An Investigation of Stochastic Cooling in the Framework of Control Theory

This report provides a description of unbunched beam stochastic cooling in the framework of control theory. The main interest in the investigation is concentrated on the beam stability in an active cooling system. A stochastic cooling system must be considered as a closed-loop, similar to the feedback systems used to damp collective instabilities. These systems, which are able to act upon themselves, are potentially unstable. The self-consistent solution for the beam motion is derived by means of a mode analysis of the collective beam motion. This solution yields a criterion for the stability of each collective mode. The expressions also allow for overlapping frequency bands in the beam spectrum and thus are valid over the entire frequency range. Having established the boundaries of stability in this way, the Fokker-Planck equation is used to describe the cooling process. This description does not include collective effects and thus a stable beam must be assumed. Hence the predictions about the cooling process following from the Fokker-Planck equation only make physical sense within the boundaries of beam stability. Finally it is verified that the parameters of the cooling system which give the best cooling results are compatible with the stability of the beam.Comment: 64 pages, latex, 11 eps-figures appended as uuencoded file, german hyphenation corrected I

Wake potential expansion using Gaussian basis functions

A method is described to decompose arbitrary bunch distributions into a set of Gaussian basis functions. This expansion allows the reconstruction of the wake fields generated by the bunch in its vacuum chamber environment. It is shown that the triangular-shaped basis function which have been used so far lead to substantial problems in the wake field representation. The accuracies achieved with gaussian and triangular basis functions are compared. The results show that Gaussian basis functions are more suitable to model the wake fields of the beam

Transverse coupled-bunch instabilities for non-symmetric bunch fillings

A program has been written in order to investigate transverse coupled-bunch instabilities for non-symmetric bunch fillings in the case of a large number of bunches. After a short description of the method used to find the instability growth rates, first results of the program are discussed for the SPS and LHC. In particular, a systematic study of the effect of fluctuations in the bunch populations is presented

Can Robots Replace Librarians? Experiences Using a Chat Bot to Respond to IM Questions

This poster will use text and statistical data to describe the conditions that led to development of a chat bot. It will use text and graphics to illustrate the steps involved in building and launching the bot, and it will use text and statistical data to illustrate its functionality in responding to IM reference questions. A laptop will also be available to demo backend (developer code, etc.) as well as frontend (bot responses to questions in real time Two or three takeaways - The poster session will demonstrate the basic steps that are needed to integrate a chatbot to library chat software - The session will show cases where a chatbot can be helpful (and where it is not

104. "Poseidon"-Reise "Nordostatlantik 83" Fahrtbericht 1. Abschnitt, Kiel - Ponta Delgada vom 6. September - 25. September 1983 [POS104/1]

Die Reise war Bestandteil der Arbeiten des SFB 133 "Warmwassersphäre". Der 1. Fahrtabschnitt sah neben dem Auswechseln von Langzeitverankerungen die Durchführung von hydrographischen Schnitten vor, die auf die großräumige Erfassung des Nordatlantischen Stromes beim Oberqueren des Mittelatlantischen Rückens zielte. Die Festlegung der Schnitte nördlich der Azoren war in Absprache mit französischen Kollegen erfolgt, die ein analoges Programm südlich der Azoren im Juli/August '83 durchgeführt hatten (deutsch-französisches Gemeinschaftsprojekt "Topogulf")