FLASH 2 Beam Dynamics Issues
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DESY –MPY-
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FLASH II
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FLASH II Proposal
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Principal Layout
Operation ModesSASE operation
Seeded schemes:HGHG operationHHG operationHybrid: HHG seed with HGHG stageEEHG under study
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Layout
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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 2009.01.26 and others
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1st Layout of Extraction Arc
okay for SASE but to large projectedemittance growth (factor 4-8)
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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
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Principal Solutions - Example
Triple bend achromat with total of 10 deg bending
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Open Questions
• Septum: Lambertson or Current-Sheet ?• FLASH Bypass or commissioning dump ?• Maintain FLASH collimation or move
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First Collection of Requirements (tbc)
Requirement Specifiation Priority
Intrabunchtrain switching 10 Hz switch with < 50 s rise high
Maximum Energy 1.6 GeV high
Minimum Energy 0.5 GeV high
Energy Bandwidth P2P > 1 % high
Max. projected emittance growth x 2 at low energy, x 1.5 at high to be verified
Max. energy spread EEHG smallest, SASE relaxed to be verified
Max. slice emittance growth about 10% medium
Max. slice energy spread
Arc geometry: total angle 8-11 deg high
Arc gemeotry: total length to und 24 m low
Distance Kicker Septum 6 m medium
Collimators (beta & energy) high
Extraction FLASH III high
Trans. Feedback Kickers medium
Tuneable R56 around zero high