This page contains the complete thesis of Simon Jolly, entitled “An Intra-Pulse Fast Feedback System for a Future Linear Collider”. A large amount of information in this thesis relates directly to the tests carried out as part of FONT Run 1, from February 2001 to September 2002. Each chapter of the thesis is available as both a web page and a PDF file. The HTML pages were created largely with the HTML-rendering utility TTH, with a fair bit of tinkering required to make the equations render correctly. The original thesis was typeset exclusively using pdflatex - with a little help initially from TeXShop - hence the use of JPEG and PDF graphics. All the graphics and figures used in the thesis can be found in the Figures directory - a number of the figures are available in the original PDF format (which is used in the TeX) and as JPEG's (for viewing on the web).
Please note: all figures contained in this thesis are the property of their respective authors. Reproduction and use of any of these figures is expressly forbidden without the prior permission of the relevant author. Figures that have been reproduced from a 3rd party are referenced as such: please see the accompanying References for details of the original author.
The source TeX files used by TTH to generate the HTML can be found in the TTH_TeX directory - these TeX files have been modified slightly so that TTH can understand them (problems existed with generating the matrices, for example). A number of template files were used, written by David Bailey at Oxford - all of these, along with the original TeX files, can be found in the Source Code directory. You can also find some useful files, such as the crests for Oxford and Exeter and some guidelines for including figures in LaTeX, in the Useful Files directory. Happy reading...
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Abstract
An intra-pulse Interaction Point fast feedback system (IPFB) has been designed for the Next Linear Collider (NLC), to correct relative beam-beam misalignments at the Interaction Point (IP). This system will utilise the large beam-beam kick that results from the beam-beam interaction and apply a rapid correction to the beam misalignment at the IP within a single bunch train. A detailed examination of the IPFB system is given, including a discussion of the necessary electronics, and the results of extensive simulations based on the IPFB concept for fast beam correction are presented. A recovery of the nominal luminosity of the NLC is predicted well within the NLC bunch train of 266 ns.
The FONT experiment — Feedback On Nanosecond Timescales — was proposed as a direct test of the IPFB concept and was realised at the NLC Test Accelerator at SLAC. As part of FONT, a novel X-band BPM was designed and tested at the NLCTA. The results of these tests with the NLCTA short and long-pulse beam are presented, demonstrating a linear response to the position of the 180 ns long-pulse beam: measurements show a time constant of ~1.5 ns and a precision of better than 20 μm. A novel BPM processor for use at X-band, making use of the difference-over-sum processing technique, is also presented in detail, with results given for both short and long-pulse beams.
The FONT design concepts and modification of the IPFB system for use at the NLCTA are described. The design of a fast charge normalisation circuit, to process the difference and sum signals produced by the BPM processor, forming part of the FONT feedback circuit, is detailed extensively. Bench tests of the feedback electronics demonstrate the effectiveness of the normalisation and feedback stages, for which a signal latency of 11 ns was measured. These bench tests also show the correct operation of the normalisation and feedback principles. Finally, the results of a full beam test of the FONT system are presented, during which a system latency of 70 ns was measured. These rigorous tests establish the soundness of the IPFB scheme and show correction of a mis-steered bunch train within the full NLCTA pulse length of 180 ns.
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© Simon Jolly 2003