Advanced LIGO LIGO-T000092-02-D
LIGO Laboratory / LIGO Scientific Collaboration
LIGO-T000092-02-D ADVANCED LIGO 10/4/00
Auxiliary Optics Support System
Design Requirements Document, Vol. 3:
Pickoffs and Telescopes
Michael Smith, Michael Zucker, Ken Mason, Phil Willems
Distribution of this document:
LIGO Science Collaboration
This is an internal working note
of the LIGO Project.
California Institute of TechnologyLIGO Project – MS 18-34
1200 E. California Blvd.
Pasadena, CA 91125
Phone (626) 395-2129
Fax (626) 304-9834
E-mail: / Massachusetts Institute of Technology
LIGO Project – NW17-161
175 Albany St
Cambridge, MA 02139
Phone (617) 253-4824
Fax (617) 253-7014
E-mail:
LIGO Hanford Observatory
P.O. Box 1970
Mail Stop S9-02
Richland, WA 99352
Phone 509-372-8106
Fax 509-372-8137 / LIGO Livingston Observatory
P.O. Box 940
Livingston, LA 70754
Phone 225-686-3100
Fax 225-686-7189
http://www.ligo.caltech.edu/
Table of Contents
1 Introduction 7
1.1 Purpose 7
1.2 Scope 7
1.2.1 PO Mirror Assembly and Telescope 7
1.3 Definitions 7
1.4 Acronyms 7
1.5 Applicable Documents 8
1.5.1 LIGO Documents 9
1.5.2 Non-LIGO Documents 9
2 General description 10
2.1 Specification Tree 10
2.2 Product Perspective 10
2.2.1.1 Layout 11
2.2.2 PO Mirror Assembly and Telescope Perspective 12
2.3 Product Functions 12
2.3.1 PO Mirror Assembly and Telescope Functions 12
2.4 General Constraints 12
2.4.1 PO Mirror Assembly and Telescope Constraints 13
2.5 Assumptions and Dependencies 13
2.5.1 Core Optics Parameters 13
2.5.2 Interferometer Design Parameters 14
2.5.3 ISC Interface Characteristics 14
2.5.3.1 ISC Sensor Beam Parameters 14
2.5.4 Seismic Environment 15
3 Requirements 16
3.1 PO Mirror and Telescope Requirements 16
3.1.1 Introduction 16
3.1.2 PO Mirror and Telescope Characteristics 16
3.1.2.1 PO Mirror and Telescope Performance Characteristics 16
3.1.2.2 PO Mirror and Telescope Physical Characteristics 18
3.1.2.3 PO Mirror and Telescope Interface Definitions 20
3.1.2.4 PO Mirror and Telescope Reliability 21
3.1.2.5 PO Mirror and Telescope Maintainability 21
3.1.2.6 PO Mirror and Telescope Environmental Conditions 21
3.1.2.7 PO Mirror and Telescope Transportability 21
3.1.3 PO Mirror and Telescope Design and Construction 21
3.1.3.1 Materials and Processes 21
3.1.3.2 PO Mirror and Telescope Workmanship 22
3.1.3.3 PO Mirror and Telescope Interchangeability 22
3.1.3.4 PO Mirror and Telescope Safety 22
3.1.3.5 PO Mirror and Telescope Human Engineering 22
3.1.4 PO Mirror and Telescope Assembly and Maintenance 22
3.1.5 PO Mirror and Telescope Documentation 23
3.1.5.1 PO Mirror and Telescope Specifications 23
3.1.5.2 PO Mirror and Telescope Design Documents 23
3.1.5.3 PO Mirror and Telescope Engineering Drawings and Associated Lists 23
3.1.5.4 PO Mirror and Telescope Technical Manuals and Procedures 23
3.1.5.5 PO Mirror and Telescope Documentation Numbering 23
3.1.5.6 PO Mirror and Telescope Test Plans and Procedures 23
3.1.6 PO Mirror and Telescope Logistics 23
3.1.7 PO Mirror and Telescope Precedence 24
3.1.8 PO Mirror and Telescope Qualification 24
4 Quality Assurance Provisions 25
4.1 General 25
4.1.1 Responsibility for Tests 25
4.1.2 Special Tests 25
4.1.2.1 Engineering Tests 25
4.1.2.2 Reliability Testing 25
4.1.3 Configuration Management 25
4.2 Quality conformance inspections 25
4.2.1 Inspections 25
4.2.2 Analysis 26
4.2.3 Demonstration 26
4.2.4 Similarity 26
4.2.5 Test 26
5 Preparation for Delivery 27
5.1 Preparation 27
5.2 Packaging 27
5.3 Marking 27
6 Notes 28
Appendices
Appendix A Quality Conformance Inspections 99
Table of Tables
Table 16: Wavefront distortion of PO optical train 16
Table 17: Minimum Resonant Frequency of PO Mirror, ETM Telescope and APS/PO Telescope Mounted Next to a Multi-pendula COC 19
Table 23 Quality Conformance Inspections 28
Table of Figures
Figure 1: Overall LIGO detector requirement specification tree 10
Abstract
This technical note is being generated to provide a general outline to be followed for developing a Design Requirements Document (DRD) for the LIGO Detector Group. The following pages provide the outline, including section/paragraph numbering and headings, along with a brief explanation (and some examples) of what is to go into each paragraph.
The basis for the following outline is a combination of the IEEE guide for software requirement documentation and the MIL-STD-490A guide to requirement specification. Sections 1 and 2 particularly follow the IEEE standard. The remaining sections are more in line with the MIL-STD format, with some extras or variations that I’ve found useful in the past.
This document is a MicroSoft Word template. All instructions (guidelines and examples) in this document are in normal text, and should be deleted when an individual DRD is written. This document also shows “boilerplate” text, which should appear in every LIGO detector DRD. This boilerplate appears in this document as italic text and should not be removed from individual DRDs.
This section (Abstract) was purposely titled without using the LIGO tech document template ‘Header’ paragraph format, such that the Table of Contents of this document directly reflects the outline for a DRD.
1 Introduction
1.1 Purpose
The purpose of this document is to describe the design requirements for the Auxiliary Optics Support (AOS). Primary requirements are derived (“flowed-down”) from the LIGO principal science requirements. Secondary requirements, which govern Detector performance through interactions between AOS and other Detector subsystems, have been allocated by Detector Systems Engineering (see Figure 1.)
1.2 Scope
Identify the item to be produced by name, such as Alignment Sensing and Control.
Explain what the item will and, if necessary, will not do. An example of the latter, from the CDS document is: CDS specifically does not provide: 1) Personnel safety system 2) Facilities Control System 3) etc. The point is to emphasize to reviewers what the system will not do where there may be some doubt or uncertainty.
Describe the objectives, goals of the item development.
1.2.1 PO Mirror Assembly and Telescope
The PO Mirror Assembly and Telescope subsystem will generate optical pick-off (PO) beams from core optical elements and deliver those beams with a specified beam waist and location outside the vacuum housing for use by the LSC/ASC in the feedback control of the interferometer (IFO) alignment and length, and for monitoring purposes. These PO beams include the following: BS PO, ITMx PO, ITMy PO, ETMx transmitted beams, ETMy transmitted beams, and APS beam.
The PO Mirror Assembly and Telescope subsystem will provide viewport windows for the following beams: input PSL beam, SPS beam, Input Modecleaner ASC beam, and the PSL Intensity stabilization beam; it does not include other optical pick-off beams within the IO or PSL systems.
1.3 Definitions
Define all terms used in the document as necessary to interpret its contents. For example, a CDS specification may make use of terminology, such as “real-time software”, which is subject to interpretation. This section should specifically define what “real-time software” means in the context of this document.
NOTE: This should include all standard names used in interface discussions/drawings.
1.4 Acronyms
List all acronyms and abbreviations used in the document.
LIGO - Laser Interferometer Gravity Wave Observatory
COS - Core Optics Support
IOO - Input Optics
DRD - Design Requirements Document
SRD - Science Requirements Document
RM - Recycling Mirror
BS - Beam Splitter
ITMx, ITMy - Input Test Mass in the interferometer ‘X’ or ‘Y’ arm
ETMx, ETMy - End Test Mass in the interferometer ‘X’ or ‘Y’ arm
AR - Antireflection Coating
HR - Reflective mirror coating
GBAR - Ghost Beam from AR side of COC
GBHR - Ghost Beam from HR side of COC
PO - Pick-off Beam
vh - Vacuum housing
SEI - Seismic Isolation subsystem
SUS - Suspension subsystem
ppm - parts per million
ISC- Interferometer Sensing and Control
LSC - Length Sensing and Control
COC - Core Optics Components
ASC - Alignment Sensing and Control
IFO - LIGO interferometer
HAM - Horizontal Access Module
BSC - Beam Splitter Chamber
BRDF - Bi-directional Reflectance Distribution Function
TBD - To Be Determined
APS - anti-symmetric port signal
SPS - symmetric port signal
rms - root-mean-square
p-v, peak to valley
1.5 Applicable Documents
List all documents referenced. Include only those expressly mentioned within this document.
1.5.1 LIGO Documents
Core Optics Support Design Requirements Document lIGO-T970071-03-D
Core Optics Components DRD: LIGO-Exxx
ISC Reference Design
Seismic Isolation DRD, LIGO-T960065-02-D
Locally Damped Test Mass Motion, LIGO-T970092-00-D
Advanced LIGO Detector Design Requirements Document: LIGO-Exxx
Core Optics Support Conceptual Design, LIGO-T970072-00-D
COS Beam Dump and Stray Light Baffle Revised Req. and Concepts LIGO-T980103-00-D
Up-conversion of Scattered Light Phase Noise from Large Amplitude Motions, LIGO-T980101-00D
Effect of PO Telescope Aberrations on Wavefront Sensor Performance, LIGO-T980007-00-D
LIGO Vacuum Compatibility, Cleaning Methods and Procedures, LIGO-E960022-00-D
ASC Optical Lever Design Requirement Document, LIGO-T950106-01-D
LIGO-E000007-00
LIGO Naming Convention (LIGO-E950111-A-E)
LIGO Project System Safety Management Plan LIGO-M950046-F
LIGO EMI Control Plan and Procedures (LIGO-E960036)
Derivation of CDS Rack Acoustic Noise Specifications, LIGO-T960083
Specification Guidance for Seismic Component Cleaning, Baking, and Shipping Preparation (LIGO-L970061-00-D)
COS Preliminary Design T980010-01-D
1.5.2 Non-LIGO Documents
2 General description
This section (Section 2) should describe the general factors that affect the product and its requirements. This section does not state specific requirements; it only makes those requirements easier to understand.
2.1 Specification Tree
This document is part of an overall LIGO detector requirement specification tree. This particular document is highlighted in the following figure.
2.2 Product Perspective
Figure 1: Overall LIGO detector requirement specification tree
2.2.1.1 Layout
A schematic layout of the detector assembly is shown in the figure following, indicating the physical relationship of the Stray Light Control subsystem elements to the rest of the detector system.
2.2.2 PO Mirror Assembly and Telescope Perspective
The PO Mirror Assembly and Telescope subsystem contains pick-off (PO) mirrors mounted to a BSC optical table for directing PO beams to the PO telescopes that are mounted on a HAM optical table. An APS telescope, also mounted on the HAM optical table, will receive the APS beam from the anti-symmetric port. Beam steering periscopes and steering mirrors will direct the output beams from the telescopes through the AOS viewports in the HAM chamber to the ISC system outside the vacuum.
2.3 Product Functions
This section should provide a summary of the functions that the specified item will perform. This should just be general statements, not the detail that will go into the requirements section (Section 3).
2.3.1 PO Mirror Assembly and Telescope Functions
Ghost beams from the ITMx, ITMy, and BS mirrors will be used as PO beams for sensing and control (ISC) of the COC mirrors. The PO beams will be directed by PO mirror assemblies into beam reducing telescopes and will be subsequently directed with steering mirrors through vacuum viewports to the ISC photodetectors.
The PO beams and APS beam will exit through the vacuum chamber to a specified location with a specified beam waist and a specified wavefront distortion.
2.4 General Constraints
This section should give a general description of any other items that will limit the designer’s options, such as general policies, design standards, interfaces, etc. This subsection should not be used to impose specific requirements or specific design constraints on the solution. This subsection should provide the reasons why certain specific requirements or design constraints are later specified as part of Section 3. A CDS example for the CDS PSL document might be:
The overall CDS system is being developed using VME based systems as the standard interface. Therefore, all I/O modules being developed for the PSL will be constrained to this format.
Another general example might be:
LIGO must operate continuously, therefore this subsystem must be designed with high reliability and low mean time to repair. (Note that this is a general statement, and the MTBF and MTTR will be exactly specified in Section 3).
2.4.1 PO Mirror Assembly and Telescope Constraints
The input beam diameter shall include the 100 ppm diameter of the main interferometer beam. The output beam diameter shall be the same as LIGO 1. See Core Optics Support Design Requirements Document lIGO-T970071-03-D
2.5 Assumptions and Dependencies
This section should list factors that affect the requirements i.e. certain assumptions have been made in the writing of the requirements, and, if these change, then the requirements will have to be changed. For example, it is assumed that green light wavelengths will be used as the basis for optics requirements. If this is changed to infrared, then the requirements that follow will need to change.
2.5.1 Core Optics Parameters
See Core Optics Components DRD: LIGO-Exxx
Physical Quantity / RM / SM / BS / ITMx / ITMy / ETMAR coating @ 1060 nm / <0.0005 / <0.0005 / <0.0005 / <0.0005 / <0.0005
AR coating @ 940 nm / >0.4 / >0.4 / >0.4 / >0.4 / NA
substrate thickness, cm / 10 / 4 / 10 / 10 / 10
Mirror power loss fraction / 0.00005 / 0.00005 / 0.00005
mirror reflectivity @ 1060 nm / 0.97 / 0.5 / 0.995 / 0.995 / 0.99994
mirror reflectivity @ 940 nm / >0.4 / >0.4 / >0.4 / >0.4 / >0.4
mirror reflectivity @ 670 nm / >0.04 / >0.04 / >0.04 / >0.04 / >0.04
refractive index @ 1064 nm / 1.44963 / 1.44963 / 1.7546 / 1.7546 / 1.7546
100ppm power contour radius, mm / 116 / 116 / 116 / 116 / 116
1ppm power contour radius, mm / 142 / 142 / 142 / 142 / 142
beam radius parameter w, mm / 54 / 54 / 54 / 54 / 54
Mirror diameter, mm / 280 / 280 / 280 / 280 / 280
Mirror thickness, mm / 120 / 120 / 120 / 120 / 120
2.5.2 Interferometer Design Parameters
The stray light calculations were based on the following assumed parameters:
Laser input power / 125 wattsSPS power / 2.5 watts
APS power / 1.0 Watt
IFO Gaussian beam radius, w / 54 mm
Recycling cavity gain / 16.8
Arm cavity gain / 789
2.5.3 ISC Interface Characteristics
2.5.3.1 ISC Sensor Beam Parameters
The COS PO beam characteristics will be compatible with the ISC design. ISC Reference Design:______? The beam characteristics at the exit of the HAM viewport are as follows:
Physical Quantity / CharacteristicOutput PO beam aperture: APS, BS, ITM / 20 mm
Output PO beam aperture: ETM / 20 mm
wavefront distortion / < 0.7 wave p-v
beam waist position / TBD
Gaussian beam radius parameter / w = 4.2 mm
beam height / Centered on the viewport
beam orientation / nominally horizontal
beam polarization / horizontal (TBD)
2.5.4 Seismic Environment
The scattered light noise calculations in this document are based on the assumption that the rms velocity of scattering surfaces is sufficiently low so that up-conversion of large amplitude low frequency motion does not produce in-band phase noise. This is true for the vacuum housing and is also true of the SEI platforms for stack Q’s less than 1000. See Seismic Isolation DRD, LIGO-T960065-02-D, and Locally Damped Test Mass Motion, LIGO-T970092-00-D.