Valeri Lebedev

Transverse Instabilities of Coasting Beams with Space Charge

Transverse beam stability is strongly affected by the beam space charge. Usually it is analyzed with the rigid-beam model. However this model is only valid when a bare (not affected by the space charge) tune spread is small compared to the space charge tune shift. This condition specifies a relatively small area of parameters which, however, is the most interesting for practical applications. The Landau damping rate and the beam Schottky spectra are computed assuming that validity condition is satisfied. The results are applied to a round Gaussian beam. The stability thresholds are described by simple fits for the cases of chromatic and octupole tune spreads.

Collective Instabilities in the Tevatron Complex

Although the luminosity growth for Tevatron Run II was slower than expected, steady growth of luminosity has been demonstrated during the last three years with the peak luminosity of 1.02×1032 cm−2s−1 achieved in July 2004. Suppression of instabilities has been a valuable contributor to the luminosity growth. This report discusses the transverse instabilities in the Tevatron and Recycler.

Optical Stochastic Cooling at IOTA ring

The optical stochastic cooling (OSC) represents a promising novel technology capable to achieve fast cooling rates required to support high luminosity of future hadron colliders. The OSC is based on the same principles as the normal microwave stochastic cooling but uses much smaller wave length resulting in a possibility of cooling of very dense bunches. In this paper we consider basic principles of the OSC operation and main limitations on its practical implementation. Conclusions will be illustrated by Fermilab proposal of the OSC test in the IOTA ring.

Modeling Longitudinal Dynamics in the Fermilab Booster Synchrotron

The PIP-II project will replace the existing 400 MeV linac with a new, CW-capable, 800 MeV superconducting one. With respect to current operations, a 50% increase in beam intensity in the rapid cycling Booster synchrotron is expected. Booster batches are combined in the Recycler ring; this process limits the allowed longitudinal emittance of the extracted Booster beam. To suppress eddy currents, the Booster has no beam pipe; magnets are evacuated, exposing the beam to core laminations and this has a substantial impact on the longitudinal impedance. Noticeable longitudinal emittance growth is already observed at transition crossing. Operation at higher intensity will likely necessitate mitigation measures. We describe systematic efforts to construct a predictive model for current operating conditions. A longitudinal only code including a laminated wall impedance model, space charge effects, and feedback loops is developed. Parameter validation is performed using detailed measurements of relevant beam, rf and control parameters. An attempt is made to benchmark the code at operationally favorable machine settings.

Electron Lens for the Fermilab Integrable Optics Test Accelerator

The Integrable Optics Test Accelerator (IOTA) is a research machine currently being designed and built at Fermilab. The research program includes the study of nonlinear integrable lattices, beam dynamics with self fields, and optical stochastic cooling. One section of the ring will contain an electron lens, a low-energy magnetized electron beam overlapping with the circulating beam. The electron lens can work as a nonlinear element, as an electron cooler, or as a space-charge compensator. We describe the physical principles, experiment design, and hardware implementation plans for the IOTA electron lens.