| Name: | Mahesh Dalavi |
| Affiliation: | India TMT Coordination Centre & Indian Institute of Astrophysics. |
| Conference ID : | ASI2024_915 |
| Title : | Nanometric Coating Thickness Measurement using Form Talysurf instrument for TMT Edge Sensors. |
| Authors : | Mahesh Dalavi, Debanjan Mandal, Dr. Prasanna Deshmukh. |
| Authors Affiliation: | Mahesh Dalavi, Debanjan Mandal, Dr. Prasanna Deshmukh.(India TMT Coordination Centre & Indian Institute of Astrophysics, Bengaluru) |
| Mode of Presentation: | Poster |
| Abstract Category : | Facilities, Technologies and Data science |
| Abstract : | India is responsible for the supply of 3284 edge sensors to the Thirty Meter Telescope which plays a crucial role in detecting the misalignment between the 492 hexagonal mirror segments arranged in 6 sectors to form a hyperboloid primary mirror altogether. Each edge sensor has one drive and one sense block. These edge sensor blocks are manufactured using the Ohara Clearseram ZHS glass and are coated with the base chromium layer and top gold layer. The allowable thickness for the chromium layer is 30 nm to 50 nm and 450 nm to 550 nm for the gold layer. These coatings on the edge sensors are done using the physical vapor deposition (PVD) technique. Achieving the nanometric level coating thickness is one of the crucial tasks. The measurement of this coating can be done using various techniques such as XRF, Ellipsometry, Phase measure microscope, etc. which are very costly methods and have limitations with substrate type and form. In the developmental stages where multiple trial and iterations are required to be done to achieve the coating thickness, multiple measurement of each trial needs to be done. ITCC has come up with an alternative method to check the nanometric coating thickness using the Form Talysurf roughness tester instrument. Using this process Talysurf parameters are controlled at specified values and multiple data points on coated and non-coated regions are collected. Using our custom analysis tool, the difference between the average of the coated and uncoated region can be derived which results in the coating thickness. In this poster, we will present our application, methodology, test, and validation results.
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