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Review of Scientific Instruments / Volume 76 / Issue 12 / GENERAL INSTRUMENTS

Rev. Sci. Instrum. 76, 125109 (2005); http://dx.doi.org/10.1063/1.2149191 (13 pages)

Resonant-cavity approach to noninvasive, pulse-to-pulse emittance measurement

J. S. Kim1, C. D. Nantista2, R. H. Miller2, and A. W. Weidemann3

1FAR-TECH, Inc., 10350 Science Center Drive, San Diego, California 92121
2Stanford Linear Accelerator Center, Menlo Park, California 94025
3FAR-TECH, Inc., 10350 Science Center Drive, San Diego, California 92121 and Stanford Linear Accelerator Center, Menlo Park, California 94025

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(Received 23 June 2005; accepted 14 November 2005; published online 29 December 2005)

We present a resonant-cavity approach for noninvasive, pulse-to-pulse, beam emittance measurements of noncircular multibunch beams. In a resonant cavity, desired field components can be enhanced up to QLλ/π, where QLλ is the loaded quality factor of the resonant mode λ, when the cavity resonant mode matches the bunch frequency of a bunch-train beam pulse. In particular, a quad cavity, with its quadrupole mode (TM220 for rectangular cavities) at beam operating frequency, rotated 45° with respect to the beamline, extracts the beam quadrupole moment exclusively, utilizing the symmetry of the cavity and some simple networks to suppress common modes. Six successive beam quadrupole-moment measurements, performed at different betatron phases in a linear transport system, determine the beam emittance, i.e., the beam size and shape in the beam’s phase space, if the beam current and position at these points are known. In the presence of x-y beam coupling, ten measurements are required. One measurement alone provides the rms beam size of a large aspect ratio beam. The resolution for such a measurement of rms beam size with the rectangular quad-cavity monitor presented in this article is estimated to be on the order of 10 μm. A prototype quad cavity was fabricated and preliminary beam tests were performed at the Next Linear Collider Test Accelerator at the Stanford Linear Accelerator Center. The results were mainly limited by beam jitter and uncertainty in the beam position measurement at the cavity location. This motivated the development of a position-emittance integrated monitor [ J. S. Kim et al., Rev. Sci. Instrum. 76, 073302 (2005) ].

© 2005 American Institute of Physics

Article Outline

  1. INTRODUCTION
  2. BEAM EMITTANCE MEASUREMENT VIA QUADRUPOLE MOMENT
  3. CAVITY-BEAM INTERACTION AND RMS BEAM-SIZE MEASUREMENT
    1. Single bunch versus multibunches
      1. Single Gaussian (in t ) bunch
      2. Multibunch responses
    2. Analytic pillbox model
    3. Beam-pipe effect on the resonant frequencies
    4. RMS beam-size measurement resolution based on a pillbox model
  4. COMPUTER SIMULATION
  5. QUADRUPOLE CAVITY CALIBRATION
  6. FABRICATION CONSIDERATIONS
  7. EXPERIMENTAL RESULTS
    1. rf tests and cavity tuning
    2. Beam tests
  8. DISCUSSION

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KEYWORDS and PACS

Keywords

cavity resonators, beam handling techniques, particle beam bunching, accelerator cavities, particle beam diagnostics, linear colliders

PACS

ARTICLE DATA

Digital Object Identifier
http://dx.doi.org/10.1063/1.2149191

PUBLICATION DATA

ISSN

0034-6748 (print)  
1089-7623 (online)

Publisher

$abstract.society.value is a Member of CrossRef American Institute of Physics

For access to fully linked references, you need to log in.
    A. Jansson, Phys. Rev. ST Accel. Beams 5, 072803 (2002).

    D. H. Whittum and Y. Kolomensky, Rev. Sci. Instrum. 70, 2300 (1999)RSINAK000070000005002300000001.

    J. S. Kim, R. H. Miller, and C. D. Nantista, Rev. Sci. Instrum. 76, 073302 (2005)RSINAK000076000007073302000001.


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