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  * [http://blue.ligo-wa.caltech.edu:8000/40m/IFO_Modeling/RC_lengths ideal cavity length calculations]   * [[http://blue.ligo-wa.caltech.edu:8000/40m/IFO_Modeling/RC_lengths|ideal cavity length calculations]]
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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: 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:
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Based on pictures ([http://nodus.ligo.caltech.edu:8080/40m/4585 elog #4585)]: Based on pictures ([[http://nodus.ligo.caltech.edu:8080/40m/4585|elog #4585)]]:
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  * See wiki page on cavity lengths: [[IFO Modeling/RC lengths]]   * See wiki page on cavity lengths: [[IFO_Modeling/RC_lengths]]
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 * [http://nodus.ligo.caltech.edu:8080/40m/4821 Michelson Schnupp asymmetry]  * [[http://nodus.ligo.caltech.edu:8080/40m/4821|Michelson Schnupp asymmetry]]

Vent plan for July 2011

Overview

Major tasks for vent:

  • Fix arm cavity lengths
  • 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 Koji's cavity length calculations, the ideal arm cavity length is: 

L = 37.7974 m

The current cavity lengths are:

Based on pictures (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?



Procedure and Time line

pre-vent days

CR:

  1. List up which suspensions should be touched
  2. Lock Y-arm green
  3. Reduce power to mode cleaner (appropriate level for in-air MC locking)
  4. Make sure IPANG and IPPOS are working and acquired to fb


1st day

  1. Shut down PZT HVs
  2. Vent at a speed of 1 torr/min.
  3. Change cylinders
  4. Monitor the pressure


2nd day

BS north door :

  1. Open BS north door (took ~ 15 min.)
  2. Adjust green periscope to extract Y green transmission
  3. Align X green trans through green periscope
  4. Table leveling of the BS table
  5. Check some possible beam clipping

Access connector

  1. Remove the access connector (took ~ 45 min.)
  2. Adjust the position of Green Telescope
  3. Make sure that the IR beam clears the input and output of the Faraday
  4. Check some possible beam clipping

CR:

  1. Lock X green


3rd day

CR:

  1. Take the shadow sensors' spectra

EYC north access:

  1. Open EY door
  2. Move ETMY for YARM
  3. ETMY OSEM adjustment, including minimization of coupling and OSEM range

  4. ETMY shadow sensors need to be carefully investigated

EXC west access:

  1. Open EX door
  2. Move ETMX for XARM
  3. ETMX OSEM adjustment?

BSC north access:

  1. Adjust IPANG
  2. BSC OSEM adjustment?
  3. PRM OSEM adjustment?


4th day

IXC east access:

  1. Adjust POP, POX for vacuum extraction
  2. ITMX OSEM adjustment?

IYC north access:

  1. Adjust POY for vacuum extraction
  2. ITMY OSEM adjustment?
  3. SRM OSEM adjustment?


5th day

  1. Check all the OSEM values
  2. Check POP, POY and POX
  3. Check IPANG and IPPOS
  4. Drag and wipe ETMY
  5. Close EYC door
  6. Drag and wipe ITMY
  7. Close IYC door
  8. Drag and wipe ITMX
  9. Close IXC door
  10. Drag and wipe ETMX
  11. Close EX door
  12. Close BS door
  13. Place the access connector
  14. Pumping down

6th day

  1. Pumping down

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.

Measurements: 

MICH = lx - ly = 3.62 cm
PRCL = (lx+ly)/2 + lsr = ?
SRCL = (lx+ly)/2 + lpr = ?

Vent

door removal

  1. BSC north
  2. ITMYC north
  3. ITMXC west
  4. ETMYC north
  5. ETMXC west

Procedure

This is a preliminary procedure plan:

CR:

  1. Lock Y-arm green
  2. 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
  2. Align pick-offs

vent/201107 (last edited 2012-01-03 23:02:39 by localhost)