Beam-loss Monitors Tn the Slc Final Focus'

Beam-loss monitors in the SLC Final Focus System &e used for protection of accelerator and detector components, optimizing adjustment of beam halo collimators, and as diagnostics of beam size and halo. Construction of a variety of monitors based on discrete ion chambers, proportional tubes, continuous 'ion chambers, and signals from the Mark II detector is reported. The interfaces to the SLC control system, the Mark II detector data acquisition system, and the SLC machine protection system are discuss& Experience with the system during SLC commissioning and operation is presented. The e+ and e-beams of the Stanford Linear Collider (SLC) must be precisely controlled so as to produce luminosity without creating unacceptable backgrounds in the Mark II detector. To assist in this process, the Final Focus System (FFS) and Interaction Region (IR) of the SLC have been instrumented with several types of radiation monitors. These provide information to the machine operators in a variety of forms optimized for specific uses. Three basic problems are addressed: 1. Protection of the accelerator and detector from beam: j related damage.' 2. Identification of the sources of unacceptable detector backgr6tinds.2 3. Optimization of machine tuning and collimation to reduce background to acceptable levels.2*3 The FFS was originally equipped with loss monitors only for protection against accelerator component damage. The monitors were later upgraded and augmented for &e. in background monitoring and minimization. Other monitors were created for protecting the Mark II detector against radiation damage. Ultimately , real time data from the Mark II has been utiiized for background minimization. When beams were first being brought into the SLC FFS in early 1987,-radiation levels were high. On several occasions dose rates of tens of thousands of rads per hour were recorded in the tunnel, with rates above a thousand rads per hour common. (All dose rates in this paper are quoted for 10 pps beams). This was sufficient to endanger accelerator control electronics, which have since been relocated to the surface. Improvements in beam quality , steering and alignment quickly brought the radiation level down. During Fall of 1988, dose rates in the FFS were routinely below 100 rads/hr, with rates near many collimators often below the resolution of the monitors. These rates, combined with recently increased shielding, are believed to be compatible with Mark II requirements.. : Since the Mark II detector was installed in early 1988, the accumulated dose near it is within …