Paper | Title | Page |
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MOA1I1 | Beam Performance with the LHC Injectors Upgrade | 1 |
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The LHC Injectors Upgrade (LIU) project was put in place between 2010 and 2021 to increase the intensity and brightness in the LHC injectors to match the challenging requirements of the High-Luminosity LHC (HL-LHC) project, while ensuring reliable operation of the injectors complex up to the end of the HL-LHC era (ca. 2040). During the 2019-2020 CERN accelerators shutdown, extensive hardware modifications were implemented in the entire LHC proton and ion injection chains, involving the new Linac4, the Proton Synchrotron Booster (PSB), the Proton Synchrotron (PS), the Super Proton Synchrotron (SPS) and the ion PS injectors, i.e. the Linac3 and the Low Energy Ion Ring (LEIR). Since 2021, beams have been recommissioned throughout the injectors’ chain and the beam parameters are being gradually ramped up to meet the LIU specifications using new beam dynamics solutions adapted to the upgraded accelerators. This paper focuses on the proton beams and describes the current state of the art. | ||
Slides MOA1I1 [10.002 MB] | ||
DOI • | reference for this paper ※ doi:10.18429/JACoW-HB2023-MOA1I1 | |
About • | Received ※ 29 September 2023 — Revised ※ 05 October 2023 — Accepted ※ 09 October 2023 — Issued ※ 18 October 2023 | |
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TUA2C2 | Recent Advances in the CERN PS Impedance Model and Instability Simulations | 86 |
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Transverse instability growth rates in the CERN Proton Synchrotron are studied thanks to the recently updated impedance model of the machine. Using this model, macroparticle tracking simulations were performed with a new method well-suited for the slicing of short wakes, which achieves comparable performance to the originally implemented method while reducing the required number of slices by a factor of 5 to 10. Dedicated beam-based measurement campaigns were carried out to benchmark the impedance model. Until now, the model underestimated instability growth rates at injection energy. Thanks to a recent addition to the impedance model, namely the kicker magnets¿ connecting cables and their external circuits, the simulated instability growth rates are now comparable to the measured ones. | ||
Slides TUA2C2 [0.736 MB] | ||
DOI • | reference for this paper ※ doi:10.18429/JACoW-HB2023-TUA2C2 | |
About • | Received ※ 28 September 2023 — Revised ※ 07 October 2023 — Accepted ※ 09 October 2023 — Issued ※ 21 October 2023 | |
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WEA1C1 | Bunch-by-bunch Tune Shift Studies for LHC-type Beams in the CERN SPS | 194 |
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After the implementation of major upgrades as part of the LHC Injector Upgrade Project (LIU), the Super Proton Synchrotron (SPS) delivers high intensity bunch trains with 25 ns bunch spacing to the Large Hadron Collider (LHC). These beams are exposed to several collective effects in the SPS, such as beam coupling impedance, space charge and electron cloud, leading to relatively large bunch-by-bunch coherent and incoherent tune shifts. Tune correction to the nominal values at injection is crucial to ensure beam stability and good beam transmission. Measurements of the bunch-by-bunch coherent tune shifts have been performed under different beam conditions. In this paper, we present the measurements of the bunch-by-bunch tune shift as function of bunch intensity for trains of 72 bunches. The experimental data are compared to multiparticle tracking simulations (including other beam variants such as 8b4e beam and hybrid beams) using the SPS impedance model. | ||
Slides WEA1C1 [2.613 MB] | ||
DOI • | reference for this paper ※ doi:10.18429/JACoW-HB2023-WEA1C1 | |
About • | Received ※ 29 September 2023 — Revised ※ 08 October 2023 — Accepted ※ 09 October 2023 — Issued ※ 09 October 2023 | |
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THAFP01 | Probing Transverse Impedances in the High Frequency Range at the CERN SPS | 393 |
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Funding: CERN The SPS transverse impedance model, which includes the major impedance contributions in the machine, can be benchmarked through measurements of the Head-Tail mode zero instability. Since the SPS works above transition energy, the head tail mode zero is unstable for negative values of chromaticity. The measured instability growth rate is proportional to the real part of the transverse impedance. Studies performed after the LHC Injectors Upgrade (LIU) showed a relevant impedance around 2 GHz with high-gamma transition optics (Q26). This paper presents the follow-up studies to probe the behavior of this beam coupling impedance contribution. |
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Slides THAFP01 [2.262 MB] | ||
Poster THAFP01 [1.149 MB] | ||
DOI • | reference for this paper ※ doi:10.18429/JACoW-HB2023-THAFP01 | |
About • | Received ※ 29 September 2023 — Revised ※ 05 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 10 October 2023 | |
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THAFP05 | A Wireless Method for Beam Coupling Impedance Measurements of the LHC Goniometer | 407 |
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The beam coupling impedance (BCI) of an accelerator component should be ideally evaluated exciting the device with the beam itself. However, this scenario is not always attainable and alternative methods must be exploited, such as the bench measurements techniques. The stretched Wire Method (WM) is a well established technique for BCI evaluations, although nowadays its limitations are well known. In particular, the stretched wire perturbs the electromagnetic boundary conditions. Therefore, the results obtained could be inaccurate, especially below the cut-off frequency of the beam pipe in the case of cavity-like structures. To overcome these limitations, efforts are being made to investigate alternative bench measurement techniques that will not require the modification of the device under test (DUT). In this framework, a wireless method has been identified and tested for a pillbox cavity. Its potential for more complex structures, such as the LHC crystal goniometer is explored. | ||
Slides THAFP05 [1.088 MB] | ||
Poster THAFP05 [1.151 MB] | ||
DOI • | reference for this paper ※ doi:10.18429/JACoW-HB2023-THAFP05 | |
About • | Received ※ 29 September 2023 — Revised ※ 05 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 11 October 2023 | |
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THBP05 | CERN SPS Dilution Kicker Vacuum Pressure Behaviour under Unprecedented Beam Brightness | 447 |
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The Super Proton Synchrotron (SPS) is the second largest synchrotron at CERN and produces high-brightness beams for the Large Hadron Collider (LHC). Recently, the dilution kicker (MKDH) of the SPS beam dump system (SBDS) has demonstrated unanticipated behaviour under high beam brightness conditions. During the 2022 and 2023 beam commissioning, the MKDH, which is routinely pulsed at high voltage, was subjected to intensities of up to 288 bunches of 2·1011 protons per bunch and bunch lengths as low as 1.5 ns. Under these conditions, all the SPS kickers and septa exhibited a rapid vacuum pressure rise and a significant temperature increase with the MKDH playing the dominant effect in restricting the maximum line density that can be attained. This paper presents the results of the collected data, emphasizes the dependence on beam parameters, and introduces a probabilistic model to illustrate the effect of MKDH conditioning observed to forecast the pressure behaviour. Finally, potential countermeasures and outlook are discussed. | ||
Poster THBP05 [1.913 MB] | ||
DOI • | reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP05 | |
About • | Received ※ 29 September 2023 — Revised ※ 07 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 19 October 2023 | |
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THBP11 | MKP-L Impedance Mitigation and Expectations for MKP-S in the CERN-SPS | 466 |
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Beam coupling impedance mitigation is key in preventing intensity limitations due to beam stability issues, heating and sparking. In this framework, a very good example is the optimization of the SPS kickers beam-coupling impedance for beam-induced heating mitigation. After the optimization of the SPS extraction kickers, the SPS injection kickers became the next bottleneck for high intensity operation. This system is composed of three MKP-S tanks and one MKP-L. To accommodate LIU beam intensities, it was necessary to mitigate the beam induced heating of the MKP-L, using a shielding concept briefly reviewed in this paper. Moreover, temperature data from the 2023 run are analyzed to qualify the accuracy of the models and assess the effectiveness of the impedance mitigation. Finally, the expected limitations from the MKP-S, expected to become the new bottleneck in terms of beam induced heating, are discussed. | ||
Poster THBP11 [1.655 MB] | ||
DOI • | reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP11 | |
About • | Received ※ 29 September 2023 — Revised ※ 07 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 24 October 2023 | |
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THBP31 | Electron Cloud Effects in the CERN Accelerators in Run 3 | 538 |
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Several of the machines in the CERN accelerator complex, in particular the Large Hadron Collider (LHC) and the Super Proton Synchrotron (SPS), are prone to the build-up of electron clouds. Electron cloud effects are observed especially when the machines are operated with a 25 ns bunch spacing, which has routinely been used in the LHC since the start of its second operational run in 2015. After the completion of the LHC Injectors Upgrade program during the latest long shutdown period, the machines are currently operated with unprecedented bunch intensity and beam brightness. With the increase in bunch intensity, electron cloud effects have become one of the main performance limitations, as predicted by simulation studies. In this contribution we present the experimental observations of electron cloud effects since 2021 and discuss their implications for the future operation of the complex. | ||
DOI • | reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP31 | |
About • | Received ※ 01 October 2023 — Revised ※ 06 October 2023 — Accepted ※ 10 October 2023 — Issued ※ 23 October 2023 | |
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THBP52 | A Python Package to Compute Beam-Induced Heating in Particle Accelerators and Applications | 611 |
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High-energy particle beams interact electromagnetically with their surroundings when they travel inside an accelerator. These interactions may cause beam-induced heating of the accelerator’s components, which could eventually lead to outgassing, equipment degradation and physical damage. The expected beam-induced heating can be related to the beam coupling impedance, an electromagnetic property of every accelerator device. Accounting for beam-induced heating is crucial both at the design phase of an accelerator component and for gaining an understanding of devices¿ failures. In this paper, an in-house developed Python tool to compute beam-induced heating due to impedance is introduced. The different features and capabilities will be showcased and applied to real devices in the LHC and the injector chain. | ||
Poster THBP52 [0.544 MB] | ||
DOI • | reference for this paper ※ doi:10.18429/JACoW-HB2023-THBP52 | |
About • | Received ※ 29 September 2023 — Revised ※ 06 October 2023 — Accepted ※ 09 October 2023 — Issued ※ 11 October 2023 | |
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