A high-current electron-beam accelerator for pumping of a Xe 2 lamp was developed. It is intended for injection of an electron beam into cylindrical gas cavity (diameter of 400 mm, length of 1600 mm, and the absolute pressure up to 3 bars). Two electron diodes in parallel are used in the accelerator. Each diode is connected to a linear transformer driver with vacuum insulation of a secondary turn. The next parameters of the accelerator have been obtained: diode voltage -550-600 kV, diode current -276-230 kA, current rise time -160 ns, maximum power of the electron beam -130 GW, pulse width on half maximum -160 ns, electron beam energy at power level not less than half of maximum value -20 kJ. The total energy of electrons, which pass through a 40 μm Ti foil into the Xe cell, is 8-9 kJ in the 150-160 ns pulse (full width at half maximum) mean specific power of energy input into gas cavity is about 330 kW/cm 3 . Design of the accelerator and test results are presented and discussed in this paper.
Linear transformer driver (LTD) technology is actively developed at the Institute of High Current Electronics in Tomsk, Russia. This technology is being examined for use in high current high voltage pulsed accelerators. Recent development of high voltage low inductance capacitors and low inductance switches enabled to achieve ~100 ns rise time of the LTD output pulse. This technique allows one to eliminate intermediate pulse forming sections, used in the present accelerator technology, which would keep the footprint of an LTD accelerator small. LTD based drivers are currently considered for many applications, including future very high current Z-pinch drivers for inertial confinement fusion, medium current drivers with adjustable pulse length for isentropic compression experiments, and finally relatively low current accelerators for radiography and X-pinches. In this article, we present the design and test results for a new LTD stage, that operates at 100 kV charging voltage. Current amplitude up to 850 kA with ~140 ns rise time was obtained on a 0.05 Ω load. Stack of the LTD stages can be easily assembled in series or in parallel, thus providing voltage or current multiplication, respectively. Design of multi-mega-volt and multi-mega-ampere generators becomes straightforward with the LTD technology.
In the Linear Transformer Driver (LTD) technology, the low inductance energy storage components and switches are directly incorporated into the individual cavities (named stages) to generate a fast output voltage pulse, which is added along a vacuum coaxial line like in an inductive voltage adder. LTD stages with air insulation were recently developed, where air is used both as insulation in a primary side of the stages and as working gas in the LTD spark gap switches. A custom designed unit, referred to as a capacitor block, was developed for use as a main structural element of the transformer stages. The capacitor block incorporates two capacitors GA 35426 (40 nF, 100 kV) and multichannel multigap gas switch. Several modifications of the capacitor blocks were developed and tested on the life time and self breakdown probability. Blocks were tested both as separate units and in an assembly of capacitive module, consisting of five capacitor blocks. This paper presents detailed design of capacitor blocks, description of operation regimes, numerical simulation of electric field in the switches, and test results.
High voltage, high current inductors are required for many high pulsed power systems, incorporating capacitor banks. Those inductors simultaneously serve both as a pulse shaping and protection element in R-L-C circuits. A 25 kV/ 70 kA protection inductor on inductance of 1 mH with low stray field was designed, manufactured, and tested. It was designed as a quasi-toroidal system, consisting of four coils (with 0.25 mH inductance each) evenly distributed in the perimeter of a square. The structure of coils was optimized to withstand a huge electromagnetic force produced by a 70 kA current. The 0.25 mH coil is made as multi-layer solenoid (six layers) from a copper wire (6 × 4 mm 2 net crosssection) with fiberglass insulation. Layers are connected in parallel in order to decrease active resistance of the coil. This 0.25 mH coil was tested at 70 kA peak current with a pulse length of about 20 ms, which corresponds to the action integral at about 32 × 10 6 A 2 s. Maximum magnetic field inside the coil is about 12 T. A finite element analysis with the ELCUT software was used to calculate the magnetic field, temperature rise, and stresses in the protection inductor. The typical maximum stresses in our design are 100 MPa in copper coils and 140 MPa in fiberglass body tubes; these are both below the yield strength for these materials. Simulations results are compared with the experimental tests and good agreement is observed.
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