1. Cascina 26 Aug 2008 Weekly Meeting1 Viewport cleaning & inspection Procedure and Results Richard Day EGO optics group R. Maillet N. Menzione C. Bradaschia E. Genin

2. Cascina 26 Aug 2008 Weekly Meeting2 Motivation l80 new viewports to be installed in the ITF. lEach viewport needs to be cleaned and inspected before installation. lCreate database containing state of viewports at time of installation. lTest bench and procedure required in order maximize efficiency and quality of cleaning and inspection process.

3. Cascina 26 Aug 2008 Weekly Meeting3 Outline lPresent test bench created and steps in procedure. lReport on Larson viewport quality and selection process. lFurther actions to be taken.

4. Cascina 26 Aug 2008 Weekly Meeting4 Procedure 1.Engraving and frame cleaning. 2.Vacuum compatibility inspection. 3.Cleaning of optical surface. 4.Inspection of optical surface. 5.Polariscope inspection. 6.Packing Window. 7.Update database.

5. Cascina 26 Aug 2008 Weekly Meeting5 Procedure Bench installed by Nicola & Rodolphe in the “locale lavagio”

6. Cascina 26 Aug 2008 Weekly Meeting6 Engraving & frame cleaning Each viewport engraved with an “EGO” reference number UXX = Uncoated HXX = Antireflection coating for HeNe YXX = Antireflection coating for YAG

7. Cascina 26 Aug 2008 Weekly Meeting7 Engraving & frame cleaning Grease and loose particles cleaned from metal frame “knife” inspected for vacuum compatibility

8. Cascina 26 Aug 2008 Weekly Meeting8 Cleaning of optical surface Blow off loose dust and particles with clean air

9. Cascina 26 Aug 2008 Weekly Meeting9 Cleaning of optical surface The bigger the optical the surface the harder it is to clean without leaving alcohol stains Revolutionary technique using turntable. Drag “wet” optical tissue from the center to the outer rim.

10. Cascina 26 Aug 2008 Weekly Meeting10 Inspection of optical surface Fiber illuminator reveals those stains not seen by conventional light sources

11. Cascina 26 Aug 2008 Weekly Meeting11 Inspection of optical surface What are we looking for? “micro-scratches” Glass Scratches Glass Pits Glass Mark Glass Bubble Glass chipping Coating scratches (coated windows only): Coating mark (coated windows only In red indicates a potential vacuum risk

12. Cascina 26 Aug 2008 Weekly Meeting12 Inspection of optical surface Take photos of most serious damage Glass Scratches

13. Cascina 26 Aug 2008 Weekly Meeting13 Inspection of optical surface Take photos of most serious damage Glass marks

14. Cascina 26 Aug 2008 Weekly Meeting14 Inspection of optical surface Take photos of most serious damage Glass bubbles

15. Cascina 26 Aug 2008 Weekly Meeting15 Inspection of optical surface Difficult to have an overview of window damage just from photos Make a map of all the damage for each side with a key code

16. Cascina 26 Aug 2008 Weekly Meeting16 Polariscope inspection Viewport placed between two crossed polarizers. If glass is stressed it becomes birefringent. We see light where there is stress Small areas with high stress can indicate defects in glass

17. Cascina 26 Aug 2008 Weekly Meeting17 Polariscope inspection Stress higher at edges Stress direction parallel to the edge of glass

18. Cascina 26 Aug 2008 Weekly Meeting18 Polariscope inspection Same viewport turned by 45 degrees

19. Cascina 26 Aug 2008 Weekly Meeting19 Packing window Remove dust Place in cover Wrap in cellophane

20. Cascina 26 Aug 2008 Weekly Meeting20 Update database Temporary location has been created: http://wwwcascina.virgo.infn.it/optics/viewport_inspection See Franco’s demonstration of definitive database

21. Cascina 26 Aug 2008 Weekly Meeting21 Results All 20 uncoated Larson viewports have been cleaned and inspected Vacuum inspection: No problems Optical inspection: Viewports arrive relatively dirty Many viewports have light scratches >10% have glass bubbles at the edge Almost all viewports have glass marks often near the center → Maybe dirt baked onto surface 10% have non-uniform interface between glass and rim However: inspection of existing viewports reveals similar defects. Polariscope inspection: No areas of high stress observed Conclusion Optical quality is not good. Almost all viewports do not show signs of having a vacuum risk.

22. Cascina 26 Aug 2008 Weekly Meeting22 Work to follow Contact Larson to see how they can improve their handling procedures Introduce selection process. For every 10 viewports: Choose 3 best → to be used in areas where good optical quality needed. Choose 3 worst → to be used areas where we don’t care. Any viewports that seem non-conform and could have a vacuum risk are put aside for closer inspection of destructive testing Due to viewports being very dirty on arrival, review cleaning procedures to minimize risk of scratching during cleaning.