Time-jitter reduction on the RF buncher signal for the Los Alamos proton storage ring (PSR)

The PSR at LAMPF will accumulate protons from the linear accelerator in both long- and short-bunch operational modes. Beam accumulation takes place for hundreds or thousands of turns. Ring buncher frequencies for these modes are 2.795 and 503.125 MHz, respectively. The bunching waveforms must be accurately correlated with the linac frequency standard so that the injected bunches fall into the ring RF buckets at precisely zero phase angle during accumulation. The PSR's RF wave also must have excellent phase stability. Long-term stability is assured by locking the PSR frequency reference to the linac's low-noise, temperature-stabilized crystal standard and by using delay-correction circuits in the transmission-line paths. However, the short-term stability of the RF reference signal is not as easily controlled because additive spurious signals can enter the long RF-signal transmission path (1-km linac-to-PSR), causing sideband energy increases very close to the carrier frequency. This increases time jitter. The measure of control pursued by the described circuit design will provide RF references with timing uncertainty much less than the expected uncertainty in the micropulse time of arrival at the ring. This paper discusses the steps taken to develop the low-level RF reference signal with some measure of margin relative to this + or - 10-ps budget. Phase-locked loop stabilizers, narrow-band high rejection-rate filters, and low-noise multipliers/dividers provided the means to achieve the goal