Spatially Resolved Dark Current in High Gradient Traveling Wave Structures

Paszkiewicz, Jan; Burrows, Philip; Wuensch, Walter

doi:10.18429/jacow-ipac2019-weprb062

Cited by 2 publications

(4 citation statements)

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“…However, during high-field operation, electrons are emitted from the cavity surface and accelerated. This phenomenon, which is undesired in real operation, is known as dark current [18][19][20]. This dark current is an important measure to detect cavity breakdowns, as will be shown later.…”

Section: Methodsmentioning

confidence: 95%

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Explainable Machine Learning for Breakdown Prediction in High Gradient RF Cavities

Obermair¹,

Cartier-Michaud²,

Apollonio³

et al. 2022

Preprint

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Radio Frequency (RF) breakdowns are one of the most prevalent limiting factors in RF cavities for particle accelerators. During a breakdown, field enhancement associated with small deformations on the cavity surface results in electrical arcs. Such arcs lead to beam aborts, reduce machine availability and can cause irreparable damage on the RF cavity surface. In this paper, we propose a machine learning strategy to discover breakdown precursors in CERN's Compact Linear Collider (CLIC) accelerating structures. By interpreting the parameters of the learned models with explainable Artificial Intelligence (AI), we reverse-engineer physical properties for deriving fast, reliable, and simple rule based models. Based on 6 months of historical data and dedicated experiments, our models show fractions of data with high influence on the occurrence of breakdowns. Specifically, it is shown that in many cases a rise of the vacuum pressure is observed before a breakdown is detected with the current interlock sensors.

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Section: Methodsmentioning

confidence: 95%

“…The identified portion in the signal in Fig. 14 has been previously studied in detail [18,22]. The shape of the dark current signal is generally defined by several quantities.…”

Section: B Explainable-aimentioning

confidence: 99%

Explainable Machine Learning for Breakdown Prediction in High Gradient RF Cavities

Obermair¹,

Cartier-Michaud²,

Apollonio³

et al. 2022

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…Approximately, 0.15% of the total pulses recorded during the BDR measurements were of this type, and as the operating conditions were changed, these measurement periods have been excluded in the calculation of the total and primary BDRs. The results of these studies have been previously reported in detail [53]. Where relevant, any ramping in power required to reach the target operating gradient between measurements has also been excluded.…”

Section: B Breakdown Rate Measurementsmentioning

confidence: 99%

“…Given that the final 101 MV/m data point for the 100 ns data point was taken last, a larger exponent should be expected if the structure had continued to condition throughout the measurements. However, prior to recording the final 100 ns data point at 101 MV/m (between measurements M8 and M9), several breakdowns were intentionally induced as part of one of the previously referenced field emission experiments [53]. A close-up of the conditioning history in this region is shown in Fig.…”

Section: B Breakdown Rate Measurementsmentioning

confidence: 99%

High-Power Test of Two Prototype X-Band Accelerating Structures Based on SwissFEL Fabrication Technology

Millar

Wuensch

Lasheras

et al. 2023

IEEE Trans. Nucl. Sci.

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This paper presents the design, construction, and high-power test of two X-band radio-frequency (RF) accelerating structures built as part of a collaboration between CERN and the Paul Scherrer Institute (PSI) for the Compact Linear Collider (CLIC) study. The structures are a modified "tuning-free" variant of an existing CERN design and were assembled using Swiss Free Electron Laser (SwissFEL) production methods. The purpose of the study is twofold; the first objective is to validate the RF properties and high-power performance of the tuning-free, vacuum brazed PSI technology. The second objective is to study the structures' high-gradient behaviour to provide insight into the breakdown and conditioning phenomena as they apply to high-field devices in general. Low-power RF measurements showed that the structure field profiles were close to the design values, and both structures were conditioned to accelerating gradients in excess of 100 MV/m in CERN's high-gradient test facility. Measurements performed during the second structure test suggest that the BDR scales strongly with the accelerating gradient, with the best fit being a power law relation with an exponent of 31.14. In both cases, the test results indicate that stable, high-gradient operation is possible with tuning-free, vacuum brazed structures of this kind.

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Spatially Resolved Dark Current in High Gradient Traveling Wave Structures

Cited by 2 publications

References 0 publications

Explainable Machine Learning for Breakdown Prediction in High Gradient RF Cavities

Explainable Machine Learning for Breakdown Prediction in High Gradient RF Cavities

High-Power Test of Two Prototype X-Band Accelerating Structures Based on SwissFEL Fabrication Technology

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