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