Sergey N. Volkov

100 ns current rise time LTD stage

LTD stages are designed to be used as a primary energy storage in high power pulsed generators. Previously the LTD stages with the current rise time of 1000 ns and 450 ns were reported. Present report describes the design and test results of the LTD stage that provides /spl sim/200 kA rising in 100 ns in the matched /spl sim/0.4 Ohm load.

1 MV ultra-fast LTD generator

Fast LTD technology looks promising for making the pulsed power generators for some applications more compact and less expensive because it does not need any pulse forming lines to produce nanosecond output pulses. In the report we present the 1 MV generator that is being produced to demonstrate the technology capability. The generator is designed to deliver a 1 MV, 125 kA, /spl sim/50 ns width at 80% of peak amplitude pulse to the /spl sim/8 Ohm vacuum diode. The stored energy of the generator is 14 kJ, the footprint /spl sim/ 2 m/sup 2/.

Development of the ultra-fast LTD stage

The technology of the fast LTD stages is proposed for 1 MV driver with the goal to get a 60 ns pulse width at 80 % of peak voltage in the diode. For this driver a new LTD-100R stage is designed consisting of 20 GA 35389 capacitors. A 1 MV driver will include 7 such stages in series and provide 1 MV, 125 kA pulse in a critically matched load. The footprint of the whole system is ∼1.75 m2. The report includes the design of the new stage and results of the tests.

Super Fast 75 ns LTD Stage

Summary form only given. In the report, we present the new super fast LTD prototype which delivers a 75 ns FWHM voltage pulse into a -0.5-0.6 Ohm matched load at ~20 GW power. The stage is designed without of peaking capacitors, it includes 32 GA35436 (8 nF, 100 kV) storage capacitors, 16 spark gap switches and magnetic core with reduced thickness of the tape (50 mum) to reduce the current losses. This stage prototype was specifically designed with an hemispherical vessel to operate with compressed gas (SF6, SF6/dry air mixtures, and pure dry air) up to 6 ata pressure, as well as with transformer oil. Test results of the stage prototype will be given and compared with numerical simulation.

Lifetime of the HCEI spark gap switch for linear transformer drivers

Spark gap switches, storage capacitors, and ferromagnetic cores are the most important components of the Linear Transformer Driver (LTD) cavities. Depending on their output voltage and current, LTD-based accelerators may need several thousands switches, hence the switch lifetime is of crucial importance. Unlike the capacitors and the cores, the LTD switches are still in the developmental stage and are designed and built mainly by various laboratories; thus the lifetime of different switches may vary. In this paper we present recent results of the first full-scale experiments that were aimed to evaluate the life-time of the LTD switches developed by HCEI.

Square pulse LTD

The usual LTD architecture [1, 2] provides sine shaped output pulses that may not be suitable in flash radiography, high power microwave production, z-pinch drivers, and certain other applications. A more suitable driver output pulse would have a flat or inclined top (slightly rising or falling). In this paper, we present the design and first test results of an LTD cavity that generates this type of the output pulse by including within its circular array some number of the third harmonic bricks in addition to the standard bricks.

Externally triggered gas diverters for water line protection

Summary form only given, as follows. As the capacitive storage discharges into the inductive load, the energy is oscillating and after the peak of the load current the capacitive storage begins to charge in opposite polarity. The electrical strength of the water storage depends on the polarity of the charge voltage, and therefore, as it is charging in opposite polarity, this may result in water breakdown and damage of the water line hardware. Diverters are the devices that are used to protect water storages from the reversal voltage. They represent closing switches with some resistance connected in series with the diverter discharge gap. The diverters are located at the output of the water line, and the discharge gap has to break down close to the time the current in the load peaks. At this time the storage is bypassed by the diverters and the reflected energy is dissipated in the diverter resistors. Usually the discharge gap of the diverters locates in water and operates in self breakdown mode. This implies several problems like synchronization, and shock wave in water that may destroy the hardware. In order to avoid these problems, the diverters for SYRINX/GSI facility were designed with external electrical triggering and with the discharge gap operating in SF/sub 6/ instead of water. The report presents test results of triggerable gas diverters at HCEI at charge voltage up to 1 MV, and the performance of four such diverters on SYRINX/GSI water line.

Operation of triggerable gas diverters on SYRINX/GSI water transmission line

SYRINX/GSI is a 640 kJ installation that has been created at CEG in order to test advanced pulsed power technologies. Four fast Marxes charge a 110 ns, 0.135 Ohm Water Transmission Line (WTL) in /spl sim/700 ns to /spl sim/600 kV, downstream the WTL locates the 110 nH vacuum inductive storage, and the POS. During tests in full configuration it was found that the WTL can be damaged due to breakdowns in water as the reversal voltage in WTL exceeds /spl sim/350 kV. The report presents the design and the operation of the triggerable gas diverters that were developed at HCEI and installed on SYRINX/GSI to protect the WTL from reversal voltage.