• 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. 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. corresponding elog entry

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

- Estimated finesse and arm loss

X Arm:

• Arm visibility (given): 0.875 +/- 0.005 (34 pts)
• Cut off freq (given): 1650 +/- 70 [Hz]
• ---

• Finesse (derived): 1181 +/- 50

• Round Trip loss (estimated): 162 +/- 10 [ppm]

• Front Mirror T (estimated): 0.0051 +/- 0.0002

Y Arm:

• Arm visibility (given): 0.869 +/- 0.006 (26 pts)
• Cut off freq (given): 1720 +/- 70 [Hz]
• ---

• Finesse (derived): 1128 +/- 46

• Round Trip loss (estimated): 179 +/- 12 [ppm]

• Front Mirror T (estimated): 0.0054 +/- 0.0002

Measurements after the cleaning

- Visibility measurement

Most recent arm visibility measurement has been done on Dec 14, 2009. corresponding elog entry

Measured arm reflectivity R_cav:
X arm: 0.897 +/- 0.005
Y arm: 0.893 +/- 0.004

- Cavity pole measurement

Most recent arm visibility measurement has been done on Dec 14, 2009. corresponding elog entry

Measured arm cavity pole frequency f_pole [Hz]:
X arm: 1616 +/- 14
Y arm: 1590 +/- 4

- Estimated finesse and arm loss

X Arm:

• Arm visibility (given): 0.897 +/- 0.005 (20 pts)
• Cut off freq (given): 1616 +/- 14　[Hz]
• ---

• Finesse (derived): 1206 +/- 10

• Round Trip loss (estimated): 127 +/- 6 [ppm]

• Front Mirror T (estimated): 0.00506 +/- 0.00004

Y Arm:

• Arm visibility (given): 0.893 +/- 0.004 (20 pts)
• Cut off freq (given): 1590 +/- 4 [Hz]
• --

• Finesse (derived): 1220 +/- 3

• Round Trip loss (estimated): 131 +/- 6 [ppm]

• Front Mirror T (estimated): 0.00500 +/- 0.00001

Loss calculation

• Mathematica Notebook

• PDF

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

• ~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

  • Prepare the air cylinders (x6)
  • 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

    • Close: PSL shutter and place manual block into main beam path
    • Prepare left handed pressure regulator for instrument grade air,
    • Identify "VACUUM NORMAL" state of valve positions based on the 40M VACUUM SYSTEM STATES and SEQUENCES user manual
      • Note: this operation is FULLY MANUAL and two person required to change condition (one has to be experienced )

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

    • Check: particle count

    • Turn off: all OPLEV damping to all sus [DONE]

    • Turn off: PZT power to IOO steering and OMC [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

    • Follow "vacuum normal to chamber open" from 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.
      • Approximate vent rate 150torr/hour
  • 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

    • Tank Opening

      • Open outside heavy door
      • Open outside heavy door
      • Open inside heavy door (nearest to CES building)

    • Before touching

      • Take photos of ETMX to check magnet centering in OSEMS (Side OSEM + 4 OSEMS)

    • Clamp ETMX with earthquake stops:

      • Make note of where they are, and how much they are turned to touch the optic, so we can go back to the same place
      • First do bottom 4, until barely touching the optic
      • Screw in the back 4, until barely touching the optic
      • Screw in 3 of the front stops - on the top and sides of the front face

    • Remove the bottom front face EQ stop

      • Unscrew the clamp and fully remove the stop and the holder.

    • (Inspect the coating surface with a fiber introduced halogen light source)

      • Wrap the fiber bundle of the halogen light source with UHV Al foil
      • One dirty person hold the light source and the fiber out side the chamber.
      • One fully dressed person hold the end of the fiber and inspect the mirror surface

    • Deionize the optic

      • Blow the optic by ionized Nitrogen flow.

    • (Inspect the coating surface with a fiber introduced halogen light source)

    • Drag wiping

      • Person 1: Prepare a syringe with ~110 microliters of acetone
        • Load it fully with acetone, and squirt it all out onto a kimwipe. Repeat at least once more, to fully rinse the inside.
        • Load it to the correct volume of acetone for wiping.
      • Person 2: Lay a piece of lens paper gently against the front face of the optic
      • Person 1: Spray all of the acetone onto the lens paper, in a single spot just barely above the center of the optic
      • Person 2: Gently pull down on the lens paper, using a clean allen wrench held almost even with the face of the optic, but below the bottom of the optic, to help guide the paper. This must be done fairly quickly, since acetone evaporates quickly.
      • Repeat acetone until satisfied that you have gotten everything off, using a new lens paper every time.
      • Person 1: Using a new syringe, rinse it using isopropyl by filling it completely and squirting all the liquid onto a kimwipe. Repeat.
      • Person 1: Load ~50 microliters of isopropyl into the syringe.
      • Person 2: Lay a new piece of lens paper against the front of the optic
      • Person 1: Spray all of the isopropyl onto the lens paper, in a single spot just barely above the center of the optic
      • Person 2: Gently pull down on the lens paper, using a clean allen wrench to guide the paper. This should be done slower, since isopropyl takes longer to evaporate.
      • Repeat isopropyl until satisfied that you have gotten everything off the optic

    • (Inspect the coating surface with a fiber introduced halogen light source)

    • Release all of the earthquake stops, in reverse order from clamping order.

    • Check OSEM values, to confirm that they are consistent with the way they were

    • Check that no tools are left behind in the chamber.

    • Close inner door with the heavy door

    • Close the outer door with a light door (will be replaced with heavy doors before pump down)

• Tuesday:

  • ETMY wipe

  • ITMX wipe

• Wednesday:

  • Invac optics inspection

  • Distance between the tables

  • ITMY wipe
  • Take pictures of the ITMX after the wipe as we forgot to do it on Tuesday.

• Thursday:

  • Closing Tanks

    • Inspect ETMX with the halogen light as we did not use it on Monday.

• Friday:

  • Pumping Down

    • Slowly!