Drive Beam Feedforward and Compression  Current layout  Issues  Ideas for changes in the layout

Current Layout Final Compression, Phase Correction PETS First Compression, Phase and Energy Measurement Combiner Rings DB Accelerator Gun

Issues  Energy spread is limited, i.e. a huge R56 is required for compression  An incoming energy jitter will cause a huge phase jitter  The phase correction must allow a huge correction range while maintaining an accurate phase correction (0.1deg @ 12GHz)  The correction kickers must be strong and accurate  The kickers require a lot of space and will be expensive (remember that we need 48 of these systems)

Some ideas for layout changes 1  Split phase correction in two parts => more accurate correction  Zero total R56 behind final acceleration => phase becomes independent of energy jitter Final Re-compression, Phase Correction PETS DBA 2 First Re-compression, Phase and Energy Measurement Final compression, Phase Correction CR Uncompression DBA 1 Gun First Compression, Phase and Energy Measurement

Some ideas for layout changes 2  Since we don't expect any phase jitter to be induced in the beam lines behind the combiner rings* we could use a single correction system instead of 24 => simplify beam lines and reduce cost *there might be some jitter from the loop, but this cannot be corrected in any case Final Re-compression, Phase Correction PETS First Re-compression, Phase and Energy Measurement Final compression, Phase Correction CR DBA 2 Uncompression DBA 1 Gun First Compression, Phase and Energy Measurement

Some ideas for layout changes 3  If the combiner rings and the loops could be build in a way that CSR is small even for final bunch lengths we could remove uncompression and re-compression. Phase measurement and correction could be integrated in the loops => simplify beam lines and reduce cost Phase Correction via orbit bump in loop PETS Phase Measurement Final compression, Phase Correction CR DBA 2 DBA 1 Gun First Compression, Phase and Energy Measurement

Some ideas for layout changes 4  Again one can argue that we might not need 24 feed-forward systems on each side => simplify beam lines and reduce cost PETS Phase Correction via orbit bump in loop Final compression, Phase Correction CR DBA 2 Phase Measurement DBA 1 Gun First Compression, Phase and Energy Measurement