DARHT Axis-I Diode Simulations II: Geometrical Scaling

Ekdahl, Carl A. Jr.¹ 

[1] Los Alamos National Laboratory

关键词: ACCELERATORS;    ATTENUATION;    BEAM CURRENTS;    CATHODES;    CHEMICAL EXPLOSIVES;    DESIGN;    DIAGNOSTIC TECHNIQUES;    ELECTRONS;    HYDRODYNAMICS;    KINETIC ENERGY;    NUCLEAR WEAPONS;    RADIATIONS;    SCALING LAWS;    TESTING;   

DOI  :  10.2172/1044077
RP-ID  :  LA-UR-12-22199
PID  :  OSTI ID: 1044077
Others  :  TRN: US1203439

美国|英语

来源: SciTech Connect

【 摘 要 】

Flash radiography of large hydrodynamic experiments driven by high explosives is a venerable diagnostic technique in use at many laboratories. Many of the largest hydrodynamic experiments study mockups of nuclear weapons, and are often called hydrotests for short. The dual-axis radiography for hydrodynamic testing (DARHT) facility uses two electron linear-induction accelerators (LIA) to produce the radiographic source spots for perpendicular views of a hydrotest. The first of these LIAs produces a single pulse, with a fixed {approx}60-ns pulsewidth. The second axis LIA produces as many as four pulses within 1.6-{micro}s, with variable pulsewidths and separation. There are a wide variety of hydrotest geometries, each with a unique radiographic requirement, so there is a need to adjust the radiographic dose for the best images. This can be accomplished on the second axis by simply adjusting the pulsewidths, but is more problematic on the first axis. Changing the beam energy or introducing radiation attenuation also changes the spectrum, which is undesirable. Moreover, using radiation attenuation introduces significant blur, increasing the effective spot size. The dose can also be adjusted by changing the beam kinetic energy. This is a very sensitive method, because the dose scales as the {approx}2.8 power of the energy, but it would require retuning the accelerator. This leaves manipulating the beam current as the best means for adjusting the dose, and one way to do this is to change the size of the cathode. This method has been proposed, and is being tested. This article describes simulations undertaken to develop scaling laws for use as design tools in changing the Axis-1 beam current by changing the cathode size.