INTERFEROMETER LASER GRAVITATIONAL WAVE OBSERVATORY - LIGO CALIFORNIA INSTITUTE OF TECHNOLOGY MASSACHUSETTS INSTITUTE OF TECHNOLOGY
Specification
LIGO-E960022- B- E
03/13/2003
LIGO Vacuum Compatibility, Cleaning Methods and Qualification Procedures
LIGO Systems Engineering
This is an internal working note of the LIGO Project.
California Institute of Technology
LIGO Project - MS 51-33 Pasadena CA 91125 Phone [phone] Fax [phone] E-mail: [e-mail]
Massachusetts Institute of Technology
LIGO Project - MS 20B-145 Cambridge, MA 01239 Phone [phone] Fax [phone] E-mail: [e-mail]
CHANGE RECORD
Revision
A B
Date
28 January 2000 13 March 2003
Authority
Initial Release DCN E030125
Pages Affected
All All
Item(s) Affected
All All
Organization/Group
System Engineering and Chair, LIGO Vacuum Review Board
Name
Albert Lazzarini Fred Raab David Shoemaker
Signature
Date
LIGO Vacuum Review Board Rainer Weiss John Worden Project Manager Gary Sanders
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TABLE OF CONTENTS
Nomenclature and Acronyms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1. Scope 1.1 1.2 1.3 ............................................................6
Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Content .................................................... 6 Vacuum Review Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2. Applicable Documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3. Vacuum Compatible Material Usage in LIGO. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.1 3.2 4.1 4.2 Material Approval Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Component Qualification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Commercially Produced Components. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Internally Produced Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4. Cleaning and Preparation of Materials Procedures . . . . . . . . . . . . . . . . . . . . . . . 9
5. Handling and Storage Procedures
6. Qualification and Screening Tests for Materials and Components. . . . . . . . . . . 11 Initial Qualification & Screening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 6.1.1 High Power Exposure Tests of Cavity Mirrors. . . . . . . . . . . . . . . . . . . . . . . 12 6.1.2 Outgassing Screening Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 6.1.2.1 Bake Out . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 6.1.2.1.1 Vacuum Bake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 6.1.2.1.2 Air Bake. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 6.1.2.2 Residual Gas Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 6.2 QA Screening . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Appendix A Appendix B Appendix C Cleaning and Baking Procedures for Approved and Provisionally Approved Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Cleaning and Baking Procedures for Approved Sub-Assemblies . . . . . 20 Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 C1: Parts Cleaning Request. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 C2: LIGO Vacuum Bake Oven Procedure and Check List. . . . . . . . . . . 24 Appendix D Calculation of Vacuum Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 6.1
LIST OF FIGURES
Figure 1: Figure 2: Figure 3: Figure 4: Figure 5: Exposure Test Setup. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12 Typical Vacuum Bake Test Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Geometrical arrangement of source, mirror, and pumping system. . . . . . . . 27 Schematic for the calculation. .. . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . .31 Relation between the surface coverage and the equilibrium pressure for the Dubinin-Radushkevich theory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
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LIST OF TABLES
Table 1: Table 2: Table 3: Table 4: Table 5: Applicable Documents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Parameters for estimating contaminant buildup on LIGO optics. . . . . . . . . 26 Physical Constants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Typical values for water on hot rolled 304L stainless steel. . . . . . . . . . . . . . 32 Sample parameters leading to 200 day equilibration time. . . . . . . . . . . . . . .32
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NOMENCLATURE AND ACRONYMS
ADP AMU CO2 DI FDR HC HF JPL KDP LIGO LOS OFHC NEO PFA PTFE PZT RGA RTV SEI TBD UHV Ammonium Di-hydrogen Phosphate [(NH4)H2 PO4] Atomic Mass Unit Carbon Dioxide Deionized Water Final Design Review Hydrocarbons Hydrofluoric acid Jet Propulsion Laboratory Potassium Di-hydrogen Phosphate [KH2PO4] Laser Interferometer Gravitational Wave Observatory Large Optics Suspension Oxygen Free High-Conductivity Copper Neodymium Iron Boron Perfluoroalkoxy fluoropolymer (Du Pont) Polytetrafluorethylene (Du Pont) Lead-Zircomate-Titanate Residual Gas Analyzer Room Temperature Vulcanizing Silicone Elastomer Seismic Isolation System To Be Determined Ultra High Vacuum
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1.
SCOPE
1.1 Purpose
The goal of this document is to provide reasonable assurance against the inadvertent introduction into the LIGO vacuum envelope of material which could contaminate optics and/or produce excess phase noise by forward scattering. This document sets forth certain procedures and standards by which material to be used in LIGO interferometers may be qualified and assayed for compatibility in operation with high-power resonant cavities inside an ultra-high vacuum (UHV) system. All items to be installed inside LIGO vacuum equipment or onto beam tube pump ports shall conform to this policy for selection of components and exposed materials, for preparation, handling, testing and storage prior to assembly and during assembly. These items are considered Class A hardware. For definition of Class A hardware, refer to LIGO-M990034 (Section 5). It is intended that the total optical contamination produced by detector components placed into the LIGO vacuum envelope shall be limited to < 0.5 ppm/yr/optic absorption and < 10 ppm/yr/ optic scatter.
1.2 Content
All materials/parts (commercial and custom designed) must undergo vacuum outgassing and contamination evaluation to ensure compatibility with operation in high-power laser cavities within UHV systems. Certain materials needed to fabricate LIGO interferometers, although used in other UHV applications, need to be evaluated for possible deleterious effects which their outgassing products may produce on high reflectivity mirrors while these mirrors are under laser irradiation at power levels of tens of kW. A determination of the rate of increase of optical losses by exposure of test cavity mirrors to substances in question shall be the basis for vacuum qualification whenever possible for such substances. It is also necessary to ensure proper cleaning of components fabricated from acceptable materials. Cleaning of LIGO components shall be performed in accordance with recognized and accepted cleaning practices. Some of these cleaning procedures are generic and baking will be carried out generally at the maximum temperature permissible for a given material: other procedures have been developed to handle specialized or oversized components that could otherwise not be cleaned.
1.3 Vacuum Review Board
Outgassing data and, whenever possible or necessary, optical loss data of materials/parts shall be submitted to the Vacuum Review Board for review and acceptance. The Vacuum Review Board must approve tested materials/parts before they may be included in the LIGO vacuum
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compatible materials approved list (E960050). The Vacuum Review Board members are selected by the Systems Engineering and the Detector Systems group management. The Vacuum Review Board will recommend the disposition of issues where policy and schedule are in conflict. This document will be updated as irradiance exposure data become available.
2.
Applicable Documents
The documents cited in Table 1 have been used to develop some of these guidelines and serve as reference material.
Table 1: Applicable Documents
Document Title
LIGO Project Management Plan LIGO Project System Safety Plan LIGO Project QA Plan LIGO Configuration Management Plan LIGO Vacuum Compatible Materials List Stanford Synchrotron Radiation Project User Specifications for Vacuum Systems and Components which Interface with the SPEAR Vacuum System Detail Specification for General Cleaning Requirements for Spacecraft Propulsion Systems and Support Equipment LIGO Seismic Isolation System: Fabrication Process Specification Material, Process, Handling and Shipping Specification for Fluorel Parts Material, Process, Handling and Shipping Specification for Welded Diaphragm Bellows Material, Process, Handling and Shipping Specification for Damped Coil Springs Specification for the LIGO Bakeout Ovens Small Optics Cleaning Procedures Large Optics and COC Cleaning Procedures Cleaning Procedures for LIGO Commercial Optics (Other Than Core or IO Optics) Process Specification: CO2 Cleaning Procedures Cleaning and Baking Viewports LIGO Hanford Observatory Contamination Control Plan Viton Spring Seat Vacuum Bake Qualification Outgassing Documents from 1988-1992
ID Number
LIGO-M950001 LIGO-M950046 LIGO-M970076 LIGO-M950005 LIGO-E960050 LIGO-E870001 LIGO-E740001 LIGO-E970063 LIGO-E970130 LIGO-E970129 LIGO-E970131 LIGO-T980008 LIGO-E990034 LIGO-E990035 LIGO-E000007 LIGO-E990316 LIGO-E990190 LIGO-M990034 LIGO-T970168 LIGO-T920009
3.
Vacuum Compatible Material Usage in LIGO
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3.1 Material Approval Process
LIGO maintains an updated list of materials considered safe to use in LIGO vacuum systems. This approved list is LIGO-E960050. New material must go through the prescribed screening process before it may be added to this list. The screening process is described in Section 6 of this document. The vacuum data of the tested materials/parts will be compared to the LIGO vacuum outgassing and contamination requirements before being included in the LIGO vacuum compatible materials approved list. In cases where any of the cleaning procedures cannot be followed due to considerations such as material durability or sensitivity to elevated temperatures, a waiver shall be completed and submitted to the Vacuum Review Board for consideration and approval. The waiver shall be accompanied by an alternative preparation procedure which has been demonstrated to achieve the desired cleaning effects.
3.2 Component Qualification
A component or subassembly is itself considered approved if all its exposed materials are approved and if its pre-installation treatment is consistent with the preparation procedures for those materials. All blind holes and trapped volumes shall be explicitly vented to avoid virtual leaks; provision for cleaning such volumes adequately (e.g., by solvent flushing) shall also be considered in the design process. A material is considered "exposed" unless it is encapsulated fully and hermetically within another material. All designs using hermetic containment must be approved specifically by the Vacuum Review Board. Components composed of materials from a single class are to be prepared, handled and stored according to the corresponding procedure for that class. Irreducible subassemblies comprising more than one material class are to be prepared and handled according to the most stringent subset of procedures consistent with all materials involved. A Qualification and Screening Test Report must be written for the candidate material/ component after completion of tests. This report must include the amounts of materials, outgassing rates (approved or not), residual gas analyses and RGA scan data, molecular species that is outgassed, amount of hydrocarbons outgassing, and surface contamination information if available. A material usage list must be compiled for every subassembly or component that is placed in the vacuum and be included in the report. This information shall be available by the FDR of the subject system or subsystem. The material usage list for each assembly shall be updated to maintain it current. The Qualification and Screening Test Report and associated raw data (e.g., RGA scans) shall be processed as follows:
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o o o
File original with the LIGO QA Officer. Submit a copy to the requester of the qualification tests. Submit a copy to the LIGO Document Control Center.
4.
Cleaning and Preparation of Materials Procedures
All materials/parts (both commercial and LIGO-produced) must be scrutinized for vacuum cleanliness compatibility before being accepted for utilization with the LIGO vacuum system.
4.1 Commercially Produced Components
If a vendor is required to provide clean components, then the vendor shall use recognized UHV practices. The vendor shall submit to LIGO a description of the practices for prior approval by LIGO as part of the quote or proposal for the work in accordance with the procurement process. For commercially produced components with potentially many materials used in the construction, a detailed accounting of all materials and the amounts used shall be submitted for review. It may be necessary for some components to require certifications (per article or serial number) for the materials employed in their manufacture, so that material substitutions by the manufacturer are visible to LIGO. The vendor shall notify LIGO of any material substitutions which occur after the agreed-upon list of materials has been determined. LIGO QA shall have oversight to ensure such notification is obtained. Where practicable, a first article screening using an RGA scan and outgassing measurement shall be performed by LIGO prior to receiving shipment of all other components.
4.2 Internally Produced Components
LIGO shall clean in accordance with documented procedures all components produced internally. Cleaning procedures shall be defined for all materials on the LIGO approved materials list. Present procedures are listed in Appendix A. These will be updated periodically. The LIGO approved materials list includes: Generic materials: Metals Ceramics and glasses Hard crystalline minerals, excluding electro-optical elements
Fabricated materials: LIGO optical components Composite Assemblies Commercially purchased mechanical assemblies Electronic Components Suspension Sensor/Actuator Head assemblies
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There are also provisionally approved materials b eing used in prototype interferometers. It is permissible to incorporate provisionally accepted materials in LIGO interferometer designs; however before the designs may be actually implemented, promotion of their constituent materials to the accepted materials list must be performed in accordance with the procedures set forth in this document. Provisionally approved materials list includes: Silicone rubber (see notes in Appendix A, item F) Solder, lead/tin (Kester 6337) (see also Appendix A, item H) Sm-Co permanent magnets PZT piezoelectric ceramics Hygroscopic crystalline optics
5.
Handling and Storage Procedures
Latex1 gloves are to be worn for handling, assembly and installation of cleaned or partially cleaned parts. Unless otherwise indicated, gloves a to be changed when proceeding to re handle components at different stages of processing. Tools and fixtures which may contact cleaned parts in assembly or transport are to be cleaned and baked as Class B material. (See Class B processing procedure, Appendix A, Section 3.) Processed parts awaiting installation or further assembly will be triple wrapped for storage or shipping as follows: (a) Wrap the part(s) with UHV quality aluminum foil. (b) Place each part(s) in an anti-static bag fabricated from Ameristat poly sheet and cleaned to Class 100. (c) Compress the bag tightly around the part(s) to purge excess air. Tie wrap the bag for closure, or use a bag with a zipper. (d) Two labels must be used on the outer layer of all bagged components: (i) a warning label stating: "UHV CLEAN PART -- HANDLE ONLY WITH PROPERLY GLOVED HANDS" and (ii) an identification label. If the labels are not self-adhesive, then they shall be affixed with tape. All empty fields on the ID label shall be filled in with the relevant information; use "N/A" rather than leaving a field blank. (e) Place the part(s) in a second anti-static polyethylene bag, as specified above, remove excess air, and heat seal or tape shut, making sure both labels are visible. (f) Place the double bagged part(s) in an appropriate shipping container, using care to not puncture or cut the bags. Seal the shipping container closed. Attach a label with the LIGO
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Latex gloves from Ansell Edmont (AccuTech-Ultra Clean 91-300)
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part number (drawing number(s), including revision letter) and serial number(s) to the outside of the container. The shipping containers must be such that they insure that the double bags do not get punctured and that the parts are properly supported during transit. For a list of approved contamination supplies and vendors refer to LIGO-M990034, Appendix 1. Small parts may also be stored in stainless steel or glass containers which are cleaned and prepared in the same way as vacuum equipment. Tables and work areas for cleaning, packing/unpacking, assembly, alignment and testing of cleaned parts are to be lined or covered with fresh contamination-free foil or Ameristat immediately before starting work. Ameristat shall not be used if a solvent incompatible with the film is involved in the assembly or cleaning process. Final assembly of any small subassembly or component intended for installation in LIGO shall be assembled under a Class 100 laminar flow bench. Assemblies too large for handling on laminar flow benches shall be unwrapped and assembled in portable clean rooms assembled around open chambers.
6. Qualification and Screening Tests for Materials and Components
Tracking and control of material usage in LIGO has two aspects: Initial determination that a particular material (or component assembly if it cannot be disassembled) is benign with regard to its effect on optical surfaces and interferometer excess phase noise caused by forward scattering. This shall be done by exposing mirror surfaces in test resonant cavities with resonant optical power representative of the worst-case LIGO irradiances. A corroborating RGA scan of the material, whenever possible, shall be recorded in order to develop a database containing both optical effects and related outgassing measurements. QA screening of components fabricated from approved materials. The basis of such screening shall be the measurement of hydrocarbon outgassing of the subject components using RGA scans after appropriate vacuum preparation. The RGA levels for a pre-determined and specified group of species masses which represent hydrocarbon fragments shall be compared to those obtained in the material qualification step. Excess RGA levels shall indicate inadequate cleaning and preparation of the component under test. Reliance on RGA scans for screening is required to provide a faster process to accommodate fabrication schedules.
6.1 Initial Qualification & Screening
All candidate materials must satisfy the criterion of screening and qualification testing before being considered for addition to the vacuum compatible "approved" or "provisionally approved" list. The distinction between approved and provisionally approved materials lies at present with
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lack of definitive data for provisional materials about their behavior in mirror cavities at LIGO irradiance levels. The high power exposure (qualification) test of cavity mirrors and screening test are described in detail in the following paragraphs. Materials which are intrinsically free of organic compounds (after suitable cleaning) may be excluded from laser cavity testing.
6.1.1
High Power Exposure Tests of Cavity Mirrors
The purpose of the exposure test is to evaluate the candidate material for optical contamination potential under high laser power in the presence of high reflectance mirrors. Outgassing can lead to contamination of the optics with the result of increased optical losses and ultimately failure due to heating. The amount of outgassing is less important than the molecular species that is outgassed. There are two test procedures in the exposure test, which are briefly described below; a complete procedure shall be developed. Efforts to date have been directed at developing comparison tests between empty cavities and cavities exposed to candidate materials. A typical cavity setup is shown in Figure 1.
Figure 1: Exposure Test Setup
MIRRORS VACUUM ENCLOSURE LASER
TO ION PUMP QUARTZ SPACER TEST SAMPLE MATERIAL [one of either location used]
The qualification procedure includes the following steps: Vacuum bake candidate materials according to the procedure for that material, then cool and take an RGA scan to quantify the outgassing. The scan must be calibrated against one or more standard leaks. Run an optical exposure test at > 150 kW/cm2 in a resonant cavity to qualify material at the level of optical losses discussed in Section 1.1. The run shall be the shorter of 2 months or when a measurable effect is observed.
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If the candidate material is deemed safe for incorporation into LIGO designs, then subsequent components made of this material shall be screened in the manner described below.
6.1.2
Outgassing Screening Tests
There are two steps of the screening test: (1) a bakeout for driving volatile substances (HCs) off the component; and (2) a residual gas analysis (RGA). 6.1.2.1 Bakeout
The default bakeout procedure shall be conducted under vacuum. With large components, which it may not be feasible to bake under vacuum, an air bake will be considered acceptable providing cautions are taken to preclude contamination from the ambient air. All bakes shall be performed in LIGO-approved ovens; these may be located at vendors. 6.1.2.1.1 Vacuum Bake Vacuum baking of the candidate component/material is performed to obtain hydrocarbon and other outgassing data information. The typical vacuum bake test setup is shown in Figure 2. Typical testing procedures are: Prepare a sample of candidate component/material to be tested. Prepare a "Parts Cleaning Request" form (see Appendix C, Form C1), as an example, for Caltech specific vacuum preparation. Follow the cleaning methods and handling procedures in Sec tions 4 and 5 above according to the type of material, and indicate the procedures on the form. Prepare a "LIGO Vacuum Bake Oven Procedure and Check List" (see Appendix C, Form C2). Provide the component/material baking time and temperature and any requirements for temperature ramptime or soaktime. Baking temperatures shall follow written procedures discussed in Sections 4 and 5. Perform a system calibration according to the defined procedure. Perform a vacuum bake of candidate component/material.
At the end of the vacuum bake period, obtain a record of the partial pressures of suspect HC masses to document results.
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Figure 2: Typical Vacuum Bake Test Set
6.1.2.1.2 Air Bake The air bake procedure for large in-vacuum components which cannot be handled otherwise is set forth in E970063, LIGO Seismic Isolation System: Fabrication Process Specification. It applies to all similar components in LIGO. 6.1.2.2 Residual Gas Analysis
Cleaning and baking of components/materials must be followed by a residual gas analysis. This analysis shall be performed and documented according to LIGO defined procedures.
6.2 QA Screening
All components fabricated from approved materials and which are intended for installation into the LIGO vacuum envelope shall be screened to ensure that proper preparation of the subject components has been achieved. This screening follows the procedure outlined in Section 6.1.2, Outgassing Screening Tests. In cases where a large number of components are to be screened, it may be permissible to perform a statistical sampling of components instead of 100% testing. However in this case, it must be assured that the results of the screening test for the sampled article are determined to be acceptable before any intervening untested articles are integrated into LIGO. In this way a screening failure can be tracked to all potentially affected articles. The sampling frequency shall be submitted for approval by the Detector Engineer Cognizant to the Vacuum Review Board.
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In the event that a component fails the screening test, it must either be re-processed or if there are sufficient reasons, a request must be made of the Vacuum Review Board for a waiver. In the case of a screening test failure with statistical sample, it must be assumed that all intervening untested articles are also suspect and must thus be reprocessed unless it can be shown that the reason for failure is specific to the failed article.
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Appendix A - Cleaning and Baking Procedures for Approved and Provisionally Approved Materials
1. Approved Materials
These procedures are consistent with: 1) a materials bakeout at the maximum temperature possible; and, 2) achievement of the summed mass pressure limit. Any deviation from these procedures must be cleared with the Vacuum Review Board with an approved waiver. Ultrasonic cleaning shall be done in a unit comparable to the system presently in use at MIT. 2 A. Metals: For all small metal parts do the following: o Machine all sides. o Ultrasonic clean in Liquinox3 for 10 minutes. o Rinse in distilled water at least 3 times, changing the rinse water every time. o Ultrasonic clean in methanol for 10 minutes. Subsequent to the above steps bake the metal as follows: o Stainless Steel Bake in vacuum at 200 C for 48 hours. o Aluminum Bake in vacuum at 120 C for 48 hours. SEI damped springs shall be cleaned per the procedure outlined in E970131.
SEI large in-vacuum components shall be cleaned per the procedure outlined in E970063. NOTES: In the case of gross contaminants, the above may be proceeded by an acid bath (i.e., 3% Protex solution (diluted with distilled water) for aluminum or 2% Gosh solution for stainless steel), or an appropriate degreasing agent such as trichloroethane or acetone. Follow these steps with a DI water rinse. Then clean as in A. Stainless steel brushes and pads could be used. Cotton swabs, wetted with methanol, must be used after cleaning blind holes to test for cleanliness.
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Branson Ultrasonics Corp. (Tel: [phone]) Model 8210(latest model as of March, 1998: #8510) has a 5.5 gal. tank (19.5"x18"x6"). Transducer output is 320 watts @ 40khz. The tank can also be heated.
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Standard Liquinox solution is 1 tablespoon in 1 gallon of water.
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Solvents must be reagent grade. Methanol is the preferred solvent. Isopropanol and/or acetone may be substituted.
. B. Ceramics and Glasses: Clean off contaminants with Liquinox and water, be sure to rinse thoroughly. Ultrasonic clean in methanol for 10 minutes. Soak in isopropyl alcohol for 10 minutes, agitating regularly. Bake in a vacuum at 120 degrees C for 48 hours. C. LIGO optical components: Clean and bake LIGO core and IO optical components according to Process Specification E990034 and/or E990035. Clean LIGO optical components other than core or IO optics to Process Specification E000007. Clean installed optics utilizing a CO2 cleaning system according to Process Specification E990316. D. Fluorel - Viton: Seals and O-rings: o Wipe with clean, dry lens tissue or polywipe. o Bake in vacuum for 48 hours at 120 degrees C. At least 24 hours prior to installation, process all Fluorel or Viton seals and O-rings as follows: o Soak 10 minutes in DI water. o Dry with cleanroom wipes. o Place on a class 100 flowbench for 24 hours to dry. o Wrap for transport to the installation. Molded castings: o Follow procedure in LIGO-T970168. o Then, at least 24 hours prior to installation, process as in Fluorel-Viton above. o Wrap for transport to the installation. E. Teflon and PFA 440 HP Parts requiring high dimensional tolerances are not to be made of Teflon Cleaning of parts made of PFA 440 HP not requiring high dimensional tolerances: o Ultrasonic clean in acetone for 10 minutes. o Ultrasonic clean in methanol for 10 minutes. o Bake in vacuum at 120 C for 48 hours. F. NEO 35 - permanent magnets: Ultrasonic clean in methanol for 10 minutes. Bake in vacuum at 80 C for 48 hrs. When the magnets became part of a magnet/standoff assembly, after sanding, and prior to bonding, clean using a CO2 cleaning system (LIGO-E990316).
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2. Provisionally Approved Materials (3/1998)
A. Silicone rubber: Small pieces, less than 1.5 cm thick: o Soak in methylene chloride for 4 days, changing solvent every 24 hours. o Let air dry at room temperature (under fume hood) for 48 hours. o Bake in vacuum oven for 10 days at 200 Degrees C. Large pieces: Not allowed. NOTE: This material may be used in LIGO in isolated evacuated vessels which do not communicate directly with the LIGO vacuum envelope (e.g., low-power reference cavities). B. Solder: Lead-tin (Kester 6337) Same as metals, but flux is to be removed first by spraying Deflux solution. C. Perkin Elmer Vacseal: Ultrasonic clean in methanol for 10 minutes. Bake in vacuum at 80 C for 48 hrs. D. Sn-Co permanent magnets: Ultrasonic clean in methanol for 10 minutes. Bake in vacuum at 80 C for 24 hours. . E. PZT piezoelectric ceramics: Ultrasonic clean in methanol for 10 minutes. Bake in vacuum at 80 C for 24 hrs. F. Ryton: Ultrasonic clean in methanol for 10 minutes. Bake in vacuum at 120 C for 48 hrs. G. Hygroscopic crystalline optics: Spot clean mounting fixtures with toluene to remove shipping material residue; cleaning shall be under a fume hood. NOTE: DO NOT BAKE CRYSTAL NOTE: DO NOT LET SOLVENT CONTACT CRYSTALS; DO NOT EXPOSE CRYSTALS TO SOLVENT FUMES -- KEEP OPEN CONTAINERS OF SOLVENT AT LEAST 1m FROM CRYSTALS. KEEP CONTAINERS CLOSED WHENEVER POSSIBLE. H. Peek connectors/Kapton cabling/wire harnesses: Ultrasonic clean in methanol for 10 minutes. Bake in vacuum at 200 C for 48 hrs.
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3. Class B Cleaning Procedure
Follow cleaning procedures in Sections 1 and 2 above and airbake instead of vacuum bake, at the specified temperatures for a minimum of 24 hours for all listed materials. Brass Cleaning Use acetone first with clean room cloth and a bottle brush (for internal threads) or wool (preferably stainless steel or brass wire brush or steel wool) over the threaded areas. Ultrasonic clean in methanol or isopropyl for 10 minutes at room temperature in a fume hood. Blow the parts with dry N2 Wrap in UHV aluminum foil NOTES: 1. Do not use water or water-based cleaners since this will cause an oxide layer on the brass part. 2. DO NOT vacuum bake brass since it may contaminate the vacuum oven with lead. For the same reason, do not air bake part either.
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Appendix B - Cleaning and Baking Procedures for Approved Sub-assemblies
A. LOS Cleaning Procedure: Use flashlight and inspect every cavity; if contaminated send out for another pickle and passivate (using local vendor who has experience in handling and wrapping per our procedures). Note: A few areas of reddish surface contamination (rust) in the interior is acceptable. Check all threaded holes with UHV cleaned and baked silver-plated, stainless screws to confirm that the threads are clear; if necessary chase the threads with a clean tap using no lubricant except DI water or approved solvents. Wipe all exposed surfaces with a clean room cloth (not a clean room paper/tissue) and isopropanol. Flush thoroughly with DI water using stainless steel brushes; turn the structure end-overend and on all sides to get as much of the particulates in the interior cavities out. Blow dry (as much as possible) with N2 (do not allow the water to sit and dry). Wipe the exposed surfaces again with a clean room cloth (not a clean room paper/tissue) and isopropanol to see if any particulates have been flushed out of the cavities and onto the exterior; flip the structure end-for-end. Vacuum bake at 200 ? ? 48 hours. C for Spot check after the vacuum bake for particulates as the structure is turned end-for-end; wipe any particulates off with a clean room cloth (not a clean room paper/tissue) and isopropanol. B. Composite Assemblies B.1 Commercial Stages: Disassemble and clean parts in ultrasonic cleaner with Liquinox for 10 minutes. Rinse in DI water. Clean in ultrasonic cleaner with methanol for 10 minutes. Replace all plastic parts with appropriate metal or Teflon replacement part (Teflon PFA 440 HP pieces). Remove Teflon parts and clean thoroughly. Reassemble stages. Bake in vacuum at 120 oC for 24 hours. B.2 Electronic Components: Clean with Liquinox solution and rinse with DI water. Bake in vacuum at highest temperature compatible with manufacturer's maximum rating. B.3 Sensor/Actuator Head Assemblies 1st. Assembly: Ceramic body, Teflon tape and Teflon coated wire o Ultrasonic clean in methanol for 10 minutes. o Soak in isopropyl alcohol for 10 minutes agitating regularly. o Bake in vacuum at 200 oC for 48 hours.
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Complete Assembly: o Ultrasonic clean in methanol for 10 minutes. o Soak in isopropyl alcohol for 10 minutes agitating regularly. o Bake in vacuum at 80oC for 48 hours. B.4 Sensor /Actuator "Pigtail" Cables Ultrasonic clean in methanol for 10 minutes. Bake in vacuum at 120C? 48 ?ours. for? h B.5 Cleaning and Baking Viewports Refer to LIGO-E990190.
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Appendix C - Forms
Form C1: Form C2:
Parts Cleaning Request LIGO Vacuum Bake Over Procedure and Check List
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Form C1 PARTS CLEANING REQUEST
Requestor: ___________________________ Phone _________________
Date _________
Parts Description, Drawing # _______________________________________Rev#_________ ___________________________________________________________________________ Used In (next higher assembly) __________________________________________________ Material: Al Macor SST Teflon CST Viton Bronze Glass
Other: ______________________________________________________ Special Handling: _____________________________________________________________ ____________________________________________________________________________ Baked In Oven: ____________ Date In ___________________ Quantity: ____________ No. of Units: __________ and/or (as appropriate) total surface area ______________ cm2 Describe total quantity required per LIGO interferometer: _______________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ Load # ____________ Temp.: ___________ C
Date Out __________________
Baked By: ________________________________
Form C1. Parts Cleaning Request
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Form C2 LIGO VACUUM BAKE OVEN PROCEDURE AND CHECK LIST
Oven: A B C D VSA Load # ___________ Date: ___ /___ /____
Load Contents: ________________________________________________________________ Cap Torqued: ______ ft/lbs ______ ft/lbs ______ ft/lbs _____ ft/lbs Metal Valve Open: Y N Vent Valve Closed: Y N TP on: TP on: TP on: TP on: Pressure: ________ Torr Pressure: ________ Torr Date:___/___ Time:___:___ Date:___/___ Time:___:___ Date:___/___ Time:___:___ Date:___/___ Time:___:___
Date:___/___ Time On:___:___ Date:___/___ Time On:___:___
NOTE: Do not turn heat on when pressure is above 5E-5 Torr.
AUTO/MANUAL: Ramp Time: Soak Time:
o
Heat on: Date:___/___ Time:___:___ Oven:____ Hrs, Oven:____ Hrs, Pumpline:____Hrs Pumpline:____Hrs
BAKE TEMPERATURE (C): Oven: ______ PumpLine: ______ TEMPERATURE (C): P-Line 1. 2. TP Heat Off: DEGAS: Fil On? Y N W/Dycor# ____ Date:___/___ Time On:___:___ Time Off:___:___ Date:___/___ Time On:___:___ Time Off:___:___ Date:___/___ Time On:___:___ Time Off:___:___ Date:___/___ Time On:___:___ Time Off:___:___ PURGE: N2 AIR Comments:____________________________________________________________________ _____________________________________________________________________________ _____________________________________________________________________________ Form C2. LIGO Vacuum Bake Oven Procedure and Check List Y N Temp Cont. sw Off: Y N Reset PROG off: Y N End Body Cap Date & Time P(Torr)
o
Turbo Pump Heat On:
Y
N
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Appendix D -- Calculation of Vacuum Load
In order to account for the anticipated load on the LIGO vacuum system arising from the introduction of LIGO Detector components into the chambers, it is necessary to develop an accounting system to track the contribution made to the partial pressure gas load by individual detector subsystem components.
D.1 Database
This could be done by assembling a suitably designed database in which the results of all screenings and high-power exposure tests will be logged. The database shall be searchable/ listable according to any of its entries. As a minimum, the database shall contain the following data: Inventory data: 1. Material, exposed surface area, material volume. 2. Subsystem and system comprising material. 3. Location, by chamber, of component material. Physical data: 4. Approximate distance to nearest mirror and indication whether there is a direct viewing path. 5. Approximate orientation of surface to mirror surface -- needed to estimate viewing factor. 6. Pumping speed for HCs in specific location. Measured data: 7. Outgassing rates, by mass number for important complex HC masses. 8. Ringdown and frequency shift data: (absorption + loss) and loss rates: ppm/yr. 9. Source of information -- LIGO document number or other traceable reference. Derived quantities: 10. Partial pressure by mass. 11. Predicted accumulation on target mirror, monolayers/yr and estimated (absorption + loss) and loss rates: ppm/yr, where possible or relevant.
D.2 Estimation of Material Buildup
Optical performance degradation of the LIGO interferometers from material contamination within the vacuum vessels involves three elements: an outgassing source ("culprit"), a target mirror ("victim"), and a path. The outgassing source is most simply characterized by the set of parameters: {A, Ji, mi, i, ai}. A(m2) is the source surface area exposed to the vacuum, Ji(W/m2) is the outgassing rate for the ith species of contaminant, having mass mi(AMU), i is the affinity for the species to adhere to a (clean) vacuum surface (0 < i < 1), and ai is the characteristic linear dimension of a molecule of species i (molecular area ~ ai2). The vessel is maintained at
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ultrahigh vacuum by a pumping system characterized by a pumping speed for the ith species, Si (m3/s). The target mirror is characterized by the parameters: {dm , m , Am }. dm(m) is the distance between mirror surface and outgassing source, m is the orientation of the surface normal to the mirror relative to the line-of-sight to the contamination source and Am (m2) is the mirror surface area. These parameters are summarized in Table 2.
Table 2: Parameters for estimating contaminant buildup on LIGO optics
Parameter
Outgassing rate for species i Source area Species molecular weight Sticking affinity Molecular linear dimension Distance to mirror Mirror area Mirror orientation Pumping speed for species i Partial pressure for species i Rate of increase of optical losses with time .
Symbol
Ji Ai mi
Value or Units (SI)
(N-m)/m2/s or W/m2 m2 AMU
Value or U...