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Reports until 01:56, Tuesday 22 March 2016
H1 TCS
kiwamu.izumi@LIGO.ORG - posted 01:56, Tuesday 22 March 2016 - last comment - 10:33, Tuesday 22 March 2016(26184)
CO2Y laser unable to set the power

We are having a trouble with the CO2 Y laser where every time when we request an angle to the rotation stage, it trips the laser for unknown reason. According to the MEDM screen, "RTD/IR SENS. ALARM" turns in red when we request an angle to the rotation stage. We needed to hit the gate button at the floor in order to untrip the laser. If we do not change the rotation stage angle, the laser seems to stay on,

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Comments related to this report
alastair.heptonstall@LIGO.ORG - 07:51, Tuesday 22 March 2016 (26186)
This sensor channel covers two separate possible errors on the laser.  The first thing to do is for someone to go and take a look at the front of the laser controller chassis to check whether the IR sensor fault light is on.  It sounds to me like it is most likely the laser temperature channel tripping. 
 
If it is the temperature of the laser causing the trip then check the flow rate of the chiller and the laser temperature readout channel on the MEDM screen to make sure this is not a real effect.
 
The setpoint at which the laser trips can be changed by altering a potentiometer inside the controller chassis.  It has been seen before that large electrical spikes can cause the laser to trip on/off because of the temperature monitor channel and for this reason it now has some filtering on it.  However we have never seen it before from the rotation stage which makes me think something else may also be going on here - perhaps something has changed in the rotation stage motor, or the wiring has moved closer to the RTD.
 
For the safety of the laser the temperature shutoff setpoint should be set carefully, and this was pre-set in the electronics lab on the bench, so that we could calculate the temperature that we expect it to shut off.  A simple very short term solution is to open up the chassis and slightly tweak the temperature shutoff pot till this stops happening (this is a short term solution only to get the laser running right now, so you can use it).  The resistor to change is R51 (diagram is at https://dcc.ligo.org/DocDB/0070/D1101835/007/Contr_CO2_Laserv7.pdf ).  However I would suggest that what should really be done is to set up the spare chassis (this would also need the pot set) and then swap it in for this one, then test this one.  There is a test and set up procedure I wrote at T1400234.
 
If this starts to be more of a regular problem we may need to revisit this controller chassis design.
kiwamu.izumi@LIGO.ORG - 10:33, Tuesday 22 March 2016 (26189)

Fixed.

It was loosely connected D-sub calbes. I went to the floor and was going to inspect the controller box as suggested by Alastair. However, it turned out that tightening up all the D-sub cables on the front panel of the controller box apparently fixed the problem. I did not even try to reproduce the issue.

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