RU2031501C1 - Device of excitation of bulk charge in pulse laser - Google Patents

Abstract

FIELD: quantum electronics. SUBSTANCE: device of excitation of bulk charge in pulse laser has first capacitor charged by pulses and n pulse voltage generators connected in parallel to it through magnetic key. Each generator has first LC inverter manufactured in the form of two capacitors coupled in series to which extreme leads-out inductance coil is connected and thyratron is linked to one of capacitors. For increase of amplitude of pulse voltage and implementation of capability of growth of laser aperture, its generation energy and average radiation power each generator of pulse voltages is inserted with second and k-th LC inverters connected in series. Joint leads-out of capacitors of each LC inverter are interconnected by means of additional second and k-th inductance coils and each thyratron is linked to proper capacitor through saturable choke. EFFECT: increased amplitude of pulse voltage, capability of growth of laser aperture. 1 dwg

Description

 The invention relates to quantum electronics and can be used for pumping systems mainly in wide-aperture pulse-periodic excimer lasers.

 A device is known for exciting a pulsed volume discharge with a thyratron as a switch, in which one capacitor is recharged to another, connected inductively to the laser electrodes [1]. The device is simple, high service life at a high pulse repetition rate.

 A limitation of the device is the small value of the discharge voltage, which does not allow increasing the laser aperture and its generation energy.

 The indicated drawback is devoid of a device for exciting a volume discharge, containing a cascade Marx generator with spark gap as switches, a pulse-charged symmetrical Blumlyayn line with water insulation, connected through the spark gap to the laser electrodes [2]. When used in an excimer laser, the device allows one to obtain generation energy two orders of magnitude greater than in the previous analogue.

 However, the device has a large mass and dimensions and cannot be used to operate in the frequency mode.

 The prototype of the invention is a device for exciting a volume discharge in a pulsed laser, containing the first capacitor and connected to it through a magnetic key, the first - nth pulse voltage generators (GIN), connected to each other in parallel, and each of the GIN contains the first LC inverter, made in the form of two series-connected second and third capacitors, to the extreme terminals of which the first inductor is connected, and the extreme output of the second capacitor through the thyratron is connected to the output voltage chnika [3]. When used in an excimer electric discharge laser, the prototype allows one to obtain a high average laser radiation power in a repetitively pulsed mode and has a long service life. The specified device allows you to approximately double the discharge voltage compared with the first analogue.

However, in the prototype, it is difficult to further increase the voltage and, accordingly, the volume discharge aperture, the generation energy, and the average laser radiation power due to the limited voltage range up to U _t ≈30 kV, at which the thyratrons operate stably in a pulse-periodic mode. In this regard, when using the device in an excimer laser, its generation energy is approximately an order of magnitude lower than in the previous analogue.

 The objective of the invention is to increase the amplitude of the pulse voltage and the possibility of increasing the aperture of the laser, its generation energy and average radiation power.

 The task can be carried out by a device of a new design, containing the first capacitor and connected to it through a magnetic key, the first n-th GIN connected in parallel, each of the GIN contains the first LC-inverter, made in the form of two series-connected second and third capacitors, to the extreme terminals of which the first inductor is connected, and the extreme terminal of the second capacitor is connected through the thyratron to the output of the voltage source. The difference between the device is that a second-Kth series-connected LC inverter, a second-Kth inductor and a first-Kth saturable inductor are introduced into each GIN, and the common conclusions of the second and third capacitors of the first-Kth LC inverters are interconnected respectively through the second-K-th inductors, while the aforementioned common leads are connected to the corresponding thyratron through the first-K-th saturable chokes, respectively.

The implementation of the device in this form allows using standard high-frequency frequency switches to increase the amplitude of the voltages exciting the volume discharge in a pulsed laser several times. This makes it possible to increase the laser aperture and substantially, approximately by a factor of ² , increase its generation energy, where K is the number of LC inverters connected in series in each GIN. At the same time, connecting each thyratron to the corresponding second capacitor through a saturable inductor reduces switching losses, which minimizes the number of thyratrons and, accordingly, the number of GINs.

 The drawing schematically shows a device for exciting a volume discharge in a pulsed laser.

The device contains n GIN 1, each of which includes K series-connected LC inverters 2. The drawing shows the case of two, n = 2, parallel-connected GINs, each of which includes two, K = 2, series-connected LC -inverter. To the extreme terminals of the second 3 and third 4 capacitors of each LC-inverter 2 connected in series, the first inductance coil 5 is connected. The common conclusions of the second 3 and third 4 capacitors connected in series to the first-K-th LC inverters 2 in each GIN are connected by second-K-inductors 6. A thyratron 7 is connected to the second capacitor 3 of each first-K-th LC inverter via a saturable inductor 8, and in each GIN, the thyratron of the first LC inverter is connected to the output of the voltage source U _о . Parallel to each other GIN 1 through a magnetic key 9 are connected to the first capacitor 10, which is connected to the cathode 11 and the anode 12 of the laser.

 A device for exciting a volume discharge in a pulsed laser operates as follows.

, где L₁ - индуктивность контура, включающего тиратрон 7, второй конденсатор 3 и дроссель 8; С - величина емкости второго конденсатора 3, происходит инвертирование напряжения на вторых конденсаторах 3. При равенстве емкостей конденсаторов 3, 4 на каждом LC-инверторе 2 разность потенциалов на последовательно соединенных конденсаторах 3, 4 достигает величины -2U_о. На выходе каждого ГИН 1, состоящего из К последовательно соединенных LC-инверторов 2, напряжение достигает величины -2KU_о. Происходит срабатывание магнитного ключа 9, представляющего собой малоиндуктивный одновитковый дроссель с замкнутым сердечником, насыщение которого происходит за время ≈10 нс. Осуществляется импульсная зарядка первого конденсатора 10, малоиндуктивно подсоединенного к катоду 11 и аноду 12. В процессе импульсной зарядки происходит перекачка энергии из n параллельно соединенных между собой ГИН 1 в первый конденсатор 10 за время τ₂. Для эффективной передачи энергии параметры устройства выбираются такими, что

>>τ₁ и τ₂

(τ₁/5), где L₂ - величина индуктивностей катушек 5, 6. Во время импульсной зарядки первого конденсатора 10 происходит нарастание напряжения между катодом 11 и анодом 12. Одновременно производится предыонизация разрядного объема между электродами 11, 12 устройством, не показанным на чертеже. Когда напряжение между катодом и анодом достигает значения пробивного напряжения U_пр, происходит основной объемный разряд между ними, что позволяет получить генерацию. Через время ≅0,1 мс, необходимое для восстановления электрической прочности тиратронов, цикл работы устройства повторяется. Во время импульсного срабатывания часть тиратронов ГИН 1 оказывается под высоким напряжением. В связи с этим устройства, обеспечивающие работу тиратронов во втором-К-м LC-инверторах: накальные трансформаторы, импульсные трансформаторы блоков запуска и др. снабжены обмотками с высоковольтной изоляцией.Contained in GIN 1, each of which consists of K series-connected LC inverters 2, the second 3 and third 4 capacitors are charged to the initial voltage U _о (voltage source is not shown). With the exception of the second capacitors 3 of the first LC inverters, capacitors 3, 4 are charged through inductors 5, 6. The thyratrons 7 are launched. The saturable chokes 8 delay for a short time, ≈100 ns, the onset of a sharp increase in current through the thyratrons 7 during their closure, which reduces the starting losses in them. After saturation of the chokes 8 for the time τ ₁ = π

where L ₁ is the inductance of the circuit, including the thyratron 7, the second capacitor 3 and the inductor 8; C is the capacitance value of the second capacitor 3, the voltage is inverted at the second capacitors 3. If the capacitances of the capacitors 3, 4 on each LC inverter 2 are equal, the potential difference on the series-connected capacitors 3, 4 reaches -2U _о . At the output of each GIN 1, consisting of K series-connected LC inverters 2, the voltage reaches a value of -2KU _about . The magnetic key 9 is activated, which is a low-inductance single-turn choke with a closed core, the saturation of which occurs in a time of ≈10 ns. Pulse charging of the first capacitor 10 is carried out, which is inductively connected to the cathode 11 and the anode 12. In the process of pulse charging, energy is transferred from n parallel connected GIN 1 to the first capacitor 10 in time τ ₂ . For efficient energy transfer, the device parameters are chosen such that

>> τ ₁ and τ ₂

(τ _1/5), where L ₂ - the value of inductance coils 5, 6. During the pulse charging of the first capacitor 10 voltage increase occurs between the cathode 11 and anode 12. Simultaneously produced preionization discharge space between the electrodes 11, device 12, not shown in drawing. When the voltage between the cathode and the anode reaches the breakdown voltage U _pr , the main volume discharge occurs between them, which allows generation. After a time of ≅0.1 ms, necessary to restore the electric strength of the thyratrons, the cycle of the device is repeated. During pulsed operation, part of the thyratrons of GIN 1 is under high voltage. In this regard, devices that ensure the operation of thyratrons in the second K-m LC inverters: filament transformers, pulse transformers of the launch units, etc. are equipped with windings with high voltage insulation.

U

(2)
Из выражений (1), (2) следует условие для величины К - количества последовательно соединенных LC-инверторов в каждом ГИН:
K>0,5

U_пр/U

(3)
Для упрощения устройства количество К последовательно соединенных LC-инверторов выбирается минимальным, удовлетворяющим условию (3):
K=

0,5

U_пр/U

+I
(4)
При работе устройства за каждый импульс через каждый тиратрон протекает заряд Q_о, величина которого определяется необходимой для накачки лазера суммарной энергией Е_о, запасаемой в n ГИН, количеством тиратронов, равным nK, и величиной зарядного напряжения:
Q_o = 2E_o/nKU_о . (5)
Для высокоресурсной работы тиратронов величина Q_о не должна быть выше некоторого номинального значения заряда Q_т, определяемого паспортными данными тиратрона:
Q_o ≅ Q_т. (6)
С учетом выражений (1), (5), (6) условие для величины
n ≥ 2E_o/(KU_тQ_т) . (7)
Для упрощения устройства количество n параллельно соединенных ГИН выбирается минимальным, удовлетворяющим условию (7):
n = [2E_o/(KU_тQ_т)] при {2E_o/(KU_тQ_т)} ≈0 или
n = [2E_o/(KU_тQ_т)] + I при {2E_o/(KU_тQт_} > 0. (8)
Введение в цепь коммутации тиратронов насыщаемых дросселей 8 снижает потери в тиратронах, что позволяет использовать для выбора величины n первое равенство выражения (8), минимизируя количество параллельно соединенных ГИН.When the device is operating, the range of charging voltages U _{о is} limited by the maximum allowable voltage value U _t , at which the stable high-resource operation of thyratrons is carried out in a pulse-periodic mode:
U _o ≅ U _t . (1)
To carry out breakdown and ignition of a uniform volume discharge in a laser, the voltage amplitude 2KU _о at the output of the GIN must be higher than the voltage U _pr , at which a breakdown occurs between the laser electrodes:
2KU _o >

U

(2)
From the expressions (1), (2) the condition for the value K - the number of series-connected LC-inverters in each GIN follows:
K> 0.5

U _pr / U

(3)
To simplify the device, the number K of series-connected LC inverters is selected as minimal, satisfying condition (3):
K =

0.5

U _pr / U

+ I
(4)
During operation of the device, for each pulse, a charge Q _о flows through each thyratron, the value of which is determined by the total energy E _о necessary for pumping the laser, stored in n GIN, the number of thyratrons equal to nK, and the value of the charging voltage:
Q _o = 2E _o / nKU _o . (5)
For high-life operation of thyratrons, the value of Q _o should not be higher than a certain nominal value of the charge Q _t determined by the passport data of the thyratron:
Q _o ≅ Q _t. (6)
Taking into account expressions (1), (5), (6), the condition for the quantity
n ≥ 2E _o / (KU _t Q _t ). (7)
To simplify the device, the number n of parallel connected GINs is selected as minimal, satisfying condition (7):
n = [2E _o / (KU _t Q _t )] for {2E _o / (KU _t Q _t )} ≈ 0 or
n = [2E _o / (KU _t Q _t)] + I at {2E _o / (KU _{Qt} t>} 0 (8)
The introduction of saturated chokes 8 into the thyratron switching circuit reduces losses in thyratrons, which makes it possible to use the first equality of expression (8) to select the value of n, minimizing the number of parallel connected GINs.

 Using the proposed device for exciting a volume discharge in a pulsed laser, in comparison with the prototype, it provides an increase in the aperture of the volume discharge, an increase in the generation energy and the average laser radiation power.

Currently, the proposed device in accordance with the drawing when K = 2, n = 2 tested to excite the XeCl laser with an aperture of 9x6 cm ² . The total capacitance of two GIN “in shock” was 100 nF. At a pulse repetition rate of 70 Hz and a voltage charge of 30.5 kV, a generation energy of 12 J was obtained, which is currently the maximum for electric-discharge pulse-periodic excimer lasers.

Claims (1)

 A DEVICE FOR EXCITING A VOLUME DISCHARGE IN A PULSED LASER containing the first capacitor and n pulse voltage generators connected to each other in parallel, each of the generators containing the first LC-inventor, made in the form of series-connected second and third capacitors, to the extreme ones the conclusions of which are connected, respectively, the first and second conclusions of the first inductor, and the extreme output of the second capacitor through the thyratron is connected to the output source and voltages, characterized in that a second — Kth LC inverters connected in series, a second Kth inductor and a first Kth inductor are introduced into each pulse voltage generator, and the common terminals of the second and third inverter capacitors are interconnected respectively, through the second - K-th inductor, while the common conclusions are connected to the corresponding thyratron through these chokes, respectively.

Images