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Residual Gas Fluorescence for Profile Measurements at the GSI UNILAC
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137 |
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- A. Bank, P. Forck
GSI, Gesellschaft für Schwerionenforschung, Darmstadt, Germany
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The high beam currents, delivered at the LINAC at GSI (UNILAC) can
destroy intercepting diagnostics within one macro-pulse. As an
alternative for a non-destructive profile measurement the methode for
residual-gas-fluorescence is investigated. The fluorescence light is
emitted by the N2 molecules of the residual gas at the blue wavelength
range and can be monitored with a modern CCD-camera. The images are
transferred via digital bus (IEEE 1394 'FireWire') and the profiles are
generated by analysis of the images with a modern software tool (National
Instruments 'LabView'). Due to the short beam pulses (about 0.2 ms) the
light intensities emitted by the residual gas are low and require a high
amplification (gain >106) which is realized with an image intensifier
with double MCP (multi channel plate), connected with a fiber taper to
the CCD-chip. The design parameters of the optics and electronics are
discussed as well as the advantages of the digital data transmission.
Measurements with heavy ion beams of several 100 μA and a comparison to
other profile measurement methods show a good signal-to-noise ratio and
prove a good applicability.
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