Designing SSC quadrupole supports to minimize the effects from vibrational noise

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G. Stupakov has shown theoretically that the emittance at the SSC should increase linearly with time and the seismic noise spectrum associated with quadrupole motion at the betatron frequency {approximately} 750--1500 Hz. While the motion is also affected by overtones of the knockout frequencies, the frequencies are so high that the seismic noise becomes vanishingly small. Feedback control would be required to control emittance growth for a power spectrum in excess of 10{sup {minus}12} microns{sup 2}/Hz, assuming unit transmission at the betatron knockout frequency through the quadrupole supports. At the 1991 Corpus Christi Workshop on Beam Dynamics, N. Dikanski predicted ... continued below

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16 p.

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Ritson, D. September 1, 1993.

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  • Ritson, D. Stanford Linear Accelerator Center, Menlo Park, CA (United States)

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Description

G. Stupakov has shown theoretically that the emittance at the SSC should increase linearly with time and the seismic noise spectrum associated with quadrupole motion at the betatron frequency {approximately} 750--1500 Hz. While the motion is also affected by overtones of the knockout frequencies, the frequencies are so high that the seismic noise becomes vanishingly small. Feedback control would be required to control emittance growth for a power spectrum in excess of 10{sup {minus}12} microns{sup 2}/Hz, assuming unit transmission at the betatron knockout frequency through the quadrupole supports. At the 1991 Corpus Christi Workshop on Beam Dynamics, N. Dikanski predicted unacceptable emittance growths of minutes for the SSC collider in the absence of protective measures. In view of this prediction a workshop was convened in February of 1992 to discuss vibrational issues. At this workshop G. Fischer referred participants to an early study based on the then best compilation from Aki and Richards of seismic measurements. Aki and Richards showed ambient ground noise for a generic site many orders of magnitude lower than the INP measurements for the 750--1500 Hz range. Fischer referred to later extensive measurements in the US and USSR that had confirmed the Aki results and also showed that instrumental noise in the 750--1500 Hz region could dominate measurement precision. Later measurements made by the Russian group at the SSC site measure quiet noise spectra of Hz five orders of magnitude lower than the original values. Under noisy conditions measurements indicate that culturally induced vibrations might still lead to marginal emittance growth, assuming unit transmission in the relevant frequency range, and 100% efficient coupling of resonant modes to the beam. This is certainly an overestimate as relevant wavelengths are small compared with quadrupole dimensions.

Physical Description

16 p.

Notes

INIS; OSTI as DE94009086; Paper copy available at OSTI: phone, 865-576-8401, or email, reports@adonis.osti.gov

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  • Other Information: PBD: Sep 1993

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  • Other: DE94009086
  • Report No.: SLAC-TN--93-7
  • Report No.: SSCL--645
  • Grant Number: AC03-76SF00515
  • DOI: 10.2172/10136718 | External Link
  • Office of Scientific & Technical Information Report Number: 10136718
  • Archival Resource Key: ark:/67531/metadc1315096

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  • September 1, 1993

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  • Nov. 3, 2018, 11:47 a.m.

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Ritson, D. Designing SSC quadrupole supports to minimize the effects from vibrational noise, report, September 1, 1993; United States. (digital.library.unt.edu/ark:/67531/metadc1315096/: accessed November 15, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.