E. Benedetto
SC meeting 19/3/15
Update on the LIU curveemittance vs. intensity
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Simulations with PTC-Orbit
• On a straight line & depends on longitudinal emittance• BUT: the slope for 1.20eVs is a factor 25% lower
1.2 eVs
Nov 2014 and HB workshop
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Space-Charge simulations (PTC-Orbit)
• Transversely MATCHED distribution (Gaussian) (*)– With a given emittance– Scan on the Intensity
• Let it evolve for ~7ms, during fall of the chicane bump • Quadrupolar errors at the chicane magnets + Eddy
currents + Compensation QDE3, QDE14 (time varying)– Beta-beating (mostly in vertical) corrected– Excitation of half-integer corrected– Excitation of the integer line
(*) In longitudinal (for the time being): I let a “rectangular” distribution evolve in an accelerating bucket, h1+h2. NOT YET optimized…
Nov 2014 and HB workshop
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Space-Charge simulations (PTC-Orbit)
• 200 SC nodes• 2.5 Direct SC module• 128x128x128• 250k macroparticles
• Emittance reached at the end of the chicane bump is ~“independent” of the starting value
I=350 ppb
Initial and final longitudinal distribution
Nov 2014 and HB workshop
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Space-Charge simulations (PTC-Orbit)
• H and V Tune spread• Initial DQx extending below the integer blow-up
Red: initial 350e10 ppb,1mm Blue: final (after 7ms) for the same beam. Green: initial 350e10 ppb, 1.7 mm..
Nov 2014 and HB workshop
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What has still to be done
• Scan working point EB ongoing, see next slides
• Integration of the injection process – Transverse Jose– Longitudinal Vincenzo ongoing
• Benchmark code vs. today injection done in the past by V. Raginel but not conclusive due to uncertainties in measurements, new MDs will be done this year +GP simulations?
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Scan with working point
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However…
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Conclusions
• Working point has an effect– If Qx is increased, brightness is improved
• Is it possible to inject at (4.43,4.60)?, also (4.33,4.55)
• Is it possible to produce in a controlled way (i.e. no successive blow-up) any emittance sitting on the curve? – beam should be as Gaussian as possible
• Spikes (back again…) origin to be understood – but I’m confident they do not invalidate results – perhaps
give more blow-up -
Appendix
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• How to preserve small emittance?– Optimize optics parameters– Optimize initial distribution (also longitudinal!)– Optimize KSW– Minimize foil crossings– Optimize PSB working point
Small Emittance - High Brightness
What shall we expect in case of errors/non optimal parameters?
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Working point during PSB cycle
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te • Edge effects (rectangular magnets)• Proposed corrugated Inconel vacuum chamber new baseline (ceramic in the
original design) • Influence on beam dynamics of induced Eddy currents:
– Delay of ~50us – Higher order field components (sextupolar)
• Quadrupolar feed-down • Excitation 3rd order resonance
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BSW4
BSW3BSW2BSW1
3D magnet simulation by
B. Balhan, J. Borburgh
Perturbation by the chicane magnets
E. Benedetto, et al. IPAC14
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Shape for the chicane ramp down
• Realistic shape with a 125Hz content (So far, assumed linear decay in 5ms)
• Correction for V Beta-Beating has been computed• Almost identical results (blow-up and/or losses) than with the linear decay
Input from D. Aguglia, D. Nisbet
Computed strength in the QDE3, QDE14 and in the other quadrupoles
BSW ramp-down function and sextupolar component generated by eddy-currents
E. Benedetto, et al. IPAC14
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