W. van Asselt

Resonant extraction parameters for the AGS Booster

Brookhavens AGS Booster is the injector for the AGS. It is being modified to send resonant extracted heavy ions to a new beam line, the Booster Applications Facility (BAF). The design of the resonant extraction system for BAF was described previously. This note will give a more detailed description of the system and describe the predicted resonant beam time structure. We will describe tune space manipulations necessary to extract the resonant beam at the maximum Booster rigidity, schemes for performing resonant extraction, and describe the modifications required to perform bunched beam extraction to the BAF facility.

A fast chopper for programmed population of the longitudinal phase space of the AGS

A fast beam chopper has been built that can produce an arbitrary pulse program of the 200-MeV H/sup -/ beam for synchronous injection into moving RF buckets in the Alternating Gradient Synchrotron (AGS). The chopper will eliminate RF capture losses and can be used to tailor the initial distribution in longitudinal phase space by varying the pulse parameters, width and phase, on a bunch-by-bunch time scale during multiturn injection. The chopper also serves as a studies tool, because it can provide controllable beam intensity with fixed longitudinal emittance (or conversely) and/or missing bunches. It is an electrostatic deflection device with 15 pairs of plates located above and below the 35-keV H/sup -/ beam between the ion source and the RFQ (radio-frequency quadrupole) preinjector. The plates are spaced 26-mm apart in the beam direction and connected as a slow-wave structure by coaxial cables. They are driven to +or-760 V by DC-coupled pulse generators. Beam current rise and fall times are less than 10 ns.<<ETX>>

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.

Digital transverse beam dampers for the Brookhaven AGS

A wide band, digital damper system has been developed and is in use at the Brookhaven Alternating Gradient Synchrotron (AGS). The system consists of vertical and horizontal capacitive pickups, analog and digital processing electronics, four 500 Watt wide band power amplifiers, and two pairs of strip line beam kickers. The system is currently used to damp transverse coherent instabilities and injection errors, in both planes, for protons and all species of heavy ions. This paper discusses the system design and operation, particularly with regard to stabilization of the high intensity proton beam. The analog and digital signal processing techniques used to achieve optimum results are discussed. Operational data showing the effect of the damping is presented.

Observation and correction of resonance stopbands in the AGS Booster

At the design intensity of 1.5/spl times/10/sup 13/ ppp, the space charge tune shift in the AGS Booster at injection has been estimated to be about 0.35. Therefore, the beam is spread over many lower order resonance lines and the stopbands have to be corrected to minimize the amplitude growth by proper compensation of the driving harmonics resulting from random errors. The observation and correction of second and third order resonance stopbands in the AGS Booster, and the establishment of a favorable operating point at high intensity are discussed.<<ETX>>

An AGS experiment to test bunching for the proton driver of the muon collider.

The proton driver for the muon collider must produce short pulses of protons in order to facilitate muon cooling and operation with polarized beams. In order to test methods of producing these bunches they have operated the AGS near transition and studied procedures which involved moving the transition energy {gamma} to the beam energy. They were able to produce stable bunches with RMS widths of {sigma} = 2.2-2.7 ns for longitudinal bunch areas of {minus}1.5 V-s, in addition to making measurements of the lowest two orders of the momentum compaction factor.

Overcoming intrinsic spin resonance by using an AC dipole

Depolarization from an intrinsic spin resonance can be avoided by adiabatically exciting a coherent betatron oscillation. Experimental results of creating sustained coherent betatron oscillations in the Brookhaven National Laboratory AGS, and relevant spin tracking calculations are discussed.

Multiple single bunch extraction to the AGS switchyard

In this report we will describe the multiple single bunch extraction system as utilized to deliver beams to the Brookhavens Alternating Gradient Synchrotron (AGS) switchyard area. We will describe modifications of the AGS switchyard, necessary to allow it to accept bunched beam, and results of the first commissioning of this system. The AGS Switchyard has for many years been used to simultaneously deliver (unbunched) resonant extracted beam to a set of fixed target experiments. In order to accommodate new fixed target experiments which require bunched beams, a method of sending the bunched beams to the AGS Switchyard was required. In addition, by using the AGS switchyard instead of the upstream section of the Brookhavens Relativistic Heavy Ion Collider (RHIC) injection line the accelerators can be reconfigured quickly and efficiently for filling RHIC. We will present results of the commissioning of this system, which was done in January 2001.

Effects of enhanced chromatic nonlinearity during the AGS /spl gamma//sub t/-jump

The /spl gamma//sub t/-jump designed to reduce the bunch self-field mismatch and intensity loss during the AGS transition crossing can cause significant orbit and lattice distortions and dramatically enhance chromatic nonlinear effects. Employing a low-intensity, small emittance proton bunch crossing transition with the /spl gamma//sub t/-jump quadrupoles excited, we found that the nonlinear momentum-compaction factor /spl alpha//sub 1/ increases from 2.2 to about 90 in the presence of the /spl gamma//sub t/-jump. On the other hand, this enhancement can be effectively suppressed by properly exciting the chromaticity sextupoles, reducing /spl alpha//sub 1/ from 90 to 16. The experimental measurement agrees well with computer simulations using MAD and TIBETAN.

First results of proton injection commissioning of the AGS booster synchrotron

Beam performance results for the injection phase of proton beam commissioning of the Alternating Gradient Synchrotron (AGS) booster synchrotron are presented. The beam from the 200 MeV LINAC is transported through a new beam line into the booster. This LINAC-to-booster (LTB) beam line includes a 126 degrees bend and brings the injected beam onto the Booster injection orbit through the backleg of a main-ring dipole magnet. Transfer of the beam from the LINAC to the booster, the spiralling beam, and closing of the orbit in the booster ring are discussed. Injection and transport through one sector of the ring were accomplished.<<ETX>>