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| MOPGW041 | Transverse Profile Shaping of a Charged-Particle Beam using Multipole Magnets - Formation of Hollow Beams - | target, optics, multipole, radiation | 184 |
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| The use of multipole magnets enables us to shape the transverse profile of a charged-particle beam into various ones that can never be realized through linear beam optics. To date, the formation of a large-area beam with a uniform transverse intensity distribution has been actually realized using octupole magnets in several accelerator facilities. In this presentation, we demonstrate the formation of different beam profiles using multipole magnets rather than existing rectangular uniform beams. Results of tracking simulations and beam-formation experiments will be shown on the formation of clear-cut beams with different cross-sectional shapes, depending on the order and strength of applied multipole magnets. The dynamic behavior of a beam focused with multipole magnets is also investigated theoretically to better understand the numerical and experimental results. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW041 | ||
| About • | paper received ※ 19 April 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019 | ||
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| MOPGW072 | Reconfiguration of SPS Landau Octupole Circuits to Minimise Second Order Chromaticity | optics, operation, target, acceleration | 262 |
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| In the SPS Q20 optics presently used for LHC beams, the Landau octupole families of the SPS (LOF and LOD circuits) generate large second order chromaticity due to the relatively high dispersion at their locations. Since the induced second order chromaticity results in enhanced losses due to the large incoherent tune spread, these octupoles cannot be used for mitigating transverse instabilities for LHC beams. A new cabling scheme was proposed, exploiting additional octupoles that were already installed in the machine but not used, which allows minimizing the induced second order chromaticity in both the Q20 optics used for LHC beams, as well as the original SPS optics used for fixed target beams. This paper summarises the optics calculations as well as the experimental verification of the reduced chromatic detuning of the new octupole scheme. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW072 | ||
| About • | paper received ※ 12 May 2019 paper accepted ※ 17 May 2019 issue date ※ 21 June 2019 | ||
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| MOPGW078 | Change of Beam Distribution Due to Decoherence in the Presence of Transverse Feedback | feedback, simulation, damping, emittance | 281 |
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| The effect of Landau damping is often calculated based on a Gaussian beam distribution in all degrees of freedom. The stability of the beam is however strongly dependent on the details of the distribution. The present study focuses on the change of bunch distributions caused by the decoherence of the excitation driven by an external source of noise, in the presence of both amplitude detuning and a transverse feedback. Both multiparticle tracking simulations and theoretical models show a similar change of the distribution. The possible loss of Landau damping driven by this change is discussed. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW078 | ||
| About • | paper received ※ 08 April 2019 paper accepted ※ 19 May 2019 issue date ※ 21 June 2019 | ||
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| MOPGW105 | Preliminary Lattice Studies for the Single-Invariant Optics Experiment at the University of Maryland | lattice, experiment, optics, resonance | 367 |
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Funding: This work is supported through DOE-HEP Award DESC0010301 and NSF Award PHY1414681. A novel approach to transverse resonance suppression in next generation high-intensity accelerators is the use of nonlinear optical elements to induce large tune spreads which result in reduced responses to resonance driving perturbations*. In order to test this theory, we have built and characterized an octupole channel insert for use in the University of Maryland Electron Ring (UMER). This paper presents experimental lattice studies using a low space-charge intensity beam at an energy of 10keV with a beam current of ~150uA, tune depression < 0.005, and unnormalized RMS emittance of 4.3 mm-mr. We apply beam based measurement techniques in order to evaluate the quality of our single-invariant lattice and better understand the nonlinearities created by the octupole channel. * V. Danilov and S. Nagaitsev, Nonlinear accelerator lattices with one and two analytic invariants, PRSTAB, 13, 084002, 2010. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW105 | ||
| About • | paper received ※ 11 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019 | ||
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| MOPGW113 | Experimental Demonstration of the Henon-Heiles Quasi-Integrable System at IOTA | experiment, lattice, optics, alignment | 386 |
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Funding: Work supported by National Science Foundation award PHY-1549132, the Center for Bright Beams. Fermi Research Alliance operates Fermilab under Contract DE-AC02-07CH11359 with the US Dept. of Energy. The Integrable Optics Test Accelerator is a research electron and proton storage ring recently commissioned at the Fermilab Accelerator Science and Technology facility. Its research program is focused on testing novel techniques for improving beam stability and quality, notably the concept of non-linear integrable optics. In this paper, we report the first results of experimental investigation of a quasi-integrable transverse focusing system with one invariant of motion, a Henon-Heiles type system implemented with octupole magnets. Good agreement with simulations is demonstrated on key parameters of achievable tune spread and dynamic aperture preservation. Resilience to perturbations and imperfections in the lattice is explored. We conclude by outlining future research plans and discussing applicability to future high intensity accelerators. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPGW113 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | ||
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| MOPMP005 | Field Quality for the Hadron Option of Future Circular Collider | injection, dipole, collider, target | 4397 |
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Funding: This Research and Innovation Action project submitted to call H2020-INFRADEV-1-2014-1 receives funding from the European Union’s H2020 Framework Program under grant agreement No. 654305. The updated field quality for the baseline design option of the Nb3Sn dipoles for Future Circular Collider (FCC-hh) is discussed. The impact on the expected dynamic aperture is shown at injection and collision energy and the consequent non-linear correction schemes together with their integration in the optics are defined. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPMP005 | ||
| About • | paper received ※ 14 May 2019 paper accepted ※ 20 May 2019 issue date ※ 21 June 2019 | ||
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| MOPRB005 | Study of Higher-Order Achromat Lattice as an Alternative Option for the SOLEIL Storage Ring Upgrade | lattice, sextupole, storage-ring, injection | 586 |
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| A ring composed of 20 symmetrical 7BA cells in which of a pair of chromaticity correcting sextupoles placed around horizontal dispersion bumps à la ESRF-EBS was developed as a baseline lattice for the SOLEIL storage ring upgrade (presented at IPAC2018). The strict phase relation between the two dispersion bumps provides an efficient way of optimizing the (on-momentum) nonlinear optics with a limited number of sextupoles. As an alternative, a scheme known as Higher-Order Achromat (HOA) develops a MBA (Multi-Bend Achromat) lattice where chromaticity correcting sextupoles are distributed in each M unit cell with a strict phase relation cell-wise such as to cancel basic geometric and chromatic resonance driving terms. The beam dynamics in a 20-fold 7BA HOA ring is compared with those of the baseline lattice, with focus on off-momentum properties such as Touschek lifetime, which are important for medium energy rings like SOLEIL. The robustness against errors, the reduction of the ring symmetry by introducing 4 longer straight sections, as well as a horizontal dispersion bump to cope with longitudinal on-axis injection scheme are also presented. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPRB005 | ||
| About • | paper received ※ 22 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | ||
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| MOPTS089 | Transverse Beam Dynamics Studies With High Intensity LHC Beams in the SPS | injection, emittance, impedance, electron | 1062 |
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| In order to reach the target beam parameters of the LHC injectors upgrade (LIU), about twice the presently operational intensity of LHC type beams has to be achieved. Although the planned upgrade of the main RF system will occur during the long shutdown, a series of measurements have been performed to assess the beam dynamics challenges with these very high intensity beams on the long SPS injection plateau. Bunch-by-bunch transverse emittance blow-up measurements suggested the presence of electron-cloud. After a period of running with the high intensity beam for a couple of days, a clear improvement of beam quality was observed which is attributed to scrubbing. In addition, a horizontal headtail instability is encountered for the usual operational settings of chromaticity and transverse damper. The stability limit as a function of chromaticity and Landau octupole settings has been explored and will be discussed, together with possible sources of the instability and mitigation strategies. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-MOPTS089 | ||
| About • | paper received ※ 06 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019 | ||
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| TUPGW040 | Study of Seven-Bend Achromat Lattices with Interleaved Dispersion Bumps for HALS | lattice, storage-ring, emittance, linear-dynamics | 1495 |
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| Previously, we proposed a multi-bend achromat (MBA) lattice concept, called the MBA with interleav-ed dispersion bumps, which was then used to design a 7BA lattice for the Hefei Advanced Light Source (HALS) storage ring. Recently, such a 7BA lattice was further designed and optimized for the HALS by changing the number of lattice cells, scanning working point and employing octupoles. And two new HALS designs with such 7BA lattices have been made, one with 30 lattice cells and a natural emittance of 25 pm·rad and the other with 28 cells and 33 pm·rad. They had much better nonlinear dynamics perfor-mances than the previous design. The detailed study for these two HALS lattices will be presented in this paper. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-TUPGW040 | ||
| About • | paper received ※ 15 May 2019 paper accepted ※ 18 May 2019 issue date ※ 21 June 2019 | ||
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| WEPMP031 | SPS Slow Extraction Losses and Activation: Update on Recent Improvements | extraction, operation, proton, alignment | 2391 |
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Annual high intensity requests of over 1019 protons on target (POT) from the CERN Super Proton Synchrotron (SPS) Fixed Target (FT) physics program continue, with the prospect of requests for even higher, unprecedented levels in the coming decade. A concerted and multifaceted R&D effort has been launched to understand and reduce the slow extraction induced radioactivation of the SPS and to anticipate future experimental proposals, such as SHiP* at the SPS Beam Dump Facility (BDF)**, which will request an additional 4·1019 POT per year. In this contribution, we report on operational improvements and recent advances that have been made to significantly reduce the slow extraction losses, by up to a factor of 3, with the deployment of new extraction concepts, including passive and active (thin, bent crystal) diffusers and extraction on the third-integer resonance with octupoles. In light of the successful tests of the prototype extraction loss reduction schemes, an outlook and implications for future SPS FT operation will be presented.
* A. Golutvin et al., Rep. CERN-SPSC-2015-016 (SPSC-P-350), CERN, Geneva, Switzerland, Apr. 2015. ** M. Lamont et al., Rep. CERN-PBC-REPORT-2018-001, CERN, Geneva, Switzerland, 11 Dec 2018. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP031 | ||
| About • | paper received ※ 14 May 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | ||
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| WEPMP033 | Slow Extraction Loss Reduction With Octupoles at the CERN SPS | extraction, septum, multipole, proton | 2399 |
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| The powering of octupoles during third-integer resonant slow extraction has been studied and recently tested with beam at the CERN Super Proton Synchrotron (SPS) in order to increase the extraction efficiency and reduce the induced radioactivity of the extraction straight. The octupoles distort the particle trajectories in phase space in such a way that the extracted separatrix is folded, which decreases the particle density impinging the wires of the extraction septum at the expense of increasing the extracted beam emittance. During experimental SPS machine studies a reduction of over 40% in the specific (per extracted proton) beam loss measured at the extraction septum was demonstrated. In this paper, the prerequisite studies needed to safely but efficiently deploy the new extraction scheme in a limited time-frame are described, the experimental results are presented and an outlook is given towards the next steps to bring slow extraction with octupoles into routine operation. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP033 | ||
| About • | paper received ※ 14 May 2019 paper accepted ※ 23 May 2019 issue date ※ 21 June 2019 | ||
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| WEPMP045 | Higher Multipoles in 3rd Integer Resonance Extraction | extraction, sextupole, multipole, simulation | 2437 |
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| The efficiency of slow extraction is becoming a limiting factor, as the demand for delivered beam power is constantly growing. New methods for improving extraction efficiency include folding the extraction separatrix using the higher multipoles. In this report we discuss a simple and effective approach to determine an optimal placement of those multipoles in the storage ring. This allows reduction of the beam losses and therefore, the level of prompt and residual radioactivity in the accelerator components and surrounding buildings by as much as 40% or more. We also explore here manipulating the higher order effects produced in the pure sextupole configurations for the same purpose and demonstrate that similar results can be achieved by only rearranging the sextupole magnets in the lattice. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPMP045 | ||
| About • | paper received ※ 10 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | ||
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| WEPTS044 | Instability Latency in the LHC | experiment, feedback, damping, simulation | 3204 |
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| The Large Hadron Collider (LHC) has experienced multiple instabilities that occur between minutes and hours after the last modification of the machine settings. The existence of instabilities with high latency has been reproduced also in simulations. Dedicated experiments, injecting a controlled noise into the beam, have now been performed to discover the dependence of this latency on key parameters. The results seem compatible with a mechanism linked to a steady and slow modification of the transverse beam distribution leading to a loss of Landau damping. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS044 | ||
| About • | paper received ※ 30 April 2019 paper accepted ※ 21 May 2019 issue date ※ 21 June 2019 | ||
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| WEPTS056 | Can a Paul Ion Trap Be Used to Investigate Nonlinear Quasi-Integrable Optics? | lattice, optics, experiment, quadrupole | 3251 |
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| Here we describe the design of an experimental setup using the IBEX Paul trap to test nonlinear quasi-integrable optics, an accelerator lattice design to create stable high intensity beams. In 2010 Danilov and Nagaitsev found a realisable nonlinear potential which can create integrable optics in an accelerator when embedded in a linear lattice that provides round beams. This concept will be tested in the IOTA ring at Fermilab. It is important to further test this concept over a wide parameter range, preferably in a simplified experimental setup such as IBEX. The IBEX Paul trap is capable of replicating the transverse dynamics of a high intensity accelerator without dispersion or chromaticity. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-WEPTS056 | ||
| About • | paper received ※ 30 April 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | ||
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| THPTS011 | Design, Production, and Testing of Superconducting Magnets for the Super-FRS | dipole, quadrupole, cryogenics, superconducting-magnet | 4128 |
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| The Super FRS is a two-stage in flight separator to be built next to the site of GSI, Darmstadt, Germany as part of FAIR (Facility for Anti-proton and Ion Research). Its purpose is to create and separate rare isotope beams and to enable the mass measurement also for very short lived nuclei. Due to its three branches a wide variety of experiments can be carried out in frame of the NUSTAR collaboration. Due to the large acceptance needed, the magnets of the Super-FRS have to have a large aperture and therefore only a superconducting solution is feasible. A superferric design with superconducting coils was chosen in which the magnetic field is shaped by an iron yoke. For the dipoles this iron yoke is at warm and only the coils are incorporated in a cryostat. The multiplets, assemblies of quadrupoles and higher order multipole magnets, are completely immersed in a liquid Helium bath. With the exception of special branching dipoles all superconducting magnets of Super-FRS have been contracted and are being built by Elytt in Spain (dipoles) and ASG in Italy (multiplets). The cold test of all magnets will take place in a dedicated test facility at CERN. This contribution will present the status of manufacturing of dipoles and multiplets, and also gives a short overview on the test facility. | |||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2019-THPTS011 | ||
| About • | paper received ※ 14 May 2019 paper accepted ※ 22 May 2019 issue date ※ 21 June 2019 | ||
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