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. 5:
Initial Alignment System
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 Initial Alignment System (IAS) 7
1.3 Definitions 7
1.4 Acronyms 7
1.5 Applicable Documents 9
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 Initial Alignment System Perspective 12
2.3 Product Functions 12
2.3.1 Initial Alignment System Functions 12
2.4 General Constraints 12
2.4.1 Initial Alignment System 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 Initial Alignment System Requirements 16
3.1.1 Introduction 16
3.1.2 Initial Alignment System Characteristics 16
3.1.2.1 Initial Alignment System Performance Characteristics 16
3.1.2.2 Initial Alignment System Physical Characteristics 17
3.1.2.3 Initial Alignment System Interface Definitions 18
3.1.2.4 Initial Alignment System Reliability 19
3.1.2.5 Initial Alignment System Maintainability 19
3.1.2.6 19
3.1.2.7 Initial Alignment System Environmental Conditions 19
3.1.2.8 Initial Alignment System Transportability 20
3.1.3 Initial Alignment System Design and Construction 21
3.1.3.1 Materials and Processes 21
3.1.3.2 Initial Alignment System Workmanship 22
3.1.3.3 Initial Alignment System Interchangeability 22
3.1.3.4 Initial Alignment System Safety 22
3.1.3.5 Initial Alignment System Human Engineering 22
3.1.4 Initial Alignment System Assembly and Maintenance 22
3.1.5 Initial Alignment System Documentation 23
3.1.5.1 Initial Alignment System Specifications 23
3.1.5.2 Initial Alignment System Design Documents 23
3.1.5.3 Initial Alignment System Engineering Drawings and Associated Lists 23
3.1.5.4 Initial Alignment System Technical Manuals and Procedures 23
3.1.5.5 Initial Alignment System Documentation Numbering 23
3.1.5.6 Initial Alignment System Test Plans and Procedures 24
3.1.6 Initial Alignment System Logistics 24
3.1.7 Initial Alignment System Precedence 24
3.1.8 Initial Alignment System 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
6.1.1 This section should contain information of a general or explanatory nature, and no requirements shall appear here. This could be such items as modeling data/results, R&D prototype information, 28
Appendices
Appendix A Quality Conformance Inspections 99
Table of Tables
Table 1 Environmental Performance Characteristics 19
Table 2 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.
The Initial Alignment subsystem will provide a means of positioning the LIGO-2 suspended core optics in global coordinates and provide angular alignment to within 10% of the core optics adjustment range. This will allow the operator to use the CDS control system to position the beam back upon itself and to switch to the ASC Alignment Sensing and Control system.
Initial Alignment will be similar to the LIGO-1 system with revisions to accommodate changes to suspensions, core optic materials, and the active seismic isolation system.
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 Initial Alignment System Perspective
The Initial Alignment system interfaces with Suspension design, Core Optic design, and all other AOS subsystems. The core optic provides reflectivity at 670 nm for the laser autocollimator to sense the return beam. The Suspensions system provides a means of measuring its position and the ability to make rough and fine linear and angular adjustments.
Initial Alignment is performed on each core optic individually. An AOS autocollimator operating at 980 nm is then used to verify the optical path thru a group of core optics.
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 Initial Alignment System Functions
The Initial Alignment system will provide the monuments, instrumentation, and procedures to position and align the final Input Optic and all Advanced LIGO core optics to within the positioning and angular alignment requirements.
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 Initial Alignment System Constraints
Initial Alignment is constrained by existing internal vacuum and external equipment, which requires setting up from an offset centerline and the use of various optical techniques, and auxiliary equipment to meet positioning and orientation requirements.
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 / ~0.001 / <0.0001 / <0.0001 / 0.0006 / 0.0006 / <0.0003
AR coating @ 940 nm / >0.4 / >0.4 / >0.4 / >0.4 / NA
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 / 265 / 265 / 350 / 314 / 314 / 314
Mirror thickness, mm / 100 / 100 / 60 / 130 / 130 / 130
Note: the mirror sizes and AR coatings are up to date from Gari’s COC table, July 15 2003. All else is inherited. Note FM is missing.
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.
The ground noise spectrum for the scattered light noise calculations is assumed to be the LIGO Composite Ground Noise Spectrum for frequencies between 10 and 1000 Hz, as described in figure 10, LIGO-T960065.