Here is my mail regarding the laser incident from 29 May-2May:

My summary of events:
1)	GPIB error Sunday 29,  21h28. Restart all 00:57 am.  
Comment: linearity scan for the ENCAP finished at 21h11 thus sequence was changed. 

2)	Laser1 OFF- restart: 01 MAY, 19h10. 
Restart of laser1 OK and sequence restarted ~20h20. Laser1 is ‘fault state’. I don’t know what was the error display on the laser...
Comment:  -  linearity scan start at 17h08 , stop at 18h52: elog “change config to normal”. 
                        - power glitch at 6am, following by CMS wide water cooling disturbance.

3)	Laser1 OFF à Laser2: 02 MAY, 2h54
Laser2 ON at 5h20.

4)	Laser2 à Laser1 : 02 MAY, 16h30.
                
Laser1  investigation and problem: 

No problem at all regarding the operation:  device rebooting for 1) and spare laser2 online  OK thus all OK for ecal  laser operation at it is defined. Good !
The others things  are details and transparent regarding ECAL. 

Laser1 yesterday; 
-	Put back 20 degrees on room temperature at is was to avoid light disparity. 
-	Laser1 error : “water flow error”. While Emanuele got “water Di error” . The error remain ON all the time despite reset the laser power suppy and even before the pump start !
-	Swap the 2 chips relay on logic unit: no effect
-	Replace the flow sensor with spare one: no effect
-	Replace one relay chip on logic unit: OK , error disappeared !
-	Start laser: lamp can’t start  ignition , no current à dismount it. Found lamp broken. Succeed to remove piece of glass inside the flow tube without dismount all. 
-	Restart laser with no tuning at ALL to avoid big monitoring step. Power of TiS laser same as 13 April (new lamp)

Conclusion : 

i)	I have no idea why laser1 went OFF in 2). which error ? If it was  “water temperature error”  that’s mean no input cooling, id.  the water -  pump stopped.
Anyway  laser restart after that thus nothing to suspect on laser side. 
BUT this is for sure very bad for the lamp in general when the laser stop suddenly. This for me can explain why the lamp brake,  also because laser1  not only stopped once but twice like this . 

ii)	For the case 3) failure of a chip happened already in the past (thus I have spare).  Maybe there was disturbance on the power line from the laser which make this electronic chip in bad shape after a while and then failed  later on ! this is not excluded but this is not important: nothing to be done regarding power line and laser electronic for a such rare default. 

iii)	What is suspect for me and I am not confident is the linearity scan and thus the changing of the sequence configuration: in both case 1) and 2) the sequence was just change before and thus run stop, ect…. this is maybe coincidence but I remember it’s not the first time..

iv)	The following 3 things which was mentioned have nothing to do with laser default and further discussion is useless: 
-	Level of water
-	Temperature of water
-	Room temperature

David