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Persistent URL http://purl.org/net/epubs/work/49123
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Record Id 49123
Title Beam Dynamics Simulations Through Diagnostic Devices
Abstract In this note we explore the possibility of performing matching with space charge present. Space charge gives rise to a mismatch for low energy beams. This mismatch can be very harmful for certain applications, for example the PITZ2 tomography diagnostics line. In this case, the Twiss parameters at the start of the tomography section have to be as close as possible to the design ones. As can easily be shown by a thin lens approximation, all the Twiss parameters at the start of the tomography section are fully determined, including the quadrupole strength, once the length of the FODO cells is chosen. By 'matching with space charge' we mean introducing a modification to the original matching performed with a standard optimizing routine (for example MAD8). The idea is that this modification can only compensate for the linear part of space charge and it does so by changing the quadrupole strengths. The additional problem is that the space charge force is defocusing in both planes whereas quadrupoles alternate between focusing and defocusing in either plane. However, as is known, it is possible to achieve an overall focusing effect with two or more quadrupoles. Therefore, we intend to investigate whether it is possible to modify the quadrupole strength in a precisely determined way in order to achieve the correct Twiss parameters at the entrance of the tomography section (first screen) in the presrence of space charge. The note is divided into two parts, the first part explains the theoretical aspects of the problem and the second looks at practical examples of matching with space charge. In the second part, the matching is done with the General Particle Tracer (GPT) tracking program as this is one of the few programs with which it is possible to do matching with space charge. Two examples are considered, one is an arbitrary model consisting of two quadrupoles separated by a drift at various charges, the second is the PITZ2 diagnostic line. The former is used to investigate the dependency of the space charge mismatch on the charge of the bunch. As shall be shown, there comes a point where increasing the quadrupole strength no longer has an effect on the ability to suppress the mismatch. The PITZ2 diagnostic line is used as a concrete example of this technique of compensation for a space charge-induced mismatch as shown in.
Organisation ASTeC , ASTeC-AP , CI , STFC
Keywords Matching , Physics , Space charge , EUROFEL
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Language English (EN)
Type Details URI(s) Local file(s) Year
Report CI Preprints Cockcroft-07-67. 2008. Cockcroft-07-67.pdf 2008
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