PROTECTION OF STORAGE-RINGS AND ION-BEAM DEVICES FROM MELTING

At normal incidence high-power beams can produce vapour and plasma at the surface immediately. However, the material of walls, septa, cups a nd other beam diagnostic devices can be protected by making use of hea t conduction into cold regions. To achieve this, the material surface is tilted against the beam axis. The limiting tilt angle is evaluated from a solution of the equation of heat dissipation, as a function of beam power density and irradiation time. Of all practical materials, c opper presents the largest tilt angle, for instance 1.2 mrad for a bea m power density of 1.5 GW/cm(2) lost over 4 mu s Since the stopping ra nge does not appear in the formula but only in a condition of validity , the result is of interest as well for high-power proton accelerators as for heavy-ion machines in the plasma-generating regime. (C) 1998 E lsevier Science B.V. All rights reserved.