Motions of trapped dust particles around the electron beam in the TRISTAN accumulation ring

Saeki, Hiroshi; Mutoh, T.; Ishimaru, Hajime

doi:10.1063/1.1142230

Cited by 14 publications

(7 citation statements)

References 2 publications

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“…This suggested that the dust particles traveled longitudinally and passed through the bending magnets while being trapped by the beam. Although such a behavior was not always observed in our experiments, similar observations have been reported previously [3,10,20,21]. Temperature increases were observed when electrodes B were brought close to the beams.…”

Section: B Dust Production Experiments By Bringing Electrodes Close supporting

confidence: 33%

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

Tanimoto

Honda

Sakanaka

2009

Phys. Rev. ST Accel. Beams

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Sudden decreases in the beam lifetime, which are attributed to the dust trappings, sometimes occur at the electron storage ring Photon Factory Advanced Ring (PF-AR). Since these dust events cause difficulties in user operations, we have been carefully observing this phenomenon for many years. Our observations indicated that the dust trappings could be caused by electric discharges in vacuum ducts. In order to demonstrate this hypothesis experimentally, we designed a new vacuum device that intentionally generates electric discharges and installed it in PF-AR. Using this device, we could repeatedly induce sudden decreases in the beam lifetime because of the generated electric discharge. We also detected decreases in the beam lifetime caused by mechanical movement of the electrodes in the device. Moreover, we could visually observe the dust trapping phenomenon; the trapped dust particle was observed by two video cameras and appeared as a luminous body that resembled a shooting star. This was the first direct observation of a luminous dust particle trapped by the electron beam.

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Section: B Dust Production Experiments By Bringing Electrodes Close supporting

confidence: 33%

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

Tanimoto

Honda

Sakanaka

2009

Phys. Rev. ST Accel. Beams

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“…Motions of trapped microparticles in the ring were observed with lead-glass counters, as shown in Reference [2].…”

Section: Observation Of Trapped Microparticle Motions In the Trismentioning

confidence: 95%

Observation and analysis for motions of trapped microparticles in the TRISTAN accumulation ring

Saeki

Mutoh²,

Ishimaru³

Proceedings of International Conference on Particle Accelerators

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Signals of high-energy bremsstrahlung in the TRISTAN accumulation ring was observed with lead-glass counters, accompanied by a sudden decrease in the electron beam lifetime which occurred due to microparticle trapping in the electron beam. The observation showed a trapped microparticle made a periodic oscillation; the period was 1s. The observation coincides with the result based on our newly developed theory for vertical oscillation of a trapped microparticle. Furthermore, the calculated variation in the beam lifetime also coincides with the actual variation in the beam lifetime.

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“…During dust trapping investigations at TRISTAN AR bremsstrahlung observations with γ-ray detectors [15] suggested both longitudinal motion and transverse oscillations of dust particles.…”

Section: Experimental Investigationsmentioning

confidence: 99%

“…This "hysteresis" effect has also been observed at HERA, and is not yet understood. Simple considerations predict that the image charge force on a dust particle exceeds the beam electric field force within a few mm of the vacuum chamber wall for both HERA and TRISTAN AR [3,15].…”

Section: Experimental Investigationsmentioning

confidence: 99%

Dust in accelerator vacuum systems

Kelly

Proceedings of the 1997 Particle Accelerator Conference (Cat. No.97CH36167)

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Many accelerators of electron beams are susceptible to persistent beam lifetime disruptions, with correspondingly reduced performance. One distinguishes between three prevailing explanations of these disruptions: (1) trapping of positive atomic ions in the negatively charged beam; (2) trapping of small highly positively ionised micro-objects ("dust") in the negatively charged beam; (3) disruptions due to stray magnetic objects trapped in the magnetic field of undulators.The lifetime disruption of certain electron storage rings that employ ion-getter pump systems are attributed by most researchers to explanation (2), the trapped dust hypothesis. Systematic experimental studies of HERA, PETRA and DORIS reinforce the suspicion that specifically this type of pump system is the culprit.Examples of beam lifetime disruptions are presented, together with a summary of observations and experiments performed at various afflicted storage rings to investigate dust trapping and the connection between ion getter pumps and dust particle release. Observations of the disrupted beam are found to agree with the dust trapping hypothesis. . The complementary experience at these machines has built a consistent picture of the symptoms of macroparticle lifetime disruptions, and this picture agrees quantitatively with the dust trapping model detailed in [3,4].This electron beam lifetime problem is beam charge dependent, i.e. it only occurs with electron beams, as evidenced by the problem-free switch to positron operation in HERA and DORIS.Observations confirm that the ion getter pumps of all above-mentioned machines are implicated in casting dust particles into the beam pipe. The lifetime disruption can be provoked by switching an ion getter pump on and off, or by abruptly increasing the pump voltage, when a discharge within the pump can be sometimes be observed.Such lifetime disruptions are not observed in the nonevaporative getter (NEG) pump based storage ring LEP or at ESRF (with NEG pumps and auxilliary lumped ion pumps), with the exception of the possible capture of magnetic dust in undulators [7]. Trials over a limited region of HERA with NEG pumps indicate a strong if not complete reduction of the release of disrupting particles within this NEG pump region.It will be illustrated in this report that the extensive observations of beam lifetime disruptions in a number of accelerators are well described by the trapped dust hypothesis. However, the formation or liberation of dust particles within the complicated environment of the ion-getter pump chamber is poorly understood. Relatively few direct observations of the processes within these pumps systems are available, whereas many observations of pump configurations and operating conditions conducive to the onset of beam lifetime disruptions have been performed, in particular with HERA, PETRA and DORIS. Such observations are however not sufficient to form a causal model of dust particle release into the beam pipe; our knowledge of the processes on the pump side of the vacuum ch...

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Motions of trapped dust particles around the electron beam in the TRISTAN accumulation ring

Cited by 14 publications

References 2 publications

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

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

Observation and analysis for motions of trapped microparticles in the TRISTAN accumulation ring

Dust in accelerator vacuum systems

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