K. Reece

High intensity proton acceleration at the Brookhaven AGS-an update

The AGS accelerator complex is into its third year of 60+/spl times/10/sup 12/ (teraproton=Tp) per cycle operation. The hardware making up the complex as configured in 1997 is briefly mentioned. The present level of accelerator performance is discussed. This includes beam transfer efficiencies at each step in the acceleration process, i.e. losses; which are a serious issue at this intensity level. Progress made in understanding beam behavior at the Linac-to-Booster (LtB) injection, at the Booster-to-AGS (BtA) transfer as well as across the 450 ms AGS accumulation porch is presented. The state of transition crossing, with the gamma-tr jump is described. Coherent effects including those driven by space charge are important at all of these steps.

Generalized emittance measurements in a beam transport line

A generalized emittance-measurement program has been developed. Beam line specifics are entirely resident in data tables, not in program code. For instrumentation, the program requires one or more multiwire profile monitors; one or multiple profiles are acquired from each monitor, corresponding to one or multiple tunes of the transport line. Emittances and Twiss parameters are calculated using generalized algorithms. The required matrix descriptions of the beam optics are constructed by an online general beam modeling program. Design of the program, its algorithms, and initial experience with it is described.<<ETX>>

Overcoming weak intrinsic depolarizing resonances with energy-jump

In the recent polarized proton runs in the AGS, a 5% partial snake was used successfully to overcome the imperfection depolarizing resonances. A polarized proton beam was accelerated up to the required RHIC injection energy of 25 GeV. However, a significant amount of polarization was lost at 0+/spl nu//sub y/, 12+/spl nu//sub y/ and 36+/spl nu//sub y/, which is believed to be partially due to the coupling resonances. To overcome the coupling resonance, an energy-jump was generated by rapidly changing the beam circumference using the powerful AGS RF system. It clearly demonstrates that the novel energy-jump method can successfully overcome coupling resonances and weak intrinsic resonances.

Partial Siberian snake experiment at the AGS

A 9° solenoidal spin rotator or 5% partial Siberian snake was used to successfully accelerate polarized protons for the first time to 10.8 GeV kinetic energy in the Brookhaven AGS. It was found that a 5% partial snake can effectively overcome 18 imperfection resonances in this energy range. We also observed an interference between the spin flip induced by an intrinsic resonance and linear coupling due to the solenoid field of the partial snake.