Attachment G - Specification for Fabrication and Cleaning CAD-1119.pdf

Spec. CAD-1119 Page 2 of 10

CAD Vacuum Chambers/Assemblies

BROOKHAVEN NATIONAL LABORATORY

Brookhaven Science Associates, Inc.

Upton, New York 11973

SPEC. CAD-1119

Rev. B Date: January 14, 2012

Specification for Fabrication and Cleaning of CAD Vacuum Chamber/Assemblies and Vacuum Components

1.0 SCOPE

This specification, in conjunction with the associated drawing(s) and other applicable documents, defines the requirements, for the design configuration, materials, workmanship, cleaning, fabrication, assembly, inspection, quality assurance and packaging of CAD Ultra High Vacuum Chamber/Assemblies (Chambers, hereafter) and Vacuum Components.

2.0 APPLICABLE DOCUMENTS

2.1 The following documents form a part of this Specification to the extent specified herein.

Unless otherwise specified, the document issue date or revision level shall be that which is in effect on the requested bid submission date. Exceptions must be approved in writing by the Buyer.

Standards:

ASTM-E498/E498M, Standard Practice for Leaks Using the Mass Spectrometer Leak

Detector or Residual Gas Analyzer in the Tracer Probe Mode

2.2 Order of Precedence

Unless otherwise noted herein or in the contract, in the event of a conflict between the text of this document and the references cited herein (except for related specification sheets), the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been obtained

3.0 REQUIREMENTS

3.1 Ultra High Vacuum Design

Chambers and Components shall be suitable for use as ultra high vacuum (UHV) hardware. The chambers shall be free of oils, particulate, organic matter and chlorides. All surfaces of each chamber shall be smooth and free of scale, stains and residues of any kind upon receipt by the buyer.

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The basic design rule for UHV Chambers is to minimize the gas load, providing the benefit of low operating pressure. The gas load derives from outgassing, both thermal and desorbed, diffusion and leaks, which can vary by several orders of magnitude. Gas load is minimized by the selection of proper materials, careful fabrication processing and surface treatment, and by minimizing the surface area exposed to vacuum.

Trapped volumes between atmosphere and UHV environments, which may connect through microscopic orifices, capillaries, or other defects must be avoided under all circumstances, whether created by a threaded fastener, sealing weld or other fabrication process. All volumes should be vented, either to atmosphere or to vacuum to allow UHV leak detection if defects are present. For the same reason a vacuum sealing weld should always be a single weld, never a double weld. All threaded fasteners located in blind holes inside vacuum are to be vented.

Vacuum sealing welds, whenever possible, shall be internal welds. Where this is not possible, full penetration external welds with internal inert gas purge is specified. Similarly, vacuum brazing must result in a smooth, homogeneous and complete joint on the vacuum side of the chamber.

Extreme care should be taken so that there is no possibility of delaminating or peeling of specified vacuum surface coatings and or plating. The surface to be coated should be clean and free from defects which could otherwise result in trapped volumes under the coatings and or plating. A high-temperature vacuum bake of >200ºC is recommended to test the adhesion.

Chambers shall be rejected with any evidence of peeling. If acid bath is used for plating or coating, a vacuum bake at > 400ºC shall be applied to remove any acid residues from electroplating unless lower temperature brazing was specified.

Cleanliness is important at all times during the chamber and component fabrication process.

Frequent cleaning of items before, during, and after manufacturing processes may be required to meet UHV performance requirements specified herein. Care should be taken not to cross-contaminate “clean” and “dirty” components.

Proper support of the Chamber, subassemblies and components shall be considered at the process design stage to eliminate the potential for distortion and damage during fabrication and evaluation. All Chambers, subassemblies and components must be designed to safely withstand the loading exerted by atmospheric pressure while under vacuum. Chamber assemblies utilizing bellows or geometries which result in differential loading while under vacuum must include proper restraints that prevent lateral and axial movement due to the differential pressure loading.

3.2 Parts, Materials and Processes

3.2.1 UHV Compatible Materials – Only UHV-compatible metal and ceramic materials shall be selected for fabrication of CAD Chambers and components. Some UHV materials may be excluded based on the specific application, e.g., magnetic permeability, temperature limitation, or radiation resistance. The following materials are UHV-compatible, after proper cleaning and degassing using the procedures listed herein.

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a. Stainless steel – Austenitic, 300-series vacuum arc remelt (VAR) or hot-forged electron slag remelt (ESR). Preferred types are ASTM 304L, 304LN, 316L, 316LN, 321, and 347. L and LN are specified where applicable to reduce carbide precipitation during welding which can lead to corrosion, reduced strength, and high magnetic permeability.

b. Inconel® alloy 625, 750 or 718.

c. Aluminum alloys 2219, 5086, A6061-T6, and A6063-T6 for their high strength, ease of welding, and non-magnetic properties.

d. Copper – Oxygen-free high conductivity, OFHC or OFS grades, Beryllium Copper, GlidCop.

e. Titanium – Commercially pure, aircraft quality, type 50A.

f. Ceramics, Refectories – Alumina (> 96% Al2O3) and similar oxide ceramics (however, beryllia is not permitted without written approval by C-AD.

g. Others – glass, sapphire, Inconel®, beryllium windows, Monel, Kovar, Mu Metal, Macor.

3.2.2 UHV Incompatible Materials – Materials including, but not limited to the following are not UHV-compatible and shall not be used in the chambers:

a. Zinc and zinc alloys with high vapor pressure at elevated temperature, found in bearings, silver solders,

b. Brass and bronze components

c. Cadmium and cadmium alloys with high vapor pressure, found in bearings, solders, and steel rust proofing.

d. Elastomers – O-ring seals for flanges and valves.

e. Organics with high outgassing rates which tend to trap hydrocarbon contaminants; and are less radiation resistant. Use of Teflon® is specifically prohibited.

3.2.3 Knife-edge flanges - As indicated on the applicable drawing(s) shall be ConFlat®. Knife edge with a 90° angle is preferred over a 70° angle. The leak check grooves on Conflat flanges shall be aligned on the vertical center line when the flange is vertical and when not shall be aligned parallel to the beam direction unless otherwise specified on the associated drawing.

3.2.3.1 Stainless Steel UHV flanges shall be fabricated from ASTM 304L, ASTM 316L or ASTM 316LN vacuum arc remelt (VAR) or electro slag remelt (ESR) stainless steel.

3.2.3.2 Bi-Metal UHV flanges - Explosion-bonded plates between aluminum and stainless steel (e.g., ATLAS® flanges) are permissible for chambers that require welding of knife-edge flanges

Spec. CAD-1119 Page 5 of 10 to aluminum cores. 100% detailed inspection including, but not limited to, thermal cycling and leak tests, must be made before and after fabrication.

3.2.4 Machining - Only water soluble machining lubricants are allowed. The use of silicone- or sulfur-based machining lubricants is prohibited. All machining is to be carefully controlled to ensure that no foreign matter is embedded in the surface of the material. The use of abrasive wheels or cloths, wire brushes, files, sand, polishing pastes, and compounds is prohibited.

3.2.5 Cleaning - It is recommended that all parts be chemically cleaned and/or vacuum baked prior to welding, assembly, and testing. The cleaning process shall remove residual surface contaminants such as dirt, grease, oils, etc. without etching the vacuum side of the surface.

Therefore, the cleaning process shall not include strong acid or alkaline etching except as noted in 3.2.5.2 and 3.2.5.3. Mechanical operations to remove surface stains shall be kept to an absolute minimum. Any metal brushing, sand blasting, or other harsh abrasives on the vacuum side are prohibited.

The exact cleaning process depends on materials, sizes of the Components, and available Vendor facilities. Components shall be carefully inspected so that any areas which might form potential contamination traps (e.g., blind holes, crevices, or cracks) are identified to ensure that they are properly cleaned. Bellows shall be cleaned while fixed in their specified normal full extension condition.

The following cleaning procedures shall be used for all component parts of the chambers prior to welding.

BNL approval is required for alternate methods which shall be considered if local codes or health, safety and environmental regulations prohibit their use. A procedure determined by BNL, in writing, to be equivalent may also be used. Regardless of which cleaning procedures are used, assemblies shall be received at BNL free of all organics and acids that meet the performance requirements specified in paragraph 3.4 herein.

3.2.5.1 Cleaning Procedure: Remove all excessive dirt oil and grease prior to starting the following cleaning process. All soak times specified are a minimum depending on the conditions of the tank solutions and subject parts. De-ionized water in each tank shall measure a minimum resistivity of 500,000 ohm-cm.

a. Tank 1- Buff-Off: Soak for 2 minutes at 170oF with ultrasonics off. Follow with a soak for 3 minutes at 170oF with ultrasonics on at 20 kHz. The tank solution will consist of 2 pounds of product per 10 gallons of de-ionized water.

b. Tank 2- De-ionized water: Soak for 2 minutes at 140oF.

c. Tank 3- Ridoline 18: Soak for 2 minutes at 170oF with ultrasonics off. Follow with a soak for 3 minutes at 170oF with ultrasonics on at 20 kHz. The tank solution will consist of

2.33 pounds of product per 10 gallons of de-ionized water.

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d. Tank 4- Citronox: Soak for 2 minutes at 140oF. The tank solution will consist of 1.6 gallons of product per 100 gallons of de-ionized water.

e. Tank 5- De-ionized water: Soak for 2 minutes at 140oF.

f. Oven: Thoroughly dry in an air oven at 175oF.

g. Wrap openings in lint-free paper and an outer wrap of vacuum grade aluminum foil. Use clean white gloves for handling assembly components.

3.2.5.2 Alternate Cleaning procedure: The following cleaning process or equivalent (which will be provided in writing and subject to BNL approval) may be used if local codes and health and safety regulations allow.

a. Degrease in ZEP Pride E degreaser or other commercial degreaser according to manufacturer's direction for five (5) minutes.

b. Cold water tap rinse for one (1) minute.

c. Soak in non-etch alkaline cleaner (e.g., Oakite 166, ENBOND Q567, etc.) for five (5) minutes at > 65oC with air agitation.

d. Rinse in cold running tap water for > 2 minutes. If water beading appears, repeat step c.

e. Rinse in deionized water (minimum resistivity 500,000 ohm-cm) for > 2 minutes. Parts shall be sequentially rinsed in a minimum of three (3) in-line baths each using the type of deionized water specified above.

f. Dry parts of all traces of water in an air oven at a temperature of 65oC.

g. Wrap the part in lint-free paper and then tightly wrap the part in vacuum grade aluminum foil. Use clean white gloves for handling assembly components.

3.2.5.3 All Inconel® and 300 series stainless steel tube or pipe specified for the chambers shall be pickled prior to welding. Between steps d. and e. above, pickle in Hydrofluoric-Nitric acid solution (one part Hydrofluoric Acid 48%, one part Nitric Acid, 42o Baume, one part distilled water) at room temperature for 5 to 10 minutes or such time as necessary to remove scale and oxide without over etching the surface. The solution may be air agitated or the parts may be scrubbed with a 300 series stainless steel brush, used only on 300 series stainless steel, to help oxide removal. This is followed by a rinse in cold running tap water for > 2 minutes.

3.2.5.4 Alternate methods of pickling, pickling solutions, Diversey® polishing, or electro-polishing may be acceptable with BNL approval. Deviations from the procedures listed above may be made only with the written approval of BNL.

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3.2.5.5 Baking - Subsequent to final cleaning and prior to welding all stainless steel and inconel parts shall be vacuum fired at 450oC for 48 hours.

3.2.6 Welding - If there is any doubt whether the parts have been contaminated prior to welding, those parts shall be cleaned again. Cleaning of the chambers after welding is not permitted.

All parts shall be deburred prior to welding to ensure proper fit at assembly, and to prevent a handling hazard from sharp edges and burrs.

All welding shall be performed in a clean area. The welder(s) shall follow guidelines including those specified in section 3.1 of this specification. Therefore, clean gloves shall always be worn.

All jigs, fixtures, and heat sinks shall be clean. Only clean 300 series stainless steel brushes, used only on 300 series stainless steel, are to be used for removing oxides from welds. Power driven brushes, abrasive papers and abrasive wheels shall not be used.

The chambers shall be welded using the GTAW (Gas Tungsten Arc Weld) or Electron Beam (EB) processes. Unless otherwise indicated on the chamber drawings, all vacuum welds are to be made on the "vacuum side" of the chambers. When external vacuum welds are specified, the welds shall have 100% penetration and the inside of the chambers shall be purged with Argon throughout the welding operation, and cool down of the weld.

Where high strength requires welding on both sides of thick sections, the side facing the vacuum shall be a continuous weld and the opposite side shall be a skip weld. Continuous welds on both sides are not permitted.

There shall be no machining and or cleaning operations done after welding without written approval from BNL.

3.2.7 Brazing - Hydrogen or vacuum furnace brazing are acceptable for copper to stainless steel joints, for copper alloy cooling tubes to copper alloy absorbers, and for ceramic to metal joints.

All brazing joints shall have adequate filler metal to provide a flush, smooth fillet free from voids, blow holes, etc., and there shall be no visible evidence of inclusion. No silver soldered or soft soldered joints are permitted unless specified on applicable drawings.

3.3 Design, Construction and Workmanship

3.3.1 Applicable Drawings - The chambers shall comply with the dimensions, tolerances and notes specified on the applicable drawing(s).

3.3.2 Clean assembly procedures - After cleaning, all parts shall be handled in accordance with their intended use in an ultra-high vacuum system. They shall be kept free of smudges and blotches, which may result from handling and contact with dirt or oil.

The following guidelines shall be followed to keep the chambers and its component parts free from contamination:

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a. Assembly, welding, inspection, and packaging of the chambers shall take place in a dedicated clean area. This area shall not be located near machine tools, compressors, oily or dirty parts and tools, etc., which can contaminate the work area with hydrocarbons and dirt.

In addition, no eating, drinking, or smoking shall be permitted in this clean area.

b. All cleaned chambers and parts shall be kept wrapped in clean vacuum grade aluminum foil unless they are being worked on.

c. Clean parts shall only be handled with clean white nylon or cotton gloves. Clean gloves should only contact clean parts and tools in the clean work area. Replace gloves that contact unclean surfaces (hair, face, chair, floor, tools, door knob, etc.).

NOTE: Do not use nylon gloves on hot parts or surfaces; they can melt, causing injury.

d. If it is required that the arms or bodies of workers come in contact with the chambers, clean lab coats and separate elastic-cuffed sleeves shall also be worn. The lab coat sleeves and the open ends of the gloves shall be tucked into the elastic-cuffed sleeves to prevent debris (e.g., hair, etc.) from falling into the chambers. Replace lab coats that contact unclean surfaces (hair, face, chair, floor, tools, door knob, etc.).

e. All tools and inspection gages shall be cleaned in accordance with steps d and e of section

3.2.5.1 of this specification prior to contact with cleaned chambers and parts. When the tools are not in use, they shall be covered and stored to prevent their use on dirty parts.

Tools shall not be made of materials which can contaminate the clean parts (e.g., brass, plastic, zinc, and cadmium).

f. Work surfaces shall be thoroughly cleaned with detergent, rinsed with water, and wiped with alcohol before use in the assembly area. Surfaces shall be hard and non-absorbent (stainless steel, formica, etc.). Wood bench tops or similar materials are not acceptable.

3.4 Performance

3.4.1 Leak Rate - The chambers shall be leak tight when measured with a helium mass spectrometer with a minimum sensitivity < 1x10-10 Atm..cc He/sec. Leak tight is hereby defined as a total allowable leak rate of less than 2 x 10-10 Atm.cc He/sec with the chamber evacuated to a pressure of <1x10-5 Torr and externally pressurized to 760 Torr minimum.

3.4.2 Environment - The chambers shall meet all performance requirements when subjected to the following conditions:

a. Internal Pressure: Vacuum (0 psia) to 27 psia, with the chamber externally pressurized to atmospheric condition.

b. External Pressure: A minimum of 18 psia, with the chamber evacuated to < 1 psia.

c. Rate of Temperature Change: 75oC/hour

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3.4.3 Outgassing

3.4.3.1 The outgassing rate of the interior surfaces of the chambers shall not exceed 1 x 10-10 Torr Liters/sec cm2 after pumping on the chambers under vacuum for 100 hours. Conventional all-metal ultra-high vacuum (UHV) practices shall be used in making these measurements.

3.4.3.2 The chambers shall exhibit no traces of HCl, oils or other contaminants with atomic mass of 35 or greater than 40 amu with the exception of 44 when tested using a residual gas analyzer with a minimum detectable partial pressure of 1x10-11 torr N2. The predominat gas compoinent shall be hydrogen and be at least 60% of the total pressure after being pumped for 100 hours.

The sum of partial pressures of atomic mass 35 and 40 thru 100 excluding atomic mass 44, shall be less than 1% of the total pressure of the system.

3.4.4 Bake out Requirements

3.4.4.1 The ramp rates of the bake out shall be 50oC/hr. unless otherwise specified to protect the chamber from damage resulting from excessive thermal stress. The duration of the bake out will be specified to optimize schedule and resulting vacuum improvement.

3.4.4.2 Stainless steel, inconel® and ceramic chambers shall be bakeable, if required, to temperatures of up to 300oC with internal vacuum.

3.4.4.3 Aluminum and copper chambers shall be bakeable, if required, to temperatures of up to 150oC with internal vacuum.

4.0 VERIFICATION/ACCEPTANCE TESTING

4.1 Classification of inspection/tests

The inspection/test requirements specified herein are as follows:

• In process/Pre-Shipment

• BNL Performed

Articles furnished in compliance with this Specification shall be produced under the controls established herein and as required by the applicable contract. The seller is responsible for providing chambers and or components that are in complete compliance with this specification.

Evidence of noncompliance with any requirement specified herein, shall constitute cause for rejection.

4.2 In process/Pre-Shipment

The seller shall perform all inspection/tests specified herein on all chambers supplied under this contract. All chambers shall pass these tests prior to delivery. The seller shall supply to BNL with each delivered chamber, the associated certificate of conformance and seller test data in accordance with this section.

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4.2.1 Visual Inspection - The chambers shall be inspected for any dents or damage, poor workmanship, repairs of welds and internal and external cleanliness.

4.2.2 Dimensional Inspection - Measurements shall be performed with the chambers in a relaxed and unrestrained state. Dimensions of the chambers shall conform, within the allowable tolerances, to the dimensions specified on the drawings.

4.2.3 Leak Rate Test - The seller shall verify that each chamber is leak tight to the requirements specified herein. Leak checking shall be performed with a helium mass spectrometer leak detector having a minimum sensitivity of less than or equal to 1x10-10 Atm. cc He/sec and in accordance with ASTM-E498/E498M. Viton O-rings may be used as temporary seals for leak detection. However, the use of lubricants or greases of any kind is prohibited.

4.3 BNL Tests

BNL reserves the right to perform any test on the chambers, at BNL expense and facilities, for verifying full compliance with any requirements of this contract. Evidence of noncompliance with any requirement specified herein, shall constitute cause for rejection.

4.3.1 Outgassing Measurements - Conformance to the outgassing requirements of section 3.4.3 of this specification shall be tested using conventional all-metal ultra-high vacuum (UHV) practices. During initial pump down and after bake out, if specified, a residual gas analyzer scan shall be performed for atomic mass 0 to 100. The results of these readings shall be used to determine conformance with sections 3.4.3 of this specification.

5.0 PREPARATION FOR DELIVERY

5.1 The Seller is responsible for the proper packing or crating to ensure that damage is not incurred during shipment.

5.2 The chambers shall be packaged individually by the seller in clean, transparent chloride-free plastic bags. The chambers shall be shipped to BNL in boxes which are durable enough to facilitate subsequent storage at BNL after completion of incoming inspection without damage.

6.0 NOTES

6.1 Performance Objectives

The supplier is encouraged to make recommendations for changes in the configuration which might lead to an improvement in performance, reliability, or safety, or a reduction in cost.

Simplicity in operation, ease of maintenance, and an improvement in the performance and reliability of the specific functions beyond the requirements of this specification are objectives which shall be considered in the production of this article. Where it appears a substantial improvement in simplicity of design, performance, ease of maintenance or reliability will result from the use of materials, parts and processes other than those specified, it is desirable that their use be investigated.

Specification for Fabrication and Cleaning of CAD Vacuum Chamber/Assemblies