IPAC2021 - List of Authors (Natochii, A.)

Paper	Title	Page
WEXA07	Beam Background Measurements at SuperKEKB/Belle-II in 2020	2532
	H.N. Nakayama, T. Koga KEK, Tsukuba, Japan K. Kojima Nagoya University, Nagoya, Japan A. Natochii, S. Vahsen University of Hawaii, Honolulu,, USA
	The SuperKEKB electron-positron collider began collision operation in 2018 and achieved the world-record luminosity of 2.4x10³⁴~cm^-2s^-1 in June 2020. We pursue higher luminosity by squeezing beam sizes and increasing beam currents. Beam backgrounds induced by stray particles will also increase and might cause severe radiation damage to Belle II detector components and worsen the quality of collected physics data. To mitigate these backgrounds, we have carefully designed our interaction region and installed movable collimators in the machine. We present recent measurements of beam background at SuperKEKB. We have performed dedicated machine studies to measure each background component separately and found that beam-gas scattering and Touschek scattering in the positron ring are the dominant sources of background rates in Belle II. We also present the latest observations of injection background, which determines the timing of a required Belle II data acquisition trigger veto and therefore affects the integrated luminosity. We show the beam background extrapolation toward the expected higher-luminosity operation and our plans for further background mitigation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEXA07
About •	paper received ※ 20 May 2021 paper accepted ※ 25 June 2021 issue date ※ 13 August 2021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPAB358	Development of Low-Z Collimator for SuperKEKB	3537
	S. Terui, T. Abe, Y. Funakoshi, T. Ishibashi, H.N. Nakayama, K. Ohmi, D. Zhou KEK, Ibaraki, Japan A. Natochii University of Hawaii, Honolulu,, USA
	Collimator jaws for SuperKEKB main ring, which is an electron-positron collider, installed to suppress background noise in a particle detector complex named Belle II. The collimators are successful to reduce backgrounds when the collimator was closed. But, in high current operations with 500 mA or more, jaws were occasionally damaged by hitting abnormal beams. This trouble is a low-frequency, which is once-a-commissioning period currently, but a high-consequence one because we are not able to apply high voltage on detectors in Belle II by high backgrounds. Low-Z collimator jaw, that is durable through hitting uncontrollable beam, have been designed due to protect important component as the solution of the trouble. The low-Z collimator jaws are installable in a present collimator chamber, have a pair of vertically opposed movable jaws. One pair of low-Z collimator jaws was installed. The paper is to describe what did we calculate and measure to make a low-Z collimator, how did we make a low-Z collimator, the impact of the installed low-Z collimator, mainly transverse mode coupling instability.
	Poster WEPAB358 [0.788 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB358
About •	paper received ※ 16 May 2021 paper accepted ※ 22 July 2021 issue date ※ 10 August 2021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Beam Background Measurements at SuperKEKB/Belle-II in 2020

2532

H.N. Nakayama, T. Koga
KEK, Tsukuba, Japan
K. Kojima
Nagoya University, Nagoya, Japan
A. Natochii, S. Vahsen
University of Hawaii, Honolulu,, USA

The SuperKEKB electron-positron collider began collision operation in 2018 and achieved the world-record luminosity of 2.4x10³⁴~cm^-2s^-1 in June 2020. We pursue higher luminosity by squeezing beam sizes and increasing beam currents. Beam backgrounds induced by stray particles will also increase and might cause severe radiation damage to Belle II detector components and worsen the quality of collected physics data. To mitigate these backgrounds, we have carefully designed our interaction region and installed movable collimators in the machine. We present recent measurements of beam background at SuperKEKB. We have performed dedicated machine studies to measure each background component separately and found that beam-gas scattering and Touschek scattering in the positron ring are the dominant sources of background rates in Belle II. We also present the latest observations of injection background, which determines the timing of a required Belle II data acquisition trigger veto and therefore affects the integrated luminosity. We show the beam background extrapolation toward the expected higher-luminosity operation and our plans for further background mitigation.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEXA07

About •

paper received ※ 20 May 2021 paper accepted ※ 25 June 2021 issue date ※ 13 August 2021

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPAB358

Development of Low-Z Collimator for SuperKEKB

3537

S. Terui, T. Abe, Y. Funakoshi, T. Ishibashi, H.N. Nakayama, K. Ohmi, D. Zhou
KEK, Ibaraki, Japan
A. Natochii
University of Hawaii, Honolulu,, USA

Collimator jaws for SuperKEKB main ring, which is an electron-positron collider, installed to suppress background noise in a particle detector complex named Belle II. The collimators are successful to reduce backgrounds when the collimator was closed. But, in high current operations with 500 mA or more, jaws were occasionally damaged by hitting abnormal beams. This trouble is a low-frequency, which is once-a-commissioning period currently, but a high-consequence one because we are not able to apply high voltage on detectors in Belle II by high backgrounds. Low-Z collimator jaw, that is durable through hitting uncontrollable beam, have been designed due to protect important component as the solution of the trouble. The low-Z collimator jaws are installable in a present collimator chamber, have a pair of vertically opposed movable jaws. One pair of low-Z collimator jaws was installed. The paper is to describe what did we calculate and measure to make a low-Z collimator, how did we make a low-Z collimator, the impact of the installed low-Z collimator, mainly transverse mode coupling instability.

Poster WEPAB358 [0.788 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2021-WEPAB358

About •

paper received ※ 16 May 2021 paper accepted ※ 22 July 2021 issue date ※ 10 August 2021

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)