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| CT02 |
Single Shot Measurements of the 4-Dimensional Transverse Phase Space Distribution of Intense Ion Beams at the UNILAC at GSI
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56 |
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- L. Groening, W. Barth
GSI, Gesellschaft für Schwerionenforschung, Darmstadt, Germany
- D.A. Liakin
ITEP, Institute for Theoretical and Experimental Physics, Moscow, Russia
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The UNILAC is used as an injector for the synchrotron SIS. It is designed
to fill the synchrotron up to its space charge limit. The upper limit for
the useful beam emittance of the UNILAC is given by the finite acceptance
of the SIS during the injection process. In order to remain within this
acceptance the emittance growth during beam acceleration and
transportation due to space charge effects must be minimized by applying
an appropriate beam focusing. Therefore, the influence of the magnetic
focusing strength on the beam emittance growth was investigated
experimentally for different beam currents. Measurements of transverse
phase space distributions were performed before and after the Alvarez
accelerator with a periodic focusing channel, respectively. In order to
perform such a wide parameter scan within a reasonable time with respect
to machine stability, the pepper pot technique was applied. The pepper
pot method allows for single-pulse measurements. For comparison several
measurements using the slit-grid technique, which averages over many
pulses, were performed. Both transverse planes were measured
simultaneously. Using two pepper pot devices more than 60 single shot
measurements of the full 4-dimensional transverse phase space
distribution were performed within 8 hours. In this paper we report on
the results of the measurements and we compare them to beam dynamic
simulations and we give an outlook on further developments on pepper pot
devices.
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| PM28 |
Application of Beam Diagnostics for Intense Heavy Ion Beams at the GSI UNILAC
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161 |
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- W. Barth, L. Dahl, J. Glatz, L. Groening, S. Richter, S. Yaramishev
GSI, Gesellschaft für Schwerionenforschung, Darmstadt, Germany
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With the new High Current Injector (HSI) of the GSI UNILAC the beam pulse
intensity had been increased by approximately two orders of magnitudes.
The HSI was mounted and commissioned in 1999; since this time the UNILAC
serves as an injector for the synchrotron SIS, especially for high
uranium intensities. Considering the high beam power of up to 1250 kW and
the short stopping range for the UNILAC beam energies (≤12 MeV/u),
accelerator components could be destroyed, even during a single beam
pulse. All diagnostic elements had to be replaced preferably by
non-destructive devices. The beam current is mainly measured by beam
transformers instead of Faraday cups, beam positions are measured with
segmented capacitive pick-ups and secondary beam monitors instead of
profile harps. The 24 installed pick-ups are also used to measure
intensities, widths and phase of the bunches, as well beam energies by
evaluating pick-ups at different positions. The residual gas ionization
monitors allow on-line measurements of beam profiles. The knowledge of
the real phase space distribution at certain position along the linac is
necessary for optimizing the machine tuning, for the improvement of the
matching to the synchrotron and for a better understanding of beam
dynamic issues under space charge conditions. The paper will report the
application of different beam diagnostic devices for the measurement of
transverse beam emittances at different UNILAC beam energies and for
different beam intensities. Additionally, measurements of the bunch
structure after the HSI and a the design of a new device for the
measurement of the longitudinal emittance at the end of the UNILAC will
be included.
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