THE MULTILEVEL PROTECTION SYSTEM FOR THE VACUUM CHAMBERS OF THE HIGH-INTENSITY 590 MEV PROTON BEAM LINES

The range of 590 MeV protons in steel is about 28 cm. Therefore, the PSI proton beam with its small diameter and with more than one megawatt of power acts like a welding torch when it hits the steel walls of a vacuum chamber. At the Targets M and E for example, the diameter of the beam is as small as 4 mm (σx ≈ σy ≈ 1 mm). For this case, the time to heat up steel to its melting point as a function of beam intensity is given in Fig. 1. For a 2 mA beam, the machine interlock system has to switch-off the beam in less than about 5 ms to avoid a damaged vacuum chamber or seal where the beam diameter is small. It should be pointed out here, that a hole in one of the vacuum chambers in the Target E region could cause a shutdown of up to one year duration. In order to protect the p-channel vacuum-chamber system from being damaged by the proton beam, five different classes of devices or services are installed (see also [1]):