Realization and high power test of damped 
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-band accelerating structures

Alesini, D.; Bellaveglia, M.; Cardelli, Fabio; Raddo, R. Di; Gallo, A.; Lollo, V.; Piersanti, L.; Variola, A.; Palumbo, L.; Poletto, Fabio; Favaron, P.

doi:10.1103/physrevaccelbeams.23.042001

Cited by 8 publications

(2 citation statements)

References 13 publications

(30 reference statements)

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“…The concept of using WGs in accelerating cavities has been stressed with the proposal of a 3-WG loaded cylindrical resonator which is free of HOMs [29]. WGs dampers have been adopted at SLAC for the PEP-II B-Factory project [30], for the accelerating cavity installed in the DAΦNE machine [31] and recently for the C-band linac in the framework of the Extreme Light Infrastructure-Nuclear Physics (ElI-NP) project [32] . However such solution is also expensive.…”

Section: Introductionmentioning

confidence: 99%

Investigations on the multi-sector hard X-Band Structures

Dolgashev¹,

Faillace²,

Migliorati³

et al. 2022

Preprint

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The development of ever advanced, high gradient accelerating structures is one of the leading activity of the accelerator community. In the technological research of new construction methods for these devices, high-power testing is a critical step for the verification of their viability. Recent experiments showed that accelerating cavities made out of hard copper fabricated without hightemperature processes, can achieve better performance as compared with soft copper ones. The results of experiments showed that welding, a robust and low-cost alternative to brazing or diffusion bonding, is an optimal solution for high-gradient operation, providing, with a gradient of about 150 MV/m, in the X-band, a breakdown rate of 10 −3 /pulse/meter using a shaped pulse with a 150 ns flat part. Within this framework, we are involved in the design, construction and higher power experimental tests of three cells standing-wave (SW) 11.424 GHz (X-band) accelerating cavities fabricated with hard Cu/Ag materials in order to study the RF breakdown physics. Our aim is to fabricate the accelerating structures with innovative technologies easier to handle and cheaper; easier for surfaces inspection; easier for data elaboration and validation of joining techniques. The choice of these new technological approaches and design methods provides also the possibility of allocating the parasitic Higher Order Mode (HOM) dampers in case of regular multi-cells structure, both standing and traveling-wave accelerating structures, of advanced generation. This paper describes the design of an optimised cavity made with sectors that allows an increase of the frequency separation of longitudinal modes, and it provides a high longitudinal shunt impedance R sh of the operating mode. The cavity will be fabricated by using the Tungsten Inert Gas (TIG) process in order to realise a hard Cu/Ag structure. Two three-cells SW X-band accelerating cavities, to be operated in the π-mode and made out of hard Cu/Ag alloy, were already fabricated at INFN-LNF by means of clamping and welding by using the TIG approach. Finally, we also report the RF characterisation and low-power RF tests of a two-halves split hard Cu/Ag structure that will be consequently TIG welded and employed for high-gradient tests and for the study of the RF breakdown physics.

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Section: Introductionmentioning

confidence: 99%

Investigations on the multi-sector hard X-Band Structures

Dolgashev¹,

Faillace²,

Migliorati³

et al. 2022

Preprint

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“…The BDR is defined as the probability of a breakdown event per a RF pulse normalized to the length of the accelerating structure for a given RF pulse length. C-band accelerating structures have been previously studied by multiple institutions and projects, such as SwissFEL [17], SINAP [18], SPARC LAB [19], the FEL Spring-8 [20], and the Korean National Fusion Research Institute (KNFRI) [21]. All previous projects used traveling-wave C-band structures with exception of KN-FRI [21] that used standing-wave structures.…”

mentioning

confidence: 99%

High Gradient Testing of off-Axis Coupled C-band Cu and CuAg Accelerating Structures

Schneider¹,

Zuboraj²,

Dolgashev³

et al. 2022

Preprint

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We report the high gradient testing results of two single cell off-axis coupled standing wave accelerating structures. Two brazed standing wave off-axis coupled structures with the same geometry were tested: one made of pure copper (Cu), and one made of a copper-silver (CuAg) alloy with a silver concentration of 0.08%. A peak surface electric field of 450 MV/m was achieved in the CuAg structure for a klystron input power of 14.5 MW and a 1 µs pulse length, which was 25% higher than the peak surface electric field achieved in the Cu structure. The superb high gradient performance was achieved because of the two major optimizations in the cavity's geometry: 1) the shunt impedance of the cavity was maximized for a peak surface electric field to accelerating gradient ratio of ∼2 for a fully relativistic particle, 2) the peak magnetic field enhancement due to the input coupler was minimized to limit pulse heating. These tests allow us to conclude that C-band accelerating structures can operate at peak fields similar to those at higher frequencies while providing a larger beam iris for improved beam transport.

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