FLASH 2 Beam Dynamics Issues Winni Decking DESY –MPY-

Winni Decking FLASH II

Winni Decking FLASH II Proposal

Winni Decking Principal Layout Operation Modes SASE operation Seeded schemes: HGHG operation HHG operation Hybrid: HHG seed with HGHG stage EEHG under study

Winni Decking Layout

Winni Decking Extraction into FLASH II Preserve beam quality Simultaneous operation of FLASH & FLASH II –Kicker – Septum extraction –No optics changes –R56 = 0 to have similar compression behavior Arc should allow for energy collimation Space for laser beam ‘injection’ Foresee space for additional beamline (FLASH III) Challenges: Very limited space between ACC7, extraction and collimation CSR induced projected emittance growth, especially important for cascaded HGHG and HHG schemes See also BD meeting and others

Winni Decking 1 st Layout of Extraction Arc okay for SASE but to large projected emittance growth (factor 4-8)

Winni Decking Principal Solutions Keep bends shorter than overtaking length and try to minimize dispersion downstream Avoid high betas where CSR transients still cause energy loss Try cancellation effects with appropriate phase advance between bending sections Optimization tends to minimum emittance cell solutions

Winni Decking Principal Solutions - Example Triple bend achromat with total of 10 deg bending

Winni Decking Open Questions Septum: Lambertson or Current-Sheet ? FLASH Bypass or commissioning dump ? Maintain FLASH collimation or move

Winni Decking First Collection of Requirements (tbc) RequirementSpecifiationPriority Intrabunchtrain switching 10 Hz switch with < 50  s rise high Maximum Energy1.6 GeVhigh Minimum Energy0.5 GeVhigh Energy Bandwidth P2P> 1 %high Max. projected emittance growthx 2 at low energy, x 1.5 at highto be verified Max. energy spreadEEHG smallest, SASE relaxedto be verified Max. slice emittance growthabout 10%medium Max. slice energy spread Arc geometry: total angle8-11 deghigh Arc gemeotry: total length to und24 mlow Distance Kicker Septum6 mmedium Collimators (beta & energy) high Extraction FLASH III high Trans. Feedback Kickers medium Tuneable R56 around zero high