Online Phase Space Tomography Steve Hancock The idea is to “see” into longitudinal phase space at the click of a mouse. The Tomoscope application serves to simplify the acquisition of a mountain range of bunch profile data and to automate the reconstruction.

Motivation Tomography provides a phase space image that is not only instructive, but affords beam measurements of unprecedented precision that are remarkably immune to both systematic errors and noise. Cf., a Gaussian fit.

Hardware Requirements A digitizer with: fast sampling and good analogue bandwidth (depending on bunch length); moderate segmentable memory; trigger fine delay; short trigger re-arm deadtime (compared with the synchrotron period); time stamps. A revolution train with: low jitter; divide-by-N burst generator. A well-matched longitudinal pick-up with: sufficient bandwidth (to resolve bunch structure); good low-frequency response (to establish the zero-particle baseline).

Acquisitions In addition to the digitized bunch profile data, several machine parameters are also required: the rf voltage and harmonic number; the dipole magnetic field and ramp rate. These must be acquired at the same (coarse) timing that starts the burst of (fine) triggers for the digitizer. All other machine parameters are static and can be loaded from a template.

Application Program (1)

Application Program (2) Tomography has never been a formal project with its own budget. It was well- established offline (see http://cern.ch/tomography) long before the resources could be found to produce an application program. This has shaped the software, which is written in C and borrows chunks of code from the BSM to control a Tektronix oscilloscope via GPIB. The processing steps rely on the effort invested offline: all the acquired data, static parameters and some relevant ’scope settings are piped into a Fortran 95 reconstruction program; the results are written to intermediate files; Mathematica is invoked via MathLink to post-process these files; the Mathematica output appears as Postscript graphics on the display. The data at step 1 can also be saved for processing offline because a consistent en clair file format has been established. Archived data can even be loaded into the application for direct comparison with current beam performance.

Extensions…