₂ > = <U ₃ > = ... = <U _N > = <U _fl > = 1 / 2U _C2 = 1 / 2U _C3 = 1 / 2U _CN = 1 / 2U _fl . (9)
U _C2 , U _C1 , U _CN - amplitude of the charging voltage of the capacitors of a magnetic pulse generator. If C _N > C _fl , then the charging voltage on the single forming line 2 will be
U _fl = 2C _N U _CN / (C _fl + C _N ). (10)
In addition, the single forming line 2 is charged to a higher voltage, it is discharged to the load in a shorter time (less capacity). This allows you to increase the pulse power at the load. Moreover, the smaller the capacity of the forming line, the greater the power given to it in the load.

 We calculate the power allocated to the load, representing the forming line in the form of a capacitor C, discharged through the inductance L to the ohmic load R. Since the analytical calculation of the processes of the joint discharge of the capacitor of the last circuit of the magnetic pulse generator and the forming line to the load is complicated, we present the results of computer simulation using Electronic Workbench software product.

For our case, C corresponds to C _fl , L = L _k + L _e.g. + L _fl ≈18.7 • 10 ⁹ H, where L _k is the inductance of the switch; L _heat. - load inductance; L _fl - the inductance of the forming line; R = 50Ω / n ² ≈0.25Ω, where n = 14 is the number of cores of the induction system of the accelerator (since the processes occurring in the primary circuit of the linear induction accelerator are considered). Take С _N = 0.3 • 10 ⁶ F and calculate for options with 1) C _fl = 0.3 • 10 ^-6 F, 2) C _fl = 0.2 • 10 ^-6 F and 3) C _fl = 0 , 1 • 10 ^-6 F value of the charging voltage of the forming line and power at the load. In the first embodiment, U _fl = U _N = 50 kV (the amplitudes of the voltage across the capacitor C _N and the forming line are equal). In the second and third options, U _fl = 2C _N • U _N / (C _fl + C _N ) = 61.2 and 70 kV. The allocated power at the load is P ₁ = 2.12 • 10 ⁹ W, P ₂ = 2.78 • 10 ⁹ W. P ₃ = 3.43 • 10 ⁹ W. Thus, the increase in power allocated to the load at C _N = 3C _fl in comparison with C _N = C _fl is 62%, and at C _N = 1.5C _{fl it} is 23%.

где L_N - индуктивность дросселя насыщения последнего контура магнитного импульсного генератора, W_k, S_k, ΔB - число витков, сечение стали, размах индукции в стали магнитного коммутатора, <U>=U_фл/2=U_N/2 - действующее зарядное напряжение формирующей линии, U_фл, U_N - амплитуда зарядного напряжения формирующей линии и кондденсатора последнего контура магнитного импульсного генератора. Приведенное соотношение физически означает, что параметры магнитного коммутатора выбраны таким образом, что как только при разряде конденсатора последнего контура магнитного импульсного генератора величина зарядного напряжения формирующей линии достигает зарядного напряжения конденсатора, происходит насыщение сердечника магнитного коммутатора и начинается совместный разряд конденсатора и формирующей линии на нагрузку. Другими словами, используется эффект перекрытия фаз разряда конденсатора и заряда формирующей линии.However, the process of increasing power is accompanied by a significant increase in the charging voltage of the forming line, which can exceed the breakdown values. Based on experience with strip lines, it is undesirable to exceed a voltage of more than 60-65 kV. Therefore, in the proposed accelerator, the parameters of the magnetic switch are in a certain ratio with the capacities of the forming line and the capacitor of the last loop of the magnetic pulse generator, namely

where L _N is the inductance of the saturation inductor of the last loop of the magnetic pulse generator, W _k , S _k , ΔB is the number of turns, the cross section of the steel, the magnitude of the induction in the steel of the magnetic switch, <U> = U _fl / 2 = U _N / 2 is the current charger the voltage of the forming line, U _fl, U _N - the amplitude of the charging voltage of the forming line and capacitor of the last loop of the magnetic pulse generator. The above relation physically means that the parameters of the magnetic switch are selected in such a way that as soon as the capacitor discharge of the last loop of the magnetic pulse generator reaches the charging voltage of the forming line of the capacitor, the core of the magnetic switch is saturated and the capacitor and the forming line begin to discharge to the load. In other words, the effect of overlapping the phases of the discharge of the capacitor and the charge of the forming line is used.

В свою очередь этот момент времени определяется величиной потокосцепления магнитного коммутатора, а именно числом витков, сечением стали, материалом сердечника (размах индукции)
t₁ = W_k, S_kΔB/<U>. (13)
Выражения (11) и (12) позволяют получить соотношение для параметров магнитного коммутатора и элементов ускорителя

Рассчитаем мощность, выделяемую на нагрузке при выполнении данного условия с использованием программного продукта Electronic Workbench. Интервал изменения С_фл относительно C_N составлял 2-4 раза, индуктивности разрядного контура и дросселя насыщения последнего контура сжатия составляют L= 18,7•10^-9 Гн, L_N=13•10^-9 Гн, что соответствует реальным параметрам ускорителя ЛИУ 04\ 4000 [Бутаков Л.Д., Винтизенко И.И. Частотный линейный индукционный ускоритель ЛИУ 04\4000.ПТЭ, 2000, 3, с. 159-160]. Наибольшая рассчитанная мощность наблюдалась при 3С_фл=С_N и выполнении условия (13), которая составила 3,83 ГВт. По сравнению со случаем без использования эффекта перекрытия фаз при том же соотношении емкостей мощность равна 3,43 ГВт (см. результаты расчета выше). Таким образом, увеличение мощности составило 11%. Отметим, что поскольку величина емкости формирующей линии значительно уменьшилась, то сократилось время перезаряда конденсатора и формирующей линии. Это позволяет уменьшать величину потокосцепления магнитного коммутатора, что автоматически приводит к уменьшению габаритов, а значит, и снижению индуктивности магнитного коммутатора согласно (8). В расчетах этот параметр изменялся от 18,7•10^-9 Гн до 16•10^-9 Гн, что вызывало рост мощности на нагрузке еще на 3%, которая составила 3,942 ГВт.From a relation similar to (4), it is possible to determine the time moment of the condition U _fl = U _N , which is equal to

In turn, this moment of time is determined by the magnitude of the flux linkage of the magnetic switch, namely, the number of turns, the cross section of steel, the core material (range of induction)
t ₁ = W _k , S _k ΔB / <U>. (thirteen)
Expressions (11) and (12) allow us to obtain the ratio for the parameters of the magnetic switch and accelerator elements

We calculate the power allocated to the load when this condition is met using the Electronic Workbench software product. The change interval of C _fl relative to C _N was 2-4 times, the inductances of the discharge circuit and the saturation inductor of the last compression circuit are L = 18.7 • 10 ^-9 H, L _N = 13 • 10 ^-9 H, which corresponds to the real parameters of the LIU accelerator 04 \ 4000 [Butakov L. D., Vintisenko I.I. Frequency linear induction accelerator LIU 04 \ 4000. PTE, 2000, 3, p. 159-160]. The highest calculated power was observed at 3С _fl = С _N and the fulfillment of condition (13), which amounted to 3.83 GW. Compared with the case without using the phase overlap effect with the same ratio of capacities, the power is 3.43 GW (see calculation results above). Thus, the increase in power was 11%. Note that, since the value of the capacitance of the forming line decreased significantly, the time for recharging the capacitor and the forming line was reduced. This allows one to reduce the magnitude of the flux linkage of the magnetic switch, which automatically leads to a decrease in size, and hence a decrease in the inductance of the magnetic switch according to (8). In calculations, this parameter varied from 18.7 • 10 ^-9 Gy to 16 • 10 ^-9 Gy, which caused an increase in load power by another 3%, which amounted to 3.942 GW.

вызывает увеличение мощности выделяемой на нагрузке на 86%.An example of a specific implementation is a module of a linear induction accelerator manufactured at the Scientific Research Institute of Nuclear Physics with the following design parameters C ₁ = C ₂ = C ₃ = 0.3 • 10 ⁶ F. Saturation chokes L ₁ , L ₂ have identical cores made of 6 rings with outer and inner diameters of 250 and 110 mm, respectively 25 mm wide, wound from permalloy tape 50 NP 0.02 mm thick. The throttle L ₁ has 14 turns, L ₂ 4 turns. The single-turn saturation choke L ₃ has a core of 3 rings with outer and inner diameters of 500 mm and 220 mm, respectively 25 mm wide, wound from permalloy tape 0.02 mm thick. The single-turn magnetic switch, as well as the cores of the induction system, is made of rings with external and internal diameters of 360 mm and 150 mm, respectively 25 mm wide, wound from permalloy tape 50 NP 0.01 mm thick. Capacitors C ₁ -C ₃ with lumped parameters of type K75-74 0.1 μF in 3 in parallel. The forming line consists of two electrodes 4 meters long, 0.2 meters wide with syntoflex insulation with a total thickness of 1.2 mm. The capacity of the forming line is 0.1 • 10 ^-6 F. The forming line is wound around the cores of the induction system in a spiral of Archimedes. All elements of a linear induction accelerator are placed in a cylindrical stainless steel case with an inner diameter of 670 mm. Capacitor C ₁ is charged up to 50 kV from an external power source for a time interval of 12 μs. C ₂ charging takes place in 3 μs, C ₃ - in 1 μs, C _fl - in 0.2 μs and the discharge time of C _fl to the induction system is ~ 0.18 μs. The pulse power of a linear induction accelerator is 3.94 GW, which is 86% higher than when using a forming line with a capacity of 0.3 • 10 ^-6 F, as proposed in the prototype device. Thus, the use of a forming line in a linear induction accelerator with a capacity of 2-4 times less than the capacitor of the last stage of compression of a magnetic pulse generator and a magnetic switch with parameters that are in the following ratio with the parameters of the accelerator elements

causes an increase in power allocated to the load by 86%.

Claims (1)

A linear induction accelerator containing a ferromagnetic induction system in the form of a set of ferromagnetic cores covered by magnetization turns, to the ends of which the ends of the electrodes of a single forming line are connected, the electrodes at the opposite end being connected to a magnetic pulse generator consisting of series circuits, each of which is formed by a capacitor and a saturation reactor and a magnetic switch is included in the gap of the grounded electrode of the single forming line, characterized by the fact that the single forming line is made with a capacitance C _fl 2-4 times less than the capacitance C _{N of the} capacitor of the last loop of the magnetic pulse generator, and the magnetic switch has parameters that are in the following ratio with the elements of the accelerator

where L _N is the inductance of the saturation inductor of the last loop of the magnetic pulse generator;
W _k , S _k , ΔB is the number of turns, the cross section of the steel, the magnitude of the induction in the steel of the magnetic switch;
<U> = U _fl / 2 = U _N / 2 is the effective charging voltage of the forming line, U _fl , U _N are the amplitudes of the charging voltage of the forming line and the capacitor of the last loop of the magnetic pulse generator.