FZD, Dresden
For good operating the ELBE linear accelerator it is essential to have RF signals with high phase stability and purity on all cavities and buncher RF signals. Therefore a large number of low level RF control loops are used. But sometimes problems with these circuits occur. For further investigations a multichannel phase supervising device is required to have knowledge of phase noise and long term drifts. The circuit under development at ELBE allows the simultaneous phase measurement of up to 32 signals of 1.3 GHz (accelerator), 260 MHz (buncher) or 13 MHz (gun) frequency with 2 deg accuracy. Using an additionally 1.3 GHz PLL locked to the 13 MHz master oscillator (OCXO) of the machine as reference the phase measurement device is completely independent from the circuits used in the accelerator low level RF. Under normal conditions a programmable logic controller (SIMATIC) is used for data acquisition. This leads to approx. 5 measurements per second for all channels. But the measurement device is much faster, feeding the signals to a National Instruments PXI-6115 12-Bit, 10 MS/s/channel multifunction DAQ card enables also microphonic and phase noise measurements up to 10 kHz.
