Physical processes in plasma focus chambers that determine their lifetime as a pulsed neutron source
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更新：2025-04-03 15:12:37 浏览：97次
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摘要
The present work considers devices that implement the plasma pinch effect in the form of plasma focus (PF) chambers, which forms a non-cylindrical z-pinch. Such PF chambers are used as part of pulsed current generators to produce nanosecond-duration pulsed neutron radiation. Neutron generation occurs through the implementation of nuclear fusion reactions D+D or D+T, resulting in neutron energies of 2.5 MeV and 14 MeV, respectively.
A crucial issue for the practical application of these devices is the total number of PF chamber operations with neutron pulse generation within the required range - the operational lifetime. The lifetime depends on various factors, such as the design of the PF chamber, working pressure, gas composition, electrical characteristics of the circuit, and others. However, ultimately, all these characteristics can be reduced to several types of effects on the PF chamber:
- pulsed thermal impact on the electrodes due to the motion and compression of the plasma-current sheath in to the pinch with a characteristic duration of several microseconds;
- pulsed electrical impact on the insulator due to the pulse voltage surge, which significantly exceeds the charging voltage of the pulsed current generator, at the moment of pinching with a characteristic duration of tens of nanoseconds;
- pulsed mechanical impact on structural elements due to the action of ponderomotive forces at currents with amplitudes in the range of hundreds and thousands of kA, lasting for tens of microseconds or more.
The Dukhov Research Institute of Automatics (VNIIA) developed PF chambers that covers a range of neutron yields from 105 to 1012 neutrons per pulse at neutron energies of 2.5 MeV and 14 MeV. This work presents a generalization of experimental studies on the operation of these chambers in terms of the above-mentioned effects impact on PF chamber lifetime. The experimentally achieved values of the operational lifetime of hermetically sealed PF chambers with D-D and D-T fillings are presented, which amount to several thousand operations for PF chambers with discharge currents I = 200–300 kA, more than 500 operations for PF chambers with I = 600 kA, and around 150–200 operations for I > 1 MA. Recommendations for further increasing the operational lifetime of hermetically sealed PF chambers are also provided.
A crucial issue for the practical application of these devices is the total number of PF chamber operations with neutron pulse generation within the required range - the operational lifetime. The lifetime depends on various factors, such as the design of the PF chamber, working pressure, gas composition, electrical characteristics of the circuit, and others. However, ultimately, all these characteristics can be reduced to several types of effects on the PF chamber:
- pulsed thermal impact on the electrodes due to the motion and compression of the plasma-current sheath in to the pinch with a characteristic duration of several microseconds;
- pulsed electrical impact on the insulator due to the pulse voltage surge, which significantly exceeds the charging voltage of the pulsed current generator, at the moment of pinching with a characteristic duration of tens of nanoseconds;
- pulsed mechanical impact on structural elements due to the action of ponderomotive forces at currents with amplitudes in the range of hundreds and thousands of kA, lasting for tens of microseconds or more.
The Dukhov Research Institute of Automatics (VNIIA) developed PF chambers that covers a range of neutron yields from 105 to 1012 neutrons per pulse at neutron energies of 2.5 MeV and 14 MeV. This work presents a generalization of experimental studies on the operation of these chambers in terms of the above-mentioned effects impact on PF chamber lifetime. The experimentally achieved values of the operational lifetime of hermetically sealed PF chambers with D-D and D-T fillings are presented, which amount to several thousand operations for PF chambers with discharge currents I = 200–300 kA, more than 500 operations for PF chambers with I = 600 kA, and around 150–200 operations for I > 1 MA. Recommendations for further increasing the operational lifetime of hermetically sealed PF chambers are also provided.
关键字
plasma focus,neutron source,pinch,plasma focus chamber,fusion neutrons
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