today, I locked the laser on the FP-cavity and the FP-cavity on the RF reference with 47kW inside the FP-cavity.
equivalent jitter :
when lock is OFF : sine signal V=V0*sin(phi(t)) with V0=300mV => Vrms = 300/sqrt(2)) = 210mV rms
when lock is ON : noise 10mV < dV < 20mV
for low phase values : dV=V0*dphi
when the RF locking is done, this voltage is about dV = 20mV rms => dphi = dV/V0 = 67 mrad
dphi = 2*pi*f0*dt => jitter dt = dphi/(2*pi*f0) = dV * T0/(2*pi*V0)
T0/(2*pi*V0) ~ 1ps/mV => jitter ~ 10-20 ps rms
previous measurements were exhibiting a jitter lower than 5ps rms : https://elog.lal.in2p3.fr/FPC/THOMX+commissioning/299
| Ronic Chiche wrote: |
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this morning, with Vincent Chaumat, we made a beating (phase detection) between the laser 33MHz and the 33MHz coming from the Rigol generator locked by the 10MHz link onto the 500MHz ring generator.
once the laser and the FP-cavity are locked on the RF reference, the 33MHz phase detection is stabilized and confirm the laser/FP-cavity lock on the RF reference.
we plan to make a drift measurement and a jitter measurement to estimate this lock quality.
the 33MHz frequency being quite small, the quality of this estimation will be poor but it can give a "worse case" estimation.
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