T. Ellison

Status and performance of the IUCF 270 keV electron cooling system

The IUCF (Indiana University Cyclotron Facility) 270-keV electron cooling system has demonstrated collection efficiencies of 100% (+0/-2 p.p.m.) operating with a 2-A electron beam (0.4 A/cm/sup 2/). In addition, a very complete set of longitudinal drag rate measurements have been completed. These measurements span rest frame electron-proton velocity differences of over three orders of magnitude and include the region where the average longitudinal electron-proton velocity difference is less than the electron beam longitudinal velocity spread (a region which has not previously been measured). No obvious Schottky signal suppression (evidence of beam crystallization) has been observed for low-intensity cooled proton beams, though many interesting collective phenomena have been observed for high-intensity cooled proton beams.<<ETX>>

Space charge effects and intensity limits of electron-cooled bunched beams

For stripping injection of proton beams in the IUCF Cooler, electron cooling permits us to accumulate beam currents several times higher than what can be obtained without cooling. Paradoxically, the electron cooling system also appears to be responsible for limiting peak currents in the ring at 45 MeV to about 6 mA. Thus the tool which allows us to accumulate beam also prevents us from accumulating more beam. At this point we can account for some of the observed beam features when we include space charge effects. Presently, we do not, however, have any techniques to counteract the space charge effects and thus raise this intensity limit.

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.

Experimental simulation of ground motion effects

Synchro-betatron coupling in a proton storage ring with electron cooling was studied by modulating a transverse dipole field close to the synchrotron frequency. The combination of the electron cooling and transverse field modulation on the synchrotron oscillation is equivalent to a dissipative parametric resonant system. The proton bunch was observed to split longitudinally into two pieces, or beamlets, converging toward strange attractors of the dissipative system. These phenomena might be important to understanding the effect of ground vibration on the SSC beam, where the synchrotron frequency is about 4/spl sime/7 Hz, and the effect of power supply ripple on the RHIC beam, where the synchrotron frequency ramps through 60 Hz at 17 GeV/c.<<ETX>>

The development of a prototype multi-MeV electron cooling system

Next generation electron cooling systems require a multi-MeV, 2 A DC electron beam source. Such electron cooling systems can reduce the emittances of proton and heavy ion beams leading to corresponding increases in luminosity. The technology needed to produce the necessary DC electron beams is being developed by the MEBEC group and tested at the National Electrostatics Corporation (NEC). This paper will outline the design considerations behind the system, improvements made over previous systems and the current status of the project.<<ETX>>

Betatron "Ping" tune measurement system for the IUCF cooler synchrotron/storage ring

A system has been developed for nearly real-time measurement of the coherent betatron fractional tune, /spl Delta/Q, in the IUCF cooler synchrotron/storage ring. This system measures the horizontal and vertical beam position on a turn-by-turn basis for beam currents in the range from <1 /spl mu/A to >1 mA. A fast Fourier transform of this position data is performed by a PC-based DSP module at a rate of 10 measurements per second yielding the betatron fractional tune. This tune information has been used to modify ramp parameters in order to minimize the tune shift. This paper describes the ping tune systems overall design principles, details of the various electronics systems, and compares the theoretical performance with the measured performance.<<ETX>>

Single board op-amp beam position monitors electronics

A new approach has been developed for beam position monitors (BPM) in the new 600 keV beamline. A single four layer printed circuit board, attached with short (0.3 m) cables to the electrodes, processes the raw signals and outputs voltages proportional to the beam intensity, horizontal and vertical position, and quadrapole moment. Newly-available high-speed operational amplifiers are used exclusively instead of more conventional RF components. The RF input frequency can be as high as 36 MHz, and the IF frequency is 100 kHz. The output signals from each monitor will be digitized by the VME-based control system which will provide operator displays and use the information as feedback in automatic loops controlling the beam position, envelope, and dispersion. The signal processing at each BPM location eliminates the need for expensive multiplexing and routing of signals to a central processing location. The cylindrical electrode is split into four equal segments allowing both horizontal and vertical information to be obtained at each location thus minimizing the required beamline insertion length.<<ETX>>

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.