Experiments on Gradient Limits for Normal Conducting Accelerators

Dolgashev, Valery

doi:10.2172/815258

Cited by 8 publications

(13 citation statements)

References 17 publications

(19 reference statements)

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“…Sensors were located in a similar way as shown in Fig.1, 0 • being the top of the structure. The help of the autopsy as a validation of our localization method has led us to better understand the cause of the breakdown occurring inside the input couplers, and especially on the sharp edges of those horns [6]. A new design of the coupler as well as the cells has been implemented for the next structures.…”

Section: Implication Of the Acoustic Resultsmentioning

confidence: 99%

“…One of the main results has been to identify that breakdown in the input coupler, of our test accelerating structure, were happening on the side of the coupler. With the help of surface analysis and some theoretical work [1] [6] [21] the structure has been redesigned. Localization of pieces of foreign materials inside the structures, has shed light on the handling procedures needed to keep the structures clean.…”

Section: Resultsmentioning

confidence: 99%

“…During processing the structures occasionally respond by arcing, or breakdown. A breakdown is characterized by a shut off of the transmitted power and up to 80% of the incident power is absorbed in the arc [6]. This extra energy is deposited in the copper, and a part of it is converted in extra phonons (heat and acoustic) that can be picked up by our acoustic sensors.…”

Section: Introductionmentioning

confidence: 99%

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Localization of RF Breakdown in Copper RF Structure by the Use of Acoustic Sensors

Pimpec¹

2004

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This note documents a set of expressions used to explore the issue of whether or not it is reasonable to consider a conventional positron source for a Tesla formatted beam. The critical issue is that of energy deposition in the conversion target and the comparison of the induced stress with the ultimate tensile strength of the target material. Since the length of the incident beam pulse is large in comparison to the ratio of beam size to the speed of sound, the concurrent pressure pulse dissipates in a time short compared to the overall pulse duration and one is left with only the

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Section: Implication Of the Acoustic Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Localization of RF Breakdown in Copper RF Structure by the Use of Acoustic Sensors

Pimpec¹

2004

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“…Tests have resulted in instances where the RF power does not transmit nor reflect, but rather is absorbed by the wave structure. Such a collapse of the RF field within the cavity is termed as RF breakdown and is accompanied by a surge of current [1] as well as visible craters on the structure.…”

Section: Rf Breakdownmentioning

confidence: 99%

The Effect of Mechanical Hardness on RF Breakdown

Adamson¹

2003

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Preliminary high-energy tests have been performed on the next linear collider test accelerator and the traveling wave structures have been examined with a scanning electron microscope. This has yielded the locations of radio frequency breakdowns, characterized by surface craters, occurring on the oxygen-free electric copper traveling wave structure. It has been proposed that the occurrence of high voltage breakdown may be related to material hardness. We have examined this possibility by measuring the hardness of various crystal grains within the copper structure and searching for any correlations to the breakdown events. The hardness of various copper crystals grains has been measured with a nano-indenter and the crystal grains have subsequently been analyzed for breakdown damage. This preliminary analysis does not show any explicit indications that mechanical hardness may be related on the occurrence of RF breakdown. Further research is suggested to verify these initial results.

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“…This unexpected result prompted the redesign of the coupler to reduce pulse heating (possibly due to high magnetic fields) on the four input waveguide matching irises. This work is summarized in [6,7].…”

Section: X-band Structure Input Couplermentioning

confidence: 99%

Use of acoustic emission to diagnose breakdown in accelerator RF structures

Nelson

Ross

Frisch

et al.

Proceedings of the 2003 Bipolar/BiCMOS Circuits and Technology Meeting (IEEE Cat. No.03CH37440)

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Accelerator structures of a wide variety have been damaged by RF breakdowns. Very little is known about the mechanisms that cause the breakdown and the damage although there has been theoretical work [1,2]. Using an array of ultrasonic acoustic emission sensors we have been able to locate and classify breakdown events more accurately than possible using microwave techniques. Data from the technique has led to improvements in the design of the NLC X-band RF structure. We report results of acoustic emission studies at the DESY TESLA Test Facility and the SLAC NLC Test Accelerator. Contributed to Particle Accelerator Conference 2003Portland, Ore., 12-16 May 2003 * Work supported by Department of Energy contract DE-AC03-76SF00515. 2 AbstractAccelerator structures of a wide variety have been damaged by RF breakdowns. Very little is known about the mechanisms that cause the breakdown and the damage although there has been theoretical work [1,2]. Using an array of ultrasonic acoustic emission sensors we have been able to locate and classify breakdown events more accurately than possible using microwave techniques.Data from the technique has led to improvements in the design of the NLC X-band RF structure. We report results of acoustic emission studies at the DESY TESLA Test Facility and the SLAC NLC Test Accelerator.

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Experiments on Gradient Limits for Normal Conducting Accelerators

Cited by 8 publications

References 17 publications

Localization of RF Breakdown in Copper RF Structure by the Use of Acoustic Sensors

Localization of RF Breakdown in Copper RF Structure by the Use of Acoustic Sensors

The Effect of Mechanical Hardness on RF Breakdown

Use of acoustic emission to diagnose breakdown in accelerator RF structures

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