Design, prototyping, and testing of a compact superconducting double quarter wave crab cavity

Xiao, Binping; Alberty, Luís; Belomestnykh, S.; Ben‐Zvi, I.; Calaga, R.; Cullen, Chris; Capatina, Ofelia; Hammons, L.; Li, Zenghai; Marques, C. N.; Skaritka, J.; Verdú-Andrés, Silvia; Wu, Qiong

doi:10.1103/physrevstab.18.041004

Cited by 26 publications

(25 citation statements)

References 21 publications

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“…4). The weak head-tail approximation precisely matches the exact solution for 1 radial ring, obtained from (10), (14), and (18), as seen in Fig. 4.…”

Section: Weak Head-tail Limitsupporting

confidence: 80%

“…If the mode frequency is so low that ω r ω ξ , it can be neglected in the arguments of Bessel functions in (18). Then the last term of the product in (18)…”

Section: B Flat Wake Limitmentioning

confidence: 99%

“…High-Luminosity LHC employs two sets of crab cavities, each consisting of four cavities per IP and per beam: one set with the crossing in the horizontal and the other -in the vertical plane. Currently, there are two different designs of the crab cavities being considered: Double Quarter Wave (DQW) [18] and RF Dipole (RFD) [19][20][21][22]. Both designs feature a large number of high order modes, some of which might be dangerous for the coupled-bunch stability.…”

Section: Crab Homs For Hl-lhcmentioning

confidence: 99%

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Effect of crab cavity high order modes on the coupled-bunch stability of High-Luminosity Large Hadron Collider

Antipov

Biancacci

Komppula

et al. 2019

Phys. Rev. Accel. Beams

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High frequency High Order Modes can significantly affect the coupled-bunch stability in a circular accelerator. With a large enough shunt impedance they may drive a coupled-bunch transverse instability. We have developed an analytical model and implemented it in the NHT Vlasov solver. The results show that the instability is characterized by the excitation of many azimuthal intra-bunch modes, which have similar growth rates, that make the traditional remedies such as a flat resistive feedback and chromaticity inefficient in suppressing it. For the High Luminosity Large Hadron Collider this could result in a significant increase of the stabilizing Landau octupole current, up to ∼ 100 A (∼ 20% of the maximum available current). In order to limit the increase below 10 A (∼ 2%), the transverse shunt impedance has to be kept below 1 MΩ/m. I.

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“…4). The weak head-tail approximation precisely matches the exact solution for 1 radial ring, obtained from (10), (14), and (18), as seen in Fig. 4.…”

Section: Weak Head-tail Limitsupporting

confidence: 80%

“…If the mode frequency is so low that ω r ω ξ , it can be neglected in the arguments of Bessel functions in (18). Then the last term of the product in (18)…”

Section: B Flat Wake Limitmentioning

confidence: 99%

Section: Crab Homs For Hl-lhcmentioning

confidence: 99%

See 1 more Smart Citation

Effect of crab cavity high order modes on the coupled-bunch stability of High-Luminosity Large Hadron Collider

Antipov

Biancacci

Komppula

et al. 2019

Phys. Rev. Accel. Beams

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“…The PoP DQW cavity exhibited multipacting below 0.5 MV and between 2 and 3 MV. Low field multipacting could be quickly processed through during the first test of the PoP cavity and was not seen again in later cold tests at BNL [12].…”

Section: B Multipactingmentioning

confidence: 99%

Design and vertical tests of double-quarter wave cavity prototypes for the high-luminosity LHC crab cavity system

Verdú-Andrés

Artoos

Belomestnykh

et al. 2018

Phys. Rev. Accel. Beams

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Crab crossing is essential for high-luminosity colliders. The High Luminosity Large Hadron Collider (HL-LHC) will equip one of its Interaction Points (IP1) with Double-Quarter Wave (DQW) crab cavities. A DQW cavity is a new generation of deflecting RF cavities that stands out for its compactness and broad frequency separation between fundamental and first high-order modes. The deflecting kick is provided by its fundamental mode. Each HL-LHC DQW cavity shall provide a nominal deflecting voltage of 3.4 MV, although up to 5.0 MV may be required. A Proof-of-Principle (PoP) DQW cavity was limited by quench at 4.6 MV. This paper describes a new, highly optimized cavity, designated DQW SPS-series, which satisfies dimensional, cryogenic, manufacturing and impedance requirements for beam tests at SPS and operation in LHC. Two prototypes of this DQW SPS-series were fabricated by US industry and cold tested after following conventional SRF surface treatment. Both units outperformed the PoP cavity, reaching a deflecting voltage of 5.3-5.9 MV. This voltage -the highest reached by a DQW cavity -is well beyond the nominal voltage of 3.4 MV and may even operate at the ultimate voltage of 5.0 MV with sufficient margin. This paper covers fabrication, surface preparation and cryogenic RF test results and implications.

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“…The model is compared to the design frequencies of the CEBAF RF separator cavity [6] and the proposed HL-LHC 4-rod crab cavity [7,8] which both show a good agreement between the equivalent circuit model and simulation results. Other deflecting cavity designs exist, such as the double quarter-wave crab cavity [9] and the RF dipole crab cavity [10]; which are also proposed for HL-LHC.…”

Section: Introductionmentioning

confidence: 99%

An improved equivalent circuit model of a four rod deflecting cavity

Apsimon

2017

Nuclear Instruments and Methods in Physics Research Section A:

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In this paper we present an improved equivalent circuit model for a four rod deflecting cavity which calculates the frequencies of the first four modes of the cavity as well as the R T Q for the deflecting mode. Equivalent circuit models of RF cavities give intuition and understanding about how the cavity operates and what changes can be made to modify the frequency, without the need for RF simulations, which can be time-consuming. We parameterise a generic four rod deflecting cavity into a geometry consisting of simple shapes. Equations are derived for the line impedance of the rods and the capacitance between the rods and these are used to calculate the resonant frequency of the deflecting dipole mode as well as the lower order mode and the model is bench-marked against two test cases; the CEBAF separator and the HL-LHC 4-rod LHC crab cavity. CST and the equivalent circuit model agree within 4% for both cavities with the LOM frequency and within 1% for the deflecting frequency. R T Q differs between the model and CST by 37% for the CEBAF separator and 25% for the HL-LHC 4-rod crab cavity; however this is sufficient for understanding how to optimise the cavity design. The model has then been utilised to suggest a method of separating the modal frequencies in the HL-LHC crab cavity and to suggest design methodologies to optimise the cavity geometries.

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Design, prototyping, and testing of a compact superconducting double quarter wave crab cavity

Cited by 26 publications

References 21 publications

Effect of crab cavity high order modes on the coupled-bunch stability of High-Luminosity Large Hadron Collider

Effect of crab cavity high order modes on the coupled-bunch stability of High-Luminosity Large Hadron Collider

Design and vertical tests of double-quarter wave cavity prototypes for the high-luminosity LHC crab cavity system

An improved equivalent circuit model of a four rod deflecting cavity

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