Experiment in PS G. Franchetti, GSI CERN, 20-21/5/ /05/14G. Franchetti1

PS measurements /05/14G. Franchetti2 R. Wasef, A. Huschauer, F. Schmidt, S. Gilardoni, G.Franchetti q y0 = s Resonance:q x +2 q y = 19 I = 2A Dqx = Dqy = Measurement Q x0 SPACE CHARGE 2013

Presence of natural resonance was not included, then we tried by enhancing the resonance strength 21/05/14G. Franchetti3 I=4A Simulation q y0 = 6.47

For a stronger resonance excitation but this is an artificial enhancement 21/05/14G. Franchetti4 I=6A Simulation q y0 = 6.47

Modeling was still incomplete 21/05/14G. Franchetti5 I=2A q y0 =6.47 Simulation new simulations performed after the visit of Frank Schmidt at GSI. Correcting the PS model in computer code.

Adding random errors 21/05/14G. Franchetti6 sigma = 10% sigma = 10% but distribution of errors with inverted sign, same seed (“inverted seed”)

For larger random errors of the same seed 21/05/14G. Franchetti7 sigma = 20% inverted seedsigma = 40 % inverted seed

Emittance evolution 21/05/14G. Franchetti8 q x0 = sec q y0 = 6.47 Measurement Simulation “inverted seed” 10%

Final/Initial distribution for the “inverted seed” 10%, I=2A 21/05/14G. Franchetti9 initial final initial final q y0 = 6.47 q x0 = 6.11 q y0 = 6.47 q x0 = 6.11

With a stronger current I=4A, to include artificially a pre-existing resonance 21/05/14G. Franchetti10 core growth thick halo initial final initial final Y [mm] X [mm] q y0 = 6.47 q x0 = 6.11 q y0 = 6.47 q x0 = 6.11 Simulation “inverted seed” 10%

Halo formation: experiment 21/05/14G. Franchetti11 q y0 = 6.47 q x0 = 6.11 Measurement YX

Challenges 21/05/14G. Franchetti12 The main challenges are 2 1) Reliable modeling of the nonlinear lattice 2) Understanding the coupled dynamics in the resonance crossing + space charge

1D dynamics well understood 21/05/14G. Franchetti13 The asymmetric beam response is mainly attributed to the resonance crossing of a coupled resonance. Third order resonance 1D

Halo formation/core formation 21/05/14G. Franchetti14 If the island of the frozen system go far out, than an halo is expected If the islands of the frozen system remain inside the beam edge  core growth

Halo formation through non adiabatic resonance crossing 21/05/14G. Franchetti15 Third order resonance 1D Halo

Coupled dynamics much more difficult 21/05/14G. Franchetti16 What is it an island ? What is it a fix point ? Resonance 

Fix-lines 21/05/14G. Franchetti17 Fix points are points in phase space that after 3 turns go back to their initial position In 4D this dos not happen, but in 4D after 3 turns a point does not return back on the same point. However there are points that after each turn remains on a special curved line. This line is closed and it span in the 4D phase space. 3 Qx = N Qx + 2Qy = N

Fix-line projections 22/5/2014G. Franchetti18 Frank Schmidt PhD

Properties 22/5/2014G. Franchetti19 What are the parameters that fix these sizes ? Δ r K2 (driving term) Stabilizing detuning (space charge, octupole, sextupole-themself)

What happen to the islands ? 21/05/14G. Franchetti20

What happen to the islands ? 21/05/14G. Franchetti21 fix- line “island”

For sextupoles alone fix-lines set DA ! 21/05/14G. Franchetti22 From trackingFrom theory ax ay

What do the stable fix-lines do to the beam ? 21/05/14G. Franchetti23 After turns Here we change the distance of the resonance. Stabilization with an octupole

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21/05/14G. Franchetti26 Halo Core growth y x

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Effect of space charge: Gaussian round beam 21/05/14G. Franchetti30 Qx + 2 Qy = N DQy DQsc

3 rd order fix-line controlled by the space charge of a Gaussian CB 21/05/14G. Franchetti31 DQsc = DQy = 0.08

21/05/14G. Franchetti32 DQsc = DQy = 0.08

21/05/14G. Franchetti33 DQsc = -0.3 DQy = 0.08 x [1] y [1]

trapping/non trapping 21/05/14G. Franchetti34 Resonance crossing without trapping Resonance crossing with trapping FAST (10000 turns) SLOW (10000 turns)

21/05/14G. Franchetti35 Resonance crossing with trapping + larger fix-line

time evolution fast crossing 21/05/14G. Franchetti36

time evolution slow crossing 21/05/14G. Franchetti37

Summary 21/05/14G. Franchetti38 After the lattice model is improved the simulation shows an emittance increase ratio of 2 Beam distribution from simulations have the same pattern as for the measured Theory of the fix-lines with detuning (space charge or octupoles) is essential to understand the extension and population of the halo/core growth  hence to control the negative effects: impact on effective resonance compensation in SIS100…. but it would be nice to measure it! Random errors have a significant effect and may bring the emittance growth ratio to 2.5 A pre-existing resonance is not properly included The asymmetric beam response is explained in terms of the periodic crossing of fix-lines with the beam