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Science and metrology windows specification release 1.doc

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MRO Delay Line

Specification of the Science and Metrology Windows for the MROI Delay Lines
INT-406-TSP-0004

The Cambridge Delay Line Team

rev 1.1 20 April 2010

Cavendish Laboratory JJ Thomson Avenue Cambridge CB3 0HE UK


Change Record
Revision Date Author(s) Changes 0.1 2009-05-27 MF Initial draft 0.2 2010-01-26 MF Corrections Revised wave-front spec to be on transmitted beam rather than surfaces because Infrasil 301 can still have significant 0.3 2010-02-25 MF refractive index variations. Placed parallelism spec on metrology windows Revised science window transmitted wave-front spec to 1.0 2010-03-18 MF 1/10th wave to be consistent with optical budget. Revised metrology window parallelism to 1 arc-minute. Added words to section 3.1 and a clear aperture of 40mm to 1.1 2010-04-20 MF the metrology window specifications.

Objective
To present the manufacturing specifications for the science and metrology windows for the MROI delay lines.

Scope
The specifications produced are for the science window and the two metrology windows of the delay line. The science window specification also covers the windows that would be introduced to preserve the vacuum when the removable section of the beam relay pipe is not installed. The science window specification also covers the window at the telescope end of the beam relay pipe.

Reference Documents
RD1 Top Level Requirements INT-406-TSP-0002 RD2 MROI Delay Line Derived requirements INT-406-VEN-0107 RD3 Draft window specifications for the MROI delay lines RD4 Internal memo on parallelism requirement of science windows

Applicable Documents
AD1 Drawing of science window AD2 Drawing of metrology window

Acronyms and Abbreviations
BCA BCF BRS DL DLA ICD ICS Beam Combining Area Beam Combining Facility Beam Relay System Delay Line Delay Line Area Interface Control Document Interferometer Control System (now SCS) Interferometer MRAO Mullard Radio Astronomy Observatory NMT New Mexico Tech OPD SCS TBC TBD Optical Path Delay Supervisory Control System To be confirmed To be determined

MROI Magdelena Ridge Observatory


Science and metrology windows specification release 1.doc

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Table of Contents
Introduction .................................................................................................................................. Science Window .......................................................................................................................... 2.1 Science Window Requirements ........................................................................................... 2.2 Science Window Specifications ........................................................................................... 2.2.1 Dimensions .................................................................................................................. 2.2.2 Optical quality .............................................................................................................. 2.2.3 Material ........................................................................................................................ 2.2.4 Coating ......................................................................................................................... 2.2.5 Suitable suppliers ......................................................................................................... 3 Metrology Window ...................................................................................................................... 3.1 Metrology window requirements ......................................................................................... 3.2 Metrology Window Specifications ...................................................................................... 3.2.1 Dimensions .................................................................................................................. 3.2.2 Optical quality .............................................................................................................. 3.2.3 Material ........................................................................................................................ 3.2.4 Coating ......................................................................................................................... 3.2.5 Suitable suppliers ......................................................................................................... Suppliers ...................................................................................................................................... 4 1 2 4 4 4 4 4 4 4 4 4 5 5 5 5 5 5 5 5 5


Science and metrology windows specification release 1.doc

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Introduction

The science and metrology windows have differing requirements but are present here in one document. The science window is approximately 150mm in diameter and the metrology window is approximately 50mm in diameter. Both are subject to vacuum on one side and atmospheric pressure on the other. The science window must operate over a wide waveband while the metrology window need only operate at the laser wavelength and therefore the coatings are quite different. The science window specification is also suitable for the beam relay windows.

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2.1

Science Window
Science Window Requirements

The requirements of the science window and the justification for most of the design parameters are presented in RD3. The requirement on parallelism of the window is set out in RD4 and further requirements are specified in RD2. An additional requirement is placed on the tolerance of the thickness of the window in order to achieve a suitable vacuum seal from a single O-ring design. Although for reasons of longitudinal dispersion the windows should be matched to 0.5mm in thickness, the mechanical design of the window holder requires a tolerance of ±0.1mm to be adhered to. Note that normally just two science windows would be used giving a total of 30mm in thickness but at times a further two windows would be introduced, doubling this thickness, when a section of beam relay pipe is removed.

2.2

Science Window Specifications

The following subsections list the detailed manufacturing specifications for the science windows.

2.2.1 Dimensions Circular with diameter 150mm ±0.25mm Clear aperture required: 140mm Thickness 15mm ±0.1mm Chamfer 1mm at 45° both edges 2.2.2 Optical quality Transmitted wave-front quality: lambda/10 (633nm, peak-valley) over any 125mm diameter patch within the clear aperture. Surface quality: 40-20 scratch dig, or better Surface parallelism: 10 arc-seconds Sub-surface damage: consistent with surface quality and safety for operation as a vacuum window. 2.2.3 Material INFRASIL 301 2.2.4 Coating No coating 2.2.5 Suitable suppliers
ICOS, OSL (see section 4)


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3.1

Metrology Window
Metrology window requirements

Other than the specifications given below there are no particular requirements on the metrology windows. The tolerance on the thickness specification arises out of the design of the holder and vacuum seal rather than any optical considerations. It is intended that catalogue listed windows should be able to fulfil the requirements and the dimensions were chosen to suit this.

3.2

Metrology Window Specifications

3.2.1 Dimensions Circular with diameter 50mm ±0.2mm Clear aperture required: 40mm Thickness 10mm ±0.1mm Chamfer 0.5mm at 45° both edges unless stock item 3.2.2 Optical quality Surface figure: lambda/10 or better for each face Surface quality: 60-40 scratch dig, or better Surface parallelism: 1 arc-minute or better 3.2.3 Material
BK7 or fused silica

3.2.4 Coating
MgF2 ј wave at 633nm

3.2.5 Suitable suppliers
Melles-Griot

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Suppliers

IC Optical Systems Ltd 190-192 Ravenscroft Road Beckenham Kent BR3 4TW United Kingdom
Optical Surfaces Limited Godstone Road Kenley Surrey CR8 5AA ENGLAND