E. Benedetto SC meeting 19/3/15 Update on the LIU curve emittance vs. intensity.

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

--

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