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85ff9c9f-8ec8-459a-9677-68c53fab8ae7 | themeasuredbeamphase. Hencetheeffectivephasejumpis
always𝜋−2𝜙 𝑠,TOF. Thelongitudinalpotentialwell 𝑈(𝜙)
after this jump can be calculated as
𝑈(𝜙) =𝑒
2𝜋ℎ∫𝑉ind(𝜙)+𝑉 RF(𝜙)−𝛿𝐸𝑠
𝑒𝑑𝜙.(2)
Above transition the EAST bunch starts at 𝜙𝑠,EAST, and the
dipoleoscillationamplitudecanbeestimatedtobethewidth
ofthepo... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5112.pdf | 1 |
f548a22f-348c-4596-a2eb-a35a7da5fd58 | COMPENSATION OF OSCILLATIONS
To equalize the ideal phase jump at transition, the differ-
ence in energy loss from beam induced voltage must be
compensated. The main RF system of the PS consists of
ten tunable ferrite-loaded cavities, each with an RF voltage
ofupto20kV.Theresonancefrequencycanbecontrolled
from 2.8MHz to... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5112.pdf | 1 |
df292bb2-3fbd-41c9-bd2d-23eb7b7158b7 | IEAST=8×1011 p/bFigure 3: Expected dipole oscillation amplitude calculated
usingtheparametersinTable 1,butvaryingTOFandEAST
intensities.
Table1: ParametersattransitioncrossingfortheEASTcycle,
as it is currently implemented in operation. The quoted
intensities are the smallest EAST and highest parasitic TOF
intensities ... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5112.pdf | 1 |
9c4b2125-2a8e-4532-8fb7-5bc75aa157db | TOF and EAST bunches both before and after transition.
Therefore, the phase is not switched at transition. With one
cavity tuned to harmonic ℎ = 7, the voltage on the princi-
pal harmonic, ℎ = 8is reduced by 10% around transition
crossing. Thecontributionfromthedetunedvoltageensures
thatthebucketareafortheTOFbunchremai... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5112.pdf | 1 |
29e814db-bd55-4128-86df-b2be6c554a8a | tests showed that a slightly higher voltage of 𝑉det= 20kV
was required. This is the maximum available voltage. Thus
perfect compensation would not be possible at a parasitic
TOF bunch intensity of 8.4×1012p/b, in this configuration.
Additionalvoltagecanbesourcedfromthebeaminduced
voltage. At the current bunch spacing ... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5112.pdf | 1 |
4c65f2f7-dc6f-4d2f-a001-c62f4ca058d4 | Figure4: Estimatedamplitudeofresidualdipoleoscillationswhendetuningoneofthemaincavitiestocompensatethe
difference in beam induced voltage. The left contour shows the configuration were the bunch spacing and TOF intensity is
unchanged from Table 1. The right contour shows the configuration were the bunch spacing is redu... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5112.pdf | 2 |
24b214e8-12e3-4d1e-8005-3f41504f8624 | ments indicate that strong beam induced voltage persists up
to 500ns behind the parasitic TOF bunch [ 4]. The beam
inducedvoltagecanthereforeextractenergyfromtheEAST
bunch, if it is placed in the bucket just after the TOF bunch.
Withthismethoditispossibletoreducetherequiredvolt-
agefromthedetunedcavity. Itenablesperfec... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5112.pdf | 2 |
11d25eb5-bad8-44ee-b803-c2a89a3afca3 | induced by the parasitic TOF bunch.
Detuningoneof themain cavitiesforoperationalbeam
production will not be feasible until 2028, when all of the
main cavities will become individually tunable. An attempt
was made to partially compensate dipole oscillations by
utilizing a wideband cavity with a bandwidth of 0.5 to
5MHz ... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5112.pdf | 2 |
5596bdf5-c5e6-4fee-96aa-040c2a19a3ab | stopthequadrupoleoscillationsinducedintheEASTbunch
by the first rotation. The large longitudinal emittance of theEAST bunch in the presence of the parasitic TOF, limits
the best achievable bunch compression, due to losses and
filamentation from non-linear synchrotron motion. For this
reasontherotationperformedonthepara... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5112.pdf | 2 |
8a7ffc7e-d0c5-4aa2-951d-de52fbfb63af | bunch to match in both intensity and longitudinal profile
at the moment of extraction. The change did not lead to a
discernible decrease in EAST bunch quality, although work
is still ongoing to study the implications.
CONCLUSION
Transition crossing with bunches of very different intensity
without dipole oscillations ha... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5112.pdf | 2 |
6a7abb0e-9fea-487c-a674-dfa5f41c9e6d | teams for their help configuring beam tests with varying
bunch spacings.17th International Particle Accelerator Conference, Deauville, France JACoW Publishing
ISBN: 978-3-95450-252-3 ISSN: 2673-5350 doi: 10.18429/JACoW-IPAC2026-WEP5112
2528 MC5.D09: Emittance manipulation, Bunch Compression and CoolingWEP5112 WEP: Post... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5112.pdf | 2 |
99b0c6d0-7b4a-47ff-89e8-d690c50e41aa | REFERENCES
[1]J.Bernhard etal.,”CERNProtonSynchrotronEastAreaFa-
cility”,CERN,Geneva,Switzerland,Rep.CERN-2021-004,
2021. doi:1/zero.alt4.23731/CYRM-2/zero.alt421-/zero.alt4/zero.alt44
[2]G.Tagliente etal.,”The n_TOFfacilityat CERN”,EPJWeb
Conf., vol. 297, p. 01013, 2024.
doi:1/zero.alt4.1/zero.alt451/epjconf/2/zero.al... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5112.pdf | 3 |
eac7b78a-29eb-4c8c-ab75-2898c8da9e09 | pp. 618-621. doi:1/zero.alt4.18429/JACoW-IPAC2/zero.alt416-MOPOR/zero.alt412
[5]J. P. Burnet et al., ”Fifty years of the CERN Proton Syn-
chrotron”, CERN, Geneva, Switzerland, Rep. CERN-2011-
004, 2011. pp. 85-87. doi:1/zero.alt4.517/zero.alt4/CERN-2/zero.alt411-/zero.alt4/zero.alt44
[6]R.Cappietal.,”PSmachinedevelopme... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5112.pdf | 3 |
5d2fb582-43b6-4dd0-ba04-a1b1300cd0c9 | ISBN: 978-3-95450-252-3 ISSN: 2673-5350 doi: 10.18429/JACoW-IPAC2026-WEP5112
MC5.D09: Emittance manipulation, Bunch Compression and Cooling 2529WEP: Poster session WEP5112
Content from this work may be used under the terms of the CC BY 4.0 licence (© 2026). Any distribution of this work must maintain attribution to the... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5112.pdf | 3 |
eb353ec9-26ad-47e4-8f69-e73a3bedf33c | CHARACTERIZATION OF LONGITUDINAL ELECTRON BEAM
QUALITY AT THE SOFT X-RAY BEAMLINE OF SwissFEL
R. Provvedi∗, E. Prat, S. Reiche
PSI Center for Accelerator Science and Engineering, Villigen, Switzerland
Abstract
LongitudinalelectronbeamqualityiskeyatX-rayfree-
electron lasers (FELs), where electron beams with small
slice... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5114.pdf | 0 |
0b044e80-911d-40f6-8ba2-5b36c2a9535f | phase-space measurements using radiofrequency transverse-
deflectingstructuresfordifferentacceleratorandcompres-
sionconditions. Thesecharacterizationstudiesrepresenta
firststeptowardstheoptimizationofmulti-stagecompres-
sion schemes aimed at mitigating MBI and IBS effects.
INTRODUCTION
X-ray free-electron lasers (XFEL... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5114.pdf | 0 |
69bae0e6-16c8-487d-9062-a91a82f42fc9 | this process is essential for maximizing FEL gain, it concur-
rently enhances collective effects that can severely degrade
thebeamquality,therebylimitingtheachievablegainand
spectral purity, particularly in seeded FEL configurations.
Amongtheeffectsarisingfrombeamself-interactions,in-
trabeam scattering (IBS), i.e., mu... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5114.pdf | 0 |
7174651f-0517-407c-81ac-bcbfa9fb3e99 | contrast,ischaracterizedbytheamplificationoftheinitial
density and energy modulations over a broad wavelength
spectrum, primarily driven by longitudinal space-charge
(LSC)forcesandcoherentsynchrotronradiation(CSR),dur-
ing bunch compression and dispersive transport [ 3,4].
∗roberta.provvedi@psi.chThe SwissFEL facility ... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5114.pdf | 0 |
1c41c427-7d36-4e42-a818-74ec6e198737 | is therefore needed to understand and control the impact
of collective effects. In this work, experimental studies of
the longitudinal beam quality at SwissFEL Athos are pre-
sented,combininghigh-resolutionmeasurementswithon-
going simulation studies. Emphasis is placed on different
bunch compression schemes to investi... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5114.pdf | 0 |
361e44be-5c13-4abd-9478-49e8526203a9 | the longitudinal coordinate onto one transverse screen axis,
while the relative energy deviation is encoded along the
orthogonal axis via the local dispersion. The temporal coor-
dinateiscalibratedusingtheappliedTDSvoltageandphase,
whereas the energy scale is determined from the dispersion
attheobservationscreen. Swiss... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5114.pdf | 0 |
306e5052-9515-4aa5-9f62-44a4bbc29f18 | LPSdistributions,severalkeyparameterscanbeextracted,
namely the current profile, energy centroid and slice energy
spread(SES) as function of thelongitudinal coordinate, as
well as the energy chirp along the bunch. To ensure a sys-
tematic and reproducible analysis of the measured data, a
dedicatedanalysisframework(MBIA... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5114.pdf | 0 |
aa8cddc2-a21d-4402-bbbf-c55c5ff10199 | Figure1: SchematiclayoutoftheSwissFELacceleratorlattice,includingmagneticbunchcompressors,RFaccelerating
cavities and relevant diagnostics. Beam stoppers,dumps and transverse-deflectingstructures (TDS) are indicated.
adaptive masking techniques to suppress uncorrelated back-
ground contributions. Subsequent spectral an... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5114.pdf | 1 |
42a1980a-ba52-4eca-bff8-7061270a7740 | and gain curves, enabling a comprehensive characteriza-
tion of the MBI‑induced microstructures. The experimental
studiespresentedin the followingsectionsinvestigateIBS‑
andMBI‑drivenphase‑spaceevolutionatSwissFELunder
multiple compression schemes.
Simulations
Start-to-endsimulationsareongoingtosupporttheexper-
imental... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5114.pdf | 1 |
5250f5be-7a5c-4f39-9278-083516383f8d | impact on the macroparticle trajectories in the considered
regime, while their cumulative effect on the longitudinal
beamdynamicscanbecapturedusingreducedmodels. MBI
dynamicsisdescribedusingaone-dimensionallinearmodel
based on the Bosch–Kleman formalism [ 9], tracking the
evolutionofthebunchingfactor 𝑏(𝑘)andthecorres... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5114.pdf | 1 |
5e10e87a-9d05-4100-9c9d-0b0462182951 | single-stagebunchcompressionconfiguration,withonlythefirstbunchcompressor(BC1)operated indispersivemode
(𝑅56= 63.34mm). The beam peak current was scanned
from95Aupto ∼1.4kAbyvaryingthecompressionstrength
in BC1. Observations were carried out at different locations
along the accelerator, namely downstream of the inject... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5114.pdf | 1 |
4f17be27-1732-4b23-99ac-9a69d6decc33 | tegrated piecewise, in agreement with previous studies at
SwissFEL[ 10]. Incontrast,measurementsdownstreamof
Linac 3 significantly exceed the expected IBS scaling, in-
dicatinganon-negligiblecontributionofMBItothebeam
energy spread, at frequencies that cannot be resolved by the
TDS measurements. Ongoing simulations aim... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5114.pdf | 1 |
9790c8f1-39c8-4bab-9103-22777a0e1f62 | ISBN: 978-3-95450-252-3 ISSN: 2673-5350 doi: 10.18429/JACoW-IPAC2026-WEP5114
MC5.D06: Coherent and Incoherent Instabilities Measurements and Countermeasures 2531WEP: Poster session WEP5114
Content from this work may be used under the terms of the CC BY 4.0 licence (© 2026). Any distribution of this work must maintain a... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5114.pdf | 1 |
46986811-eaf5-4c47-873b-2d0000831f4f | beam dump. Compared to the single-stage compression,
pronounceddistortionsoftheLPSandanincreaseinSES
areobserved,asshowninFig. 3. Thesefeaturesindicatethe
onset of collective effects beyond IBS, with high-frequency
longitudinal structures consistent with MBI development.
Figure3: ElectronbeamLPSmeasuredattheAthosbeam
d... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5114.pdf | 2 |
7640f2a3-a090-4715-9e7f-13fbc5292c23 | withrmsbunchlengthof 20.21±0.70 fsandadecompressed
beamof45.89±0.89 fs. Thescanned 𝑅56enablescontrolled
LPS manipulation, modifying both the coupling between
energyanddensitymodulations,andthedampingofhigh-
frequencycomponents through the finite SES. Considering
the definition of the bunching spectrum as the Fourier t... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5114.pdf | 2 |
b29b7bb4-8076-4bb7-941d-da14d9791aaf | at specific 𝑅56values, indicating the existence of operat-
ing conditions where partial suppression of MBI can be
achievedthroughanappropriatetuningofthelocaldisper-
sive strength. This behaviour can be understood in terms
ofareductionofthefirstterminsquarebracketsinthelin-
earized expression for the bunching factor d... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5114.pdf | 2 |
eb4f9b7d-8db3-4e67-916d-66ef66cf9189 | suggests that small dispersive chicanes inserted between
compressionstagescouldprovideaneffectivestrategyfor
mitigating the microbunching instability.
CONCLUSIONS AND OUTLOOK
This work establishes a consistent experimental frame-
workforinvestigatingIBSandMBIatSwissFEL,providing
quantitativebenchmarksforanalyticalmodel... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5114.pdf | 2 |
590a43e1-e34d-47b1-9722-8987a25852dc | the microbunching amplification can be partially mitigated
throughappropriatetuning ofthecompression parameters.
Futureworkwillfocuson comparisonswith macroparticle
trackingcodesandadvancedanalyticalMBImodels,aswell
as on the systematic optimization of multi-stage compres-
sionschemesaimedatreducingtheimpactofMBIonthe
... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5114.pdf | 2 |
b9ebc891-4a1e-4c30-b72a-d78d5fb3a5e0 | ISBN: 978-3-95450-252-3 ISSN: 2673-5350 doi: 10.18429/JACoW-IPAC2026-WEP5114
2532 MC5.D06: Coherent and Incoherent Instabilities Measurements and CountermeasuresWEP5114 WEP: Poster session
Content from this work may be used under the terms of the CC BY 4.0 licence (© 2026). Any distribution of this work must maintain a... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5114.pdf | 2 |
9dedd253-ac32-4464-8926-68231fe0dc8b | REFERENCES
[1]Z.HuangandK. -J.Kim,“Reviewofx-rayfree-electronlaser
theory”,Phys. Rev. Accel. Beams, vol. 10, p. 034801, 2007.
doi:1/zero.alt4.11/zero.alt43/PhysRevSTAB.1/zero.alt4./zero.alt4348/zero.alt41
[2]A.Piwinski,“Intra-beam-scattering”, in Proc.9thInt.Conf.
on High-Energy Accelerators, pp. 405–409, May 1974.
doi... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5114.pdf | 3 |
d18db305-3c71-41fe-9da4-2f950e1270c1 | doi:1/zero.alt4.11/zero.alt43/PhysRevSTAB.5./zero.alt4644/zero.alt41
[5] E. Prat et al., “A compact and cost-effectivehard x-rayfree-
electron laser driven by a high-brightness and low-energy
electron beam”, Nat. Photonics, vol.14, pp. 748–754, 2020.
doi:1/zero.alt4.1/zero.alt438/s41566-/zero.alt42/zero.alt4-/zero.alt4... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5114.pdf | 3 |
f7161d7c-a425-4d32-b8cf-0ad97aa1dcb4 | gorithm”, DESY, Hamburg, Germany, Mar. 2017,
https: / / www . desy . de / ~mpyflo / Astra _ manual /
Astra -Manual_V3.2.pdf
[9]R. A. Bosch and K. J. Kleman, “Modeling Two-Stage Bunch
Compression with Wakefields: Macroscopic Properties and
Microbunching Instability”, Phys. Rev. Spec. Top. Accel.
Beams, vol. 11, no. 9, ... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5114.pdf | 3 |
0a4af34c-96d0-4254-9e37-6b0d4ffb16e6 | ISBN: 978-3-95450-252-3 ISSN: 2673-5350 doi: 10.18429/JACoW-IPAC2026-WEP5114
MC5.D06: Coherent and Incoherent Instabilities Measurements and Countermeasures 2533WEP: Poster session WEP5114
Content from this work may be used under the terms of the CC BY 4.0 licence (© 2026). Any distribution of this work must maintain a... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5114.pdf | 3 |
d00ac08a-85ff-49c3-9ad1-ffefa40c09e5 | COHERENT TRANSVERSE INSTABILITIES ON THE ISIS PROTON
SYNCHROTRON AT INJECTION ENERGY
D. W. Posthuma de Boer∗,1, 2, C. M. Warsop1, R. E. Williamson1, A. Oeftiger2
1ISIS Neutron and Muon Source, Didcot, United Kingdom
2University of Oxford, Oxford, United Kingdom
Abstract
ISIS is the short-pulsed spallation neutron and m... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5115.pdf | 0 |
dae5ed14-1296-4b09-bc44-cef95454c9dd | bility’sdrivingimpedance,were-examineobservationsof
instabilitiesonISISwhenoperatingasastorageringatits
injection energy. We present the updated vertical driving
impedancemodel,computeanalyticalpredictionsofinsta-
bilitygrowthratesexcludingspace-chargeeffectswiththe
PyTMCI Vlasov solver, and compare these with experime... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5115.pdf | 0 |
62c586ab-45f3-4b4a-9b30-cb15d42013f4 | Number of Bunches ( 𝑀) 2
Average Radius ( 𝑅) 26m
No. of Superperiods 10
Gamma Transition 5.034
Nominal Tunes ( 𝑄x,𝑄y) 4.31, 3.83 (variable)
Peak Incoherent Tune Shift ∼-0.5 [1]
Chromaticity ( 𝜉x,𝜉y) -1.1, -1.1 [ 2]
ISIS is a beam-loss limited facility, so minimising beam-
loss is a primary objective of R&D effort... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5115.pdf | 0 |
5b60cbf1-c03e-428e-8e16-b056a77375d6 | plex, making studies challenging with operational beams.
BunchedStorageRingMode(BSRM)wasdevelopedasa
waytooperatetheISISsynchrotronforinstabilitystudies,in
aregimemoreconsistentwithanalyticalmodels[ 5]. Stud-
ies in this mode identified a narrowband vertical impedance
centredat ∼ 85kHz. Althoughitsfrequencywasfoundtobe... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5115.pdf | 0 |
f0bef779-7968-45dc-ad70-8e37c8170b70 | 85kHz instabilitywill be identified.
EXPERIMENTAL RESULTS
Experimental Set-up
The injection and accumulation procedures of BSRM
are similar to RCS mode, but the injected beams are stored
with primary bending and focusing magnets operating with
DC. Beams are not extracted, so 100%beam-loss occurs
in the synchrotron hall... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5115.pdf | 0 |
7413b486-e1da-4926-923f-32ddbf4bb578 | reduced to 1.68×1012protons-per-bunch with two bunches
circulatingatarevolutionfrequencyof ∼ 675kHz. Horizon-
taltunewasconstant,whilstverticaltunewasvariedbetween
injected pulses. Measurements were performed with fast
acquisitionofverticalbeampositionmonitor(BPM)signals.
Withcertaintunesettingsthebuncheswereobservedto... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5115.pdf | 0 |
52fb563e-fcc0-4096-95a7-5215cd6daa96 | window indicated by a shaded region.17th International Particle Accelerator Conference, Deauville, France JACoW Publishing
ISBN: 978-3-95450-252-3 ISSN: 2673-5350 doi: 10.18429/JACoW-IPAC2026-WEP5115
2534 MC5.D06: Coherent and Incoherent Instabilities Measurements and CountermeasuresWEP5115 WEP: Poster session
Content ... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5115.pdf | 0 |
1b830fc2-bb51-41c5-96be-1a3ecf385fba | 0 200 400 600
Time (ns)024BPM Diff blue (AU)
Sum orange (AU)(a)
−1 1 3 5 7
Time (ms)−1.0−0.50.00.51.0BPM Diff. blue (AU)
Inten. orange (AU) (b)
0.0 0.2 0.4 0.6
Frequency (MHz)10−1100101102103FFT Amplitude (V)
(c)
0.0 0.1 0.2 0.3
Time (ms)012B-band Amp. (AU)
(d)
Figure 1: Experimental data from a single dataset of the
... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5115.pdf | 1 |
7975ad4e-80b0-4971-abf1-99a1c132f412 | lation amplitude for each chunk. These amplitudes were
obtained with NAFF [ 12,13] but to help isolate the base-
band frequency, a 5thorder Butterworth bandpass filter was
first applied to each chunk with offline signal processing
tools[14]. Thecutofffrequenciesforthesefilterswereset
by manually inspecting the differen... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5115.pdf | 1 |
1b9da199-ee73-4aad-8037-08c74aa4d27a | independent sweeps of vertical tune in Fig. 2. A peak at
∼ 85kHzcan clearly be seen, as reported previously [ 1].
IMPEDANCE MODEL
A vertical driving impedance model has been developed
for theISIS synchrotronin the rangeof the beam’slowest
frequency sideband ( ∼ 100kHz) [6,7]. In this range, the
impedance model is domin... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5115.pdf | 1 |
98665ead-c340-4c8d-9f66-411032efc215 | pretedasthe 𝛽 = 1transverseshuntimpedancewithSIunits
ofΩm−1;𝜔𝑟is the resonant angular frequency, and 𝑄𝑟is
thequalityfactor. FortheRFscreens, 2𝜋/𝜔𝑟isontheorder
of> 3times the revolution period at injection, so a linear
dependence on 𝛽is assumed to be a good approximation.
The resonator parameters listed in Tabl... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5115.pdf | 1 |
f37e7b81-40d1-4b1a-8a3c-6264bf2b7d45 | resonatorstorepresenttheextractionkickers[ 6]andanindi-
rect space-chargeimpedance. The real part of the resulting
model is shown for 𝛽 = 1in Fig.3.
Table2: ResonatorParametersoftheISISImpedanceModel
Screen𝜔𝑟
2𝜋(kHz)𝑅⟂(kΩm−1)𝑄𝑟Qty
Dipole (82±5) (500±170) (6.1±0.7) 10
Doublet (94±6) (255±82) (6.7±0.2) 10
Singlet ... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5115.pdf | 1 |
05d5dbbe-817c-4f3b-a562-35a2e3b751f8 | ISBN: 978-3-95450-252-3 ISSN: 2673-5350 doi: 10.18429/JACoW-IPAC2026-WEP5115
MC5.D06: Coherent and Incoherent Instabilities Measurements and Countermeasures 2535WEP: Poster session WEP5115
Content from this work may be used under the terms of the CC BY 4.0 licence (© 2026). Any distribution of this work must maintain a... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5115.pdf | 1 |
d048120b-203b-4f2e-a584-83dae23813e5 | 104105106107
Frequency (Hz)104105106107ℜ(Z⊥)(Ωm−1)DipoleDoublet
SingletOther Scrn
KickersRes. WallFigure 3: Real part of the ISIS synchrotron vertical driving
impedance model with key elements labelled and a sum.
SEMI-ANALYTICAL PREDICTIONS
Semi-analytical predictions of instability growth rates
have been made with the... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5115.pdf | 2 |
3ec5d95d-933c-4aba-943a-ea6eb5481005 | weretakenfromTable 1,butwiththeintensityreducedto
1.68×1012protons-per-bunch. The synchrotron tune was
0.00454at the flat-top RF voltage, and a scaled value was
used fortune settings where instabilities wereanalysed dur-
ingtheRFrampbetween0and 1ms. Theinputlongitudinal
phase-spacedistributionwasderivedfromatomographic... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5115.pdf | 2 |
a97ee3e6-da6c-46ae-a949-466d23529ead | butionwiththeparameterslistedinTable 2. Thegrowthrate
ofthemostunstablemodewasfoundforeachcalculation,
and a mean and standarddeviationcomputed foreachtune
setting. These PyTMCI results are represented in Fig. 4,
with the measured growth rates overlaid from Fig. 2. The
peakat∼ 85kHzagreeswellwithobservations,occurringa... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5115.pdf | 2 |
56b43bf7-5e28-48ff-be85-e168aadee890 | deviation of the calculations.
differenttunesettings. Theindicatedfrequenciesspanthe
rangecoveredbythisexperimentandalsoincludethesetting
with the fastest growth rate. The 85kHzgrowth rate peak
in Fig.4occurs when the baseband frequency overlaps with
an impedance peak from the dipole and doublet RF screens.
Thecombinat... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5115.pdf | 2 |
398c0548-39f5-4720-b98c-3b0b57725312 | peakingrowthratearound 85kHz,whichagreeswithear-
lier studies. PyTMCI calculations also predict a peak at this
frequency, with growth rates reproduced to within an order
ofmagnitude. Considering thesimplified analyticalmodel
employedhere,thisisconsideredanexcellentlevelofagree-
ment. The drivers of this instability hav... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5115.pdf | 2 |
68a1d43d-9aa8-48a3-9fa1-d7ca509210a8 | ISBN: 978-3-95450-252-3 ISSN: 2673-5350 doi: 10.18429/JACoW-IPAC2026-WEP5115
2536 MC5.D06: Coherent and Incoherent Instabilities Measurements and CountermeasuresWEP5115 WEP: Poster session
Content from this work may be used under the terms of the CC BY 4.0 licence (© 2026). Any distribution of this work must maintain a... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5115.pdf | 2 |
0dbd5149-81e3-4a71-9361-30182f741878 | REFERENCES
[1]R.E.Williamson,B.Jones,andC.M.Warsop,“Development
ofphysicsmodels oftheISIShead-tail instability”,in Proc.
HB’16,Malmö, Sweden,Jul. 2016.
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[2]R.E.Williamson etal.,“High-intensitystudiesontheISIS
RCS and their impact on the design of ISIS-II”, in ... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5115.pdf | 3 |
03950832-9871-4b84-9c92-2a7b2567e1fa | thesis, University of Oxford, UK, 2023.
[6]D. W. Posthuma de Boer, B. Orton, C. Warsop, and R. E.
Williamson, “Development of an impedance model for the
ISISsynchrotronandpredictionsforthehead-tailinstability”,
inProc. HB’23 , Geneva, Switzerland, Oct. 2023.
doi:1/zero.alt4.18429/JACoW-HB2/zero.alt423-TUC4I2
[7]D.W.Pos... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5115.pdf | 3 |
72be8e33-2df0-4e91-b718-19bfc48b9c59 | storage ring”, Zenodo, Aug. 2025.
doi:1/zero.alt4.5281/zenodo.1694/zero.alt489/zero.alt4
[10]D. W. Posthuma de Boer, PyTMCI, Sep. 2023, https://
github.com/stfc/PyTMCI
[11]V. Kornilov and O. Boine-Frankenheim, “Instability mitiga-
tion using octupoles in buncheswith space-charge”, in Proc.
IPAC’23,Venice,Italy,May2023,... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5115.pdf | 3 |
049438ff-08c6-4ff0-979c-4d3bd19ce393 | scientific computing in python”, Nat Methods , vol. 17, no. 3,
pp. 261–272, Mar. 2020.
doi:1/zero.alt4.1/zero.alt438/s41592-/zero.alt419-/zero.alt4686-2
[15]J. S. Berg, “Coherent modes for multiple non-rigid bunches
in a storage ring”, SLAC National Accelerator Laboratory,
Menlo Park, CA, USA, Rep. SLAC–478, Mar. 1996.... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5115.pdf | 3 |
e6076752-222d-4fca-b62f-3e128e2d0ace | ISBN: 978-3-95450-252-3 ISSN: 2673-5350 doi: 10.18429/JACoW-IPAC2026-WEP5115
MC5.D06: Coherent and Incoherent Instabilities Measurements and Countermeasures 2537WEP: Poster session WEP5115
Content from this work may be used under the terms of the CC BY 4.0 licence (© 2026). Any distribution of this work must maintain a... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5115.pdf | 3 |
78081a7f-b0ed-4b31-92d5-ef2fedfbda8d | IMPACT OF LANDAU OCTUPOLES ON THE TRANSVERSE BEAM HALO
DISTRIBUTION IN THE LHC∗
P. Hermes†, C. Maccani, D. Veres,
European Organization for Nuclear Research, Geneva, Switzerland
M. Rakic, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
Abstract
The distribution of beam halo particles in the Large
Hadron... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5117.pdf | 0 |
abf10db0-8098-4bf6-b5d2-b7ab17178b92 | ations observed in different measurements. The analysis
providesafirstassessmentoftheimpactofnon-linearities
on the observed beam halo characteristics in the LHC. The
results indicate that particle amplitudes can be significantly
enhanced by non-linearities, with consequences on the halo
measured in collimator scraping... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5117.pdf | 0 |
e8f8fb2d-060a-4200-b451-2e2ccdc03755 | ceedingthisexpectation[ 1–4],withstrongvariationsacross
measurements whose origin is not fully understood.
In the LHC, sextupolar fields can drive third-order res-
onances,whiletheLandauoctupolesintroduceamplitude-
dependenttuneshifts[ 5];inthevicinityofaresonance,these
effectsresultinthedistortionofthephasespacestruct... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5117.pdf | 0 |
eb5dd1ae-f6a5-4c1c-9a0b-59b156377c34 | though the same methodology can be applied to all other
planes. Theresultsshowasignificant amplitudeexcursion,
∗Researchsupported bythe HL-LHC project
†pascal.hermes@cern.chin particular for halo particles, with a strong asymmetry
between the two collimator jaws.
THE NONLINEAR AMPLITUDE
EXCURSION MAP
Let us define the ... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5117.pdf | 0 |
0e18745d-9ba8-4494-b539-76e95e1a9952 | at(𝑋0,𝑃𝑋,0), with initial amplitude ℛ𝑖=√𝑋2
0+𝑃2
𝑋,0, can
have a different generalized amplitude as it moves along the
ring. We express amplitudes in units of beam sigma via
𝑎(𝜓) = ℛ(𝜓)/ √𝜀, with𝑎𝑖= ℛ𝑖/√𝜀the initial amplitude.
A collimator jaw intercepts particles whose transverse
displacement 𝑋at the co... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5117.pdf | 0 |
ba7a1cb6-2a15-4683-b476-e9bd824b565d | and+(−) corresponds to the left (right) side in the moving
right-handed coordinate system. In a linear machine, the
quantityΔ𝑎±alwaysequals0. In a nonlinearlattice, phase
space distortion shifts the phase at which the maximum
displacement occurs, and Δ𝑎±can differ substantially from
zero.
For a given direction ( ±), ... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5117.pdf | 0 |
46f82150-7bb0-4f9a-b799-cffd1944c643 | ISBN: 978-3-95450-252-3 ISSN: 2673-5350 doi: 10.18429/JACoW-IPAC2026-WEP5117
2538 MC5.D07: High Intensity Circular Machines Space Charge, HalosWEP5117 WEP: Poster session
Content from this work may be used under the terms of the CC BY 4.0 licence (© 2026). Any distribution of this work must maintain attribution to the ... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5117.pdf | 0 |
078b202d-f60b-413b-9dee-46725ed7f54d | can be easily scaled to any other emittance without need of
a recomputation.
SIMULATION SETUP
The NAEM is computed from symplectic tracking sim-
ulationsperformedonGPUswiththe Xsuitecode[6],us-
ingthe2025 LHCoptics at6.8TeVcorrespondingto end-
of-luminosity-levelling conditions with 𝛽∗= 60/18 cm.
Beam-beameffectsareno... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5117.pdf | 1 |
de0b408f-65be-4f2d-b353-93545bfb6625 | amplitude 𝑎𝑦at betatron phase 𝜓𝑦= 0. Tracking is per-
formed for 𝑁 = 500 turns, sufficient for each particle to
sample its accessible phase space at least once. The hori-
zontalnormalizedcoordinate 𝑋(𝑛)isrecordedturnbyturn
to evaluate Δ𝑎±via Eq. (1). Particles lost during tracking
are excluded from the analysis... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5117.pdf | 1 |
f406e157-551b-4ee6-bf5f-30aa3cc9a421 | exhibit a characteristic three-fold symmetry, consistent with
theproximityofthenominalLHCworkingpointtothethird-
order resonance line. For a given configuration, the Landau
octupoles modify small features of the local amplitude of
the NAEM but not its global structure.
For the left side, Δ𝑎+is predominantly positive a... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5117.pdf | 1 |
9cac203c-7f00-4a08-8cbb-f1b375bdc814 | does the right jaw also show a net positive enhancement.
Figure2shows the phase-space-averaged amplitude in-
crease⟨Δ𝑎±⟩(𝑎𝑖),obtainedbyaveraging Δ𝑎±overallgrid
pointsineachamplitudeannulus. Thisprojectioncondenses
the two-dimensional NAEM into a single curve per configu-
ration, directly quantifying the mean amplit... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5117.pdf | 1 |
3f80a92d-ce2d-4afb-9807-d4aa930a3862 | 𝜀𝑛= 3.5µmrad,𝑄𝑥/𝑄𝑦= 62.31/60.32 ,Δ𝑄 = 0. Leftside
(positive𝑋):𝑎𝑦= 0(row1)and 𝑎𝑦= 𝑎𝑥(row2). Rightside
(negative 𝑋):𝑎𝑦= 0(row3)and 𝑎𝑦= 𝑎𝑥(row4). Columns:
𝐼oct= 0A (left) and 𝐼oct= +570A (right). White dashed
circles indicate integer- 𝜎amplitudes. Note the different
colour scales per row.
as a func... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5117.pdf | 1 |
7cc3003e-23de-496f-8f51-b9629dee2488 | ISBN: 978-3-95450-252-3 ISSN: 2673-5350 doi: 10.18429/JACoW-IPAC2026-WEP5117
MC5.D07: High Intensity Circular Machines Space Charge, Halos 2539WEP: Poster session WEP5117
Content from this work may be used under the terms of the CC BY 4.0 licence (© 2026). Any distribution of this work must maintain attribution to the ... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5117.pdf | 1 |
aa05c9b3-e61d-4c25-b1f2-b1d4508437ae | 0.2
0.00.20.40.6a+[]
Left jaw
ay=0
ay=ax
1 2 3 4 5
Initial amplitude ai[]
0.2
0.00.20.40.6a[]
Right jaw
400
200
0200400
Ioct [A]Figure 2: Phase-space-averaged amplitude increase
⟨Δ𝑎±⟩(𝑎𝑖)as a function of initial amplitude. Octupole
current encoded by colour (blue: −570A, red:+570A);
linestyle distinguishes 𝑎𝑦= 0(s... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5117.pdf | 2 |
6caa33f0-6463-4bdb-bdc2-538e939b28a6 | beam distribution, yielding the halo content above 𝑎cutas:
𝑁±(𝑎cut) =1
2𝜋𝜀∬Ω±exp(−ℛ2
2𝜀)d𝑋d𝑃𝑋,(2)
whereΩ±istheregionofinitialconditionsinterceptedbythe
left(+)orright(−)jawduringtracking. Inalinearmachine,
particle amplitudes are conserved and Ω±= {𝑎𝑖> 𝑎cut}
for both jaws, so Eq. ( 2) reduces to the Rayleig... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5117.pdf | 2 |
0ebaf0d9-3b9d-41d2-9fec-d59599070117 | To compare with measurement, the beam-based align-
mentproceduremustalsobesimulated,becauseitdirectly
influencestheactual 𝑎cut. Intheexperiment,bothjawsare
moved inward independently until a loss spike is detected atthe BLM; the midpoint of the two touch positions defines
thebeamcentre,andthehalf-gapsetsthebetatroncut... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5117.pdf | 2 |
b76b1ec1-bedb-4807-96e5-1556aaee04d3 | This introduces a bias in 𝑎cutthat propagates into the halo
estimate and will, in general, differ between the two jaws.
Once the alignment is simulated, the cumulative scraped
fractioncanbeevaluatedviaEq.( 3). Theresultisadirect
quantitativepredictionofthehalocontentinthepresenceof
non-linearities.
The model is going ... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5117.pdf | 2 |
b2fdf186-4c8e-4494-8547-10ca2666a65a | Map (NAEM), a simulation-based method to quantify how
nonlinearlatticeelementsmodifythemaximumamplitudea
particlereachesatacollimatorjaw. Appliedtothe2025LHC
configuration at 6.8TeV,the NAEMrevealsa strongasym-
metry: theleftsideisexposedtoapredominantlypositive
amplitudeexcursion,whilefortherightsidetheexcursion
ispre... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5117.pdf | 2 |
6e0db7cb-5c1d-493b-ba2a-6ba258061b09 | measurements, may be partly attributed to the nonlinear
amplitude excursion driven by the machine lattice, which
motivates further studies.
REFERENCES
[1]F. Burkart et al., “Halo Scrapings with Collimators in the
LHC”, in Proc. IPAC’11 , San Sebastian, Spain, Sep. 2011,
pp.3756–3758. https://jacow.org/IPAC2/zero.alt411... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5117.pdf | 2 |
46f2333d-27b6-413a-aa68-4b075af3d688 | [3]A. Gorzawski et al., “Probing LHC Halo Dynamics Using
CollimatorLossRatesat6.5TeV”, Phys.Rev.Spec.Top.Accel.
Beams, vol. 23, p. 044802, 2020.
doi:1/zero.alt4.11/zero.alt43/PhysRevAccelBeams.23./zero.alt4448/zero.alt42
[4]M.Rakic,“Limitationsfromthetransversebeamhaloatthe
highluminosityLHCanditsmitigation”,PhDThesis,... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5117.pdf | 3 |
bb6edf02-0ad4-48df-a7f5-8515392f4673 | ISBN: 978-3-95450-252-3 ISSN: 2673-5350 doi: 10.18429/JACoW-IPAC2026-WEP5117
MC5.D07: High Intensity Circular Machines Space Charge, Halos 2541WEP: Poster session WEP5117
Content from this work may be used under the terms of the CC BY 4.0 licence (© 2026). Any distribution of this work must maintain attribution to the ... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5117.pdf | 3 |
daaa3a6a-b5f2-48dd-8f65-b53a0b4c2320 | EFFECT ON 7 TEV PROTON BEAMS FROM THE RESIDUAL
MULTIPOLAR FIELDS IN THE HL-LHC HOLLOW ELECTRON LENS∗
D. Veres†, P. Geissler, P. Hermes, C. Maccani, S. Redaelli, A. Rossi, CERN, Geneva, Switzerland
G. Stancari, Fermi National Accelerator Laboratory, Batavia, Illinois, USA
Abstract
Hollowelectronlensesareapromisingtoolfo... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5118.pdf | 0 |
cd017334-a381-4347-bf1a-b007df3ad7a5 | thatensuresthefasteddepletionrates. Inthisstudy,updated
two-dimensionalfield maps from recent studies at CERN’s
hollowelectronbeamteststandareusedtoquantifythese
effects under HL-LHC conditions. Beam-dynamics simula-
tions are performed to evaluate the emittance evolution and
identify the dominant field components cont... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5118.pdf | 0 |
5aa2bfab-b33f-488a-8140-aaacc3d8a0b4 | LHC [3]. Combined with fast failure scenarios [ 4], such
asspuriousfiringofbeam-lossprotectionsystemsorcrab
cavityphaseslips,thatcancausesuddenorbitshiftsofup
to2𝜎, this can result in damage to the collimation system
that could be mitigated byactive beam halo depletion. The
HollowElectronLens(HEL)[ 5,6]wasaddedtotheor... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5118.pdf | 0 |
91ad19e3-d6a5-4608-b528-9f6fe1c6c5fa | ∗Researchsupported bythe HL-LHC project.
†dora.erzsebet.veres@cern.chbeamischaracterizedbyaninnerandouterradius 𝑟1and𝑟2,
respectively. Iftheelectronbeamisperfectlycylindrically
symmetric, protons below the inner radius experience no
net effect from the electrons, as the electric and magnetic
fields generated by the e... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5118.pdf | 0 |
9b6a5ac7-8412-4be2-9380-3ef18a9c8b5d | of the electrons and protons, respectively, (𝐵𝜌)𝑝is the mag-
neticrigidityoftheprotonbeam,and 𝑓(𝑟)isanamplitude-
dependent function given by
𝑓(𝑟) =⎧{{
⎨{{⎩0, for𝑟 < 𝑟1
1
𝑟𝑟2−𝑟2
1
𝑟2
2−𝑟2
1,for𝑟1≤ 𝑟 < 𝑟2
1
𝑟,for𝑟2≤ 𝑟(2)
The relevant parameters of the HEL are listed in Table 1.
Table 1: HL-LHC HEL Par... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5118.pdf | 0 |
d11eda31-d6af-4c10-b492-70e9288b133f | random pulsing can cause emittance growth and core losses.
The HEL can be operated in continuous, deterministic, or
randompulsingmodes[ 7]. Intherandommode,theHELis
switchedonandoffeachturnwithprobability 𝑝and1−𝑝,
respectively. This mode offers the besthalo depletion effi-
ciency [7,8], but has also been identified a... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5118.pdf | 0 |
c3034949-9147-413b-a533-53b136869bef | Figure 1: Electron-beam center along the HEL.
Figure 2: Comparison of the integrated electric potential
of the HEL with the same reconstructed from an order 25
Chebyshev polynomial fit.
SIMULATIONS OF THE HEL EFFECT ON
THE BEAM CORE
ToassesstheeffectofresidualfieldsinsidetheHELon
thebeamcore, athree-dimensional mapofth... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5118.pdf | 1 |
dd44eebd-a716-4a9f-bb8b-b2b107a44684 | direction and the integrated potential Φ(𝑥,𝑦)was fitted in
terms of Chebyshev polynomials 𝑇𝑛(𝑢) =cos(𝑛arccos𝑢)
as:
Φ(𝑥,𝑦) =𝑁
∑
𝑛=0𝑛
∑
𝑚=0𝐶𝑚,𝑛−𝑚𝑇𝑚(𝑥
𝑎)𝑇𝑛−𝑚(𝑦
𝑎),(3)
where𝑎 =5mmisareferenceradiusensuring 𝑥/𝑎,𝑦/𝑎 ∈
[−1,1]in the region of interest.
Figure2shows excellent agreement between the... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5118.pdf | 1 |
04dbb8af-b17b-4748-a52c-106d4e008a69 | cal (right) planes. The top panels show the kicks in the
𝑥,𝑦 ∈ [−2𝑟 2,2𝑟2]range,whilethebottom panelsshowthe
kicks for𝑟 < 𝑟1.
Simulationswerecarriedoutusingthe Xsuitesimulation
framework [ 11,12] and the latest HL-LHC optics (v1.9), at
flat-top(7TeV),withprimarycollimatorsat 6.7𝜎. TheHEL
waspositionedinInsertion... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5118.pdf | 1 |
7146600b-92c8-4191-87c4-0d4cb5de929f | wassimulatedasa2DGaussiandistributioninbothtrans-
verse planes, cut at 3𝜎. Single-particle tracking without ma-
chineerrorsof 105particleswasperformedfor674700turns
(≈60s) in random pulsing mode with 50% on-probability
each turn. The particle distribution was monitored every
1125 turns. The simulated configurations ar... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5118.pdf | 1 |
486fe163-6b2b-45fa-85ed-a99184018c5c | ISBN: 978-3-95450-252-3 ISSN: 2673-5350 doi: 10.18429/JACoW-IPAC2026-WEP5118
MC5.D07: High Intensity Circular Machines Space Charge, Halos 2543WEP: Poster session WEP5118
Content from this work may be used under the terms of the CC BY 4.0 licence (© 2026). Any distribution of this work must maintain attribution to the ... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5118.pdf | 1 |
15171969-96ac-4304-a47b-f93d1e73b838 | Figure 4: Particle survival time in initial action space (left) and distribution of transverse coordinates over time (right) for
case 5.
Table 2: Simulated Configurations.
HEL pulsing HEL residual kick ADT compensation 𝑝-beam closed orbit
(𝑥[mm],𝑦[mm])
case 1 off – – (-0.32,0.15)
case 2 random zero – (-0.32,0.15)
ca... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5118.pdf | 2 |
ed4a18cf-cc12-401f-b08e-3da9fe3c0ee2 | timefordifferentHELresidualkickandADTcompensation
scenarios.
remain stable. Figure 5shows the intensity and emittance
evolution for all the different cases. The reference cases
(1 and 2) show no intensity loss or emittance blow-up, as
expected, and the constant-kick cases (3, 4) exhibit virtu-
ally no losses as well. H... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5118.pdf | 2 |
b42f361e-4b3b-4a91-85be-37986e1e732b | canevenexacerbatelosses–withthefullfield-mapkicks,
indicatingthathigher-ordermultipolarcomponentsrather
than the dipolar terms are the dominant drivers.
CONCLUSIONS
The effect of residual multipolar fields in the HL-LHC
hollowelectronlensonthe7TeVprotonbeamcorewasstud-
iedthroughlong-termtrackingsimulationswithupdated2... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5118.pdf | 2 |
f1245520-0e1e-4db8-bdfb-ec8217fc6da7 | goodalignmentoftheelectronbeamandcompensationof
entryandexiteffectstoreducethesecomponents. Further
studiesarealreadyinprogresstoassesstheeffectoftheresid-
ualkicksonthebeamcoreinthemostefficientdeterministic
pulsing scenarios.
REFERENCES
[1]G.Apollinari etal.,High-Luminosity LargeHadronCollider
(HL-LHC): Technical Des... | D:\Daily_ihep\Conferences\IPAC2026\WEP\WEP5118.pdf | 2 |
3bcf6246-4a67-4e8f-8f2d-d38cf700325b | [2]S. Papadopoulou, F. Antoniou, T. Argyropoulos, M. Fitterer,
M. Hostettler, and Y. Papaphilippou, “Modelling and mea-
surements of bunch profiles at the LHC”, J. Phys. Conf. Ser. ,
vol. 874, no. 1, p. 012008, 2017.
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