This page describes in details the procedure how to lock and align the XARM.
First of all, let me note that it is necessary to carry out the locking procedure if the picture on video monitor chaotically jumps from one place to another. If the XARM is locked in the TEM_00 mode, the picture on the gray "Bosch" video screen (which is located above the OP 440M" computer) should be a fixed stable circle.
IMPORTANT REMARK: THE PROCEDURE OF XARM - LOCKING CAN BE DONE FROM "OP 440M" COMPUTER ONLY !
BELOW ARE THE STEPS (algorithm) OF THE PROCEDURE.
1) Open the MEDM panel.
2) Click on "IFO_" button (pink button in the bottom of the MEDM window).
3) Click on "C1IFO_CONFIGURE" in the opened menu.
- As a result, a new window with the title "C1IFO_CONFIGRE.adl" will appear.
4) Click on the small square icon depicting the exclamation sign "!" to the left from the button "XARM".
5) Click "Restore XARM" in the menu that appears after step 4.
6) Some script will be running for a short period of time (about half-a-minute).
In order to convince yourself that the XARM is becoming locked, you might open Dataviewer (either on "OP 440M" or on a different computer), click on "File" -> "Restore Settings...", and open the file "Xarm.xml" in the directory "/cvs/cds/caltech/users/Templates/Dataviewer_Templates/".
Press "Start" virtual button in Dataviewer main screen then.
A screen with 4 pictures will then appear. In the upper left part of that screen the plot entitled "Ch2: C1: SUS-ETMX_LSC_OUT" will be depicted. This plot depicts the force that is applied to ETMX in order to keep the Fabry-Perot cavity of the XARM aligned in resonance. In the lower left part of the screen there will be another plot entitled "Ch1: C1: ASC-QPDX_DC". This plot depicts the readings (more exactly, some value that is proportional to the readings in Volts) of a photodetector measuring the transmittivity of XARM. The right two graphs depict some information about Yaw and Pitch degrees of freedom of the end-test-mass, but they do not seem to be important for the XARM locking procedure.
7) After the signals in the Dataviewer have become "steady" (they are not "steady" in the literal sence, but rather it is a steady zigzag-shaped dependence, not a straight line as immediately after pressing the button "Restore XARM"), click on the "Align XARM" in the same menu on "OP 440M" computer as described at step 4 above. After clicking "Align XARM", a new black window "Diddling X Arm" will appear on monitor of "OP 440M", and there will be information about which scripts and commands are being run during the alignment..
8) Wait 2 or 3 minutes looking into the screen of the gray "Bosch" monitor above all the computers, as well as looking into the Dataviewer plots described at step 6 above.
When the XARM is aligned, there should be a fixed circular spot on the grey "Bosch" screen above the computers.
REMARK 1: If for some reason steps 6 or 8 (running of computer scripts for "restoring" or "aligning" the XARM) take very-very-very long time (more than 5 minutes), this means that there is something wrong. In that case you need to terminate the script execution, pressing the buttons "Ctrl" - "C" on the "OP 440M" computer.
REMARK 2: I described the Dataviewer graphs at step 6 above. "LSC" in the name "Ch2: C1: SUS-ETMX_LSC_OUT" stands for "Length Sensing Control", while "ASC" in the name "Ch1: C1: ASC-QPDX_DC" stands for "Alignment Sensing Control".
( Written by Andrey Rodionov on October 16, 2007 )