PS - ABP and LIU
A. Huschauer and G. Sterbini with contributions from:
F. Asvesta, S. Aumon, W. Bartmann, H. Bartosik, A. Beaumont, A. Blas, H. Damerau,
G. Favia, V. Forte, M. Fraser, I. Efthymiopoulos, H. Gasem, A. Guerrero, S. Hancock,
K. Hanke, M. Migliorati, F.X. Nuiry, A. Oeftiger, Y. Papaphilippou, K. Papastergiou,
D. Perrelet, S. Pittet, G. Romagnoli, C. Rossi, G. Rumolo, F. Schmidt,
M. Serluca, F. Sperati, M. Titze, P. Zisopoulos
Emittance blow-up at injection I
Priority 1
Context:
• A horizontal blow-up of around 40% is currently observed at PS
injection
Study objective:
• Disentangle the different contributions to the blow-up and determine
dominant factor
Steps to complete:
• Investigation of the contribution of the optics mismatch between BTP
and PS:
 detailed optics measurements (ring and TFL)
 controlled mismatch or injection error to probe effect
 transfer of large longitudinal emittance
o comparison between analytical model and simulations
• Simulations including collective effects (direct + indirect space charge)
2017
ABT, A. Huschauer, SC team
and new HSI-PS fellow
Emittance blow-up at injection II
Priority 1
2017
A. Huschauer, M. Serluca
and new HSI-PS fellow
Context:
• A horizontal blow-up of around 40% is currently observed at PS
injection
Study objective:
• Disentangle the different contributions to the blow-up and determine
dominant factor
Steps to complete:
• Evaluation of the contribution of the injection bump to the blow-up:
 Current configuration
 LIU configuration
o important input for EPC by March
Turn-by-turn position measured with PU outside
the region of the injection bump
Commissioning of new chromaticity control scheme
Context:
Priority 1
• Commissioning of horizontal and vertical (SS60 and SS94)
chromaticity correction sextupoles mainly for MD studies.
by mid-2017
A. Huschauer, G. Sterbini,
P. Zisopoulos, SC team,
optics team
Beam loss with zero chromaticity and no TFB
Study objective:
• Improved machine setup by separating the contributions of the
different planes (including coupling control and TFB). Will provide
important input for:




linear model (beta-beating, dispersion)
matching of TFL
effective non-linear model
transfer of bunches with large long. emittance
 Verify use of these sextupoles instead of PFW at low energy
Steps to complete:
• Verify effectiveness for chromaticity control
• Measurements and simulations to evaluate impact on resonances
(loss maps, driving terms, …)
TFB proven to effectively damp HT instabilities
Vertical emittance blow-up during the
low-energy part of the cycle
Priority 1
Context:
by mid-2017
F. Asvesta, H. Bartosik, H.
Damerau, A. Huschauer,
M. Serluca
Initial situation
• Observation of significant vertical blow-up on the injection plateau
Study objective:
• Further reduction of the blow-up on the plateau and on intermediate flat
bottom
Steps to complete:
• Implementation on operational LHC beams and further optimization of:
 low energy working point
 bucket area during first part of acceleration
 verification of satellite creation
After improved bucket area
Space charge studies towards the LIU beam parameters
Priority 1
Context:
• Demonstrating the equivalent required LIU brightness at 1.4 GeV relies on
the transfer of large longitudinal emittance bunches.
Study objective/questions to be answered:
• Demonstrate space charge mitigation with large longitudinal emittance
• Systematic investigations of the blow-up at injection, along the cycle, as
well as of the beam loss mechanisms.
Steps to complete:
• Transfer of large longitudinal emittance
• Further reduction of space charge tune spread (double harmonic, reduced
voltage during injections, constant bucket area during acceleration)
• continue measurements and simulations of structure resonance 8Qy = 50
and impact on space charge dominated beams
2017-2018 F. Asvesta, H. Bartosik, H.
Damerau, A. Huschauer,
M. Serluca + SC team
Non-linear model of the machine
Priority 1
Continuous
Context:
• Effective model (beam-based measurements) is currently used to reproduce
multipolar components of the lattice in simulations. This approach is however
insufficient for resonance/space charge studies.
A. Huschauer, I. Efthymiopoulos,
M. Serluca, O. Berrig + student
and close collaboration with MSC
and ACE
• Re-aligment of MUs shown to effect the integer stopband. Presently not understood.
Study objective/questions to be answered:
• Improve modelling of the PS magnets
Steps to complete:
• Understand the expected gain from improved modelling of the MU and from
including mis-alignments.
• Two major ingredients: 3D model of the 4-MU types (without PFW, but bent!) and
mis-alignment information
• Interface between optics repository and other databases (layout, NORMA,…):
 Include aperture, alignment, magnet strengths,…
 collaboration with MSC and
ACE is critical
Longitudinal impedance and PS-SPS transfer
Priority 1
2017-2018
Context:
• LIU-PS intensity limit dominated by longitudinal coupled-bunch instabilities
SPS injection losses WG
with input from impedance,
EC team and supported by
M. Migliorati (GS  AH)
Simulated distribution at SPS injection
• Increased longitudinal emittance to counteract instabilities constrained by
PS-SPS transfer
Study objective:
• Define mitigation strategy for longitudinal instability and optimization of the
transfer to the SPS to minimize losses
Steps to complete:
• Improve the present longitudinal impedance model to locate critical
elements
• Adiabatic bunch shortening at flat top to 6-7 ns with subsequent rotation
could be envisaged to improve PS-SPS transfer
• evaluation of electron cloud effect
• clarification of possible gain with the TFB
EC-induced CBI at PS flat top
Priority 2
Continuous
F. Asvesta, H. Bartosik, I.
Efthymiopoulos, A. Huschauer,
F. Schmidt, M. Serluca, P.
Zisopoulos
Context
• Variety of structure resonances around the current operational working point.
Especially the resonance 8Qy = 50 limits the possible vertical tune range for LHC
beams. Change of integer tunes being studied to avoid this resonance.
Phase space structure with real beam paramete
5
# 10
4
-3
py"[m]"
Alternative optics studies
Mechanical"
aperture"
3
Study objective/questions to be answered:
2
1
• Commission the PS for operation at significantly different working points and
understand hardware limitations.
0
-1
-2
• Verify the beneficial impact on performance of high-brightness beams.
-3
-4
Steps to complete:
• (6,6)  (5,7) or (6,6)  (7,5):
 achievable with F8L only (linear machine)
 (5,7) most promising, but possibly exceeding power
converter limits on F8L
-5
-2
y"[m]"
-1.5
-1
-0.5
0
0.5
1
1.5
2
# 10
• (6,6)  (7,7):
•
For phase space structure Frozen and self-consistent models ag
! Islands position can explain the beam-loss
19"
 Achievable only with PFW  very non-linear
machine, excitation of additional resonances
• Coupled optics
-3
Transition crossing with large longitudinal emittance
Priority 2
Context:
• Longitudinal blow-up in the PS is necessary to achieve the required 0.35 eVs
at extraction (0.35 x 12 = 4.2 eVs).
• Large longitudinal emittance stabilizes coupled bunch instabilities at high
energy
• Past observation: long. emittance limited to 1 eVs at transition
Study objective:
• Determine largest possible longitudinal emittance to cross transition without
beam loss
Steps to complete
• Verify margin for vertical instability at transition with single and multi-bunch
beams
2017
Driven by RF and supported by
HSC (M. Migliorati et al.), G.
Sterbini, A. Huschauer, S.
Aumon
Transverse impedance and chromaticity
Priority 2
2017-2018
Context:
• Measurements revealed a positive correlation between transverse impedance and
chromaticity
• Confirmed by measurements at different energies
Study objective:
• Verification and explanation of the past observations
Steps to complete:
• Measurements, simulations and analytic considerations
• Improved chromaticity control allows improved measurement setup
HSC (impedance team),
M. Migliorati, A.
Huschauer
Hollow bunches to mitigate space charge on the flat
bottom
Priority 2
2017-2018
Context:
• Decreased direct space charge tune spread at PS injection due to reduced longitudinal
density by means of hollow bunch creation in the PSB
Study objective:
• Verify expected gain
• Improve robustness of the scheme
Steps to complete:
• further flattening of the longitudinal distribution
• improving the reproducibility of the scheme
• Creation of hollow bunches with large longitudinal emittance
A. Oeftiger, SC team, in
collaboration with RF
Conclusions
• Multitude of critical studies to be addressed in 2017
• Significant amount of manpower required
• Provided that following additional resources are allocated, the different topics
are well covered:
 HSI fellow for PS activities
 Ph.D. student for optics and space charge studies
 HSC support
• LIU-PS intensity reach limited by longitudinal effects
 Close follow up of activities by ABP required
• LIU baseline for ions has been demonstrated  no priority 1 topics
• PS-LIU task coordination: GS  AH?
Summary of the activities
Topic
Priority
Timeline
People
Emittance blow-up at injection I
1
2017
ABT, AH, SC team, HSI fellow
Emittance blow-up at injection II
1
2017
AH, MS, HSI fellow
Commissioning of new chromaticity control scheme
1
by mid-2017
AH, GS, PZ, SC + optics team
Vertical blow-up at low energy
1
by mid-2017
FA, HB, HD, AH, MS
Space charge studies towards the LIU beam parameters
1
2017-2018
FA, HB, HD, AH, MS + SC team
Non-linear model of the PS
1
continuous
AH, IE, MS, OB, student +
MSC and ACE
Longitudinal impedance and PS-SPS transfer
1
2017
Alternative optics studies
2
continuous
Transition crossing with large longitudinal emittance
2
2017
Transverse impedance and chromaticity
2
2017-2018
HSC, MM, AH
Hollow bunches to mitigate space charge
2
2017-2018
AO, SC team + RF
SPS injection losses WG, HSC,
MM
FA, HB, IE, AH, FS, MS, PZ
RF + HSC, GS, AH, SA