• Optics_Cleaning

Cleaning of the suspended test mass (Dec 2009)

Motivation

The round trip loss in the 40m cavity is estimated to be around 170ppm. We are going to confirm whether this comes from the hydrocarbon contamination and wiping of the mirror by acetone and isopropyl may result in improvement of the optical loss, or not.

In addition we can evaluate the use of those solvents. If we observe the degradation of the loss or the finesse, we will forbid them.

Measurements before the cleaning

- Visibility measurement

Most recent arm visibility measurement has been done on Oct 07, 2009. [http://nodus.ligo.caltech.edu:8080/40m/2070 corresponding elog entry]

Measured arm reflectivity R_cav:
X arm: 0.875 +/- 0.005
Y arm: 0.869 +/- 0.006

- Cavity pole measurement

Most recent arm visibility measurement has been done on Nov 10, 2009. [http://nodus.ligo.caltech.edu:8080/40m/2226 corresponding elog entry]

Measured arm cavity pole frequency f_pole [Hz]:
X arm: 1720 +/- 70
Y arm: 1650 +/- 70

- Estimated finesse and arm loss

Measurements after the cleaning

- Visibility measurement

- Cavity pole measurement

- Estimated finesse

Overview of the plan

• We plan for the vent from 7th Dec to 11th Dec in 2009.

• Preparation

  • Wiping Preparation
  • Vent Preparation

• Monday:

  • Pre-vent check 8:00~
  • Vent from 9:30~
  • Stop venting ~14:00
  • Check OSEM/Oplev values
  • Wipe ETMX 14:00~
    • Open ETMX 14:00~15:00
    • Mirror wiping 15:00~16:00
    • Check alignment / Close up 16:00~17:00

• Tuesday:

  • (ETMX wipe)
  • ETMY wipe
  • ITMY wipe
  • Check of the optics in the chambers (ITMY)

• ~ Wednessday:

  • ITMX wipe
    • Record ITMX position (pushing screws)
    • ITMX BB leveling
    • measure the distance of the breadboards
  • 40m meeting
  • Check of the optics in the chambers (ITMX/BS)

• Thursday:

  • Evacuation

• Friday:

  • Reserve

Detailed plan

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• ~Friday, 4 Dec:

  • Wiping preparation
    • Chemicals:
      • Small bottles (like 250ml) / 3 bottles each (no matter how the size is)

      • Acetone Spectral Grade, dehydrated (if possible)

      • Isopropyl alcohol Spectral Grade, dehydrated (if possible)

    • glass sylinges with metal needles, 50ul, at least three sets
    • mirror wiping paper, usual lens paper from Kodak or whatever
    • tools (well cleaned)
    • clamps to mark the position of ITMX: 3pcs
    • halogen light or whatever: light during the work

• Vent Preparation

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• Prepare the air cylinders (x6)

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• Clean clean-tools again
• Alignment

  • Recenter: IPANG/POS, oplevs with the mirrors fully aligned [DONE]

  • Align the aux beam as a reference [DONE]

  • Update snapshots of all MEDM screens for OSEMs/OPLEVs/QPDs/PZT&strain gauges [DONE]

• Move extraneous equipment around chamber doors: Make sure we have clear access (esp. seismometers need moving) [DONE]

• Monday:

  • Check before the vent

    • Before venting, check that all the recentering done on Friday is still good. If not, redo. [DONE]

    • Turn off all OPLEV damping [DONE]

    • Turn on the shutter for the PSL beam. Put a manual block so that any failure can put the beam into the vacuum system [DONE]

    • Turn off all HV in vacuum (Input/Output PZT) [DONE]

    • Check the jam nuts of the bellows on the vacuum system (Two at the vertex, one at the MC tube) [DONE]

  • Vent

    • Operate the valves according to the operation manual

      • Isolate the main vacuum manifold [DONE]

      • Introduce N2 up to 25torr [DONE]

      • Change the N2 cylinder to the instrument grade air. We need 6 cylinders to fill up the tank.
  • During the vent - Door opening preparation
    • Test drive crane drives

    • Move and store abs. length setup to a safe place [DONE]

    • Practice drag wiping a spare random optic (with an arbitrary 2" CVI optic)
    • Practice cutting viton, so we can get the correct sizes if we need to replace stops. (Jenne)
    • Cut some viton tips for spare earthquake stop screws
  • Environment
    • Keep eyes on particle counter: abort over 10,000
    • Look that we have good RGA scan
  • Open ETMX
    • Take photos of ETMX before touching

  • ETMX wipe

  • Close up ETMX with light doors for the night

• Tuesday:

• Wednesday:

• Thursday:

• Friday: