Direct comparison of wire, foil, and hybrid X-pinches on a 200 kA, 150 ns current driver

Abstract

Wire X-pinches (WXPs) have been studied comprehensively as fast ( ∼ 1\u2009ns pulse width), small ( ∼ 1\u2009 μm) x-ray sources, created by twisting two or more fine wires into an “X” to produce a localized region of extreme magnetic pressure at the cross-point. Recently, two alternatives to the traditional WXP have arisen: the hybrid X-pinch (HXP), composed of two conical electrodes bridged by a thin wire or capillary, and the laser-cut foil X-pinch (LCXP), cut from a thin foil using a laser. We present a comparison of copper wire, hybrid, and laser-cut foil X-pinches on a single experimental platform: UC San Diego’s ∼ 200\u2009kA, 150\u2009ns rise time GenASIS driver. All configurations produced 1–2\u2009ns pulse width, ≤ 5\u2009 μm soft x-ray (Cu L-shell, ∼ 1\u2009keV) sources (resolutions diagnostically limited) with comparable fluxes. WXP results varied with linear mass and wire count, but consistently showed separate pinch and electron-beam-driven sources. LCXPs produced the brightest ( ∼ 1\u2009MW), smallest ( ≤ 5\u2009 μm) Cu K-shell sources, and spectroscopic data showed both H-like Cu K α lines indicative of source temperatures ≥ 2\u2009keV, and cold K α ( ∼ 8050\u2009eV) characteristic of electron beam generated sources, which were not separately resolved on other diagnostics (within 1–2\u2009ns and ≤ 200\u2009 μm). HXPs produced minimal K-shell emission and reliably single, bright, and small L-shell sources after modifications to shape the early current pulse through them. Benefits and drawbacks for each configuration are discussed to provide potential X-pinch users with the information required to choose the configuration best suited to their needs.