Steady-state solutions of split beams in electron storage rings

Recently, a novel operation method for synchrotron light sources with transversely split beams has been explored to fulfill the rising demand for flexible and high-throughput X-ray sources required in such diverse fields as time-resolved X-ray spectroscopy, molecular chemistry in organic cells, high-resolution medical imaging, quantum materials science or sustainable energy research. Within that novel operation mode, additional stable regions are produced in the horizontal phase space by operating an electron storage ring on a resonance that is driven by the nonlinear sextupole or octupole magnets. In the longitudinal phase space, a similar split can be produced by introducing an oscillation of the synchrotron phase via a modulation of the phase of the radiofrequency resonator. Strong radiation damping in electron storage rings, however, has to be overcome before additional regions in phase space can become populated by particles and form stable islands. This damping mechanism changes the dynamics of the system and causes diffusion between the different islands in phase space, raising the question what kind of equilibrium state exists in the asymptotic temporal limit. In this paper, a finite-differences approximation in rotating action-angle coordinates is used to solve the Vlasov–Fokker–Planck equation and to study the obtained equilibrium states for the longitudinal as well as the transverse case. The number of solution vectors and the magnitude of the corresponding singular values of the matrix of the underlying finite-differences equation are used as abstract indicators to define the required parameter set that provides stable additional beamlets. As a consequence, the beamlets have a stability that is close to that of the main beam in terms of diffusion caused by the radiation damping and quantum excitation

Beam Dynamics of Proton-Nucleus Collisions in the Large Hadron Collider

This thesis discusses important questions of the beam dynamics in the proton-lead operation in the Large Hadron Collider (LHC) at CERN in Geneva. In two time blocks of several weeks in the years 2013 and 2016, proton-lead collisions have so far been successfully generated in the LHC and used by the experiments at the LHC. One reason for doubts regarding the successful operation in proton-lead configuration was the fact that the beams have to be accelerated with different revolution frequencies. There is long-range repulsion between the beams, since both beams share the beam chamber around the interaction points. Because of the different revolution frequencies, the positions of the interaction between the beams shift each revolution. This can lead to resonant excitation and to an increase in the transverse beam emittance, as was observed in the Relativistic Heavy-Ion Collider (RHIC). In this thesis, simulations for the LHC, RHIC and the High-Luminosity Large Hadron Collider (HL-LHC) are performed with a new model. The results for RHIC show relative growth rates of the emittances of the gold beam in gold-deuteron operation in RHIC from $0.1\,\%/\text{s}$ to $1.5\,\%/\text{s}$. Growth rates of this magnitude were observed experimentally in RHIC. Simulations for the LHC show no significant increase of the emittance of the lead beam for different intensities of the counter-rotating beam. The simulation results confirm the measured stability of the beams in the LHC and the issue of strongly increasing emittances in RHIC is reproduced. Also, no significant increase of the emittance is predicted for the Future Circular Collider (FCC) and the HL-LHC. Using a frequency-map analysis, this work verifies whether the interaction of the lead beam with the much smaller proton beam in the proton-lead operation of the LHC leads to diffusion within the lead beam. Experiences at HERA at DESY in Hamburg and at SppS at CERN have shown that the lifetime of the larger beam can rapidly decrease under certain circumstances. The results of the simulation show no chaotic dynamics near the beam centre of the lead beam. This result is supported by experimental observation. A program code has been developed which calculates the beam evolution in the LHC by means of coupled differential equations. This study shows that the growth rates of the lead beam due to intra-beam scattering is overestimated and that particle bunches of the lead beam lose more intensity than assumed in the model. The analysis also shows that bunches colliding in a detector suffer additional losses that increase with decreasing crossing angle at the interaction point. In this work, 2016 data from beam-loss monitors in combination with the luminosity and the loss rate of the beam intensity are used to determine the cross section of proton-lead collisions at $\sqrt{s_\text{NN}}=8.16\,$TeV. Beam-loss monitors that mainly detect beam losses that are not caused by the collision process itself are used to determine the total cross section via regression. An analysis of the data recorded in 2016 at $\sqrt{s_\text{NN}}=8.16\,$TeV resulted in a total cross section of $\sigma=(2.32\pm 0.01\pm\text{(stat.)}\pm 0.20 \text{(sys.)})\,$b. This corresponds approximately to a hadronic cross section of $\sigma_\text{had}=(2.24\pm 0.01 \text{(stat.)} \pm 0.21 \text{(sys.)})\,$b. This value deviates only by $5.7\,\%$ from the theoretical value $\sigma_\text{had}=(2.12 \pm 0.01)\,$ b. The simulation code for determining the beam evolution is also used to estimate the integrated luminosity of a future one-month run with proton-lead collisions. The result of the study shows that in the future the luminosity in the ATLAS and CMS experiments will increase from $15\,$nb${^{-1}}$ per day in 2016 to $30\,$nb${^{-1}}$ per day, which is a significant increase in terms of the performance. This operation, however, requires the use of the TCL collimators to protect the dispersion suppressors at ATLAS and CMS from collision fragments. This work also gives an outlook on the expected luminosity production in proton-nucleus operation using ion species lighter than lead ions. For example, a change from proton-lead to proton-argon collisions would increase the integrated luminosity from monthly $0.8\,$nb${^{-1}}$ to $9.4\,$nb${^{-1}}$ in ATLAS and CMS. This is an increase of one order of magnitude and approximately a doubling of the integrated nucleon-nucleon luminosity. There may be a test operation with proton-oxygen collisions in 2023, which will last only a few days and will be operated with a low luminosity. The LHCf experiment (LHCb experiment) would achieve the desired integrated luminosity of $1.5\,$nb${^{-1}}$ ($2\,$nb${^{-1}}$) within $70\,\text{h}$ ($35\,\text{h}$) beam time

Beam dynamics of proton-nucleus collisions in the large hadron collider

Diese Arbeit diskutiert wichtige Fragestellungen der Strahldynamik im Proton-Blei-Betrieb im Large Hadron Collider (LHC) am CERN in Genf. In zwei mehrwöchigen Zeitblöcken in den Jahren 2013 und 2016 konnten bisher erfolgreich Proton-Blei-Kollisionen im LHC erzeugt und von den Experimenten am LHC genutzt werden. Grund für den Zweifel an dem erfolgreichen Betrieb in Proton-Blei-Konfiguration war die Tatsache, dass die Strahlen mit unterschiedlichen Umlauffrequenzen beschleunigt werden müssen. Es kommt zu einer langreichweitigen Abstoßung zwischen den Strahlen, da sich beide Strahlen um die Wechselwirkungspunkte die Strahlkammer teilen. Aufgrund der unterschiedlichen Umlauffrequenzen verschieben sich die Positionen der Wechselwirkung zwischen den Strahlen jeden Umlauf. Dies kann zu resonanter Anregung und zum Anwachsen der transversalen Strahlemittanz führen, wie es im Relativistic Heavy-Ion Collider (RHIC) beobachtet wurde. In dieser Arbeit werden Simulationen für den LHC, den RHIC und den High-Luminosity Large Hadron Collider (HL-LHC) mit einem neuem Modell durchgeführt. Die Ergebnisse für den RHIC zeigen relative Anwachsraten der Emittanzen des Goldstrahls im Gold-Deuteron-Betrieb im RHIC von 0.1 %/s bis 1.5 %/s. Anwachsraten dieser Größenordnung wurden im RHIC experimentell beobachtet. Simulationen für den LHC zeigen keinen nennenswerten Emittanzzuwachs des Bleistrahls für unterschiedliche Intensitäten des gegenläufigen Strahls. Die Simulationsergebnisse bestätigen die gemessene Stabilität der Strahlen im LHC und die Problematik stark anwachsender Emittanzen im RHIC wird reproduziert. Ebenfalls wird kein signifikanter Emittanzzuwachs für den Future Circular Collider (FCC) und den HL-LHC vorhergesagt. Mit Hilfe einer Frequency-Map-Analyse wird in dieser Arbeit überprüft, ob die Wechselwirkung des Bleistrahls mit dem viel kleineren Protonenstrahl im Proton-Blei-Betrieb des LHCs zu Diffusion innerhalb des Bleistrahls führt. Erfahrungen bei HERA am DESY in Hamburg und beim SppS am CERN haben gezeigt, dass die Lebensdauer des größeren Strahls unter Umständen rapide abnehmen kann. Die Ergebnisse der Simulation zeigen keine chaotische Dynamik nahe des Strahlzentrums des Bleistrahls. Dieses Ergebnis werden durch experimentelle Beobachtung gestützt. Ein Programmcode wurde entwickelt, der die Strahlentwicklung im LHC mittels gekoppelter Differentialgleichungen berechnet. Die Ergebnisse dieser Studie zeigen, dass die Anwachsraten des Bleistrahls durch Intra-Beam-Scattering überschätzt werden und dass Teilchenpakete des Bleistrahls mehr Intensität verlieren als im Modell angenommen. Die Analyse zeigt außerdem, dass Teilchenpakete, die in einem Detektor kollidieren, zusätzliche Verluste erleiden, die mit abnehmendem Kreuzungswinkel im Kollisionspunkt zunehmen. In dieser Arbeit werden die Daten von Strahlverlustmonitoren in Kombination mit der Luminosität und der Verlustrate der Strahlintensität aus dem Jahre 2016 genutzt, um den Wirkungsquerschnitt von Proton-Blei-Kollisionen bei der Schwerpunktsenergie von 8.16 TeV zu bestimmen. Strahlverlustmonitore, die hauptsächlich Strahlverluste detektieren, die nicht durch den Kollisionsprozess selbst hervorgerufen werden, werden genutzt um den Gesamtwirkungsquerschnitt via Regression zu bestimmen. Eine Analyse der in 2016 bei der Schwerpunktsenergie von 8.16 TeV aufgenommenen Daten ergab einen Gesamtwirkungsquerschnitt von σ=(2.32±0.01(stat.)±0.20(sys.)) b. Dies entspricht in etwa einem hadronischen Wirkungsquerschnitt von σ(had)=(2.24±0.01(stat.)±0.21(sys.)) b. Dieser Wert weicht nur um 5.7 % von dem theoretischen Wert σ(had)=(2.12±0.01) b ab. Der Simulationscode zur Bestimmung der Strahlentwicklung wird auch genutzt, um die integrierte Luminosität eines zukünftigen einmonatigen Betriebes mit Proton-Blei-Kollisionen abzuschätzen. Das Ergebnis der Studie zeigt, dass in der Zukunft die Luminosität in den Experimenten ATLAS und CMS von 15/nb pro Tag in 2016 auf 30/nb pro Tag anwachsen wird, was eine deutliche Leistungssteigerung ist. Der Einsatz der TCL-Kollimatoren ist jedoch nötig um die dispersionunterdrückenden Regionen bei ATLAS und CMS gegen Kollisionsfragmente zu schützen. Auch gibt diese Arbeit einen Ausblick der zu erwartenden Luminositätsproduktion im Proton-Nukleus-Betrieb bei Verwendung von Ionenarten, die leichter sind als Bleiionen. Ein Wechsel von Proton-Blei- zu Proton-Argon-Kollisionen würde beispielsweise die integrierte Luminosität innerhalb eines Monats von 0.8/nb auf 9.4/nb in ATLAS und CMS erhöhen. Dies ist eine Steigerung von einer Größenordnung und ungefähr eine Verdoppelung der integrierten Nukleon-Nukleon-Luminosität. Möglicherweise wird es 2023 testweise Betrieb mit Proton-Sauerstoff-Kollisionen geben, der nur wenige Tage andauern und mit einer geringen Luminosität operiert werden wird. Das LHCf-Experiment (LHCb-Experiment) würde die angestrebte integrierte Luminosität von 1.5/nb (2/nb) innerhalb von 70h (35h) Strahlzeit erreichen.This thesis discusses important questions of the beam dynamics in the proton-lead operation in the Large Hadron Collider (LHC) at CERN in Geneva. In two time blocks of several weeks in the years 2013 and 2016, proton-lead collisions have so far been successfully generated in the LHC and used by the experiments at the LHC. One reason for doubts regarding the successful operation in proton-lead configuration was the fact that the beams have to be accelerated with different revolution frequencies. There is long-range repulsion between the beams, since both beams share the beam chamber around the interaction points. Because of the different revolution frequencies, the positions of the interaction between the beams shift each revolution. This can lead to resonant excitation and to an increase in the transverse beam emittance, as was observed in the Relativistic Heavy-Ion Collider (RHIC). In this thesis, simulations for the LHC, RHIC and the High-Luminosity Large Hadron Collider (HL-LHC) are performed with a new model. The results for RHIC show relative growth rates of the emittances of the gold beam in gold-deuteron operation in RHIC from 0.1 %/s to 1.5 %/s. Growth rates of this magnitude were observed experimentally in RHIC. Simulations for the LHC show no significant increase of the emittance of the lead beam for different intensities of the counter-rotating beam. The simulation results confirm the measured stability of the beams in the LHC and the issue of strongly increasing emittances in RHIC is reproduced. Also, no significant increase of the emittance is predicted for the Future Circular Collider (FCC) and the HL-LHC. Using a frequency-map analysis, this work verifies whether the interaction of the lead beam with the much smaller proton beam in the proton-lead operation of the LHC leads to diffusion within the lead beam. Experiences at HERA at DESY in Hamburg and at SppS at CERN have shown that the lifetime of the larger beam can rapidly decrease under certain circumstances. The results of the simulation show no chaotic dynamics near the beam centre of the lead beam. This result is supported by experimental observation. A program code has been developed which calculates the beam evolution in the LHC by means of coupled differential equations. This study shows that the growth rates of the lead beam due to intra-beam scattering is overestimated and that particle bunches of the lead beam lose more intensity than assumed in the model. The analysis also shows that bunches colliding in a detector suffer additional losses that increase with decreasing crossing angle at the interaction point. In this work, 2016 data from beam-loss monitors in combination with the luminosity and the loss rate of the beam intensity are used to determine the cross section of proton-lead collisions at the center-of-mass energy of 8.16 TeV. Beam-loss monitors that mainly detect beam losses that are not caused by the collision process itself are used to determine the total cross section via regression. An analysis of the data recorded in 2016 at the center-of-mass energy of 8.16 TeV resulted in a total cross section of σ=(2.32±0.01(stat.)±0.20(sys.)) b. This corresponds approximately to a hadronic cross section of σ(had)=(2.24±0.01(stat.)±0.21(sys.)) b. This value deviates only by 5.7 % from the theoretical value σ(had)=(2.12±0.01) b. The simulation code for determining the beam evolution is also used to estimate the integrated luminosity of a future one-month run with proton-lead collisions. The result of the study shows that in the future the luminosity in the ATLAS and CMS experiments will increase from 15/nb per day in 2016 to 30/nb per day, which is a significant increase in terms of the performance. This operation, however, requires the use of the TCL collimators to protect the dispersion suppressors at ATLAS and CMS from collision fragments. This work also gives an outlook on the expected luminosity production in proton-nucleus operation using ion species lighter than lead ions. For example, a change from proton-lead to proton-argon collisions would increase the integrated luminosity from monthly 0.8/nb to 9.4/nb in ATLAS and CMS. This is an increase of one order of magnitude and approximately a doubling of the integrated nucleon-nucleon luminosity. There may be a test operation with proton-oxygen collisions in 2023, which will last only a few days and will be operated with a low luminosity. The LHCf experiment (LHCb experiment) would achieve the desired integrated luminosity of 1.5/nb (2/nb) within 70h (35h) beam time

Prospects for future asymmetric collisions in the LHC

The proton-lead runs of the LHC in 2012, 2013 and 2016 provided luminosity far beyond expectations in a diversity of operating conditions and led to important new results in high-density QCD. This has permitted the scope of the future physics programme to be expanded in a recent review. Besides further high-luminosity proton-lead (p–Pb) collisions, lighter nuclei are also under consideration. A short proton-oxygen run, on the model of the 2012 p-Pb run, would be of interest for cosmic-ray physics. Collisions of protons with argon, other noble gases and nuclei of lighter metals are also discussed. We provide an overview of the operational strategies and potential performance of various options. Potential performance limits from moving beam-beam encounters at injection and various beam-loss mechanisms are evaluated in the light of our understanding of the LHC to date

Moving long-range beam-beam encounters in heavy-ion colliders

Asymmetric ion beam collisions like proton-lead in the LHC or gold-deuteron in RHIC have become major components of heavy-ion physics programmes. The injection and ramp of two different ion species with the same magnetic rigidity and consequently unequal revolution frequencies generate moving long-range beam-beam encounters in the interaction regions of the collider. These encounters led to fast beam losses and can cause emittance blow-up as observed in RHIC in the early 2000s and, more recently, in 2015. Yet such effects are absent at the LHC so the difference between the two colliders requires explanation. Tools and models have been developed to describe the beam dynamics of moving long-range beam-beam encounters and to predict the evolution of emittance and other beam parameters. Besides presenting results for RHIC and the LHC we give an outlook for the HL-LHC and potential operational restrictions

Lifetime of Asymmetric Colliding Beams in the LHC

In the 2013 proton-nucleus (p-Pb) run of the LHC, the lifetime of the lead beam was significantly shorter than could be accounted for by luminosity burn-off. These effects were observed at a lower level in 2016 and studied in more detail. The beams were not only asymmetric but the differences in the bunch filling schemes between protons and Pb nuclei led to a wide variety of beam-beam interaction sequences in the bunch trains. The colliding bunches were also of different sizes. We present an analysis of the data and an interpretation in terms of theoretical models

Effect of the total RF voltage on heavy ions at injection energy in the LHC

Emittance growth and particle losses from intra-beam scattering (IBS) are an important source of beam losses, especially at injection energy, for the heavy ions in LHC. The IBS diffusion rates are, among other factors, roughly inversely proportional to the bunch length and energy spread. Since the total RF voltage affects these parameters, it can be optimized to reduce the emittance growth and particle losses introduced by the aforementioned mechanism. During the 2016 proton-lead run, observations of the lifetime of lead-ion beams at injection energy, and at different RF voltages, were made during a dedicated fill. This note summaries these observations and compares the beam evolution with tracking simulations using the Collider Time Evolution (CTE) program

Stripline Kickers for Injection Into PETRA IV

PETRA IV is the planned ultralow-emittance upgrade of the PETRA III synchrotron light source at DESY, Hamburg. The current design includes an on-axis beam injection scheme using fast stripline kickers. These kickers have to fulfill the requirements on kick-strength, field quality, pulse rise-rate and a matched beam impedance. 3D finite element simulations in conjunction with Bayesian optimisation are used to meet these requirements simultaneously. Here, we will discuss the requirements on the PETRA IV injection kickers and the current design status

NuTag: proof-of-concept study for a long-baseline neutrino beam

International audienceThe study of neutrino oscillation at accelerators is limited by systematic uncertainties, in particular on the neutrino flux, cross-section, and energy estimates. These systematic uncertainties could be eliminated by a novel experimental technique: neutrino tagging. This technique relies on a new type of neutrino beamline and its associated instrumentation which would enable the kinematical reconstruction of the neutrinos produced in $\pi^{\pm} \to \mu^{\pm} \nu_\mu$ and $K^{\pm} \to \mu^{\pm} \nu_\mu$ decays. This article presents a proof-of-concept study for such a tagged beamline, aiming to serve a long baseline neutrino experiment exploiting a megaton scale natural water Cherenkov detector. After optimizing the target and the beamline optics to first order, a complete Monte Carlo simulation of the beamline has been performed. The results show that the beamline provides a meson beam compatible with the operation of the spectrometer, and delivers a neutrino flux sufficient to collect neutrino samples with a size comparable with similar experiments and with other un-tagged long-baseline neutrino experimental proposals

Studies for an LHC Pilot Run with Oxygen Beams

Motivated by the study of collective effects in small systems with oxygen-oxygen (O-O) collisions, and improvements to the understanding of high-energy cosmic ray interactions from proton-oxygen (p-O) collisions, a short LHC oxygen run during Run 3 has been proposed. This article presents estimates for the obtainable luminosity performance in these two running modes based on simulations of a typical fill. The requested integrated luminosity, projected beam conditions, data-taking and commissioning times are considered and a running scenario is proposed