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| Pisces Upgrade - Dump Plate Fabrication |
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| Pisces Upgrade - Dump Plate Fabrication |
These dump plates are fabricated from CAD 18200 chromium copper to utilize the material's high-strength, high-temperature capability. The fabricator is Kemco, Inc., of St. Louis, MO, under subcontract to The Boeing Company. There are two dump plates, one at each end of the plasma column, which intercept the plasma column in conjunction with the plasma target.
At the target-end, the plasma interaction target is positioned directly in the path of the beam. Therefore the beam dump is annular shaped and sets behind, in the shadow of the target. The heat flux may be as high as 15 MW/m2 on the inner radii. The figure below of the partially completed target dump plate illustrates the four circular coolant passages. High pressure water enters the inlet and is distributed by the tapered manifold into the coolant passages. On the opposite side of the heat exchanger, the coolant is collected and removed through the outlet. The side shown will face the plasma. The next fabrication step is to fill all coolant channels with a wax material and electroform 0.080 inch of copper over the entire surface. This will close all coolant channels and provide a smooth surface facing the plasma.
The back side of the brazed assembly is rather simple, with only the coolant inlet and outlet pipes emanating from their braze bosses. Four small holes are provided to mount the dump plate.
On the opposite end of the plasma column from the target is a reflecting dump plate, shown in the next photo. This dump plate will also have to absorb the same heat load as the target (15 MW/m2). The same circular coolant arrangement was used on this dump plate, but the hole is closed up with a solid surface and backed up with a high performance heat exchanger. Details of this heat exchanger will be shown in a following photo. Four additional holes are provided: three viewports to examine the plasma and one gas feed.
The next photograph shows the finished reflecting dump plate with the coolant passages closed with the electroformed copper. In addition, there is a 0.005" nickel plating added to the surface to help minimize sputtering from the surface during plasma operation.
The back side of the reflecting dump plate shown below is more interesting than the target-end. Since the beam will be depositing the full heat load across the entire 9-cm diameter of the beam, the entire surface must be cooled with a high capability heat exchanger. Integral to the back of the dump plate, a finned heat exchanger is milled into the surface. High pressure water is introduced into one end of the manifold, forced at high velocity through the small passages, and removed from the opposite side. End pieces are used to enable efficient machining of the grooves. Large fins are alternated with the smaller fins to provide structural connection with the top plate. Grooves in the top plate accept the larger ribs to help support the braze connection in shear.
The following figure better illustrates the detail of the large and small ribs. The large ribs are sized to fit into slots in the cover plate (the slots are not shown in this picture). In this photo, the end plugs have not been added.
There was some difficulty getting the braze to properly adhere over the entire part, especially on the end plugs and the larger ribs and cover plate. But eventually the part was brazed to be leak-tight. The final braze assembly is shown below with the three viewports and the gas feed line installed. The part looks a little the worse for wear because of the brazing operation, but it will probably look worse after it operationally functions as the PISCES dump plate.
You may return to the PISCES Upgrade home page for more information or go directly to pages that illustrate the fabrication status of other PISCES Upgrade hardware:
The Boeing Program Manager for the PISCES Upgrade design and fabrication contract is Lester M. Waganer. The University of California - San Diego is the sponsoring agency for the Department of Energy.