A. Pei

An RF system for a compact synchrotron

A 17.4 m circumference 200 MeV proton synchrotron, the Cooler Injector Synchrotron (CIS), is being commissioned at the Indiana University Cyclotron Facility. The compact synchrotron will be used as the injector for the electron-cooled IUCF Cooler Synchrotron. The RF system design uses digital signal processing (DSP) to directly modulate a digital RF synthesizer for beam feedback control. A wide band tunable RF cavity uses non-uniform ferrite biasing to achieve a 10:1 frequency coverage with good VSWR performance and low power requirement.

The Indiana University Cooler injection synchrotron RF cavity

A small 2.2 Tesla-meter booster synchrotron is under construction at the Indiana University Cyclotron Facility to boost polarized beam performance in the electron cooled Indiana University Cooler Synchrotron. Polarized light proton or deuteron beam from a high intensity polarized ion source will be preaccelerated to 7 and 6 MeV respectively by an RFQ/DTL accelerator. The beams are then debunched to reduce the energy spread and strip-injected into the booster synchrotron. The booster RF system must accomplish the tasks of beam capture and acceleration. At the end of the acceleration cycle, the beam phase needs to be aligned to the Cooler synchrotron RF for bucket-to-bucket beam transfer. A single RF cavity in the ring will provide the necessary RF field to accomplish the above tasks.

The Indiana University Cooler injector synchrotron RF system

A 2.2 Tesla-meter synchrotron with 17.4 m circumference is being built at the Indiana University Cyclotron Facility (IUCF). The purpose of the project is to achieve higher luminosity for nuclear physics experiments using electron cooled polarized light ion beams in the IUCF Cooler synchrotron. The injection line for the booster synchrotron consists of an RFQ/DTL linear accelerator delivering a 7 MeV proton beam and a 6 MeV deuteron beam for the booster injection. A debunching system will be installed in the injection beamline to reduce the energy spread of beams out of the linear accelerators. Charge-exchange injection is used for high intensity multiturn beam accumulation. The booster output beams, 200 MeV for protons and 105 MeV for deuterons, will be transferred bucket to bucket to the IUCF Cooler synchrotron. The rf system design for the booster synchrotron is presented in this paper.

First test of orbit response matrix in proton storage ring

The orbit response matrix method is applied to experimentally determine the Cooler Ring optics at the Indiana University Cyclotron Facility (IUCF). We have carried out two experiments in Oct. And Nov. 1996 to measure the orbit response of the IUCF Cooler Ring. An analysis software was adopted from the NSLS, BNL. In our analysis, strength error in quadrupoles and steering dipoles, and amplifier gain in BPMs are included as fitting parameters. However, effects of the linear and non-linear coupling are excluded in our preliminary analysis. Since the resolution of our BPM system is of the order of 10 /spl mu/m, we will address the effect of BPM resolution on the applicability of the orbit response matrix method in proton storage rings.

A method of detecting coherent synchrotron modes

Abstract A method for measuring coherent longitudinal synchrotron modes is developed and tested at the Indiana University Cyclotron Facility Cooler Ring. This method can be used to detect the onset of coherent instability and can provide important diagnosis for the control of beam brightness. Some possible improvement of this technique is discussed.

The lattice design of Indiana University Cyclotron Facility Cooler Injector Synchrotron

This paper reports lattice design studies of a low energy booster at the Indiana University Cyclotron Facility (IUCF). This booster will be used as an injector, which is named as Cooler Injector Synchrotron (CIS), for the existing IUCF Cooler ring. The IUCF CIS will be able to accelerate high-intensity polarized protons or deuterons coming from a RFQ linac from 7 MeV (6 MeV) to 200 MeV (105 MeV). The beam bunch then will be extracted and injected into the Cooler ring for further acceleration. The finalized lattice design for the CIS has four superperiods. Each period is composed of a drift space and a dipole magnet which has 90/spl deg/ bending angle and 12/spl deg/ edge angle at both ends. The circumference of the CIS is 17.364 meters, one fifth of that of the Cooler ring. The designed horizontal and vertical tunes are 1.463 and 0.779, respectively. Possible effects from the employment of trim quadrupoles, which will be located between dipoles, are also discussed.

Hamiltonian formalism for space charge dominated beams in a uniform focusing channel

Halo formation for a test particle in a mismatched KV beam is studied. Parametric resonances of the particle Hamiltonian due to envelope modulation are studied with particular emphasis on period 2 resonance which plays dominant role in halo formation. It is shown that the onset of global chaos exhibits a sharp transition when the amplitude of modulation is larger than a critical value which is a function of a single parameter, /spl kappa/, i.e., the ratio of the space charge perveance to the focusing strength.

Longitudinal multibunch feedback experiment with switched filter bank

Fast bunch to bunch feedback is necessary to control instabilities caused by coupled bunch oscillations in high intensity machines. A time domain active feedback scheme is discussed with focus on effective error detection using simple analog filters. Fast electronic switches direct each beam bunch signal from a beam pickup to a corresponding filter. The filters are excited at steady states. The output of the filters are steady sine waves tracking the phase and amplitude variations of individual bunches, allowing easy phase comparison with a reference rf signal. Amplitude detection of the signals yields valuable information of higher order beam oscillation modes. The beam motion information is processed and multiplexed to a fast phase or amplitude modulator that drives a wideband kicker. The feedback system can also be used to correct individual bunch oscillations caused by injection errors in larger machines filled by a number of booster cycles.

Effect of parametric resonances on the bunched beam dilution mechanism

Experimental measurements of bunch dilution resulting from a modulating secondary RF cavity will be discussed. We found that parametric resonances played indeed an important role in the bunch dilution mechanism. The RMS bunch length vs. time did not satisfy the Einstein relation. Thus the bunch dilution may not be explained by a simple diffusion mechanism.