= Vent plan for July 2011 =
== Overview ==
Major tasks for vent:
* Fix arm cavity lengths
* [[http://blue.ligo-wa.caltech.edu:8000/40m/IFO_Modeling/RC_lengths|ideal cavity length calculations]]
* Extract Y green beam from vacuum
* The green locking beam from the Y-arm is currently not making it out of the vacuum. We need to fix this by adjusting the green periscope. We will then need to adjust the X-arm green beam as well.
* Align all pick-off ports: POX, POY, POP
* Make sure all of these beams are cleaning making it out of the vacuum on to the PO PDs.
* Align IPANG QPD
* Cleanly position the IPANG beam on the IPANG QPD (eliminate clipping)
* Adjust OSEMs:
* center ranges
* fix rotations to minimize couplings
Later:
* Replace PR3/SR3 steering mirrors with better coatings for green transmission
* Install green light beam dumps
== Preparation ==
Based on [[http://blue.ligo-wa.caltech.edu:8000/40m/IFO_Modeling/RC_lengths|Koji's cavity length calculations]], the ideal arm cavity length is:
{{{
L = 37.7974 m
}}}
The current cavity lengths are:
Based on pictures ([[http://nodus.ligo.caltech.edu:8080/40m/4585|elog #4585)]]:
{{{
Lx = 37.54 m
Ly = 37.54 m
}}}
Based on RF sideband location technique
{{{
Lx = 37.5918 m
Ly = 37.5425 m
}}}
This means we need to move (negative equals back, ie. away from the vertex)
{{{
ETMX -> -0.2056 m = -20.56 cm = - 8.09 in
ETMY -> -0.2549 m = -25.49 cm = -10.04 in
}}}
=== Questions ===
* '''How do we determine OSEM adjustments?'''
* Where do we need to install beam dumps?
* Do we need more black glass or polished stainless beam dumps?
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== Procedure and Time line ==
=== pre-vent days ===
CR:
1. List up which suspensions should be touched
1. Lock Y-arm green
1. Reduce power to mode cleaner (appropriate level for in-air MC locking)
1. Make sure IPANG and IPPOS are working and acquired to fb
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== 1st day ==
1. Shut down PZT HVs
1. Vent at a speed of 1 torr/min.
1. Change cylinders
1. Monitor the pressure
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== 2nd day ==
BS north door :
1. Open BS north door (took ~ 15 min.)
1. Adjust green periscope to extract Y green transmission
1. Align X green trans through green periscope
1. Table leveling of the BS table
1. Check some possible beam clipping
Access connector
1. Remove the access connector (took ~ 45 min.)
1. Adjust the position of Green Telescope
1. Make sure that the IR beam clears the input and output of the Faraday
1. Check some possible beam clipping
CR:
1. Lock X green
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== 3rd day ==
CR:
1. Take the shadow sensors' spectra
EYC north access:
1. Open EY door
1. Move ETMY for YARM
1. ETMY OSEM adjustment, including minimization of coupling and OSEM range
1. '''ETMY shadow sensors need to be carefully investigated'''
EXC west access:
1. Open EX door
1. Move ETMX for XARM
1. ETMX OSEM adjustment?
BSC north access:
1. Adjust IPANG
1. BSC OSEM adjustment?
1. PRM OSEM adjustment?
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== 4th day ==
IXC east access:
1. Adjust POP, POX for vacuum extraction
1. ITMX OSEM adjustment?
IYC north access:
1. Adjust POY for vacuum extraction
1. ITMY OSEM adjustment?
1. SRM OSEM adjustment?
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== 5th day ==
1. Check all the OSEM values
1. Check POP, POY and POX
1. Check IPANG and IPPOS
1. Drag and wipe ETMY
1. Close EYC door
1. Drag and wipe ITMY
1. Close IYC door
1. Drag and wipe ITMX
1. Close IXC door
1. Drag and wipe ETMX
1. Close EX door
1. Close BS door
1. Place the access connector
1. Pumping down
== 6th day ==
1. Pumping down
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= For a later vent: fix cavity lengths =
* Optimize cavity lengths: PRC, SRC, MICH, arms, etc.
* This will involve moving at least (but hopefully at most) one ITM to adjust the MICH Schnupp asymmetry. We will then need to move the ETMs and P/SRMs accordingly to set the proper arm/recycling cavity lengths.
* See wiki page on cavity lengths: [[IFO_Modeling/RC_lengths]]
== Preparation ==
We need precise measurements of the cavity lengths in order to determine where exactly we need to move the test masses.
* [[http://nodus.ligo.caltech.edu:8080/40m/4821|Michelson Schnupp asymmetry]]
* Power recycling cavity (PRCL)
* Signal recycling cavity (SRCL)
Measurements:
{{{
MICH = lx - ly = 3.62 cm
PRCL = (lx+ly)/2 + lsr = ?
SRCL = (lx+ly)/2 + lpr = ?
}}}
== Vent ==
=== door removal ===
1. BSC north
1. ITMYC north
1. ITMXC west
1. ETMYC north
1. ETMXC west
=== Procedure ===
This is a preliminary procedure plan:
CR:
1. Lock Y-arm green
1. Reduce power to mode cleaner (appropriate level for in-air MC locking)
IOC west access (through access connector):
1. Adjust green periscope to extract Y green transmission
CR:
1. Lock X green
BSC north access:
1. Align X green trans through green periscope
BSC north access:
1. Adjust IPANG
CR:
1. Misalign PRM
IYC north access:
1. Move ITMY into position
IXC west access:
1. Move ITMX into position
CR:
1. Realign PRM
EYC north access:
1. Move ETMY for YARM
EXC west access:
1. Move ETMX for XARM
BSC north access:
1. Move PRM for PRC
BSC north access:
1. Move SRM for SRC
1. Align pick-offs