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Reducing space charge tune shift with a barrier cavity

Description: Implementation of a barrier cavity rf system appears to be a straightforward and relatively inexpensive way to increase the output current of second stage synchrotrons. This note serves as a general introduction to the relevant beam dynamics and addresses the problem of driving a cavity in the short burst mode.
Date: December 31, 1995
Creator: Blaskiewicz, M.
Partner: UNT Libraries Government Documents Department

Copper coating specification for the RHIC arcs

Description: Copper coating specifications for the RHIC arcs are given. Various upgrade scenarios are considered and calculations of resistive wall losses in the arcs are used to constrain the necessary quality and surface thickness of a copper coating. We find that 10 {mu}m of high purity copper will suffice.
Date: December 1, 2010
Creator: Blaskiewicz, M.
Partner: UNT Libraries Government Documents Department

Longitudinal Stability Calculations

Description: Coupled bunch longitudinal stability in the presence of high frequency impedances is considered. A frequency domain technique is developed and compared with simulations. The frequency domain technique allows for absolute stability tests and is applied to the problem of longitudinal stability in RHIC with the new 56 MHz RF system.
Date: January 2, 2009
Creator: Blaskiewicz,M.
Partner: UNT Libraries Government Documents Department

SIMULATIONS OF RHIC COHERENT STABILITIES DUE TO WAKEFIELD AND ELECTRON COOLING

Description: The Electron cooling beam has both coherent and incoherent effects to the circulating ion beam. The incoherent longitudinal cooling could reduce the ion beam energy spread and hence cause 'over-cooling' of the ion beam. Depending on the beam densities and cooling length, the coherent interaction between the ion and electron beam could either damp or anti-damp the ion coherent motions. Using the tracking codes, TRANFT, the threshold for 'over-cooling' has been found and compared with theoretical estimation. The transverse coherent effect of electron cooling has been implemented into the codes and its effect for the bunched ion beam is shown.
Date: June 25, 2007
Creator: WANG,G. & BLASKIEWICZ, M.
Partner: UNT Libraries Government Documents Department

A MULTIPURPOSE COHERENT INSTABILITY SIMULATION CODE

Description: A multipurpose coherent instability simulation code has been written, documented, and released for use. TRANFT (tran-eff-tee) uses fast Fourier transforms to model transverse wakefields, transverse detuning wakes and longitudinal wakefields in a computationally efficient way. Dual harmonic RF allows for the study of enhanced synchrotron frequency spread. When coupled with chromaticity, the theoretically challenging but highly practical post head-tail regime is open to study. Detuning wakes allow for transverse space charge forces in low energy hadron beams, and a switch allowing for radiation damping makes the code useful for electrons.
Date: June 25, 2007
Creator: BLASKIEWICZ,M.
Partner: UNT Libraries Government Documents Department

Studies of eRHIC coherent instabilities

Description: In the presence of an effective coherent electron cooling, the rms ion bunch length in eRHIC will be kept at 8.3 cm for 250 GeV protons, which is much shorter than the current RHIC 45 cm rms bunch length. Together with the increased bunch intensity and total bunch number, coherent instabilities could be a potential limitation for achieving desired machine performance. In this study, we use the tracking code TRANFT to find thresholds and growth rates for single bunch and coupled bunch instabilities with linear chromaticity and amplitude dependent tune shift taken into account. Based on the simulation results, requirements of machine parameters such as rf voltage, linear chromaticity, and tune dependence of betatron amplitude are specified to suppress these instabilities.
Date: May 20, 2012
Creator: G., Wang & Blaskiewicz, M.
Partner: UNT Libraries Government Documents Department

Landau damping with high frequency impedance

Description: Coupled bunch longitudinal stability in the presence of high frequency impedances is considered. A frequency domain technique is developed and compared with simulations. The frequency domain technique allows for absolute stability tests and is applied to the problem of longitudinal stability in RHIC with the new 56 MHz RF system.
Date: May 4, 2009
Creator: Blaskiewicz,M.
Partner: UNT Libraries Government Documents Department

THE TRANFT USER'S MANUAL.

Description: The Fortran program TRANFT simulates transverse instabilities in circular accelerators using fast Fourier transform algorithms. It may be used for any particle type. Forces from transverse wakefields, longitudinal wakefields, and transverse detuning wakes are included, with linear transverse space charge forces included as a special case. This note describes the algorithms and their implementation in TRANFT.
Date: August 30, 2006
Creator: BLASKIEWICZ, M.
Partner: UNT Libraries Government Documents Department

Emittance growth from electron beam modulation

Description: In linac ring colliders like MeRHIC and eRHIC a modulation of the electron bunch can lead to a modulation of the beam beam tune shift and steering errors. These modulations can lead to emittance growth. This note presents simple formulas to estimate these effects which generalize some previous results.
Date: December 1, 2009
Creator: Blaskiewicz, M.
Partner: UNT Libraries Government Documents Department

Stochastic Cooling

Description: Stochastic Cooling was invented by Simon van der Meer and was demonstrated at the CERN ISR and ICE (Initial Cooling Experiment). Operational systems were developed at Fermilab and CERN. A complete theory of cooling of unbunched beams was developed, and was applied at CERN and Fermilab. Several new and existing rings employ coasting beam cooling. Bunched beam cooling was demonstrated in ICE and has been observed in several rings designed for coasting beam cooling. High energy bunched beams have proven more difficult. Signal suppression was achieved in the Tevatron, though operational cooling was not pursued at Fermilab. Longitudinal cooling was achieved in the RHIC collider. More recently a vertical cooling system in RHIC cooled both transverse dimensions via betatron coupling.
Date: January 1, 2011
Creator: Blaskiewicz, M.
Partner: UNT Libraries Government Documents Department

Effects of incoherent space charge forces on the fast head-tail instability

Description: The effects of incoherent space charge forces on the fast head-tail instability are studied numerically. It is found that incoherent space charge forces can dramatically increase the threshold current for a fixed wall impedance. The algorithm used for this study is described.
Date: July 1, 1997
Creator: Blaskiewicz, M.
Partner: UNT Libraries Government Documents Department

A barrier bucket experiment for accumulating de-bunched beam in the GAS

Description: The AGS accumulates four batches of two bunches from the 1.5GeV Booster at 7.5Hz. At an intensity of 6 x 10{sup 13} protons per AGS cycle, slow beam loss during the 400ms accumulation time is important. The experiment demonstrated the principle of accumulating beam and storing it in an essentially debunched state by using barrier cavities. When the beam is de-bunched the peak-to-average current ratio drops by an order of magnitude. By using two barriers with time varying relative phase, any number of injections is possible, limited only by the momentum acceptance of the ring. In a test with beam, six injections of one bunch yielded 3 x 10{sup 13} protons in the AGS. The benefits of reduced space charge tune shift from lower peak current suggest that barrier cavities may be a path to higher AGS intensities.
Date: July 1, 1996
Creator: Blaskiewicz, M. & Brennan, J.M.
Partner: UNT Libraries Government Documents Department

Implications of the PSR instability for the SNS

Description: The Los Alamos Proton Storage Ring suffers from a violent, high frequency, transverse instability at high beam current. The Spallation Neutron Source will be similar to the PSR and one must insure that the PSR instability will not keep SNS from reaching its design goal. Efforts toward understanding the instability are described.
Date: June 30, 2000
Creator: Blaskiewicz, M.
Partner: UNT Libraries Government Documents Department