J. Collins

Progress in commissioning the IUCF cooler

Some of the techniques used and results observed during the commissioning of the IUCF (Indiana University Cyclotron Facility) electron cooled storage ring are described. Measurements of machine properties and their comparison with design values, methods of closed-orbit corrections, and the methods used in ramping the beam to higher energies are discussed. Plans for enhancing the performance of the ring are described.<<ETX>>

Nonlinear beam dynamics studies at the IUCF cooler ring

The nonlinear beam dynamics of transverse betatron oscillations were studied experimentally at the IUCF Cooler Ring. Particles were kicked onto resonance islands and the properties of these islands were studied. The island tune was determined with high precision by Fourier analyzing the spectrum containing the islands and the properties of these island were studied. The island tune was determined with high precision by Fourier analyzing the spectrum containing the island oscillations. The island width was estimated based on a single resonance model. The Hamiltonian of particle motion near a resonance condition was thus deduced.

Beam diagnostic systems and their use in the new IUCF beam line

Diagnostic tools developed for and being used in a new 30 m beam line (BL1C) connecting the IUCF high intensity polarized ion source (HIPIOS) with the injector cyclotron are described and the results obtained with them are detailed. These devices include non-intercepting beam position monitors, wire scanners, and beam sweeper systems. Studies of rf beam bunching have been performed using a high bandwidth current readout. Programs have been developed for automatic emittance measurements and beam centering in the beam line.

Determination of the linear coupling resonance strength using 2D invariant Tori

Experimentally obtained Poincare maps in the resonant precessing frame for particle motion with linear coupling revealed invariant tori of the 2D Hamiltonian. Using these tori, we obtained the linear coupling strength, the tune shift with betatron amplitude coefficient and the proximity parameter to the resonance. The coupling strengh obtained with this method agreed well with that obtained from measuring the betatron tune separation of the normal modes.

Longitudinal phase‐space measurements at IUCF

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.

Betatron coupling correction at the IUCF cooler, leading to improved determination of fourth‐order resonance Hamiltonian

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.

Modeling of the IUCF cooler synchrotron

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.

Beam motions near separatrix

Experimental data on particle motion near the separatrix of the one dimensional (1-D) fourth-integer islands are analyzed. When the beam bunch is initially kicked to the separatrix orbit, we observed a strong decoherence in the coherent betatron motion. We find that, through intensive particle tracking simulation analysis, the decoherence has resulted from the beam being split into beamlets in the betatron phase space. However, we also observe an unexpected recoherence of coherence signal, which may result form a modulated closed orbit or the homoclinic structure near the separatrix.