Design, Simulation, and Fault Analysis of a 6.5-MV LTD for Flash X-Ray Radiography

We have developed two new gas switches that are designed to be used with linear transformer drivers. The switches, which can be DC charged to 200 kV and triggered with less than a 2-ns 1-jitter, have overall inductances ranging from 69 to 85 nH. When transferring 400 J of energy per shot, the switches have lifetimes in excess of 5000 shots. The two switches are insulated with 130-270 PSIA of air and are submerged in transformer oil during operation. These switches should allow development of linear transformer drivers that are more compact and have higher peak power.

Section: E Impedance Of the L3 Small-diameter Switchmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

New low inductance gas switches for linear transformer drivers

Woodworth

Stygar

Bennett

et al. 2010

“…ises to be, at a given pinch current and implosion time, more efficient and reliable. Seminal work by Kovalchuk et al [80,83,88,92], Bastrikov et al [81,90], Kim et al [74,82,85,87,89,91,94,101], McDaniel and Spielman [84], Mazarakis et al [76,79,86,102], Rose et al [93,100], Vizir et al [95], Leckbee et al [96,97,99], and Rogowski et al [98] have led to impressive advances in LTD technology.…”

Section: Introductionmentioning

confidence: 99%

Architecture of petawatt-classz-pinch accelerators

Stygar

Cuneo

Headley³

et al. 2007

212

128

We have developed an accelerator architecture that can serve as the basis of the design of petawatt-class z-pinch drivers. The architecture has been applied to the design of two z-pinch accelerators, each of which can be contained within a 104-m-diameter cylindrical tank. One accelerator is driven by slow ( 1 s) Marx generators, which are a mature technology but which necessitate significant pulse compression to achieve the short pulses ( 1 s) required to drive z pinches. The other is powered by linear transformer drivers (LTDs), which are less mature but produce much shorter pulses than conventional Marxes. Consequently, an LTD-driven accelerator promises to be (at a given pinch current and implosion time) more efficient and reliable. The Marx-driven accelerator produces a peak electrical power of 500 TW and includes the following components: (i) 300 Marx generators that comprise a total of 1:8 10 4 capacitors, store 98 MJ, and erect to 5 MV; (ii) 600 water-dielectric triplate intermediate-store transmission lines, which also serve as pulse-forming lines; (iii) 600 5-MV laser-triggered gas switches; (iv) three monolithic radial-transmission-line impedance transformers, with triplate geometries and exponential impedance profiles; (v) a 6-level 5.5-m-diameter 15-MV vacuum insulator stack; (vi) six magnetically insulated vacuum transmission lines (MITLs); and (vii) a triple-post-hole vacuum convolute that adds the output currents of the six MITLs, and delivers the combined current to a z-pinch load. The accelerator delivers an effective peak current of 52 MA to a 10-mm-length z pinch that implodes in 95 ns, and 57 MA to a pinch that implodes in 120 ns. The LTD-driven accelerator includes monolithic radial transformers and a MITL system similar to those described above, but does not include intermediate-store transmission lines, multimegavolt gas switches, or a laser trigger system. Instead, this accelerator is driven by 210 LTD modules that include a total of 1 10 6 capacitors and 5 10 5 200-kV electrically triggered gas switches. The LTD accelerator stores 182 MJ and produces a peak electrical power of 1000 TW. The accelerator delivers an effective peak current of 68 MA to a pinch that implodes in 95 ns, and 75 MA to a pinch that implodes in 120 ns. Conceptually straightforward upgrades to these designs would deliver even higher pinch currents and faster implosions.

“…Linear transformer drivers are a developing pulsedpower architecture that may dramatically reduce the size and cost of high-voltage, high-current pulsed-power accelerators [1][2][3][4][5][6]. Linear transformer drivers, however, place stringent demands on gas switches, requiring gas switches that can be DC charged to $200 kV, triggered with $5-10-ns one sigma jitter [7], be low inductance, have very low prefire and no-fire rates, and have lifetimes of at least several thousand shots.…”

Section: Introductionmentioning

confidence: 99%

“…These switches have been previously described in the literature [4,17]. Figure 3 shows a photograph of one switch used in Sandia's LTDR facility [5] and in Sandia's LTD-II cavity [18]. These switches have six $6-mm wide high-voltage gaps that are insulated by dry air.…”

Section: Introductionmentioning

confidence: 99%

Low-inductance gas switches for linear transformer drivers

Woodworth

Alexander

Gruner³

et al. 2009

We are investigating several alternate gas-switch designs for use in linear transformer drivers. To meet linear-transformer-driver (LTD) requirements, these air-insulated switches must be DC charged to 200 kV, be triggerable with a jitter of 5 ns or less, have very low prefire and no-fire rates ( $ 1 in 10 4 shots), and have a lifetime of at least several thousand shots. Since the switch inductance plays a significant role in limiting the rise time and peak current of the LTD circuit, the inductance needs to be as low as possible. The switches are required to conduct current pulses with $100-ns rise times and 20-80 kA peak currents, depending on the application. Our baseline switch, designed by the High Current Electronics Institute in Tomsk, Russia, is a six-stage switch with an inductance on the order of 115 nH that is insulated with 47-67 psia of air. We are also testing three smaller two-stage switches that have inductances on the order of 66-100 nH. The smaller switches are insulated with 92-252 psia of air.