A   B   C   D   E   F   G   H   I   J   K   L   M   N   O   P   Q   R   S   T   U   V   W   X   Y   Z    

Busby, R.

Paper Title Page
TPAT087 The Effect of Magnetic Field Errors on Dynamical Friction in Electron Coolers 4206
 
  • D.L. Bruhwiler, D.T. Abell, R. Busby, S.A. Veitzer
    Tech-X, Boulder, Colorado
  • A.V. Fedotov, V. Litvinenko
    BNL, Upton, Long Island, New York
 
  Funding: Work supported by US DOE grants DE-FG03-01ER83313 and DE-FG03-95ER40926.

A proposed luminosity upgrade to the Relativistic Heavy Ion Collider (RHIC) includes a novel electron cooling section,* which would use ~55 MeV electrons to cool fully-ionized 100 GeV/nucleon gold ions. A strong (1-5 T) solenoidal field will be used to magnetize the electrons and thus enhance the dynamical friction force on the ions. The physics of magnetized friction is being simulated for RHIC parameters, using the VORPAL code.** Most theoretical treatments for magnetized dynamical friction do not consider the effect of magnetic field errors, except in a parametric fashion.*** However, field errors can in some cases dramatically reduce the velocity drag and corresponding cooling rate. We present a simple analytical model for the magnetic field errors, which must be Lorentz transformed into the beam frame for use in our simulations. The simulated dynamical friction for the case of a perfect solenoidal field will be compared with results from this new model, for parameters relevant to RHIC.

*Fedotov et al., Proc. 33rd ICFA Adv. Beam Dynamics Workshop (2004). **Nieter & Cary, J. Comp. Phys. 196 (2004). ***Parkhomchuk, Nucl. Instr. Meth. Phys. Res. A 441 (2000).

 
TPAT092 Numerical Studies of the Friction Force for the RHIC Electron Cooler 4278
 
  • A.V. Fedotov, I. Ben-Zvi, V. Litvinenko
    BNL, Upton, Long Island, New York
  • D.T. Abell, D.L. Bruhwiler, R. Busby, P. Schoessow
    Tech-X, Boulder, Colorado
 
  Funding: Work performed under the auspices of the U.S. Department of Energy.

Accurate calculation of electron cooling times requires an accurate description of the dynamical friction force. The proposed RHIC cooler will require ~55 MeV electrons, which must be obtained from an RF linac, leading to very high transverse electron temperatures. A strong solenoid will be used to magnetize the electrons and suppress the transverse temperature, but the achievable magnetized cooling logarithm will not be large. Available formulas for magnetized dynamical friction are derived in the logarithmic approximation, which is questionable in this regime. In this paper, we explore the magnetized friction force for parameters of the RHIC cooler, using the VORPAL code.* VORPAL can simulate dynamical friction and diffusion coefficients directly from first principles.** Various aspects of the friction force, such as dependence on magnetic field, scaling with ion charge number and others, are addressed for the problem of high-energy electron cooling in the RHIC regime.

*C. Nieter & J.R. Cary, J. Comp. Phys. 196 (2004), p. 448. **D.L. Bruhwiler et al., Proc. 33rd ICFA Advanced Beam Dynamics Workshop (2004).