NAPAC2019 - List of Keywords (HOM)

Paper	Title	Other Keywords	Page
TUZBB5	Transverse Ion Beam Emittance Growth Due to Low Frequency Instabilities in Microwave Ion Source Plasma	plasma, emittance, electron, experiment	363
	C. Mallick, M. Bandyopadhyay, R. Kumar Institute for Plasma Research, Bhat, Gandhinagar, India
	The ion source is accompanied by the generation of low frequency (LF) plasma instabilities (PI). Its signature is also visible in high current heavy ion beam required for any accelerator. These LFs affect the profile of the ion beam in transverse phase-space. These issues are investigated in detail by measuring the emittance of beam. Beam oscillations are extracted from the transverse emittance data by taking Fast Fourier Transform (FFT) of it. PI frequencies are identified in the measured electromagnetic emission from the plasma, in which these frequencies appeared as sidebands around pump frequency 2.45 GHz. The PI components i.e.,ion acoustic (IA) and ion cyclotron (IC) waves are also visible in the FFT spectra. Low and high frequency oscillations in the beam are 476 kHz and ~1.3 MHz respectively. These two groups of frequencies also exist within the PI induced IA (238 - 873 kHz) and IC (1.29 - 1.3 MHz) frequency ranges. The measured emittance (rms-normalized) in horizontal and vertical phase-space varies from 0.002-0.098 𝜋 mm mrad and 0.004-0.23 𝜋 mm mrad respectively. PI induced beam oscillation is the reason behind such broad transverse emittance growth. Reference ’S. Kumar et al.,Phys. Rev. Accel. Beams 21, 093402 (2018)’ ’R. D’Arcy et al., Nucl. Instrum. Methods Phys. Res. A 815 7(2016)’ ’L. Groening et al., Phys. Rev. Lett. 113, 264802 (2014)’
	Slides TUZBB5 [5.298 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUZBB5
About •	paper received ※ 26 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPLH20	Commissioning of the CESR Upgrade for CHESS-U	MMI, wiggler, impedance, storage-ring	522
	J.P. Shanks, G.W. Codner, M.J. Forster, D.L. Rubin, S. Wang, L. Ying Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: Funding for the CHESS-U upgrade provided by New York State Capital Grant #AA737 / CFA #53676 The Cornell Electron Storage Ring (CESR) was upgraded in the second half of 2018 to become a dedicated synchrotron light source, CHESS-U. The upgrade is by far the largest modification to CESR in its 40-year history, replacing one-sixth of the storage ring with six new double-bend achromats, increasing beam energy from 5.3 GeV to 6.0 GeV, and switching from two counter-rotating beams to a single on-axis positron beam. The new achromats include combined-function dipoles, a first in CESR, and reduce the horizontal emittance by a factor of four. Eight compact narrow-gap undulators (4.6mm vacuum chamber aperture) and one high-energy 24-pole wiggler feed a total of six new and five existing x-ray end stations from a single positron beam. Commissioning of CHESS-U took place in the first half of 2019. We report on the methods and results of beam commissioning, including initial beam accumulation, optics correction, characterization, and commissioning of compact permanent-magnet insertion devices.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH20
About •	paper received ※ 26 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPLM04	Precision Cavity Higher-Order Mode Tuning Scheme for Stabilizing the Stored Beam in the Advanced Photon Source Upgrade	cavity, damping, impedance, resonance	670
	L. Emery, P.S. Kallakuri, U. Wienands ANL, Lemont, Illinois, USA D. Teytelman Dimtel, Redwood City, California, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357 The Advanced Photon Source Upgrade will suffer longitudinal multi-bunch instability because of the presence of several monopole higher-order mode (HOMs) of the 12 352-MHz rf cavities. Even with a feedback system, it would be good to mitigate any driving terms with conventional means such as tuning HOM frequencies with temperature. However the latter is problematic because there will be 90 or so HOMs that are potentially harmful. A scheme is developed, utilizing the measured spectrum of HOMs, to find the best temperature setting for each cavity. We present measurements of 30 or so HOMs, and a thermal model of HOM frequencies using cavity wall power and cooling water temperature as inputs to maintain the optimum tuning condition with sufficient accuracy. The newly acquired Dimtel iGp12 processor box is central to the HOM frequency measurements.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM04
About •	paper received ※ 29 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Other Keywords

Page

TUZBB5

Transverse Ion Beam Emittance Growth Due to Low Frequency Instabilities in Microwave Ion Source Plasma

plasma, emittance, electron, experiment

363

C. Mallick, M. Bandyopadhyay, R. Kumar
Institute for Plasma Research, Bhat, Gandhinagar, India

The ion source is accompanied by the generation of low frequency (LF) plasma instabilities (PI). Its signature is also visible in high current heavy ion beam required for any accelerator. These LFs affect the profile of the ion beam in transverse phase-space. These issues are investigated in detail by measuring the emittance of beam. Beam oscillations are extracted from the transverse emittance data by taking Fast Fourier Transform (FFT) of it. PI frequencies are identified in the measured electromagnetic emission from the plasma, in which these frequencies appeared as sidebands around pump frequency 2.45 GHz. The PI components i.e.,ion acoustic (IA) and ion cyclotron (IC) waves are also visible in the FFT spectra. Low and high frequency oscillations in the beam are 476 kHz and ~1.3 MHz respectively. These two groups of frequencies also exist within the PI induced IA (238 - 873 kHz) and IC (1.29 - 1.3 MHz) frequency ranges. The measured emittance (rms-normalized) in horizontal and vertical phase-space varies from 0.002-0.098 𝜋 mm mrad and 0.004-0.23 𝜋 mm mrad respectively. PI induced beam oscillation is the reason behind such broad transverse emittance growth.
Reference
’S. Kumar et al.,Phys. Rev. Accel. Beams 21, 093402 (2018)’
’R. D’Arcy et al., Nucl. Instrum. Methods Phys. Res. A 815 7(2016)’
’L. Groening et al., Phys. Rev. Lett. 113, 264802 (2014)’

Slides TUZBB5 [5.298 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUZBB5

About •

paper received ※ 26 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019

Export •

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

TUPLH20

Commissioning of the CESR Upgrade for CHESS-U

MMI, wiggler, impedance, storage-ring

522

J.P. Shanks, G.W. Codner, M.J. Forster, D.L. Rubin, S. Wang, L. Ying
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Funding for the CHESS-U upgrade provided by New York State Capital Grant #AA737 / CFA #53676
The Cornell Electron Storage Ring (CESR) was upgraded in the second half of 2018 to become a dedicated synchrotron light source, CHESS-U. The upgrade is by far the largest modification to CESR in its 40-year history, replacing one-sixth of the storage ring with six new double-bend achromats, increasing beam energy from 5.3 GeV to 6.0 GeV, and switching from two counter-rotating beams to a single on-axis positron beam. The new achromats include combined-function dipoles, a first in CESR, and reduce the horizontal emittance by a factor of four. Eight compact narrow-gap undulators (4.6mm vacuum chamber aperture) and one high-energy 24-pole wiggler feed a total of six new and five existing x-ray end stations from a single positron beam. Commissioning of CHESS-U took place in the first half of 2019. We report on the methods and results of beam commissioning, including initial beam accumulation, optics correction, characterization, and commissioning of compact permanent-magnet insertion devices.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLH20

About •

paper received ※ 26 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019

Export •

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

WEPLM04

Precision Cavity Higher-Order Mode Tuning Scheme for Stabilizing the Stored Beam in the Advanced Photon Source Upgrade

cavity, damping, impedance, resonance

670

L. Emery, P.S. Kallakuri, U. Wienands
ANL, Lemont, Illinois, USA
D. Teytelman
Dimtel, Redwood City, California, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357
The Advanced Photon Source Upgrade will suffer longitudinal multi-bunch instability because of the presence of several monopole higher-order mode (HOMs) of the 12 352-MHz rf cavities. Even with a feedback system, it would be good to mitigate any driving terms with conventional means such as tuning HOM frequencies with temperature. However the latter is problematic because there will be 90 or so HOMs that are potentially harmful. A scheme is developed, utilizing the measured spectrum of HOMs, to find the best temperature setting for each cavity. We present measurements of 30 or so HOMs, and a thermal model of HOM frequencies using cavity wall power and cooling water temperature as inputs to maintain the optimum tuning condition with sufficient accuracy. The newly acquired Dimtel iGp12 processor box is central to the HOM frequency measurements.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-WEPLM04

About •

paper received ※ 29 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019

Export •

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