NUMI NuMI Horn Testing Jim Hylen (FNAL) NBI02 March 13, 2002 Page 1 NuMI Prototype Horn & Final Power Supply Testing Magnetic Field Measurement Vibration Measurement Pulse-to-pulse stability Fatigue Lifetime Measurement DeBugs (Description of Horn for reference)

NUMI NuMI Horn Testing Jim Hylen (FNAL) NBI02 March 13, 2002 Page 2 Magnetic Horn General Design Features Large toroidal magnetic field Requires large current, 200 kAmp Thin inner conductor, to minimize   absorption Water spray cooling on inner conductor Most challenging devices in beam design Prototype test to check design Focus   toward detector Outer Conductor Inner Conductor Stripline Drain Insulating Ring Spray Nozzle   

NUMI NuMI Horn Testing Jim Hylen (FNAL) NBI02 March 13, 2002 Page 3 Horn Fabrication Precision Welding

NUMI NuMI Horn Testing Jim Hylen (FNAL) NBI02 March 13, 2002 Page 4 Prototype Horn at Test Stand upstream bell endcap Features: Anodize outer conductor (corrosion, insulation) Nickel plate inner conductor (corrosion, fatigue)

NUMI NuMI Horn Testing Jim Hylen (FNAL) NBI02 March 13, 2002 Page 5 Horn Power Supply Capacitor Bank + SCRs Moves as single 11 ton unit Other side looks identical Supplies 205 kA to two horns in series Variable 2 ms to 5 ms half-sin-wave pulse width 1.87 second repetition rate mF caps.

NUMI NuMI Horn Testing Jim Hylen (FNAL) NBI02 March 13, 2002 Page 6 Horn Power Supply SCRs SCRs (3 of 12) Stripline

NUMI NuMI Horn Testing Jim Hylen (FNAL) NBI02 March 13, 2002 Page 7 Horn Power Supply SCRs Charging supply and controls/interlock rack Second charging supply added in series for some cap-bank and pulse-width combos Now using one supply at 860 Volts max. output Problem during operation: on circuit with diodes to protect supply from cap. bank back-feed in case of fault – had to use higher rating component

NUMI NuMI Horn Testing Jim Hylen (FNAL) NBI02 March 13, 2002 Page 8 Horn Field Measurement Main horn field between conductors Field between conductors:  1/R as expected very symmetrical agrees within meas. error with current

NUMI NuMI Horn Testing Jim Hylen (FNAL) NBI02 March 13, 2002 Page 9 Horn Field Measurement in ‘field-free’ region through center of horn Error or fringe field in “field-free” region down center of horn is so small that no correction should need to be put into the Monte Carlo. Measurement with probe moving along horn axis 2% F/N criterion on flux in M.E. beam (approximately scaled to 0.85 ms test pulse from 2.6 ms operational pulse)

NUMI NuMI Horn Testing Jim Hylen (FNAL) NBI02 March 13, 2002 Page 10 NuMI Horn 1 Vibration Measurements Why-Confirm ANSYS modeling so believable horn lifetime estimation. -Horn resonances driven by transmission line, ground vibrations, etc.? -Archival data useful if have a stress/fatigue failure How-Use “laser” non-contact absolute position sensor; eclipseometer. Bandwidth ~ 20kHz. Sensitivity ~ 0.1 nanometer. Measure at upstream inner cond. bell, 205 kA, 850  sec half-cycle, 1.9 sec rep rate. Resonances described by a linear model x =  A i sin(  i t) exp(-t/ i ) Resonance Relative Decay Source Freq. (Hz) Amplitude Const. (sec) Horn Innerconductor Horn Innerconductor Transmission Line Transmission Line Transmission Line Horn Thermal

NUMI NuMI Horn Testing Jim Hylen (FNAL) NBI02 March 13, 2002 Page 11 NuMI Horn 1 Vibration Measurement on Horn Bell Endcap 6  m 55  m (ANSYS gives 71  m) 1.17 kHz (ANSYS 1.19 kHz) DATA Linear Model DATA Linear Model 2 sec0.03 sec

NUMI NuMI Horn Testing Jim Hylen (FNAL) NBI02 March 13, 2002 Page 12 Pulse-to-pulse Stability peak current and field monitor Bdot coil field monitor (sensitive to water temp) I1: Current in Stripline 1 I2 I3 I4 Initial warm upabout 14 hours of data 1%

NUMI NuMI Horn Testing Jim Hylen (FNAL) NBI02 March 13, 2002 Page 13 6 million pulses 2/3 of a ‘NuMI Year’ on horn prototype

NUMI NuMI Horn Testing Jim Hylen (FNAL) NBI02 March 13, 2002 Page 14 Metal Flakes in Horn Specks of metal collected on ceramic insulator at bottom of horn - appears to be Nickel Parts of horn visible through ports, both anodized O.C. and nickel plated I.C, look like new – would have to disassemble horn to locate source of flaking No operational problem noted yet, but indicates water filter important to prevent possible clogged spray nozzles In horn, under water Some flakes removed

NUMI NuMI Horn Testing Jim Hylen (FNAL) NBI02 March 13, 2002 Page 15 Lesson from Prototype Water line A water line overstressed a feedthrough, which cracked and allowed a drip to develop (The slow leak would not have been fatal to a horn in the NuMI beamline) Have modified the design Old water tube New strain-relieved water tube

NUMI NuMI Horn Testing Jim Hylen (FNAL) NBI02 March 13, 2002 Page 16 Horn and Stripline Afterthought: Unistrut brace between striplines was added to reduce vibration. Brace cracked, has been removed. More noise without brace, but vibration of horn only marginally affected (Temporary temperature probe)

NUMI NuMI Horn Testing Jim Hylen (FNAL) NBI02 March 13, 2002 Page 17 Summary of Test Minor troubles encountered Redesign water line Beef up charging supply snubber circuit Very successful test: Horn has taken 6 million pulses without breaking Magnetic field looks great Vibration matches expectations Power Supply stability is good

NUMI NuMI Horn Testing Jim Hylen (FNAL) NBI02 March 13, 2002 Page 18 General Horn System Parameters ParameterHorn 1 Horn 2 Neck Radius (cm) Wall Thickness, Neck (mm) Outer Conductor Radius to i.d. (cm) Inductance (nH) ~457 Resistance (µΩ) 208 (meas.) <112 Average Power from Current Pulse (kW) 17.0 <7.5 Power Flux at Neck (W/cm 2 ) 14.5 <4.7 Temperature Rise at Neck ( o C) 22.8 <7.1 * Note: Above heat load numbers are from original design pulse width of 5.2 msec

NUMI NuMI Horn Testing Jim Hylen (FNAL) NBI02 March 13, 2002 Page 19 Mechanical Loading and Analysis Mechanical Loading of Horn is the Result of : - Current pulse thermal expansion from resistive heating (peak at the end of the pulse) - Magnetic forces (peak at the mid-pulse) - Beam heating from particle interaction in material Horn 1Horn 2 Inner conductor resistive heating 17 kW <7.5 kW Inner conductor beam energy deposition kW 0.4 kW Outer conductor beam energy deposition 14.5 kW 5.4 kW(1” thick) * Note: Above numbers from original design pulse width of 5.2 msec

NUMI NuMI Horn Testing Jim Hylen (FNAL) NBI02 March 13, 2002 Page 20 Mechanical Loading and Analysis Areas of Highest Mechanical Loading Values for 5.2 msec Pulse Width US end cap: minimum stress before pulse is psi; maximum stress at mid-pulse is psi; mean stress is psi with an alternating stress of 3995 psi; Stress ratio R=0.11 Under the above calculated stress levels, allowable maximum stress for 10 7 cycles at endcap is 26.5 ksi resulting in fatigue safety factor of 2.9 Neck of horn: stress at mid-pulse is psi; stress at end of pulse is psi; mean stress is 304 psi with alternating stress 4047 psi; Stress ratio R = (Note: Negative value of R results in lower value of fatigue stress limit) Under the above calculated stress levels, allowable maximum stress for 10 7 cycles at neck is 15.3 ksi resulting in fatigue safety factor of 3.5 Stress in conductor weldment regions is very low (<<4 kpsi)  Fatigue data from Aerospace Structural Metals Handbook

NUMI NuMI Horn Testing Jim Hylen (FNAL) NBI02 March 13, 2002 Page 21 Corrosion Considerations Factors Affecting Fatigue Life Moisture reduces fatigue strength –For R = -1, smooth specimens, ambient temperature: N=10 8 cycles in river water,  max = 6 ksi N=10 7 cycles in sea water,  max ~ 6 ksi –Hard to interpret this data point N=5*10 7 cycles in air,  max = 17 ksi –The above data is motivation for utilizing corrosion/encapsulating barrier layer over aluminum substrate

NUMI NuMI Horn Testing Jim Hylen (FNAL) NBI02 March 13, 2002 Page 22 Horn Corrosion Barrier Layer I.C.: Electroless nickel: reasonable corrosion barrier properties, non- dielectric, more expensive, limited vendor base with large tank capacity –Conducted fatigue test of nickel coated aluminum samples at the 10 7 fatigue limit and compared results with equivalent non-coated aluminum specimens: coated samples survived 1.7x 10 7 cycles, non-coated samples failed at 0.6x 10 7 cycles –Use high phosphorus electroless nickel (0.0005” ” thick) on inner conductor and conductor supports O.C.: Anodizing: best solution for lower stress thick cross-section areas Type III (hard coat sulfuric acid, ”), R c 60-65, dielectric strength of ~800 V/mil –Type III hardcoat anodize is selected for outer conductor and thick lead in portion of inner conductor; not suitable for thinner/higher stress areas of inner conductor due to approximate 60% reduction of fatigue strength –Provides extra protection against I.C. to O.C. short circuit

NUMI NuMI Horn Testing Jim Hylen (FNAL) NBI02 March 13, 2002 Page 23 Single pass, full penetration CNC weld is required to minimizing conductor distortion, assure repeatability, and control internal weld porosity Proper cleaning, handling, fixtures, and weld parameters are crucial to minimize conductor distortion and internal weld porosity NuMI approached welding solution via parallel paths 1) Identify vendor base to subcontract critical horn conductor welding - Vendor base for CNC TIG welding extremely limited and expensive; less flexible fabrication path than in-house - Prototype horn 1 fabricated in this manner using Sciaky as prime contractor, ANL as subcontractor 2) Investigate the development of welding capability in-house - Have specified, benchmarked, purchased, and commissioned a Jetline fully automated TIG welding system for producing controlled conductor weldments - System installed at MI-8 horn facility - Long term solution for welding 4 initial horns (production and spare horn 1 and horn 2) Horn Fabrication Precision Welding

NUMI NuMI Horn Testing Jim Hylen (FNAL) NBI02 March 13, 2002 Page 24 Conductor Fabrication Inner conductor fabricated from 6061-T6 billet per QQA 200/8 Relatively good strength (UTS ~ 45 ksi, YS ~ 40 ksi, R=-1 FS ~ 16 ksi) Available in variety of sizes and shapes Welds readily Relatively good corrosion resistance All prototype horn inner conductor parts CNC machined by Medco to tolerances better than ~ 0.002” Inner conductor welding complete - CNC TIG - Overall tolerances held to ±0.010” over ” length (straightness and radial deviation from ideal) Outer conductor overall tolerances better than ±0.010” Outer conductor anodized, inner conductor uses electroless Ni coating Stripline contact surfaces use ” silver brush plating Technical Progress Prototype Horn 1 Design Summary

NUMI NuMI Horn Testing Jim Hylen (FNAL) NBI02 March 13, 2002 Page 25 Water Seals - Total of 64 water seals in horn - Utilize EVAC aluminum delta seals on KF style flange Bolted Connections - Utilize TimeSert threaded inserts, pullout exceeds 9600 lb. on 3/8” insert - As a reference, maximum end wall reaction is approximately 4270 lb. Current Contact Surfaces - Current surfaces have 32 µin finish, ” ” silver plate finish - Interface clamping pressure exceeds 1400 psi - As reference, lithium lens secondary contact lead is 5.01 in 2 for 6285 Arms; Prototype horn 1 contact area is 9.2 in 2 for 7250 Arms. Corrosion/Erosion Control - Outer conductor and thick lead in section of inner conductor employs ” thick Type III hard coat anodize followed by mid-temp nickel seal - Inner conductor utilizes ” thick high phosphorus electroless nickel Inner Conductor Spider Support Columns - Design has been experimentally tested to 36 million cycles at defections of ±0.031” with 80 lbs. axial preload with no failures Prototype Horn 1 Design Summary