Optimization of current waveform tailoring for magnetically driven isentropic compression experiments
- Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)
- Idaho State University, Pocatello, Idaho 83201 (United States)
The Thor pulsed power generator is being developed at Sandia National Laboratories. The design consists of up to 288 decoupled and transit time isolated capacitor-switch units, called “bricks,” that can be individually triggered to achieve a high degree of pulse tailoring for magnetically driven isentropic compression experiments (ICE) [D. B. Reisman et al., Phys. Rev. Spec. Top.–Accel. Beams 18, 090401 (2015)]. The connecting transmission lines are impedance matched to the bricks, allowing the capacitor energy to be efficiently delivered to an ICE strip-line load with peak pressures of over 100 GPa. Thor will drive experiments to explore equation of state, material strength, and phase transition properties of a wide variety of materials. We present an optimization process for producing tailored current pulses, a requirement for many material studies, on the Thor generator. This technique, which is unique to the novel “current-adder” architecture used by Thor, entirely avoids the iterative use of complex circuit models to converge to the desired electrical pulse. We begin with magnetohydrodynamic simulations for a given material to determine its time dependent pressure and thus the desired strip-line load current and voltage. Because the bricks are connected to a central power flow section through transit-time isolated coaxial cables of constant impedance, the brick forward-going pulses are independent of each other. We observe that the desired equivalent forward-going current driving the pulse must be equal to the sum of the individual brick forward-going currents. We find a set of optimal brick delay times by requiring that the L{sub 2} norm of the difference between the brick-sum current and the desired forward-going current be a minimum. We describe the optimization procedure for the Thor design and show results for various materials of interest.
- OSTI ID:
- 22597982
- Journal Information:
- Review of Scientific Instruments, Vol. 87, Issue 6; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BRICKS
CAPACITORS
COAXIAL CABLES
COMPRESSION
COMPUTERIZED SIMULATION
EQUATIONS OF STATE
IMPEDANCE
ITERATIVE METHODS
MAGNETOHYDRODYNAMICS
OPTIMIZATION
PHASE TRANSFORMATIONS
PULSES
SANDIA NATIONAL LABORATORIES
SWITCHES
TIME DEPENDENCE
WAVE FORMS