University Partnerships With Community Change Initiatives: Lessons Learned From the Technical Assistance Partnerships of the William and Flora Hewlett Foundation's Neighborhood Improvement Initiative

Examines the specific role of students and faculty in providing responsive research, technical assistance, and evaluation supports to the community. Contains stories and examples from Hewlett's university-community partnership program

Prediction of long term stability by extrapolation

This paper studies the possibility of using the survival function to predict long term stability by extrapolation. The survival function is a function of the initial coordinates and is the number of turns a particle will survive for a given set of initial coordinates. To determine the difficulties in extrapolating the survival function, tracking studies were done to compute the survival function. The survival function was found to have two properties that may cause difficulties in extrapolating the survival function. One is the existence of rapid oscillations, and the second is the existence of plateaus. It was found that it appears possible to extrapolate the survival function to estimate long term stability by taking the two difficulties into account. A model is proposed which pictures the survival function to be a series of plateaus with rapid oscillations superimposed on the plateaus. The tracking studies give results for the widths of these plateaus and for the seperation between adjacent plateaus which can be used to extrapolate and estimate the location of plateaus that indicate survival for longer times than can be found by tracking.Comment: 23 pages, 15 figure

Intrabeam scattering growth rates for a bi-gaussian beam

This note finds results for the intrabeam scattering growth rates for a bi-gaussian distribution. The bi-gaussian distribution is interesting for studying the possibility of using electron cooling in RHIC. Experiments and computer studies indicate that in the presence of electron cooling, the beam distribution changes so that it developes a strong core and a long tail which is not described well by a gaussian, but may be better described by a bi-gaussian. Being able to compute the effects of intrabeam scattering for a bi-gaussian distribution would be useful in computing the effects of electron cooling, which depend critically on the details of the intrabeam scattering. The calculation is done using the reformulation of intrabeam scattering theory given in [1] based on the treatments given by A. Piwinski [2] and J. Bjorken and S.K. Mtingwa [3]. The bi-gaussian distribution is defined below as the sum of two gaussians in the particle coordinates $x,y,s,p_x,p_y,p_s$. The gaussian with the smaller dimensions produces most of the core of the beam, and the gaussian with the larger dimensions largely produces the long tail of the beam. The final result for the growth rates are expressed as the sum of three terms which can be interperted respectively as the contribution to the growth rates due to the scattering of the particles in the first gaussian from themselves, the scattering of the particles in the second gaussian from themselves, and the scattering of the particles in the first gaussian from the particles in the second gaussian.Comment: 19 pages, no figures, some equations have been correcte

Theory of electron cooling using electron cooling as an intrabeam scattering process

Electron cooling that results when a bunch of electrons overlaps a bunch of ions , with both bunches moving at the same velocity, may be considered to be an intrabeam scattering process. The process is similar to the usual intrabeam scattering, where the ions scatter from each other and usually results in beam growth. An important difference is that in electron cooling the mass of the ion is different from and much larger than the mass of the electron. This difference considerably complicates the intrabeam scattering theory. It introduces a new term in the emittance growth rate, which vanishes when the particles are identical and their masses are equal, and can give rise to emittance cooling of the heavier particles . The term that gives rise to beam growth for the usual intrabeam scattering is also present but is much smaller than the cooling term when one particle is much heavier than the other. This paper derives the results found for the emittance cooling rates due to the scattering of the ions in the ion bunch by the electons in the electron bunch.Comment: 15 page

Linear Orbit Parameters for the Exact Equations of Motion

This paper defines the beta function and other linear orbit parameters using the exact equations of motion. The orbit functions are redefined using the exact equations. Expressions are found for the transfer matrix and the emittances. Differential equations are found for the beta function and the eta function. New relationships between the linear orbit parameters are found.Comment: 14 pages, gzipped postscript paper (120k

Normal Mode Tunes for Linear Coupled Motion in Six Dimensional Phase Space

The motion of a particle in 6-dimensional phase space in the presence of linear coupling can be written as the sum of 3 normal modes. A cubic equation is found for the tune of the normal modes, which allows the normal mode tunes to be computed from the 6x6 one turn transfer matrix. This result is similar to the quadratic equation found for the normal mode tunes for the motion of a particle in 4-dimensional phase space. These results are useful in tracking programs where the one turn transfer matrix can be computed by multiplying the transfer matrices of each element of the lattice. The tunes of the 3 normal modes, for motion in 6-dimensional phase space, can then be found by solving the cubic equation. Explicit solutions of the cubic equation for the tune are given in terms of the elements of the 6x6 one turn transfer matrix.Comment: 3 pages, gzipped postscript paper (77k