X-Band RF Structure Fabrication at Technical Division, Fermilab

Tug T. ArkanNLC Collaboration Meeting

June 18-20, 2003

NLC Collaboration Meeting June 17-20, 2003 2

Outline

Mission StatementRF Structure Factory & Infrastructure UpdateFXB Type RF Structures Fabrication StatusFXC Type RF Structures Fabrication R&DMilestones, Goals & Schedule

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MissionOriginal mission was to develop industrialization of the structure manufacturing process. This included:

Developing vendors to supply structure component partsDeveloping vendors to supply assembled structures

Our mission has evolved into the above, plus as a higher priority, we are to supply test structures in support of the Eight Pack Program at SLAC

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RF Structure FactoryFNAL RF Technology and Development Group goals for the RF Structure R&D Factory:

RF DesignRF Disk Fabrication & Quality AssuranceRF Structure Fabrication & Quality AssuranceInfrastructure Setup for all above

Major Infrastructure of the Factory are:Two Clean Rooms (Class 1000 & 3000, RF QC Area, Work AreaTwo Vacuum Furnaces inside a soft sided Clean Room (Class 1000)Clean Room Leak Detector, Clean Room compatible Vacuum Pumps, RGA, Anaerobic Chambers, DI water system, 2 Network Analyzers, Bead-Pull Fixture, Single Disk RF QC Fixture, etc.

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Infrastructure UpdateWe managed to fabricate FXB structures in our defective large vacuum furnace. Excessive maintenance effort & related cost needed to keep the furnace running reliablyLarge Vacuum Furnace hot zone will be replaced with a new, better design, reliable hot zone We ordered the new hot zone on 2nd

week of June 03 from Schwarzkoph, a reputable hot zone builder at Franklin, MA (Delivery in 12-14 weeks)The new hot zone will fit the existing vacuum chamber of the furnace w/o making any modification to the vacuum chamber, power feed-throughs, power supply and controller system & software of the furnace

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Infrastructure Update

Leak Detector, RGA, Ion Pumps & Turbo-Cart Pump Station

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FXB Type RF StructuresWe have currently produced three 60-cm long traveling wave structures: FXB-002, FXB-003 and FXB-004FXB-002 and FXB-003 were high power tested at NLCTA, SLAC. FXB-002 performed good for the high gradient test (4 breakdowns per hour at 65 MV/m, 240 ns pulse width). FXB-003 performed better than FXB-002 (0.25 breakdowns per hour at 65 MV/m, 400 ns pulse width) due to more care about cleanliness and clean room working proceduresFXB-004 is currently installed at NLCTA and it will be tested on midJune 03FXB-005 is currently being fabricated. Delivery due to SLAC on the last week of July 03We will produce three more FXB type (FXB-005, FXB-006 & FXB-007) RF structures. All FXB structures will be used for 8-pack test at SLAC

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FXB Type RF StructuresDesign is identical to SLAC H60VG3 structure (except brazing grooves in the disks)All brazed structures, no diffusion bondingDisks are precision machined, no diamond turningCouplers are precision machined. Fat-lipped design has some diamond turned RF surfaces (iris area). FWG design is all high precision machined

From FXA to FXB structures:Disk OD was increased from 45 mm to 61mm. Structure length was increased from 20 cm to 60 cm Fat-lipped design couplers to reduce the pulse heating (FXB-002 and FXB-003)Fermilab design waveguide (FWG) couplers (FXB-004 to FXB-007)Disk & Coupler Etching with SLAC C01 procedureStrict Clean Room Working ProceduresTraveler Development (it is currently fully implemented & controlled) Starting from FXB-004, Vacuum Bake the completed Structure before shipping to SLAC

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FXB-002, -003 & -004

FXB-002

FXB-003 FXB-004

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Fabrication Process Flow - I

Single Disk RF QC RF Disk & Coupler Etching

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Fabrication Process Flow - II

Coupler Body to Plate Brazing

35%Au – 65%Cu Braze Alloy

1030 degree C

RF Flange to Coupler Brazing

50%Au – 50%Cu Braze Alloy

990 degree C

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Fabrication Process Flow - IIIRF Disk Stack Brazing

72%Ag – 28%Cu Braze Alloy (CUSIL)

780 degree C

Coupler to Disk Stack Brazing

72%Ag – 28%Cu Braze Alloy (CUSIL)

780 degree C

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Fabrication Process Flow - IV

Final Brazing

61.5%Ag –23.5%Cu – 15%In Braze Alloy (INCUSIL)

725 degree C

Water Tube Brazing

50%Au – 50%Cu Braze Alloy

990 degree C

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Fabrication Process Flow - VBead-Pull & RF Tuning

Vacuum Bake

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Fabrication Process Flow - VI

Room Temperature RGA Readings

Strongback Assembly

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FXB-002 After High Power TestBead-Pull Measurements before & after High power test: No Phase ShiftBake at 550 degree C under 1 Torr Partial Pressure of 100% Hydrogen for 2hrs; vacuum bake at 550 degree C for 24 hrsRGA before & after hydrogen treatmentBorescope before & after hydrogen treatment

Input Coupler Disk #1 Output Coupler

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FXC type RF StructuresDesign is identical to SLAC H60VG3S17 structure (except brazing grooves in the disks)All brazed structures, no diffusion bonding. New brazing features were added to the disksDisks & Couplers are precision machined, no diamond turningWe will produce four 60-cm long traveling wave FXC RF structures: One prototype and FXC-001 to FXC-003Fermilab design FWG couplers and matching disks will be usedThese structures will be used for Eight-Pack test at SLAC along with FXB structures

From FXB to FXC structures:HOM holes and keyhole slots were introduced to the RF disksFermilab design waveguide (FWG) couplers and matching disks Tuning holes were increased from 2 to 4Rotational alignment feature on the RF disks and the V-Block FixtureRosette shape dam instead instead of circular dam to stop the braze material flow into the RF volumeHOM Couplers & Waveguides will be introduced starting from FXC-002

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Vendors & Machinability TestsLaVezzi FXC Test Disks: (H75VG4S18, Disk#1)

10 identical disks were received. 8 were measured with Single Disk RF QC. 2 were measured with Mechanical QC

Medco FXC Test Disks: (H75VG4S18, Disk#1) 15 identical disks were received. 13 were measured with Single Disk RF QC. 2 were measured with Mechanical QC

FXC Disks Stress Relieving

FWG Couplers Stress Relieving

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FXC Disks Simulations

E-Field H-Field H-Field zoom

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LaVezzi Disks RF QCLaVezzi disks are good:

absolute deviation is about: – 3 MHz

random errors: +-3 MHz

LaVezzy disks #1 for FXC-75.Deviation of set-up mode frequencies from simulated values.

-14

-12

-10

-8

-6

-4

-2

0

1 2 3 4 5 6 7 8

Number of copy

MH

z

"0"-like mode"Pi"-like mode

H-field, “0”-like mode

E-field, “0”-like mode

H-field, “Pi”-like mode

E-field, “Pi”-like mode

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LaVezzi Disks Mechanical QC

Cordax CMM, 2.5 micron accuracy, +-1 oF Temperature control in the QC lab

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LaVezzi Disks Mechanical QCDiam. 2a & Iris Profile

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LaVezzi Disks Mechanical QCRadius 0.079 and its profile

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LaVezzi Disks Mechanical QCRadius 0.020 to the 2a cup side

Radius 0.020 to the flat backside

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Medco Disks RF QCMedco first 15 test disks are not acceptable

200 MHz absolute error

random errors are acceptable (+-5 MHz)

MedCo FXC test disks #1. "0"-mode. Deviation from average.

-5

-4

-3

-2

-1

0

1

2

3

4

5

0 2 4 6 8 10 12 14 16

Disk number

Dev

iatio

n, M

Hz

E-field, “0”-like mode

E-field, “Pi”-like mode

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Medco Disks Mechanical QCRadius 0.079 and its profile

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Medco Disks Mechanical QCRadius 0.020 to the 2a cup side

Radius 0.020 to the flat backside

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Medco Disks Mechanical QCDiam. 2a & Iris Profile

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Brazing vs. Diffusion BondingReliable Diffusion Bonding (DB) of RF disks require a surface flatness of 0.5~1.0 micron on the bonding surfacesWith high precision machining, one can achieve best 2.5 micron surface flatness. Required surface flatness tolerances for DB can be achieved with single crystal diamond turning Diamond turning is a very small and specialized market. It is very costly compared to high precision machiningWe want to always keep the industrialization philosophy for NLC in our minds even though we pursue R&D for the current timeSo, we decided not to pursue further studies on diffusion bonding for FXC type RF disksWe redesigned brazing features on FXB disk for FXC (with HOM holes) disk Brazing Tests were done to evaluate the new braze joint and dam design

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Diffusion Bonding Tests

Dummy FXC DB disks:

Flatness Measurements

Diffusion Bonding

Sectioning

Polishing & Etching

Analysis under microscope

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Brazing Tests

0.89 mm diam. brazing wire

FXC Disk Rosette Shape Dam

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Brazing Tests

0.89 mm diam. CUSIL braze wire flows very good into the milled braze groove. This is good to prevent any virtual leaks and also for the RF Structure quality factor

There is a slight leakage of braze material into the RF volume.

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FXC Disks & Chemical EtchingA non hand-deburred FXC Disk macro burrs were analyzed before & after SLAC C01 procedure Chemical Etching

MedCo after etching

-4.5

-4

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

00 1 2 3 4 5 6

Disk number

MH

z

5 FXC Disks were stacked and measured before & after SLAC C01 procedure Chemical Etching

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FWG Output Coupler (FXB)3 FWG I/O Couplers were received from MEDCO for FXB type RF

StructuresMechanical QC were done. All 3 couplers have within tolerances 2a &

2b dimensionsFXB-004 output coupler has approx. +15 MHz Frequency shift that RF

group was not able to tune: Braze material flow into the RF volumeCoupler iris deformation due to weight of disk stack and Input coupler

during brazingA test was done. Spare FWG output coupler sub-assembly was brazed. A 35

lbs. dead weight was put to simulate approx. weight of a disk stack and input coupler. The coupler was baked with usual CUSIL cycle at 780 degree CSimulation of FXB FWG output coupler: 11.019 GHzMeasurement of the test output coupler before test: 11.0169 GHzMeasurement of the test output coupler after test: 11.031 GHz (+15.6 MHz)

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FWG Output CouplerAdapter

Short

Short&antenna

Coupler

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Milestones & GoalsWe will complete the FXB type RF structure

series fabrication by August 03We are buying a new hot zone for our large

vacuum furnace. The furnace will work more reliably for the fabrication of FXC type RF Structures

We evaluated our vendors for FXC type RF disk and coupler fabrication.We ordered 4 sets of RF disks and couplers for FXC structures

We will continue to fabricate RF structures in support of Eight-Pack Test Phase II @SLACWe are developing more vendors in order to

start early stage industrialization of the project. Our goal is to maximize the competition between our vendors and minimize the cost & delivery time of our parts

FXB-002 is our first RF structure fabricated and sent to SLAC for high power testing. Some of us from Fermilab RF Conventional Group, at NLCTA, SLAC with FXB-002, during last collaboration meeting