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

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

A fast, flexible magnet system, consisting of Panofsky style ferrite picture frame magnet and pulsed power supply has been developed. The magnet specifications are 8 cm × 8 cm aperture, 23 cm length, 500 A pulsed/160 A DC, and a 1 μs rise time. Designed for general accelerator physics studies, the magnet may be quickly converted from dipole to quadrupole by change the winding end terminations. In the quadrupole configuration, a field gradient of 0.5 T/m has been achieved at 500 A.

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.

We observed maintained longitudinal limiting cycle oscillations, which grew rapidly once a critical threshold in the relative velocity between the proton beam and the cooling electrons was exceeded. The threshold for the bifurcation of a fixed point into a limit cycle, also known as a Hopf bifurcation, was found to be asymmetric with respect to the relative velocity. This asymmetry of Hopf bifurcation was found to be related to the electron beam alignment with respect to the stored proton beam

The Hamiltonian system with phase modulation in a higher harmonic RF cavity is experimentally studied on the IUCF cooler ring. The Poincare maps in the resonant rotating frame are obtained from experimental data and compared with numerical tracking. The formation of the stochastic layer due to the overlap of parametric resonances is discussed. The dependence of the stochastic layer on the voltage of the higher harmonic RF cavity, amplitude and frequency of the phase modulation is studied

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.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation H. Huang, L. Ahrens, J. G. Alessi, M. Beddo, K. A. Brown, G. Bunce, D. D. Caussyn, D. Grosnick, A. E. Kponou, S. Y. Lee, D. Li, D. Lopiano, A. U. Luccio, Y. I. Makdisi, L. Ratner, K. Reece, T. Roser, H. Spinka, A. G. Ufimtsev, D. G. Underwood, W. van Asselt, N. W. Williams, A. Yokosawa; Partial Siberian snake experiment at the AGS. AIP Conf. Proc. 1 September 1995; 343 (1): 90–94. https://doi.org/10.1063/1.48939 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search

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, κ, i.e., the ratio of the space charge perveance to the focusing strength

The effects of rf voltage modulation on synchrotron motion were studied experimentally. The experimental data revealed the resonance islands generated by the rf voltage modulation. With electron cooling, beam particles were observed to damp to the basins of these resonance islands or attractors, which were observed to rotate about the origin of the phase space at a half of the modulation frequency. The measured amplitude of the attractors as a function of the modulation frequency agreed very well with the theoretical prediction. The Poincaré maps in the resonance rotating frame were obtained from the experimental data and compared with tori of the Hamiltonian flow. Based on our theoretical formulation, slow beam extraction using rf voltage modulation and a bent crystal are also studied.

The longitudinal dynamics of a stored proton beam bunch, under the influence of a nonlinear damping force produced by electron cooling, was studied experimentally. The effect of the nonlinear damping force was explored by varying the relative velocity between the cooling electrons and the stored protons. Maintained longitudinal oscillations developed, which grew rapidly once a critical threshold in the relative velocity was exceeded. The bifurcation of a fixed point into a limit cycle is also known as a Hopf bifurcation. Comparisons of experimental data with numerical simulations and analytical calculations are made. Implications for cooled beam acceleration will be discussed.

When a double rf system is subjected to sinusoidal phase modulation, the Poincare surfaces of the section display a rich spectrum of resonance islands. Stable and unstable fixed points of these resonance islands form a tree of bifurcation branches which can be explained as parametric resonances generated by external phase modulation. A semianalytic determination of the condition for the bifurcation of fixed points is presented for an autonomous Hamiltonian of one degree of freedom with sinusoidal time dependent perturbation.

Measurements of lattice parameters for the Indiana University Cyclotron Facility (IUCF) Cooler synchrotron at betatron tunes close to a sum resonance line are discussed. The measured beta functions at 36 quadrupole locations and the dispersion functions at 35 Beam Position Monitor (BPM) locations are compared with calculations. The methods used to make the above measurements and the data analysis are described.

Recently the Hamiltonian of particle motion near a resonance condition was deduced at the Indiana University Cyclotron Facility Cooler Ring. It was found that linear betatron coupling complicated the analysis. A coupling correction scheme is described which reduced the coupling coefficient from 0.03 to 0.0012. When particles were kicked onto resonance islands with the coupling reduced, the island motion was stable for upwards of 1×106 turns. This stable island motion allowed for the determination of higher‐order terms in the Hamiltonian.

Synchrotron motion in the IUCF cooler ring was studied using turn‐by‐turn beam tracking on ten‐turn intervals, where the beam phase relative to the rf and the closed‐orbit position in a high‐dispersion region were measured. The synchrotron tune shift with amplitude was measured and is compared with theory. The driven response of the system was also studied using the same techniques, and was found to share many of the same characteristics of other parametric resonant systems. The experimental results did not exhibit any effects of bunch decoherence expected from the tune shift with amplitude.

Experimentally obtained Poincare maps in the resonant rotating frame for particle motion with linear coupling revealed invariant tori of the two-dimensional Hamiltonian. Using these tori, we obtained the linear coupling strength, the tune shift with betatron amplitude coefficients, and the proximity parameter to the resonance. The coupling strength obtained with this method agreed well with that obtained from measuring the beatatron tune separation of the normal modes.

The longitudinal dynamics of a stored proton beam bunch, acted upon by a nonlinear damping force, was studied experimentally at the Indiana University Cyclotron Facility Cooler Ring. The effect of the nonlinear damping force on synchrotron motion was explored by varying the relative velocity between the cooling electron and the stored proton beams. Maintained longitudinal oscillations were observed, whose amplitude grew rapidly once a critical threshold in the relative velocity between the proton and electron beams was exceeded. We attribute this phenomenon to a negative resistance instability occurring after a Hopf bifurcation.

The synchrotron motion of a beam was tracked for the first time by digitizing the phase of the beam signal from a high bandwidth wall gap monitor relative to the rf phase and the momentum deviation with a transverse beam position measurement in a high dispersion region. The measured synchrotron tune as a function of the synchrotron amplitude agrees well with theory. When the rf stable phase angle was modulated harmonically, the response of the synchrotron motion showed characteristics of chaos and bifurcations of a parametric resonant system. Manipulating the rf system to create islands in the synchrotron phase space may offer applications in future hadron colliders.