Last update: 2019/06/25 22:53 d2:spectroscopy_module_210 https://www.vescent.com/manuals/doku.php?id=d2:spectroscopy_module_210
https://www.vescent.com/manuals/ Printed on 2019/08/21 02:55
The photodiode signal is output through an SMA connector. Connect to ERROR INPUT on the Laser
Servo.
Balance Adj.
Sets the fraction of the Reference photocurrent to be subtracted from Signal. Setting the lockpoint
close to zero Volts will give the best subtraction of relative intensity noise (RIN) on the incoming laser.
Temperature Adj.
10-turn trim pot that sets temperature from 25°C (fully CCW) to 65°C (10 turns CW). The 5-turn point
is approximately 42°C. Note that the vapor cells are heated only, so setting the temperature below
room temperature essentially disables temperature control. The following table gives approximate
temperature settings for the three available alkali options:
Alkali Turns CW Temp
cesium 2 ~30°C
rubidium 4-5 ~40°C
potassium 8-9 ~60°C
Tab. 4
Temperature Loop Gain Adj.
In newer units, there is a middle trimpot for adjusting the gain on the PID temperature loops. Higher
gain (clockwise) will result in faster temperature settling until oscillation occurs.
Temperature Bias Adj.
[Note: this adjustment is only available on older D2-210 models.] For the Doppler subtraction option
this control enables the user to input a small temperature difference between the reference and
signal vapor cells. In the fully CCW position the signal vapor cell heater gets all the current. In the full
CW position the reference cell heater gets twice the current as the signal cell. This adjustment can be
used to place the optimum point for Doppler Subtraction closer to zero Volts.
This adjustment only has an effect with the -DS, Doppler Subtraction option.
Tilt Plate
A polarizing beamsplitter (PBS) is fixed to a ball joint formed by a truncated steel ball held by a
conformal brass ring. Two cone screws clamp the ring against the ball and fix the position of the PBS.
See Alignment Procedure below for instructions on how to align and fix the PBS.
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