AL-1220-7841_UHV_Chamber_and_Component_Production_Requirements_Rev_1.pdf

UHV Chamber and Component Production Requirements

Tom Swain Release Date: 22 Oct 2019

Document Number: AL-1220-7841 Revision: A

Document Status: Working Document Type: INSTRUCTION

Category Code: AL7000

ALS-U - GENERAL

MISCELLANEOUS

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Advanced Light Source Upgrade Project Lawrence Berkeley National Laboratory

Latest version of this document can be found in the LBNL Document Control Center.

A hardcopy of this document is for reference ONLY.

TABLE OF CONTENTS

1 Revision History

2 Approvals

3 Abbreviations and Acronyms

4 Introduction

5 Environmental Requirements

Codes and Regulations

Clean Assembly Space Requirement

Hazardous Waste Mitigation

Materials for UHV Surface Fabrication

5.4.1 Allowed Materials

5.4.2 Disallowed Materials

Fasteners

5.5.1 General

5.5.2 Plated Fasteners

5.5.3 Fasteners in UHV Service

Flanges and Gaskets

Alternate Flanges

Viewports

6 Parts Fabrication

Machining

EDM (Electrical Discharge Machining)

Surface Finish

Allowed Lubricants for machining and cold work operations

Other Material removal

Additive manufacturing

7 Aqueous Parts Cleaning

General

Recommended Cleaning Agents

Initial cleaning of machined parts

7.3.1 Ferrous parts

7.3.2 Copper & Nonferrous Parts

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8 Parts Joining

Welding - Stainless

Welding - Aluminum

Brazing

Other

Parts Leak check

Marking

9 Component Cleaning

Intent

Cleaning

Electro polishing

Vacuum furnace degassing

Stress Relief Annealing (Vacuum Firing)

Component Inspection

10 Assembly

11 Bake and Quality Assurance

Bake

Residual Gas Analysis

Final leak test

HPN2 Backfill

12 Shipping

13 Appendix

Commercial Sources

14 References

1 REVISION HISTORY

Rev. CM Number Description of Change A Minor corrections

2 APPROVALS

The following individual(s) shall approve this document:

Approver Project Role

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Approver Project Role Approver Name Project Role (ex. Project Manager) Sol Omolayo Vacuum Section Leader Windchill Approved / Concurred By

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3 ABBREVIATIONS AND ACRONYMS

ALS Advanced Light Source. A particle accelerator that delivers beams of light to various users at the Lawrence Berkeley National Lab (LBNL). The transport of this light is in a vacuum system composed of vacuum components that are interconnected and shared.

UHV Ultra High Vacuum. Generally this requires bakeable, all-metal chambers with operating pressures below 1x10-8 torr that possess very low or undetectable leak rates. Without UHV, the ALS simply won’t work.

UHV Surface A common misnomer is “wetted surface”; this is any surface or collection of surfaces in direct communication with the accelerator vacuum.

Vacuum Chamber A metallic high purity vessel or enclosure that is a key component of vacuum assemblies. It manages structural, thermal, and seismic demand loads, and may contain features such as viewports, mechanical interfaces, cable-ways and survey & alignment monuments.

Vacuum Component One or more parts joined together that contain at least one UHV surface. Examples include flanges, bellows, mirrors, and chambers.

Bake out The controlled heating and cooling of a chamber or component to liberate (desorb) surface contaminants such as water and hydrocarbons. This is usually required to achieve UHV.

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CF Conflat Flange. An all-metal sealing standard developed by Varian vacuum. This is a primary sealing technology for ALS Vacuum chambers. These flanges use copper gaskets for sealing.

DN Inside diameter, in mm, of a tube or CF flange.

Unfortunately, Conflat sizes are customarily referenced by their outside diameter (OD). For example, a “ten inch Conflat” refers to a CF flange with a 10” outside diameter with 200 mm (8”) inside diameter. This will be referred to as size DN 200 (also CF 200 in other literature).

DN Size [mm] Conflat nominal OD, inches

DN 16 1.33”

DN 35 2.75”

DN 40 2.75”

DN 50 3.375”

DN 63 4.5”

DN 100 6”

DN 160 8”

DN 200 10”

DN 250 12”

DN 300 14.25

Fig. 1 - Conflat sizes

To avoid confusion we recommend that DN size be used in referring to Conflat sizes.

HMSLD Helium Mass Spectrometer Leak Detector. This equipment is necessary for identifying that a UHV chamber is leak-tight.

COTS Commercial Off the Shelf (applies to components and simple chambers).

ISO International Standards Organization

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IPA Electronic grade isopropyl alcohol. This can have 0- 10% DI Water content. Electronic grade ethanol may be substituted.

DI Water Deionized; free of salts that can cause scale and spot formation, with a volume resistivity greater than 1x106 Ω-cm

VCR An industry-standard all-metal fitting typically used in the distribution of high purity gases.

HPN2 High purity Nitrogen gas furnished from an electronic grade gas cylinder or a nitrogen dewar and then processed through a cleanroom gas filter cartridge (Fig. 2). Ideally, all the connections and hoses downstream of the filter are of all-metal construction and free of elastomers.

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Fig. 2- A High Purity Nitrogen (HPN2) Source Cleanroom Foil A specialty aluminum foil for protection and storage of UHV parts. This is free of oils and surface contaminants.

Technical Rep. This is the engineer assigned to address vendor questions of a technical nature concerning a specific procurement.

4 INTRODUCTION

This document outlines the manufacture, qualification, and packaging of vacuum chambers and vacuum components for use at Lawrence Berkeley National Laboratory’s Advanced Light Source. Required operating pressures are for UHV service. Figure 1 describes a typical manufacturing workflow.

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Fig 2. - Typical manufacturing workflow

This document focuses on practices and procedures for production and delivery of UHV chambers that do not possess leaks, contamination, or damage that renders them unusable or compromised. This requires vigilance at multiple risk points in the manufacturing workflow.

The vendor is encouraged to thoroughly review this document prior to responding to a request for quotation or information. Questions should be addressed to the Technical Rep.

Vacuum technology, the collective “art” of manufacturing, assembling, testing and packaging vacuum components at minimum production cost, is beyond the scope of this document.

Substitutions, enhancements, or deviations from this specification may appear in a higher level technical specification document. Vendor counter proposals are welcome if they can materially reduce cost or lead-time. These must be communicated to the Technical Rep. for review and approval.

5 ENVIRONMENTAL REQUIREMENTS

Codes and Regulations

Vendor shall comply with the guidelines of the following international organizations:

International Standards Organization (ISO) American National Standards Institute (ANSI) American Society for Testing and Material (ASTM)

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American Welding Society (AWS)

The following documents are relevant to joining techniques.

Material certification according to ASTM.

Welding certifications:

ISO 15614-1, ISO 15614-11, test and inspection.

ISO 13919-1, ISO 5817, weld quality: level B, rigorous.

ISO 9606-1, welder qualification.

ISO 15609-3, ISO 15609-1, welding procedure specifications, WPS

AWS D1.6, Structural Welding Code – Stainless Steel AWS D1.2, Structural Welding Code – Aluminum ASME, BPVC, Section IX, welding processes and welder certifications ASME, BPVC, Section V, non-destructive tests.

ASME, BPVC, Section II, part C, Specifications for Welding Rods Electrodes and Filler Metals.

Manufacturing:

ASME, BPVC, Section VIII, Division 2

Pressure Range Unless otherwise specified, these components are not intended for operation above 15 PSIG internal pressure.

These are exempt from Code. 10 CFR 851, Appendix A, Part Pressure Safety.

Clean Assembly Space Requirement

Clean conditions are a requirement for post-fabrication operations.

This means a work space with dedicated tooling and low foot traffic that can maintain very low levels of particulate and hydrocarbon contamination. Vendors must be able to show that written processes exist for maintaining adequate cleanliness standards. An inspector from LBNL may need to verify the adequacy of the work area. Minimum requirements include:

• An HVAC system separate from that of nearby machine shop areas, such that detectable aromatic odors are absent or minimal.

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• Posted documentation on the use of cleanroom gowns, head covers, gloves and shoe covers, and personnel that understand this documentation.

• An adequate complement of readily available UHV service hand tools and fixtures that have been appropriately cleaned and identified as such.

• Fixtures and tools that come in contact with cleaned components shall be exclusively of stainless steel, aluminum, PEEK, Delrin (POM), or Teflon. Contact with unqualified or disallowed materials, writing instruments, are not UHV compatible shall be prohibited.

• A prohibition on smoking, preparing, or consume food or beverages in the work area.

• A prohibition on the dispensing of hydrocarbon and fluorocarbon (“high vacuum”) greases and oil. These are contaminating fluids.

Hazardous Waste Mitigation

Vendor may be asked to demonstrate that they are in compliance with local codes and ordinances concerning the disposal of hazardous waste.

Materials for UHV Surface Fabrication

5.4.1 Allowed Materials

All materials for UHV surface fabrication are required to be sourced from raw material suppliers that are able to provide Certificates of Conformance that state their origin, physical and chemical properties.

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Generally acceptable UHV materials are listed below. Exceptions require approval by the Technical Rep.

Stainless Steels - AISI 304L, 304LN, 316L, 316LN, 321, 347, 17-4, 440C, Inconel Aluminum 5082. 5083, 6061, 6063 Copper ( OFHC, UNS 10700, GlidCop) Non-porous ceramics such as high density Alumina, Beryllia, Macor, machinable glass, synthetic Mica Beryllium, Beryllium Copper, Tellurium Copper Glass (SiO2), Silicon, Sapphire Gold, Silver, Tin Mu-metal, Monel metal Titanium, Tungsten Molybdenum, including TZM Bronzes, Phosphor Bronzes types 510 and 544, Ampco 18 & 22 Aluminum Bronze, Aluminum Bronze type 642 Kovar (Fe-Ni-Co)

Fig. 3- Allowed Materials for UHV Surfaces

5.4.2 Disallowed Materials

Metals The following are high vapor-pressure metals and are not acceptable: Zinc, Cadmium, Lead, Cesium, Mercury, Potassium, Magnesium, Sodium, Selenium, and Strontium. This also precludes the use of any alloy or glass containing more than 0.25% of these metals.

Nonmetals The following require prior authorization

Elastomers Organic materials Materials/alloys that are subject to atmospheric corrosion.

Adhesives and glues.

High performance plastics (PEEK, Vespel)

Counterfeit items The use of fasteners and materials that are not traceable as outlined in Section 3.2 are prohibited.

Lubricants Hydrocarbon and Fluorocarbon lubricants are prohibited from all UHV surfaces and also within the clean work area outlined in Section 3.1.2

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Fasteners

5.5.1 General

Fastener must comply with ISO standards, and be of austenitic stainless steel. Metric fasteners shall be used. Fastener heads shall be 12-point, hexagon or hexagon socket cap. ISO standards additionally apply to metric nuts and washers. Material shall be A2 (18-8) or A4 Stainless with cold rolled threads and complying with DIN 933 / ISO 4017 standard.

5.5.2 Plated Fasteners

Where stainless steel fasteners mate with stainless steel threaded components, it is essential that the threads of the fasteners shall be silver plated to a minimum thickness of 5μm.

5.5.3 Fasteners in UHV Service

If silver plated fasteners are used in UHV service, it is recommended that these be vacuum furnace degassed prior to assembly, per section 7.4 (plating processes can be a contamination source).

Screws must be vented when installed in blind tapped holes.

Flanges and Gaskets

All vacuum joints must be metal-sealed unless otherwise specified.

All flanges shall be CF type unless otherwise specified, and shall conform to ASTM standard E2734/E2734M − 10.

Flanges (including knife edge and flat flanges) shall be manufactured from stainless steel grades 304L, 304LN, 316L or 316LN.

Use of stainless steel grades 304 or 316 for weldments requires prior approval.

Allowed flange sizes are CF 16, CF 25, CF 35, CF 40, CF 50, CF 63, CF 100, CF 160, CF 200, CF250, and CF 300. Other sizes require prior approval.

CF 35 and 40 have identical knife edge and fastener group details.

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Allowances within CF ISO standard:

• It is recommended that the CF knife edge radius have a minimum radius of 0.1 mm. A maximum radius of 0.2 mm is permitted.

• It is recommended that the knife edge interior angle be 90 degrees (corresponding to a 20 degree counter-slope).

CF gaskets shall be bare copper, either stamped or machined and quarter or half hard unless otherwise agreed. Silver plated gaskets require approval.

Any blanking flanges, gaskets, fasteners and washers necessary for the delivery and shipment of sealed and backfilled chambers shall be included.

Alternate Flanges

Alternate flanges such as Aluminum CF, KF, VCR, wire seals, and REM seals require prior approval.

Viewports

Viewport shall be composed of borosilicate glass or sapphire with a kovar/glass all-metal braze interface.

6 PARTS FABRICATION

Machining

High speed machining and material removal shall be performed with diamond or carbide tools and sufficiently rigid fixturing that a smooth and chatter-free surface finish is achieved.

EDM (Electrical Discharge Machining)

EDM is permitted if part is labelled as EDM-machined and if EDM-residue is subsequently removed by etching or machining. Vendor etch process must be approved by the Technical Rep.

Surface Finish

All UHV Surfaces shall be machined. Rough, as delivered, or scaled surfaces are prohibited. Surface finishes of component UHV surfaces shall be Ra of 6.4 microns (125 micro inches) or better.

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Allowed Lubricants for machining and cold work operations

Water-soluble cutting fluids are recommended. Cutting fluids and lubricants that can cause non-removable contamination of UHV surfaces are prohibited. This includes fluids either with high organic constituents or 50 ppm or more of sulfur or silicone. A non-exhaustive list of allowed cutting fluids is shown in Fig. 4. For other fluids, vendor should contact the Technical Rep. with trade name and composition information to receive approval.

ACCU-LUBE LB-2000

ACCU-LUBE LB-2001

AQUA KOOL 21EP-5

Aqua Syn 55 Aqua Cool 21EP-5 Aqua Cool 4-EPX (

AQUA SYN 160 (FORMERLY "DIP COOL 862")

AQUA SYN 180 (FORMERLY "DIP COOL 868")

AQUA SYN 190

AQUA SYN 55

BIOCUT 1500

BIOCUT 2200

BIOCUT 3600

BIOCUT 4600

BLASOCUT 2000 CF ART 875

BLASOCUT 2000 CFSW, ART 875-21

BLASOCUT KOMBI ART 883

CIMPERIAL 1060CF

CIMSTAR 40

CIMSTAR 40 F

Cimcool 5 Star 40 Cimperial 1011 Cindol 3102

DASCOOL 2003

Diamond Way 2010 (Yamazen) Dip Kool 862 Dip Kool 868 Dip Kut 819H Extreme Cut 250C Ethanol Haloform CW-40

HANGSTERFER'S S-500 CF

HANGSTERFER'S S-506 CF

HANGSTERFER'S CRYSTAL CUT 465

HANGSTERFER'S ANTI-FOAM SL

HOCUT 801

HYCUT CF21

HYCUT ADDITIV BF

HYSOL MB 50

Isopropyl alcohol Kerosene

KOOL MIST #77

LARD CUT 240

Micro-Drop (Trico) Perkut 301GG Rapid Tap Relton A-9 Rust-Lick Vytron-N Rust-Lick G-25-J Rust-Lick WS11 Rust-Lick WS600A Rust-Lick Safetap Ultima

SPARCUT NC

Sunnen Man-852 Syntillo 9930 Tap Magic Tool Saver TAP Magic Formula 2 Eco-oil TAP Magic Formula 1 Aqueous Trigo MD1 Trim 9106 Trim E206 Trim Microsol 585 XT Trim Tap

Fig. 4 - Allowed Cutting Fluids

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Other Material removal

Sand blasting is prohibited. Bead blasting requires prior approval. The use of solid kinetic abrasive materials shall be avoided where possible, so as to avoid local surface heat and mechanical distress that promotes contaminant burial. Resin or rubber bonded abrasives are prohibited. Tungsten carbide and diamond wheels are acceptable.

The following abrasives are permitted:

3M Scotch Brite Type S, silicon carbide (gray) 3M Type A, aluminum oxide (maroon) 3M Type S, silicon carbide (gray) 3M Wetordry Fabricut (aluminum oxide or silicon carbide types).

3M 413Q silicon carbide 3M Wetordry Tri-M-ite 411Q

Fig. 5 – Permitted abrasives

Other materials require prior approval.

Additive manufacturing

Additive manufacturing (e.g., 3D printing) of UHV surfaces requires prior approval.

7 AQUEOUS PARTS CLEANING

General

Parts should be cleaned as soon as possible after machining.

For nonporous machined metal components, an aqueous, halogen and silicon-free anionic detergent cleaning agent with surfactants and builders that is neutral or mildly alkaline will suffice. Follow manufacturer’s dilution recommendations. Bath quality should be continuously monitored. Deionized (DI) water is required at final rinse steps, with a minimum volume resistivity of 1 mega ohm-cm, Mechanical agitation details (ultrasonic energy input, bath agitation, part motion, etc.) shall be competently chosen according to component size, geometry, and effectiveness so that parts are thoroughly cleaned.

All parts are to be cleaned prior to joining.

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Cleaning tool interfaces that contact UHV surface (such as bath enclosures, sprayers and lifting jigs) shall be of stainless steel, nylon polyethylene, Delrin, or PEEK.

Brushes other than organic fiber or Stainless steel are prohibited without prior approval.

After cleaning, parts must be handled with cleanroom gloves.

The direct marking of parts after cleaning with pencil, grease pen, cleanroom tape is prohibited. Parts can be wrapped in cleanroom foil (or bagged in cleanroom bags) and then marked.

Recommended Cleaning Agents

The following are recommended cleaning agents. Vendor may substitute an alternative only if they have established successful production competence with UHV cleaning. The trade name of the cleaning agent shall be disclosed in Fig. 7.

Name Manufacturer

D909 Dubois Chemicals Surtec 131 Surtec International Mirachem 500 Mirachem Corp.

Cor1 & Cor2 (232-010, 232-011) Coral Chemicals

Fig 6. - Recommended Cleaning Agents

Initial cleaning of machined parts

Parts shall be suspended in tanks by wire, hooks or in baskets.

7.3.1 Ferrous parts

1. Immerse parts in a prepared cleaning agent bath at room temperature for 10 minutes or more, depending on the amount of soil (see list in Fig. 6).

2. Rinse and spray with tap water.

3. Inspect and brush as needed to remove remaining contaminants. A Tampico fiber brush is suitable here.

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4. Manually flush blind tapped holes and other entrapment features using pressurized spray water.

5. Spray rinse parts again with tap water.

6. Verify that all surfaces sheet. Repeat steps 4-5 as required.

7. Immerse parts in room temperature DI water with appropriate energy, agitation.

8. Immerse parts in hot DI water (>50°C) with appropriate energy, agitation.

9. Blow dry with dry filtered air or HPN2.

10. As soon as is practical, wrap parts in cleanroom paper secured with cleanroom tape. For storage > 24 hours, seal in cleanroom poly bags.

7.3.2 Copper & Nonferrous Parts

1. Proceed as with steps 1-6 in section 5.3.1, ferrous parts.

2. Deoxidation: Immerse in 15% Hydrochloric acid for 2-10 minutes.

3. Rinse in deionized water.

4. Coral Chemical Bright Dip (Cor1 /Cor2 Mixed 50%/50%) – 1 to 3 minutes with occasional gentle agitation.

5. Rinse in deionized water.

6. Repeat steps 1-8 in section 7.3.1, ferrous parts.

7. Spray part with analytical grade ethanol 99.8%, to facilitate rapid drying.

8. Blow Dry with HPN2 with particular attention to regions prone to retain liquids (e.g. blind holes).

9. Bake by dry hot air flow at 60°C for 10-60 minutes and allow to cool down.

10. Pack in cleanroom paper and store in sealed poly bags.

Avoid the use of aluminum foil which can cause galvanic corrosion in the presence of entrapped moisture.

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8 PARTS JOINING

Welding - Stainless

Prior to joining, inspect surfaces being joined to ensure they are free of contamination.

Welds from the UHV side shall be continuous GTAW TIG fusion welds, with no filler material. These joints may be supplemented by external structural welds. Such external welds shall be discontinuous, laid out in a manner that does not trap volumes, yet still providing access to a helium probe for helium leak checking.

To the extent possible, these seams shall be left in the “as welded condition” without further modification or surface treatment.

To avoid excessive coloration and scaling, it is requested (to the extent possible) that the heat-affected zone during weld operations remain flushed with inert gas until it has cooled down below 400°C.

Removal of weld coloration with acid paste is discouraged.

Bead blasting of UHV surfaces as well as polishing or lapping requires prior approval. Sand blasting of UHV surfaces is prohibited.

The use of dye penetrants for weld defect detection is discouraged.

If it becomes necessary to remove defective weld material, machining is to be performed with tungsten carbide or diamond tooling. Material removal is to be adequate to provide sound weld metal on both parts prior to repeating the welding process. Filler material shall be 308 SS.

Vendor must have a Certified Welding Inspector (CWI) on staff as well as documented Welding Procedure Specifications (WPS). These WPS must be made available on request.

Component welds shall be performed in compliance with AWS D1.6 using Gas Tungsten Arc Welding (GTAW, i.e. TIG welding) with 4.5 grade (i.e.

99.995% purity) or better Helium, Argon or Argon-Helium.

Welding - Aluminum

Due to rapid oxidation, any welding of aluminum parts for UHV service shall take place in the first 24 hours after cleaning.

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To protect the weld zone from oxidation, parts shall be flushed with inert gas until they have cooled down to a temperature of 60°C.

Brazing

Flame brazing of UHV surface components requires prior approval.

Vacuum furnace brazing is strongly preferred. Vacuum furnace brazing will require a braze plan (either from vendor or from LBNL) that details the following:

• Fixturing and brazing layment

• Braze filler Materials

• Thermal ramp rate, soak time, and descent rate.

• Furnace gases and pressure schedule

• Special instructions regarding water/air and air/vacuum interfaces

• Leak and hydrostatic Testing

Other

Alternative joining methods, such as Electron Beam welding, welding or brazing of components joined with explosion bonding, friction stir welding, frit bonding, or industrial adhesive bonding require prior approval and will include detailed fabrication guidance.

Parts Leak check

After joining operations are complete, and before final assembly, it is recommended that the component be helium leak checked. See Section

9.3 for more information.

After initial evacuation, it may be prudent to inspect the component for buckling or plastic deformation.

Marking

LBNL Part Number and Serial Number shall be scribed or laser-etched onto outside of chamber.

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9 COMPONENT CLEANING

Intent

Final cleaning commences after joining and finishing operations are complete and the component is leak tight. All subsequent operations should be performed in a cleanroom.

Cleaning

Repeat step 7.3 for the component.

Prior to packaging for storage or shipment, components shall be free of particles under bright light visual inspection. There should be no evidence of water spots. Components must be completely dry and moisture free prior to bagging.

Cosmetic corrosion caused by improper storage is a cause for rejection of the part and/or rework.

Electro polishing

If electro polishing is specified, it is critical that external cracks and joints (such as under skip welds or at incomplete fusion joints on the outside of the chamber) are thoroughly flushed and cleaned afterwards.

Evidence of corrosion from electro polishing residues is more than a cosmetic issue. It is cause for rejection of the component, because joint sealing failure may eventually follow.

Vacuum furnace degassing

This may be specified in the work instructions, and is a useful method to further clean complex vacuum surfaces, removing both water and hydrocarbon contamination. Furnace and pumps must be oil-free. Furnace should be capable of achieving a base pressure of 1x-10-7 torr. A vacuum furnace degas schedule may be included in the PO instructions.

Do not to exceed 250°C for stainless steel and copper and 150°C for aluminum. COTS items such as feedthroughs, bellows, plated items, and viewports may have lower thermal limits that must be respected.

Unless otherwise specified, ramp temperature no higher than 60°C per hour and dwell for a minimum of 12 hours. Do not initiate heating until partial pressure of oxygen drops below 1x-10-3 torr. At the conclusion of degassing, the furnace must be vented in a controlled way with HPN2 such that 60°C per hour is not exceeded.

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Wrap in cleanroom foil. Mark and bag as appropriate.

Stress Relief Annealing (Vacuum Firing)

This may be specified in the purchase order to address residual joining stresses, mitigate dissolved hydrogen, or as a cleaning step. Heat treatment data and certification may be required vendor documentation.

Furnace and pumps must be oil-free. Furnace should be capable of achieving a base pressure of 1x-10-7 torr. Unless otherwise specified, treatment shall consist of two hours at 900 °C to 1000 °C (1650°F to 1830°F). Furnace cool or quench with HPN2. The parts must not have any evidence of discoloration as a result of the annealing step.

Component Inspection

Prior to initiating assembly, complete Fig. 7.

Criteria Comments Pass / Fail

LBNL Part number

LBNL Serial Number

LBNL Purchase order number

LBNL Part and serial number are inscribed on chamber (Y/N)

Trade name of cleaner(s) used for part and component cleaning

Flange knife-edges are completely smooth and interruption-free when examined by lightly running an ethanol-wetted rubber cleanroom gloved finger around them.

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General appearance of untreated weld areas is bright, shiny, clean, and free of spotting

Cleanroom wipes wetted with electronic grade ethanol do not yield debris or particles, or discoloration of the wipes.

Internal welds are visually free of cracks, porosity and inclusions under bright light inspection.

Threaded holes inspected with an electronic grade alcohol-soaked cleanroom swab do not yield particles or discoloration.

All fasteners in contact with stainless steel are silver plated.

Additional Comments

Inspector Name and Initials

Date and Time

Fig. 7 –Visual and Mechanical inspection log.

10 ASSEMBLY

Assembly shall take place in the clean area.

Care should be taken to protect knife edges from damage. Knife edges can be covered with cleanroom foil and plastic caps.

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11 BAKE AND QUALITY ASSURANCE

Fig. 8 - Bake and quality assurance test setup.

This sketch is for discussion purposes only; the actual setup may vary.

The items in blue in Fig. 8 are required vendor assets. All connections above the turbo pump should be all-metal, including the HPN2 port.

LBNL recommends this latter connection be a VCR to CF16 adapter that is replaced with a CF16 blank as the last connection to the chamber prior to shipping.

LBNL reserves the right to have a representative present during these tests.

Bake

Unless otherwise prescribed, component shall be baked at 170°C ± 20°C for a minimum of 72 hours with a turbo pump and oil free rough pump.

The ± 20°C tolerance is to ensure that all UHV surfaces achieve at least 150°C. In order to avoid thermal strain of joints and flanges that can cause plastic deformation or leaks, the thermal ramp rate shall be controlled to a maximum of 25°C/hour during both heating and cooling. This means taking nearly a day to heat to achieve dwell bake out temperature and same amount of time to cool.

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Heat can be administered with bake out jackets and heater tapes.

Insulation can be facilitated with jackets, kapton foil, and aluminum foil.

Temperature history of at least two thermocouples per zone must be recorded for the duration of the bake and these records made a part of the documentation. A sampling interval of 20 minutes is adequate. A logger is recommended (Fig. 9).

The bake should be coordinated with the RGA testing described in Section 10.2.

Fig. 9 - Temperature logger for bake out. Data is written to a memory card.

Because chambers and component walls may have poor thermal conductivity, shapes can be complicated, and heater tapes may not communicate well with walls, it may be necessary to establish heating zones with separate thermometry and heaters. Strategies for larger or more complicated chambers may be further described in a separate LBNL bake out plan. Please complete Fig. 10.

Description Target Value Actual Value

Start Date and Time

Number of Bake Zones

Thermocouple locations adequate? (Y/N)

Target Temperature 170°C ± 20°C

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Ramp Rate 25°C/hour

Dwell Time 72 hour

Maximum Pressure during bake (torr) 1x10-4

Target Temperatures within tolerance (Y/N)

Pressure at end of Dwell Time (torr]

Pressure after cool-down, <30°C

End Date and Time

Operator name and Initials

Fig. 10 –Bake out documentation

Residual Gas Analysis

A RGA (Residual Gas Analysis) scan may be required up to three times:

Prior to initiating bake out, when the bake is underway and “hot”, and after bake is complete and at room temperature again.

The RGA instrument must have a detection limit of 5x10-12 torr. Each scan shall be captured in analog mode from 1 to 100 AMU, show the full range of the peaks in log scale, and be digitally archived and transmitted to the Technical Rep. for review. These scans shall also become a part of the document traveler.

Criteria for acceptance of testing is

• With the chamber baked and at room temperature, the sum of all peaks higher than Mass 44 must be lower than 1/1,000th of total pressure.

• Mass 18 must be less than Mass 2.

• Mass 69 must be less than 1/2,000th of total pressure.

Please complete Fig. 9.

RGA Model

Detection Limit (torr)

Are there elastomers in UHV surfaces

AL-1220-7841 Rev. A Doc. Status: Working Page 27 of 31 above turbo pump? (Y/N)

RGA is operated Electron Multiplier Mode? (Y/N)

Fig. 9 - RGA Setup Documentation

For each of the three scans the following data shall be recorded.

Prior to the last scan, ensure the RGA filament has been degassed.

Description Value

Scan No. (1,2 or 3)

Date & Time

Chamber Temperature (°C)

Room Temperature (°C)

Electron Energy (V)

Ion Energy (eV)

Ion Current

Electron Emission Current (mA)

Total RGA Pressure (torr)

Gauge Pressure (torr)

PP (Partial Pressure) of Mass 2 (torr)

PP Mass 14 - N (torr)

PP Mass 16 - O (torr)

PP Mass 18 - H2O (torr)

PP Mass 18 < Mass 2 (Y/N)

PP sum of Mass 44 to Mass 100 (torr)

AL-1220-7841 Rev. A Doc. Status: Working Page 28 of 31

Above < Total RGA Pressure / 1000 (Y/N)

PP Mass 69 - Fluorocarbon (torr)

Above < Total RGA Pressure / 2000 (Y/N)

PP Mass 18 < Mass 2 (Y/N)

PP Mass 14 < Mass 18 (Y/N)

Unit passes test criteria (Y/N)

Operator name and initials

Fig. 10 - Mandatory Scan Documentation

Final leak test

Final Leak test is to be performed after Bake and RGA, with the chamber at room temperature.

The pump on the HMSLD shall be oil free. If contamination from a HMSLD poses any risk, the detector inlet should be installed downstream of a turbo pump (as shown in Fig. 7).

If there is no turbo pump, maintain the connection of the HMSLD to the chamber for as short a period of time as possible to avoid back streaming.

The chamber must be pumped down below 5 torr before leak checking commences.

It is recommended that the calibrated leak be attached directly to the test chamber and not to the detector.

The HMSLD must have an ultimate sensitivity of at least 5x10-12 torr-liters/sec.

Unless otherwise specified, the maximum allowable leak rate is 1x10-10 torr-liters/sec when immersed in a mixture of air and helium for at least 60 seconds. The fraction of helium in this mix must be at least 25%. A bagged enclosure is recommended. Otherwise perform leak detection in trace probe mode. Complete the table in Fig. 11.

Description Value

AL-1220-7841 Rev. A Doc. Status: Working Page 29 of 31

Date & Time of test

HMSLD Manufacturer (Name)

Model Number

HMSLD Sensitivity (torr-liters/sec)

Temperature of test Area (C)

Is HMSLD Downstream of Turbo? (Y/N)

System Base Pressure (torr)

Ground Noise at test start (torr-liters/sec)

Is component bagged? (Y/N)

Percentage of He in Bag (%)

Maximum Measured Leak (torr-

Helium Soak Time (sec)

Maximum Allowed Leak Rate (torr-liters /sec)

5x10-10 torr/s

Year of Reference Leak Calibration

Reference Leak Calibration Value (torr-liters /s)

Measured Reference Leak Value (torr-

Operator name & initials

Fig. 11 - Leak Check Documentation

HPN2 Backfill

A final HPN2 flow shall be established so that the HPN2 blanket gas minimizes UHV surface rehydration while equipment is disconnected and blanked (Fig. 7).

AL-1220-7841 Rev. A Doc. Status: Working Page 30 of 31

Disable any push-button vent capability (common on commercial HMSLD units). These typically vent the chamber with room air.

Exposing dehydrated metal surfaces in the chamber to room air risks rehydration and the need to re-bake the chamber.

When all tests and documentation are complete and approved, the unit can be disconnected from vendor assets.

Quickly cap the HPN2 port with a clean CF 16 and metal gasket as a final step. The chamber shall be shipped hermetically sealed with all-metal seals at 1 bar internal pressure.

Complete the Table in Fig. 12.

Is the unit hermetically sealed? (Y/N)

Were UHV surfaces exposed to room air after Bake? (Y/N)

Was unit vented to HPN2? (Y/N)

Operator Name & initials

Fig. 12 - HPN2 Backfill documentation

12 SHIPPING

Chambers shipped with exposed knife edges shall be shipped with the flange faces covered in cleanroom foil and then covered with CF plastic caps.

The sealed chamber must be properly bagged, secured and packaged to maintain cleanliness, and prevent damage and contamination during transit by commercial carriers.

AL-1220-7841 Rev. A Doc. Status: Working Page 31 of 31

13 APPENDIX

Commercial Sources

This list does not constitute any endorsement or approval.

Cleanroom Tape - p/n S-20218C Uline Corp.

Cleanroom Gloves - p/n S-13046 Uline Corp.

Cleanroom Wipes - p/n S-18512 Uline Corp.

Aqueous cleaning Brushes - Tampico Bristle - Amazon.com.

Cleanroom Foil - All-Foils, Inc.

Cleanroom Bags - p/n S-19535 Uline Corp.

Commercial Silver Plated (5 micron) fasteners - UC Components.

Vented Screws - UC Components.

Plastic Caps for CF flange knife edge protection - GNB KL Group Data Acquisition - Graphtec GL240 midi Data Logger - Dateq Corp.

Fig. 13 – Commercial Sources

14 REFERENCES

ASTM E498/E498M - Standard Practice for Leaks Using the Mass Spectrometer Leak Detector or Residual Gas Analyzer in the Trace Probe Mode.

BNL-81715-2008-IR - Vacuum System Consensus Guideline for Department of Energy Accelerator Laboratories.

14 References