| Paper | Title | Page |
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| MOPAB114 | Development of a Decoherence Kicker for the ALS Upgrade Project (ALS-U) | 414 |
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| The Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory is upgrading the existing storage-ring lattice to a nine-bend-achromat lattice with on-axis swap-out injection. The upgraded storage ring will provide a highly focused beam of about 10 um in both horizontal and vertical directions with a single bunch train energy of about 60 J at 2.0 GeV. Such a small and intense beam could cause damage to the transfer line vacuum chambers in case of extraction element failures or damage to the storage ring vacuum chamber in case of RF failures. To mitigate these potential damages, a fast kicker magnet (so-called decoherence kicker) will be installed in the ALS-U storage ring and activated to dilute the beam charge density either on a train to be swapped out a few 100s turns before extraction or on the whole beam after RF failures. In this paper, we will present both physics and engineering designs of this decoherence kicker. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB114 | |
| About • | paper received ※ 19 May 2021 paper accepted ※ 27 May 2021 issue date ※ 20 August 2021 | |
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| MOPAB115 | ATS/STA Transfer Line Design for the ALS Upgrade Project (ALS-U) | 417 |
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| At the Advanced Light Source Upgrade (ALS-U), an on-axis swap-out injection will be used to replenish depleted bunches in the storage ring with refreshed bunches from the full energy accumulator ring. To implement this scheme, two transfer lines are required between the storage ring and the accumulator ring: the accumulator-to-storage-ring (ATS) transfer line and the storage-ring-to-accumulator (STA) transfer line. The design of the ATS/STA transfer lines is a challenging task as they must fit within a tight injection region while also accommodating the storage and accumulator rings at different elevations. Moreover, the ATS/STA design needs to meet both the boundary conditions and optics requirements. In this paper, we will present a design option for these ATS/STA transfer lines. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB115 | |
| About • | paper received ※ 19 May 2021 paper accepted ※ 27 May 2021 issue date ※ 15 August 2021 | |
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| MOPAB118 | The Impact of Short-Range Wakes on Injection Into the ALS-U Accumulator Ring | 429 |
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Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DEAC02-05CH11231. As part of the ALS-U design, bunches with small charge will be added to the accumulator ring in a manner that initially leaves both the stored and injected bunches displaced from the nominal orbit. While the beam current is below instability thresholds, transient effects due to the combination of short-range wake fields and large initial displacements can have an impact on injection efficiency. In this paper, the impact of wake fields on the two bunches is detailed using the elegant simulation code, and different techniques to optimize the injection efficiency are explored. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-MOPAB118 | |
| About • | paper received ※ 19 May 2021 paper accepted ※ 31 May 2021 issue date ※ 12 August 2021 | |
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| WEPAB081 | The Broad-Band Impedance Budget in the Storage Ring of the ALS-U Project | 2779 |
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| Design work is underway for the upgrade of the Advanced Light Source (ALS-U) to a diffraction-limited soft x-rays radiation source. Like other 4th-generation light source machines, the ALS-U multiple-bend achromat storage-ring (SR) is potentially sensitive to beam-coupling impedance effects. This paper presents the SR broad-band impedance budget in both the longitudinal and transverse planes. In our modeling we follow the commonly accepted approach of separating the resistive-wall and the geometric parts of the impedance, the former being described by analytical formulas and the latter obtained by numerical electromagnetic codes (primarily CST Studio software) assuming perfectly conducting materials. We discuss the main sources of impedance. Results of our analysis are the basis for the single bunch instability study and would feedback on the design of critical vacuum components. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB081 | |
| About • | paper received ※ 20 May 2021 paper accepted ※ 01 July 2021 issue date ※ 20 August 2021 | |
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| WEPAB082 | Single Bunch Instability Simulations in the Storage Ring of the ALS-U Project | 2783 |
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| As the broad-band impedance modeling and the vacuum chamber design of the new Advanced Light Source storage ring (ALS- U) reach maturity, we report on progress in single-bunch collective effects studies. A pseudo-Green function wake representing the entire ring was earlier obtained by numerical and analytical methods. Macroparticle simulations using the computer code "elegant" and this wake function are used to determine the instability thresholds for longitudinal and transverse motion. We consider various operating conditions, such as without/with higher-harmonic RF cavities, zero/finite linear chromaticity, and without/with a transverse bunch-by-bunch feedback system. Results show enough margin for the broadband impedance budget when the single-bunch instability thresholds are compared with the design bunch charge. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB082 | |
| About • | paper received ※ 20 May 2021 paper accepted ※ 01 July 2021 issue date ※ 12 August 2021 | |
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| WEPAB123 | Multi-Bunch Resistive Wall Wake Field Tracking via Pseudomodes in the ALS-U Accumulator Ring | 2893 |
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| For the ALS-U project, particles will be injected from the booster to the accumulator ring utilizing an injection scheme that leaves the stored and injected particles with a non-trivial transient. This transient requires that multibunch feedback be masked for those buckets into which charge is injected. The masking significantly diminishes the damping capability of the multibunch feedback system. This problem is exacerbated by the large injection transient. The higher order resistive wall wake fields in the accumulator ring exceed the radiation damping time. To study whether the beam will remain multibunch stable during an injection cycle, a multibunch tracking simulation is used that simulates the multibunch feedback system and also pseudomode representation of resistive wall wake fields. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB123 | |
| About • | paper received ※ 20 May 2021 paper accepted ※ 01 September 2021 issue date ※ 23 August 2021 | |
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| WEPAB124 | The Three Dipole Kicker Injection Scheme for the ALS-U Accumulator Ring | 2896 |
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| The ALS-U light source will implement on-axis swap-out injection of individual trains employing an accumulator between the booster and storage rings. The accumulator ring design is a twelve period triple-bend achromat that will be installed along the inner circumference of the storage-ring tunnel. A non-conventional injection scheme will be utilized for top-off off-axis injection from the booster into the accumulator ring meant to accommodate a relatively narrow vacuum-chamber aperture while maximizing injection efficiency. The scheme incorporates three dipole kickers distributed over three sectors, with two kickers perturbing the stored beam and the third affecting both the stored and the injected beam trajectories. This paper describes this ‘‘3DK’’ injection scheme, how it was chosen, designed and optimized, and how we evaluated its fitness as a solution for booster-to-accumulator ring injection against alternate injection schemes. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB124 | |
| About • | paper received ※ 20 May 2021 paper accepted ※ 01 July 2021 issue date ※ 13 August 2021 | |
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| WEPAB341 | Injection and Extraction Kickers for the Advanced Light Source Upgrade Project (ALS-U) | 3487 |
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Funding: This work was supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. The Advanced Light Source upgrade project (ALS-U) at Lawrence Berkeley National Laboratory includes the construction of a new accumulator ring and the replacement of the existing storage ring. Both ferrite-loaded kickers and stripline kickers are used in the ALS-U design for injection, extraction, and decohering the beam before storage ring extraction. In the accumulator ring, the rise and fall time requirements are based on the single bunch revolution time of 608 ns which allows the use of ferrite-loaded kickers. The 10 ns spacing between bunch trains in the storage ring requires stripline kickers to meet the rise and fall time requirements. Both types of kickers are driven by solid-state inductive voltage adders using MOSFETs. Modeling and prototyping efforts have characterized the kicker impedance and beam-induced heating, and explored the effects of beam strike on electrodes. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB341 | |
| About • | paper received ※ 20 May 2021 paper accepted ※ 27 July 2021 issue date ※ 24 August 2021 | |
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