Harkay, K.

Paper	Title	Page
PST03	Methods for Quantitative Interpretation of Retarding Field Analyzer Data	91
	J. Calvey, J. Crittenden, G. Dugan, M. Palmer Cornell University - CLASSE K. Harkay Argonne National Laboratory
	A great deal of Retarding Field Analyzer (RFA) data has been taken as part of the CesrTA program at Cornell. Obtaining a quantitative understanding of this data requires use of cloud simulation programs, as well as a detailed model of the RFA itself. In some cases the RFA can be modeled by postprocessing the output of a simulation codes, and one can obtain “best fit” values for important simulation parameters using a systematic method to improve agreement between data and simulation. In other cases, in particular in high magnetic field regions, the presence of the RFA can have an effect on the cloud, and one needs to include a model of the RFA in the simulation program itself.
MOD00	Electron Cloud Issues for the APS Superconducting Undulator
	K. Harkay, Y. Ivanyushenkov, R. Kustom, E. Moog, R. Rosenberg, E. Trakhtenberg Argonne National Laboratory A. Garfinkel, L. Boon Purdue University S. Casalbuoni Karlsruhe Institute of Technology
	The APS Upgrade calls for the development and commissioning of a superconducting undulator (SCU) at the Advanced Photon Source (APS), a 7-GeV electron synchrotron. Operation of an SCU at ANKA, also an electron ring, suggests that electron multipacting may in part be responsible for the observed heat load and pressure rise, but this effect is not predicted by an electron cloud generation code. It was found at APS that while the cloud code POSINST agreed fairly well with Retarding Field Analyzer (RFA) data for a positron beam (operated 1996-98), the agreement was less satisfactory for the electron beam. The APS data suggest that the photoelectron model is not complete. Given that the heat load is a critical parameter in designing the cryosystem for the SCU and given the experience at ANKA, a study is underway to minimize the possible contribution to the heat load by the electron cloud at APS, the photoelectrons in particular. In this talk, the results from POSINST are presented. Preliminary tracking of the photon flux using SYNRAD3D for the APS SCU chamber is presented, and possible ways to mitigate the photoelectrons are discussed.
	Slides
MOD01	Analysis of Synchrotron Radiation using SYNRAD3D and Plans to Create a Photoemission Model	147
	L. Boon, A. Garfinkel Purdue University K. Harkay Argonne National Laboratory
	Electron cloud data from electron rings suggest that the photoelectron model in electron cloud generation codes is incomplete. The photoelectron model will be important in modeling the cloud generation on components downstream of wigglers, which can produce a very high photon flux on the wall in a local region. The code SYNRAD3D has been developed in the context of the Bmad accelerator physics software library. SYNRAD3D includes computation of synchrotron radiation and propagation in 3D through a vacuum chamber. The probability of reflection vs. absorption of the photons on the chamber wall is included, using data from the literature. We used SYNRAD3D to model the photon flux for the ILC damping ring. For simplicity in modeling, we started with a round chamber and varied parameters such as the number of simulation-generated photons, bin size, photon energy cutoff, and whether photons reflect off the wall. With a realistic photon flux and distribution, we can study models for the photoemission. Preliminary work has begun to develop a photoelectron model using Retarding Field Analyzer (RFA) data. The work to date and future plans are described.
	Slides