The “ Sphere Dump ” - a New Low - Cost High - Power Beam Dump Concept

This paper reveals a new high-power beam dump concept developed at SLAC. Its principal features are relatively low production costs, simple-assembly procedures , compactness, and rather high power absorption capacity. The main power absorption medium is a water-cooled bed of 1 cm diameter aluminum spheres contained in a tube. This " Sphere Beam Dump " is rated at 500 kW and its production costs are compatible with other designs at powers as low as 50 kW. The main features of the dump are discussed with emphasis on heat transfer in the bed of spheres, detection of burnout , and flow and mixing of the coolant. A prototype of such a dump was successfully tested in the electron beam at powers up to 495 kW and at an energy of 18 GeV. The experimental results are discussed and potential applications for other high-power absorbers are indicated. material. However, the length of the dump is minimized by introducing higher Z materials at appropriate distances after the shower maximum. The Power Absorption Medium To optimize power absorption and preserve compact-ness, it is desirable to have a high volume-to-surface area ratio of the power absorption medium. A catalytic hydrogen-oxygen recombiner for removal of radiolytically produced hydrogen from such a dump and other water-cooled power absorbers is described in the second part of the paper. Such topics as operational parameters, instrumentation, safety, and performance are stressed. The Sphere Beam Dump With the achievement of the Stage I design peak current of 50 mA the SLAC linac can now potentially deliver average beam powers up to approximately 600 kW at E. z 20 GeV. The result is an increasing need for beam dumps at intermediate power levels (600 ?Pav 2 100 kW). A sphere is unique in that it has the largest such ratio of any geometry. On the other hand, from a heat transfer point of view, a high surface area-to-volume ratio is most suitable. This ratio varies as 6/D for a sphere, where D is the sphere diameter. Thus, the ratio increases as the sphere becomes smaller. The minimum sphere diameter is determined by the maximum allowable pressure drop through an array or bed of spheres. The pressure drop varies inversely with the sphere diameter. The cooling fluid mass velocity should be high enough to result only in a modest bulk temperature rise and therefore preserve a large sub-cooling. The latter helps to prevent …