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. Also, some phase noise is spuriously developed by the signal-processing circuits providing frequency multiplication and division, the required processes for generating the necessary harmonic and subharmonic bunching frequencies at 503.125 and 2.795 MHz, respectively. 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, ΔT ≈ ±80 ps.