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Dehler, M.

Paper Title Page
CT08 Capabilities of the ELETTRA/SLS Multibunch Feedback Electronics 74
 
  • M. Dehler, R. Kramert, P. Pollet, D. Bulfone, M. Lonza
    PSI, Paul Scherrer Institut, Villigen, Switzerland
 
  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.  
PT21 Microwave measurement of intra bunch charge distributions 219
 
  • M. Dehler
    PSI, Paul Scherrer Institut, Villigen, Switzerland
 
  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.