Experimental demonstration and visual observation of dust trapping in an electron storage ring

Tanimoto, Yasunori; Honda, Tohru; Sakanaka, S.

doi:10.1103/physrevstab.12.110702

Cited by 13 publications

(5 citation statements)

References 13 publications

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“…Beam-dust events, on the other hand, correspond to rapid increases in a few local pressure readings and may trigger beam aborts. Thought to be the result of beam particles vaporizing microscopic or macroscopic particles, they were previously observed and studied at many accelerator laboratories such as KEK [64,65], CERN [66,67] and DESY [68].…”

Section: Improvement In Superkekb Conditionsmentioning

confidence: 99%

First measurements of beam backgrounds at SuperKEKB

Lewis

Jaeglé

Nakayama

et al. 2019

Nuclear Instruments and Methods in Physics Research Section A:

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The high design luminosity of the SuperKEKB electron-positron collider is expected to result in challenging levels of beam-induced backgrounds in the interaction region. Properly simulating and mitigating these backgrounds is critical to the success of the Belle II experiment. We report on measurements performed with a suite of dedicated beam background detectors, collectively known as BEAST II, during the so-called Phase 1 commissioning run of SuperKEKB in 2016, which involved operation of both the high energy ring (HER) of 7 GeV electrons as well as the low energy ring (LER) of 4 GeV positrons. We describe the BEAST II detector systems, the simulation of beam backgrounds, and the measurements performed. The measurements include standard ones of dose rates versus accelerator conditions, and more novel investigations, such as bunch-by-bunch measurements of injection backgrounds and measurements sensitive to the energy spectrum and angular distribution of fast neutrons. We observe beam-gas, Touschek, beam-dust, and injection backgrounds. As there is no final focus of the beams in Phase 1, we do not observe significant synchrotron radiation, as expected. Measured LER beam-gas backgrounds and Touschek backgrounds in both rings are slightly elevated, on average three times larger than the levels predicted by simulation. HER beam-gas backgrounds are on on average two orders of magnitude larger than predicted. Systematic uncertainties and channel-to-channel variations are large, so that these excesses constitute only 1-2 sigma level effects. Neutron background rates are higher than predicted and should be studied further. We will measure the remaining beam background processes, due to colliding beams, in the imminent commissioning Phase 2. These backgrounds are expected to be the most critical for Belle II, to the point of necessitating replacement of detector components during the Phase 3 (full-luminosity) operation of SuperKEB.

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Section: Improvement In Superkekb Conditionsmentioning

confidence: 99%

First measurements of beam backgrounds at SuperKEKB

Lewis

Jaeglé

Nakayama

et al. 2019

Nuclear Instruments and Methods in Physics Research Section A:

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“…The first magnet quenches induced by dust particles occurred in 2015 when the LHC operated for the first time close to its design energy [13,14]. Beam losses due to dust particles have been observed previously in other machines, particularly in electron storage rings, where they manifested themselves as a sudden and sometimes persistent lifetime degradation due to the trapping of charged dust particles in the vicinity of the beam core [75][76][77][78][79][80][81]. Dust trapping phenomena can, however, be excluded for positively charged beams like in the LHC owing to the repelling force experienced by the dust particle as it becomes ionized during its passage through the beam tails [82][83][84].…”

Section: A Beam Losses Induced By Dust Particlesmentioning

confidence: 99%

Validation of energy deposition simulations for proton and heavy ion losses in the CERN Large Hadron Collider

Lechner

Auchmann

Baer

et al. 2019

Phys. Rev. Accel. Beams

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shower simulations are essential for understanding and predicting the consequences of beam losses in high-energy proton and ion colliders. Shower simulations are routinely used at CERN for estimating the beam-induced energy deposition, radiation damage, and radioactivity in the Large Hadron Collider (LHC). Comparing these shower simulations against beam loss measurements is an important prerequisite for assessing the predictive ability of model calculations. This paper validates FLUKA simulation predictions of beam loss monitor (BLM) signals against BLM measurements from proton fills at 3.5 and 4 TeV and 208 Pb 82þ ion fills at 1.38A TeV. The paper addresses typical loss scenarios and loss mechanisms encountered in LHC operation, including proton collisions with dust particles liberated into the beams, halo impact on collimators in the betatron cleaning insertion, proton-proton collisions in the interaction points, and dispersive losses due to bound-free pair production in heavy ion collisions. Model predictions and measured signals generally match within a few tens of percent, although systematic differences were found to be as high as a factor of 3 for some regions and source terms.

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“…As the evaporation case, the oscillation is not possible if only one emitting tip provides the electron current. Let us notice that the oscillation of the MPs has been observed experimentally in the storage rings for GeV electron beams [60].…”

Section: B Scenarios Of the Mp Dynamicsmentioning

confidence: 96%

Dynamics of microparticles in vacuum breakdown: Cranberg’s scenario updated by numerical modeling

Seznec

Dessante

Jäger

et al. 2017

Phys. Rev. Accel. Beams

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Microparticles (MP) and thermofield emission in vacuum are mainly caused by the roughness present at the surface of electrodes holding a high voltage. They can act as a trigger for breakdown, especially under high vacuum. This theoretical study discusses the interactions between one MP and the thermofield emission electron current as well as the consequences on the MP's transit. Starting from Cranberg's assumptions, new phenomena have been taken into account such as MP charge variation due to the secondary electron emission induced by energetic electron bombardment. Hence, the present model can be solved only numerically. Four scenarios have been identified based on the results, depending on the electron emission current from the cathode roughness (tip) and the size of the MP released at the anode, namely (i) one way; (ii) back and forth; (iii) oscillation; and (iv) vaporization. A crash study of the MP on the cathode shows that the electron emission can decrease if the MP covers the thermoemissive tip, i.e., if the MP is larger than the tip size-a phenomenon often called "conditioning"-and helping to increase the voltage holding in vacuum without breakdown.

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Experimental demonstration and visual observation of dust trapping in an electron storage ring

Cited by 13 publications

References 13 publications

First measurements of beam backgrounds at SuperKEKB

First measurements of beam backgrounds at SuperKEKB

Validation of energy deposition simulations for proton and heavy ion losses in the CERN Large Hadron Collider

Dynamics of microparticles in vacuum breakdown: Cranberg’s scenario updated by numerical modeling

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