I. CYGNUS DESIGN AND LAYOUTThe subcritical experiment (SCE) program was initiatedIn response to the programmatic need for fielding a after the 1992 moratorium on underground nuclear testing radiographic diagnostic on SCEs, a multiorganizational in support of stockpile stewardship [1]. The dynamic team was formed to develop a prototype x-ray machine. material properties of plutonium are a major topic of The major organizations involved are: Los Alamos exploration for the SCE program. In order to provide for a National Laboratory (LANL), Bechtel Nevada (BN), multilayered containment of plutonium, the SCEs are Sandia National Laboratories (SNL), and Titan/Pulse executed in the Ula underground tunnel complex at the Sciences Division (Titan/PSD). The source design is Nevada Test Site (NTS). Cygnus is a new radiographic x-based on the following three criteria: (1) it must fulfill the ray source developed for diagnostic support of the SCE radiographic source requirements as previously stated, (2) Program at NTS.it must accommodate the Ula tunnel environment in Typically, SCEs have been limited to surface terms of footprint, operations, and safety, and (3) it must diagnostics [2]. Cygnus radiography was developed to be reliable. The key to satisfying the first criterion is use complement the existing surface diagnostics, provide a of the rod pinch diode [3] which is a low-impedance, more extensive spatial view (albeit temporally limited), high-dose diode. This approach generally yields a smaller and provide internal (penetrating) measurements. The source size in comparison with other diode types. The Stallion series of SCEs consists of the following four footprint component of the second criterion was met by shots listed in chronological order: Vito, Rocco, Mario, using a modular pulsed power design where the energy and Armando. Armando was the initial experiment for storage unit is independently located with respect to the Cygnus radiography. The Rocco, Mario, and Armando accelerating cells, and where the two are connected by a tests use identical physics packages, permitting the configurable transmission line. The reliability criterion correlation of Amnwas achieved by using proven pulsed power elements, correlaton of Armando radiographic results with surface extraordinarily conservative mechanical and pulsed power results from all three shots. The main x-ray source designs, and (most importantly) an extensive test requirements for an SCE involve spot size, intensity, program. penetration, and duration. To this end Cygnus wasThe overall Cygnus layout, which shows the two designed to satisfy the following specifications:~1 mm sources as fielded at NTS/Ula, is shown in Figure 1. The source diameter, 4 Rads dose at a distance of 1 meter, major elements of Cygnus are: Marx generator, pulse -2.25 MeV endpoint energy, and < 100 ns pulse length.forming line, water transmission line, inductive voltage Two Cygnus sources (Cygnus 1, Cygnus 2) were adder (IVA), and rod pinch diode. A high voltage trigger fielded at NTS providing ...
The rod-pinch diode[1] is a self-magnetically insulated electron beam diode that is capable of producing a very bright source of hard x-rays. As fielded on the Cygnus accelerator[2], the diode operates at an impedance of 50 Ohms and produces short pulse ( ~50 ns) bremsstrahlung radiation with a 2 MeV photon endpoint energy and dose of 4 rad measured at one meter, with an x-ray spot size ~ 1mm. The source can be used to image through ~ 40 g/cm 2 of material with spatial resolution of order 300 m.
No abstract
Anodizing creates an aluminum oxide coating that penetrates into the surface as well as builds above the surface of aluminum creating a very hard ceramic-type coating with good dielectric properties. Over time and use, the electrical carrying components (or spools in this case) experience electrical breakdown, yielding undesirable x-ray dosages or failure. The spool is located in the high vacuum region of a rod pinch diode section of an x-ray producing machine. Machine operators have recorded decreases in x-ray dosages over numerous shots using the reusable spool component, and re-anodizing the interior surface of the spool does not provide the expected improvement. A machine operation subject matter expert coated the anodized surface with diffusion pump oil to eliminate electrical breakdown as a temporary fix. It is known that an anodized surface is very porous, and it is because of this porosity that the surface may trap air that becomes a catalyst for electrical breakdown. In this paper we present a solution of mitigating electrical breakdown by oiling. We will also present results of surface anodizing improvements achieved by surface finish preparation and surface sealing. We conclude that oiling the anodized surface and using anodized hot dip sealing processes will have similar results.
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