THCO-A  —  Emittance   (18-Sep-08   08:30—10:00)

Chair: H. A. Koivisto, JYFL, Jyvaskyla

Paper Title Page
THCO-A01 Emittance Measurements of Ion Beams Extracted from the High-Intensity Permanent Magnet ECR Ion Source 199
 
  • S. A. Kondrashev, A. Barcikowski, B. Mustapha, P. N. Ostroumov
    ANL, Argonne, Illinois
  • N. Vinogradov
    Northern Illinois University, DeKalb, Illinois
 
  Funding: This work was supported by the U. S. Department of Energy, Office of Nuclear Physics, under contract number DE-AC02-06CH11357.

A pepper-pot - scintillator screen system has been developed and used to measure the emittance of ion beams extracted from the high-intensity permanent magnet ECR ion source. The system includes a fast beam shutter with a minimum dwell time of 18 ms to reduce the degradation of CsI(Tl) scintillator by DC ion beam irradiation, a CCD camera with a variable shutter speed in the range of 1 μs to 65 s. On-line emittance measurements are performed by an application code developed on LabVIEW platform. The sensitivity of the device is sufficient to measure the emittance of DC ion beams with current densities down to ~100 nA/cm2. The emittance of all ion species extracted from the ECR ion source and post-accelerated to an energy of 75-90 keV/charge have been measured downstream of the LEBT. As the mass-to-charge ratio of ion species is increased, the normalized RMS emittances in both transverse phase planes are reduced from 0.3-0.7 pi mm*mrad for light ions to 0.07-0.13 pi mm*mrad for highly charged 209Bi ions. Most measurements show a complicated structure of multiple images of individual holes. The latter can be mitigated or even avoided in some cases by re-tuning ion source parameters.

 
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THCO-A02 Systematic Comparison Between a Pepperpot and an ALLISON Emittance Meter 204
 
  • H. R. Kremers, J. P.M. Beijers, S. Brandenburg, S. Saminathan
    KVI, Groningen
 
  We discuss a new and versatile emittance meter recently built at KVI. The instrument measures 4D phase-space distributions of low-energy multiply-charged ion beams by scanning a vertical array of 20 micrometer diameter holes horizontally through the beam. The transmitted beamlets are detected with a MCP-CCD camera combination. The emittance meter can measure the full 4D emittance in less than five minutes. We will present a series of emittance measurements, including a systematic comparison with an Allison emittance scanner performed at ISN, Grenoble with the A-Phoenix source, confirming the measurement principle as well as the additional feature to measure the full four dimensional phase-space.  
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THCO-A03 A Method of Tuning ECRIS Beam Transport Lines for Low Emittance 208
 
  • J. W. Stetson
    NSCL, East Lansing, Michigan
 
  Funding: Supported under National Science Foundation Grant PHY-0110253.

Heavy-ion beams from an ECR type ion source have been shown to be structurally complex and to have a strong cross-correlation associated with their formation in and extraction from a high magnetic field with a strong sextupole content [1]. The emittances of such beams tend to be unavoidably large (compared to low magnetic field source types) yet because of cross-correlations, resistant to improvement by normal collimation methods. Recent developments with beam from the 14 GHz room temperature ECRIS at the NSCL indicate that careful beam line tuning to pass specific parts of the beam structure can allow greatly reduced 4-dimensional emittances without losing a disproportionate amount of the total intensity.

[1] "Ion beam extracted from a 14 GHz ECRIS of CAPRICE Type", P. Spaedtke, et al., 17th Int. Work. On ECR Ion Sources, 17th-21st Sep., 2006, Lanzhou, China

 
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