PXIE RFQ Engineering Design and Fabrication Project X Fall 2011 Collaboration Meeting Fermilab – October 25, 2011 Steve Virostek - Engineering Division Lawrence Berkeley National Laboratory

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, Topics LBNL RFQ experience Approach to PXIE RFQ design RFQ design features Fabrication tests Engineering analyses Current progress Fabrication Plan Schedule

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, LBNL RFQ Experience LBNL has developed approximately eight different RFQ designs over the past 30 years We have fabricated five different RFQ’s in our shops using both bolt-together and brazing techniques The SNS RFQ design team (physicist, engineer, mechanical designer) has been reassembled for the PXIE RFQ project RFQ4 (bolt-together design) SNS (RFQ5 – brazed structure)

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, SNS RFQ Photos

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, PXIE and IMP RFQ’s LBNL is working with the Institute of Modern Physics (IMP) in Lanzhou, China to design a CW RFQ The engineering design requirements for the PXIE and IMP RFQ’s are virtually identical: CW operation, MHz, 2.1 MeV beam energy, 4.4 m long (PXIE) vs. 4.2 m (IMP) LBNL is developing the detailed design for both RFQ’s in parallel during FY12 A series of fabrication tests are being undertaken by IMP which will also be of benefit to the PXIE RFQ project

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, PXIE RFQ Design Approach Develop the PXIE design based on past LBNL RFQ experience Use proven, low risk techniques from the SNS RFQ design –Four vane copper-to-copper braze –Fly cut modulated vane tips –Brazed, water cooled pi-mode rods –Low profile, bolted module joints –Removable fixed slug tuners

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, Design Approach (continued) Eliminate high risk, high cost features from the SNS RFQ –Gun drilled cooling passages instead of cut-and-cover approach saves a high risk brazing step –No Glidcop outer shell eliminates the expense of the material and the Au-Cu foil braze –O-rings and RF spring seals instead of tin gaskets for the tuners eliminates the large sealing forces

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, PXIE RFQ Design Features All OFHC copper body machined from solid billets 4-vane cavity structure with fly cut modulated vane tips Four 1.1 m long cavity modules with bolted joints MHz frequency Total length: 4.4 m Pi-mode rods for mode stabilization Distributed fixed slug tuners CAD model of assembled 4-module PXIE RFQ design concept

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, RFQ Module Design Features Each module consists of four separately machined vanes Precision ground mating surfaces High reliability copper-to-copper braze forms cavity module 20 fixed slug tuners/module 8 pi-mode stabilizing rods per module 12 field sensing loops per module RF power feed through two loop couplers

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, RFQ Module Design Features Gun drilled vane and outer wall cooling passages Two vacuum pumping ports per module Separate wall and vane cooling circuits provides active tuning capability Sealing provided by RF and O-ring seals at bolted joints Design details will be presented in the following slides

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, Cooling passages are gun drilled into vanes (from one or two ends) Blind drill modules 1 & 4 Through drill module 2 & 3 Approximately 12mm diameter Cooling Passages

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, Cooling channel distribution 4 inner channels 8 outer channels Cooling Passages

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, Vanes are completely machined along their length before oven brazing E-beam weld cooling passage plugs before machining, both ends Pre-braze machining includes: Modulations Ports and holes Braze wire grooves Radial matcher Vane cut back Grinding modulations Vane Machining

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, A special cutting tool is needed for modulating the vane tips VANE TIP Carbide cutter High strength steel holder Vane Tip Cutting

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, Pi-mode rods are brazed in during the module oven brazing step Oxygen free copper tube, hollow, 10mm outside diameter Oxygen free copper ferrule The small holes hold braze wire for the oven brazing procedure Ferrules are a tight sliding fit on the tube, both ends Pi-mode Rods

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, Threaded hole Coolant is pumped through the pi-mode rods during operation Pi-mode Rod Braze

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, Every groove filled Every braze wire staked (secured) No high spots No braze wire protruding Braze wire Braze wire in grooves Vane Braze Preparation

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, The assembly fixture used on the SNS RFQ Ends must be aligned precisely to line up modulations Fine adjustment controls Pre-braze Assembly

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, Braze in a hydrogen oven in a vertical position SNS RFQ in a braze oven Additional vertical supports Vanes are held in place with the braze clamps Module Brazing

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, Raised lip Canted spring groove O-ring groove Modules are end machined after oven brazing: Canted spring groove added O-ring groove added Raised lip added Final length machined RFQ End Machining

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, Joint Plates Stainless steel Connect modules to modules Connect RFQ to the beam line Provisions for cooling passage connections Cooling line connector Joint plate Module Joining

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, Joint plates have a step that fits into a groove in the vane and bolts that provide additional friction Step Groove Additional friction bolts - M6 Corner bolts – M8 Cooling line connector 24 per module Joint plate Module Joint Plates

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, Snap ring Set screw Screw plate Copper tuner O-ring Canted spring Top view Cross- section view 60mm Final length determined by low power RF testing after oven brazing Fixed Slug Tuners

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, Canted spring groove O-ring and groove Attaches to RFQ with bolts SNS sensing loop RF Pickup Loops

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, Vane cutting tool test Full length vane fabrication test Test module (1/2 length) Fabrication Tests Braze clamp test

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, RFQ Finite Element Analysis Finite element model of the RFQ body developed using ANSYS Model is a 3-D slice of one quadrant of the RFQ cross section –Nodes on slice surfaces constrained to be coplanar to allow axial thermal growth and correctly calculate longitudinal stresses –2-D plane strain elements would over-constrain the model longitudinally and give artificially high axial compressive stresses

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, RFQ Thermal FEA Thermal loads on FEA model –RF heating on vanes/walls from Superfish model –Cooling channel convection –Peak wall power density is approximately 0.6 W/cm 2 –Total nominal wall power is ~65 kW –Total power will be closer to 100 kW (due to cutbacks, tuners, pi-mode rods) Thermal solution provides temperature contours

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, Frequency Tuning Analysis The RFQ cavity resonant frequency can be shifted by altering the cooling water temperature Due to the sensitivity of the frequency to the vane tip spacing, a wider tuning range can be achieved by varying only the vane water temp. Displacements from the structural analysis are used in an ANSYS RF model to predict tuning performance Analysis results: Vane control: -8.7 kHz/°C Wall control: +6.1 kHz/°C Uniform control: -2.6 kHz/°C ~200 kHz tuning range possible Wall channels Vane channels

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25,  Each module has 12 cooling channels (8 wall, 4 vane)  12 mm diameter channels flow 0.26 l/s at 2.29 m/s velocity -Reynolds number is 25,900 (turbulent flow) - Maximum flow to prevent Cu erosion is 4.57 m/s - Lower flow rate used to reduce chiller size  Total system flow: 8.3 l/s wall, 4.1 l/s vane - Nominal water temperature rise is 1.9°C - Commercial closed-loop chillers that meet system requirements are readily available - Two units needed (one for vanes, one for walls)  Small flow in pi-mode rods (.04 l/s each) necessary to limit axial thermal stresses RFQ Cooling System Commercial chiller example

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25,  Primary gas loads are: module joint and tuner O-rings, cavity wall outgassing, gas from LEBT  8 vacuum ports total (2 per module)  RFQ uses four 10” cryopumps (2 per side)  Additional 4 vacuum ports are blanked off  Cavity to be detergent cleaned (no baking)  Viton O-ring seals to be pre-baked and ungreased  More detailed analysis will be required – possible that 8” pumps can be used RFQ Vacuum System Round to square manifold

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, Current Progress  RFQ preliminary engineering design is complete Accurate 3D CAD model of 4-module RFQ is nearly complete Model includes: vanes w/gun drilled passages, pi-mode rods, tuner ports, vacuum ports, sensing loop ports, RF drive ports Model will contain detail necessary to generate fab drawings  Preliminary design of RFQ related subsystems is complete RFQ cooling scheme (body, cutbacks, pi-mode rods) RFQ vacuum system configuration (analysis TBD)  Fabrication tests have been identified and modeled  Initial thermal, RF and mechanical analyses are complete

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, Additional Engineering Tasks  Finalize fabrication test design details Generate detail fabrication drawings for tests Write an engineering note describing the test procedures  Perform additional thermal and stress analyses Vane cutback thermal analysis Cooling water flow analysis RFQ support points – stress and deflection analysis  Complete the final version of the RFQ 3D CAD model  Generate a complete set of fabrication drawings  Write detailed engineering notes to document the final RFQ design and the results of the analyses

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, Fabrication Plan A series of fabrication tests will be carried out by LBNL prior to completion of the final RFQ design -Detailed procedures and drawings provided by LBNL -FNAL will likely procure materials -LBNL will carry out and oversee fabrication tests and will review and document testing results as required -Tests will take place later in FY12 -Results of the IMP testing will be considered as well

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, Fabrication Plan (cont’d) After completing the detailed RFQ design, fabrication will likely be carried out primarily in the LBNL shops -Fabrication drawing package and related documentation generated by LBNL -FNAL will procure materials and supply to LBNL -Some specialized work by outside vendors: gun-drilling, brazing, e-beam welding -LBNL will oversee all aspects of the fabrication process LBNL will specify requirements for RFQ subsystems -Support structure, cooling system, couplers, etc. -FNAL to carry out design/fab/procurement in these areas

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, Design Schedule RFQ fabrication expected to take ~1.5 years

S. Virostek: PXIE RFQ Engineering Design Project X Fall 2001 Collaboration Meeting Fermilab – October 25, Summary Preliminary engineering design and analysis of the RFQ has been completed by LBNL The PXIE and IMP RFQ’s designs are nearly identical and are being carried largely out in parallel A series of fabrication tests have been proposed -Tests to be carried out by IMP in China -LBNL will repeat some tests in the US as needed Final design to be complete by the end of FY12 Fabrication expected to start in early FY13