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Title |
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| PM20 |
A High Dynamic Range Bunch Purity Tool
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216 |
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- B. Joly, G.A. Naylor
ESRF, Grenoble, France
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The European synchrotron radiation facility uses a
stored electron beam in order to produce x-rays for the
study of matter. Some experiments make use of the time
structure of the x-ray beam which is a direct reflection of
the time structure in the electron beam itself. Avalanche
photo-diodes have been used in an x-ray beam in a photon
counting arrangement to measure the purity of single or
few bunch filling modes. Conventional techniques
measuring the photon arrival times with a time to
analogue converter (TAC) achieve dynamic ranges in the
10-6 range. We report here the use of a gated high count
rate device achieving a measurement capability of 10-10.
Such high purity filling modes are required in synchrotron
light sources producing x-ray pulses for experiments
looking at very weak decay signals as seen in M”ssbauer
experiments..
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| PM21 |
DSP and FPGA Based Bunch Current Signal Processing
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219 |
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- G.A. Naylor
ESRF, Grenoble, France
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The current in electron storage rings used as synchrotron light sources
must be measured to a very high precision in order to determine the
stored beam lifetime. This is especially so in high-energy machines in
which the lifetime may be very high. Parametric current transformers
(PCT) have traditionally been used to measure the DC or average current
in the machine, which offer a very high resolution. Unfortunately these
do not allow the different components of a complex filling pattern to be
measured separately. A hybrid filling mode delivered at the ESRF consists
of one third of the ring filled with bunches with a single highly
populated bunch in the middle of the two-thirds gap. The lifetime of
these two components may be very different. Similarly the two components
are injected separately and can be monitored separately using a fast
current transformer (FCT) or an integrating current transformer (ICT).
The signals from these devices can be analysed using high speed analogue
to digital converters operating at up to 100MHz and digital signal
processing (DSP) techniques involving the use of field programmable gate
arrays (FPGAs) in order to process the continuous data stream from the
converters.
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