Paper |
Title |
Page |
CT08 |
Capabilities of the ELETTRA/SLS Multibunch Feedback Electronics
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74 |
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- M. Dehler, R. Kramert, P. Pollet, D. Bulfone, M. Lonza
PSI, Paul Scherrer Institut, Villigen, Switzerland
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Due to the unavailability of commercial ADC and DAC boards, first
commissioning of the transverse multi bunch feedback was done in the last
year using loaned equipment from Sincrotrone Trieste. In order to remedy
that situation, development of ADC and DAC VME boards was started. The
boards do a 500 MS/s data conversion with an 8 bit resolution. The ADC
and DAC circuits are separate modules containing their own one to four
de-/multiplexing electronic reducing the data rate to 125 MS/sec. The
following stage being a common design to both ADC and DAC allows data
recording and play back using on board RAM and allows freely programmable
multiplexing/demultiplexing ratios of one to five to one to twelve. The
digital data streams flow via Front Panel Digital Ports (FPDP). A special
design criterion were low system latencies ensuring a high feedback
efficiency. Apart from lab tests, we report on full feedback system test
and show the feedback performance in the transverse and longitudinal
planes.
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PT21 |
Microwave measurement of intra bunch charge distributions
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219 |
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- M. Dehler
PSI, Paul Scherrer Institut, Villigen, Switzerland
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A direct way of obtaining intra bunch charge distributions is to measure
the amplitude roll off as well as the phase behavior of the spectrum of
the single bunch self field. To that effect, a microwave pickup together
with a microwave front end has been installed in the storage ring of the
Swiss Light Source (SLS). As pickup, button type bpms are used,
which have been designed for a broad band behavior in the excess of 30
GHz. Three bpms together with their individual front ends are used in
order to sample the beam spectrum at frequencies of 6, 12 and 18 GHz,
which compares to the standard spectrum of a 1 mA single bunch extending
to approximately 12 GHz (13 ps rms bunch length). The signals are mixed
to base band in loco using the multiplied RF frequency as a LO. By
shifting the LO phase, simultaneously the amplitude roll off as well the
complex phase of the beam spectrum can be obtained. Where using a
resonator as a pickup would smear out the response over several bunches,
allowing only the determination of average values, the current setup has
a band width of approximately 2 GHz, so that individual bunches in the
500 MHz bunch train can easily be resolved.
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