Experimental Area Beams from the Anl 12.5 Bev Proton Synchrotron

The "picture frame" magnet design, the double vacuum system and the use of tuning magnets at injection have elicited some unique features in the production of beams for the experimental areas of the ZGS. For the external proton beam, the basic method of extraction is similar to other proton synchrotrons in that an energy-loss target is used to displace the circulating beam. However, the design of the ZGS is such that the necessity for plunging extraction magnets into the aperture has been eliminated. Further, the design of these nonplunging magnets is such that they are operable at a fixed field and thus eliminate the need for complicated pulsing and timing systems. Measurements using various techniques, including scintillators and TV storage systems, poloroid film, secondary emission detectors, and radioactive foil analyses have been made. For beams from internal targets, it is desirable to produce beams with various production angles, as well as being able to achieve zero degree production. It was found possible to establish three secondary beam channels looking at a common target point near the end of an octant. This point is in a nearly field-free region so that the channel angle becomes the production angle for both positive and negative particles. It is of interest that the construction of the ZGS is such that there is practically no fringe field beyond the octant edges. Furthermore, it was found possible to run targets into the octant along the inner vacuum chamber sidewalls without interfering with the injected beam.