6
ISOMET
3.8
RF power is adjusted at the signal source to the RFA1160/4
e.g. iHHS-2 amplitude setting.
3.9
Set the power to a low value e.g. 0.2mW
3.10
Apply + 24V DC to the amplifier. Ensure the cooling water is on.
3.12
Input a constant 70MHz (80MHz) input signal to the RFA1160/4 (RFA1160/4-ZP).
Or Input a pulsed 70MHz (80MHz) input signal to the RFA1160/4-PO (RFA1160/4-ZP-PO),
with a duty cycle less than 25%.
This will operate the AO device at its mid-scan position.
3.13
Align the deflector head to insure that the incident light beam is centred in the active aperture
of the deflector.
Observe the diffracted first-order output from the acousto-optic modulator and the undeflected
zeroth order beam. Adjust the Bragg angle (rotate the deflector) to maximise first order beam
intensity.
3.14
After Bragg angle has been optimized, slowly increase the RF power until maximum first
order intensity is obtained. Record this intensity value (I
SAT
).
3.15
To equalise deflection efficiency across the extremes of the scan, alternate between the
minimum and maximum desired frequencies (e.g. 50MHz and 90MHz input resp’) and adjust
the Bragg angle to give the same efficiency at both positions. Fine tuning of the incident
Bragg angle and RF power may be necessary for optimum results.
3.16
The amplifier is now ready for use.
