1. Status Update of Ongoing Efforts for NuMI Horn 1 Stripline Redesign and Horn Change Out Kris E. Anderson All Experimenter’s Meeting 06-Jul-2015

2. Overview of Stripline Failure 7/6/15Kris E. Anderson | Status of NuMI Horn 1 Stripline Redesign and Horn Changeout2 Investigation 6/17/2015 drives replacing horn PH1-04 due to failed stripline –First 700 kW capable horn, in service since Sept. 2013, accumulated ~ 27 million pulses Spares of various configuration are on hand Stripline Fracture Location- Outer Conductor Stripline Fracture Location- Outer Conductor

3. PH1-04 Stripline Summary to Date 7/6/15Kris E. Anderson | Status of NuMI Horn 1 Stripline Redesign and Horn Changeout3 Failure is a fractured stripline conductor on lower beam-left quadrant of the horn PH1-04 cannot be pulsed and cannot easily be repaired. It must be replaced. Failure mechanism is under investigation - Previous ANSYS simulations for NOvA 700kW horn stripline indicated sufficient safety factor considering beam energy deposition and electromagnetic forces on conductors Modal characterization and pulsed operation vibration measurements conducted last year using the MI-8 horn test supply (850 µsec pulse) revealed some lightly damped modes and peak to peak displacements of ~ 165 micron in the flag region (i.e., the region where PH1-04 stripline fracture occurred) The dynamic ring down of the stripline can impose several hundred cycles of stress between the 1.33 sec cycle time pulse >>> Contributes to high- cycle fatigue

4. Test #6: Accelerometer locations @ position of maximum measured displacement vector sum X1, Y1, & Z1X2, Y2, & Z2 X3, Y3, & Z3 test650 kA0.5970.6230.562 100 kA1.8452.0321.583 200 kA5.8696.4625.002 These values are the 20 Hz to 1600 Hz total peak to peak displacement in milli- inches 7/6/15Kris E. Anderson | Status of NuMI Horn 1 Stripline Redesign and Horn Changeout4

5. Live Operating Motion –Expanded time scale – 200 kA, 1.33 Hz repetition rate, Modal measurement location 46 Time axis expanded to show t=1.8 sec to t=3.0 sec. One can see that some modes of vibration “ring down” faster than others. This is due to the variation in modal damping for the modes. lightly damped mode at 424 Hz (takes a long time to decay) highly damped mode at 788 Hz (decays quickly) 7/6/15Kris E. Anderson | Status of NuMI Horn 1 Stripline Redesign and Horn Changeout5

6. Comparison of 400kW and 700kW Style Horn 1 Stripline shape changed for enhanced convective cooling Crosshair changed from Aluminum to Beryllium PH1-03PH1-05 7/6/15Kris E. Anderson | Status of NuMI Horn 1 Stripline Redesign and Horn Changeout

7. Comparison of 400kW and 700kW Style Horn 1 Striplines at location of fracture PH1-03PH1-05 7/6/15Kris E. Anderson | Status of NuMI Horn 1 Stripline Redesign and Horn Changeout

8. Spares Situation PH1-05: NOvA Design READY SPARE –Shares stripline design with PH1-04; might expect similar lifetime of ~30M cycles –Strong preference to modify before installation PH1-03: MINOS Design READY SPARE –Initially designed for 400 kW –Stripline design unlikely to have same weakness as PH1-04 –Some modification can be rapidly implemented to increase allowable power above 400 kW PH1-02: Used 400kW MINOS Design EMERGENCY SPARE –Ran for 46 millions pulses, never failed –Still quite hot – slated for disposal in 2020 –Cannot be modified PH1-06: NOvA Design IN FABRICATION –More than one year to be ready –Will want stripline design changes PH1-07: NOvA Design PROPOSED –Now will be needed as spare 7/6/15Kris E. Anderson | Status of NuMI Horn 1 Stripline Redesign and Horn Changeout

9. Schematic Plan I. Ongoing investigation of failure mechanisms –PH1-05 and PH1-03 vibration testing @ MI-8 test stand and ANSYS simulation –More in-depth visual investigation of PH1-04 in workcell –Ang Lee and Zhijing Tang from PPD to conduct ANSYS work –Purchase Order in progress to utilize David Larson of S&V Solutions II.Modify PH1-03 for higher beam power and install this shutdown –Tight schedule, but can be effected without lost beam time –Enhanced downstream cooling to reduce stripline flag and contact terminal temperatures –Install Be cross-hair for higher beam intensity (Done) –PH1-03 vibration measurements and final outfitting needs to be done by week 8 of shutdown (8/24) –Conduct detailed ANSYS modeling to help determine fatigue safety factor vs. beam intensity (intent is to have this well understood by time of beam startup) –Operate PH1-03 at some specified power limit until PH1-05 stripline redesign is ready, then remove limits III. Modify PH1-05 stripline to enhance fatigue lifetime –Will need several months (~ 8 to 10 months) to devise and implement solution IV.Advance construction of PH1-06 and PH1-07 in parallel with above efforts (some manpower limitations) 7/6/15Kris E. Anderson | Status of NuMI Horn 1 Stripline Redesign and Horn Changeout

10. Running Plan Utilize an approach for no beam time loss Install PH1-03 with some power limit – 500kW to 600kW (?) –Run FY16 –Remove power limit when PH1-05 with stripline retrofit is ready Possible, preventative replacement in FY16 shutdown Produce spares to keep up with consumption Reminder: This Horn 1 plan does not occur in a vacuum Question: Effect of horn current –Dynamic stripline stress is a function of current pulse input –NOvA sees negligible flux loss down to 160 kA – MINOS / MINERvA? 7/6/15Kris E. Anderson | Status of NuMI Horn 1 Stripline Redesign and Horn Changeout

11. Pulses accumulated on each horn 7/6/2015Jim Hylen | Horns - MINOS+ mtg.11

12. Backup- 700kW NOvA Horn 1 Stripline FEA Summary 12 Surface LocationFlow velocity (mph)Convective Coefficient W/m 2 -C Exposed to chase air flow2012 Flare, external69 Flare, gap between strips34 Shielding block, external4?5 Surfaces sheltered4?5 Shielding block, gap between strips02 Air convective heat transfer coefficients are finalized for stripline FEA: Currently Horn1 stripline is running max. 72 °C @300 kW NuMI operations With new design and improved water cooling on Horn1 outer conductor, the stripline max. temperature will be about 82 °C @700 kW NOvA operations Stress induced by pulsed magnetic forces are low, with a safety factor of 7 with regard to material yield strength @100°C Alternating stresses during each pulse are low, therefore the fatigue strength is not an issue Stress induced by 3mm transverse shifting of Horn1 is about 1/3 of the yield strength. It is one- time deformation that falls into secondary stress category 40 7/6/15Kris E. Anderson | Status of NuMI Horn 1 Stripline Redesign and Horn Changeout

13. Backup- 700kW NOvA Horn 1 Stripline FEA Summary 13 40 Temperature ( º C) Ultimate strength (MPa)Yield Strength (MPa) Data from J. Gilbert Kaufman, Properties of Aluminum Alloys 25170140 100160140 150, ~1,000 hrs145130 Fatigue Strength at indicated cycles with completely reserved stress ratio R=-1.0 (MPa) 10 5 cycles145 10 6 cycles105 10 7 cycles85 10 8 cycles70 7/6/15Kris E. Anderson | Status of NuMI Horn 1 Stripline Redesign and Horn Changeout