UED at ASTA: LLRF and triggers

• Need < 100 fs jitter• Currently we measure > 500 fs RMS phase noise

in 10 Hz to 10 MHz bandwidth at 476 MHz• Excessive phase noise is due to the dirty

reference from LCLS (which conveniently provides triggers synced to PG&E zero crossing)

• Suggested improvements:– Import clean 119/476 MHz from linac– Local source with local trigger generation

Courtesy J. Dusatko

Fiber from LCLS

476 MHz from PLL noise measurement

Locked 562 fsec RMS jitter

Unlocked 50 fsec RMS jitter

Clean 119 MHz from LI30

• Relic of E-144 FFTB experiment: TW laser synced to beam time with 0.5 ps stability– Recomission LI30 RF fiber optic diode laser

transmitter (30 mW laser hazard)– Adapt to standard SLC fiber – Fiber patch LI30 to B44– Relocate the receiver (from B407)

• No need for a new timing system!

Local source, local triggers(cut the cord)

• The unlocked PLL has a relatively clean 476 MHz source (LCLS comparable)

• Still need triggers: Rebuild/borrow spare HW to reproduce LCLS fiducial generation in the klystron test lab

• Independence from LCLS timing outages

Courtesy J. Dusatko, D. van Winkle

LINAC triggers

Courtesy J. Dusatko

Figure 1: ASTA phase (red) and amplitude (blue) over a 6 hour period.