rus
Issue #3/2014
А.Gayoso de los Santos, Z.Pavlova, A.Temnikov, A.Fedorov
Power Supplies Diode-Pumping Lasers For Laser Fusion
Power Supplies Diode-Pumping Lasers For Laser Fusion
Increased power diode-pumped lasers energetics leads to the increase of the number of diode laser matrixes at each channel. A power supply that can power parallel connected diode arrays was designed.
Теги: diode laser pumps laser fusion power lasers electric supply диодные лазеры для накачки электропитания мощных лазеров лазерный термоядерный синтез
The idea of using high-power laser emission for thermonuclear fuel implosion belongs to Soviet academician N.G. Basov and O.N. Krohin.
Lasers have a number of unique properties that are allowed to use them as a source of thermonuclear implosion. Firstly it gives an ability to create a high energy flux density at the laser beam focus and therefore high power specific energy release in the matter. Secondly, an absence of mechanical linking between the laser and the target; output stages of laser systems may be in tens of meters from thermonuclear implosions that allows provide to at target a huge energy without destroying of structural materials. Thirdly, it gives an ability to provide high contrast radiation, that is large signal-to-noise ratio, which are always in laser, as in any amplification system, and can lead to the preheating and the target destruction before the main pulse appearing.
In the leading centers of the Soviet Union - LPI RAS, State Research Center of Russian Federation Troitsk Institute for Innovation & Fusion Research, Russian Federal Nuclear Center All-Russian Research Institute of Experimental Physics, Federal State Unitary Enterprise Scientific and Industrial Corporation "Vavilov State Optical Institute", Join Stock Company «D.V.Efremov Institute of Electrophysical Apparatus» have started works of creating of experimental facilities for experimentations of interaction processes of high-energy laser radiation with matter and solving problems of laser fusion (LF). 2009 year instigates a new round of the facilities development, intended for LF. In Lawrence Livermore National Laboratory, USA, started 192-beam laser system National Ignition Facility (NIF) with an output energy of 1.8 MJ. A similar system - Laser Mega Joule (LMJ) in France - is scheduled for completion in 2014. NIF and LMJ predecessors were: Nova and Omega (USA), Vulcan (UK), FIREX (Japan), SG (China) and photolytically pumped iodine gas laser Iskra-5 (Russian Federation). Up to 2020 Russia plans to construct of laser facility of megajoule energy level.
Up-to-date laser systems for demonstration experiments ignition are based on the most reliable, but least effective indirect compaction scheme by laser emission to X-ray radiation, providing the best uniformity and stability of the target compaction. For energy production direct compaction is prefered, where gain in the target is near 100 and is reached at full power for about 2 MJ, and laser efficiency must be ≥ 6-7%. Laser driver must have uninterrupted operation with a pulse repetition frequency of ≥ 5 Hz for 2 years performing ≥ 3 * 108 pulses to meet the technical and economic requirements for the power facility. The most advanced facilities for solving this problem are solid state diode-pumped lasers (Diode Pumped Solid State Lasers - DPSSL) and gas KrF lasers with a relativistic electron beam pumping, keeping the necessary high efficiency and can be scaling to the required energy.
Obviously, one of the most effective solutions to creating high-power solid-state laser consists in principle of a multi-channel construction. The laser, in this case, "gathering" in shape of a lattice of identical channels, each of which occures laser generation. Small cross-section of the channels allows efficiently and simply accomplish the energy pumping into the active medium and the heat rejection from its scope. Company «Northrop Grumman» built 100-kilowatt laser in the same way. Basic principles of multi-channel systems of power diode-pumped lasers are discussed in "Electrical Power Supply systems for multi-channel diode-pumped lasers" Photonics 2014 1 (43).
In the design of laser systems increased power diode-pumped lasers leads to increase of number diode laser matrixes (MLD) at each channel. Appears problems connecting to the wide quantities of matrices to a power supplies (PS), supplying a laser channel. Circuit design, that nowadays company "FEDAL" applies in the manufacture of typical products, based on partial discharge capacitive energy storage (CES), thus it leads to limitation of the voltage drop across the series-connected arrays. Compact PS with CES achieved due to using as the storage electrolytic capacitors. The maximum operating voltage of this type is limited to 450 V. This makes a limit on the possible number of MLD connected to the power supplies successively. Using polypropylene film capacitors would increase the possible voltage drop across the MLD, but this solution leads to a much larger power supplies. Increase in drive voltage of power supply is unwanted.
There is a solution that allows to connect MLD in parallel, current in them should be necessarily aligned. The device for smoothing current, that uses for parallel connection of 3, 6, 9 laser diode arrays, has been developed and successfully applied by the company, but there are cases more quantity MLD are needed. The "FEDAL" engineers’ experiments has shown, under increasing of MLD quantity, stability of current aligning decreases. Connecting to a large number of MLD to the device PLD 100 can significantly reduce the overall efficiency of the power supply. In response to this problem company has concluded to develop of power supply, based on partial discharge of inductive energy storage (INE). The power supply of this type has the output characteristics of the current source, which is ideal for powering the load with nonlinear current-voltage characteristic. In using such solutions, the load current does not depend on the number of parallely connected within the MLD average output power, which power supply is designed for. Power supply and INE don’t use large capacitors.
It is his great fault of power supply and INE extremely low efficiency. To improve this indicator measures can be taken to substantially reduce the ohmic drive, which usually leads to enormous economic costs (cooled to extremely low temperatures). Another way to increase efficiency is to use INE with energy recovery in the pause between pulses. Such schematic, providing such a mode, was designed, simulated and led to prototype. The prototype was successfully tested, it have allowed to start pre-production of such power supplies series. Were obtained three patents to the schematics, getting during the process of power supplies creation.
Converter efficiency calculation showed that system has sufficient efficiency – 70% by powering from three-phase network. It easily can be increased using a boost converter to charge the buffer capacitor. In this case, the calculated efficiency scheme can reach 91%. While power supply efficiency does not depend on the frequency of the pulse, which is important for customers.
Rectangular pulse shape is achieved by using passive correction circuit. This decision is without flaws of active correction that may occur at high power. The current pulse produced by power supply model is shown in Picture 3.
Designed power supply allows to power connected in parallel diode arrays. The total voltage drop across the MLD is limited only by the components and dimensions of the power supply. Existing in free access key elements allow to provide output current 90A under the voltage across the load to 1200V.
Lasers have a number of unique properties that are allowed to use them as a source of thermonuclear implosion. Firstly it gives an ability to create a high energy flux density at the laser beam focus and therefore high power specific energy release in the matter. Secondly, an absence of mechanical linking between the laser and the target; output stages of laser systems may be in tens of meters from thermonuclear implosions that allows provide to at target a huge energy without destroying of structural materials. Thirdly, it gives an ability to provide high contrast radiation, that is large signal-to-noise ratio, which are always in laser, as in any amplification system, and can lead to the preheating and the target destruction before the main pulse appearing.
In the leading centers of the Soviet Union - LPI RAS, State Research Center of Russian Federation Troitsk Institute for Innovation & Fusion Research, Russian Federal Nuclear Center All-Russian Research Institute of Experimental Physics, Federal State Unitary Enterprise Scientific and Industrial Corporation "Vavilov State Optical Institute", Join Stock Company «D.V.Efremov Institute of Electrophysical Apparatus» have started works of creating of experimental facilities for experimentations of interaction processes of high-energy laser radiation with matter and solving problems of laser fusion (LF). 2009 year instigates a new round of the facilities development, intended for LF. In Lawrence Livermore National Laboratory, USA, started 192-beam laser system National Ignition Facility (NIF) with an output energy of 1.8 MJ. A similar system - Laser Mega Joule (LMJ) in France - is scheduled for completion in 2014. NIF and LMJ predecessors were: Nova and Omega (USA), Vulcan (UK), FIREX (Japan), SG (China) and photolytically pumped iodine gas laser Iskra-5 (Russian Federation). Up to 2020 Russia plans to construct of laser facility of megajoule energy level.
Up-to-date laser systems for demonstration experiments ignition are based on the most reliable, but least effective indirect compaction scheme by laser emission to X-ray radiation, providing the best uniformity and stability of the target compaction. For energy production direct compaction is prefered, where gain in the target is near 100 and is reached at full power for about 2 MJ, and laser efficiency must be ≥ 6-7%. Laser driver must have uninterrupted operation with a pulse repetition frequency of ≥ 5 Hz for 2 years performing ≥ 3 * 108 pulses to meet the technical and economic requirements for the power facility. The most advanced facilities for solving this problem are solid state diode-pumped lasers (Diode Pumped Solid State Lasers - DPSSL) and gas KrF lasers with a relativistic electron beam pumping, keeping the necessary high efficiency and can be scaling to the required energy.
Obviously, one of the most effective solutions to creating high-power solid-state laser consists in principle of a multi-channel construction. The laser, in this case, "gathering" in shape of a lattice of identical channels, each of which occures laser generation. Small cross-section of the channels allows efficiently and simply accomplish the energy pumping into the active medium and the heat rejection from its scope. Company «Northrop Grumman» built 100-kilowatt laser in the same way. Basic principles of multi-channel systems of power diode-pumped lasers are discussed in "Electrical Power Supply systems for multi-channel diode-pumped lasers" Photonics 2014 1 (43).
In the design of laser systems increased power diode-pumped lasers leads to increase of number diode laser matrixes (MLD) at each channel. Appears problems connecting to the wide quantities of matrices to a power supplies (PS), supplying a laser channel. Circuit design, that nowadays company "FEDAL" applies in the manufacture of typical products, based on partial discharge capacitive energy storage (CES), thus it leads to limitation of the voltage drop across the series-connected arrays. Compact PS with CES achieved due to using as the storage electrolytic capacitors. The maximum operating voltage of this type is limited to 450 V. This makes a limit on the possible number of MLD connected to the power supplies successively. Using polypropylene film capacitors would increase the possible voltage drop across the MLD, but this solution leads to a much larger power supplies. Increase in drive voltage of power supply is unwanted.
There is a solution that allows to connect MLD in parallel, current in them should be necessarily aligned. The device for smoothing current, that uses for parallel connection of 3, 6, 9 laser diode arrays, has been developed and successfully applied by the company, but there are cases more quantity MLD are needed. The "FEDAL" engineers’ experiments has shown, under increasing of MLD quantity, stability of current aligning decreases. Connecting to a large number of MLD to the device PLD 100 can significantly reduce the overall efficiency of the power supply. In response to this problem company has concluded to develop of power supply, based on partial discharge of inductive energy storage (INE). The power supply of this type has the output characteristics of the current source, which is ideal for powering the load with nonlinear current-voltage characteristic. In using such solutions, the load current does not depend on the number of parallely connected within the MLD average output power, which power supply is designed for. Power supply and INE don’t use large capacitors.
It is his great fault of power supply and INE extremely low efficiency. To improve this indicator measures can be taken to substantially reduce the ohmic drive, which usually leads to enormous economic costs (cooled to extremely low temperatures). Another way to increase efficiency is to use INE with energy recovery in the pause between pulses. Such schematic, providing such a mode, was designed, simulated and led to prototype. The prototype was successfully tested, it have allowed to start pre-production of such power supplies series. Were obtained three patents to the schematics, getting during the process of power supplies creation.
Converter efficiency calculation showed that system has sufficient efficiency – 70% by powering from three-phase network. It easily can be increased using a boost converter to charge the buffer capacitor. In this case, the calculated efficiency scheme can reach 91%. While power supply efficiency does not depend on the frequency of the pulse, which is important for customers.
Rectangular pulse shape is achieved by using passive correction circuit. This decision is without flaws of active correction that may occur at high power. The current pulse produced by power supply model is shown in Picture 3.
Designed power supply allows to power connected in parallel diode arrays. The total voltage drop across the MLD is limited only by the components and dimensions of the power supply. Existing in free access key elements allow to provide output current 90A under the voltage across the load to 1200V.
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