HORN PROTOTYPE FOR NUFACT PROJECT Overview of mechanical design & construction

1. HORN PROTOTYPE FOR NUFACT PROJECT Overview of mechanical design & construction S.Rangod

2. Contents • Goal • Concept • Main parameters & dimensions • Water cooling system • Material & Welding • Mechanical design • Construction phases (CERN workshop) • Minimum lifetime • Tests foreseen • Conclusions S.Rangod

3. Horn prototype developed in the frame of the NUFACT Target-Collector activity Working Group Autin B. - Gilardoni S. - Grawer G - Haseroth H. - Maire G. Maugain J-M. - Rangod S. - Ravn H. - Sievers P. - Voelker F. Reference: CERN-NUFACT Note 80 S.Rangod

4. Goal • Verify the reliability of a300kA-50Hzhorn built according the conventional technique of pulsed horns and providing a minimum lifetime of one month. S.Rangod

5. Proposed concept • This horn, subject of the presentation, could be the inner component of a two stages coaxial horns system. • The second outer horn could complete the focusing effect of the first inner one. • This second outer horn is not considered in this phase of the project. S.Rangod

6. Main Parameters • Radius of the waist 40 mm • Peak current 300 kA • Repetition rate 50 Hz • Pulse length 93 ms • Voltage on the horn 4200 V • rms current in the horn 14.5 kA • Power dissipation (by current) 39 kW • Skin depth 1.25 mm S.Rangod

7. Main Dimensions • Total length 1030 mm • Outer diameter 420 mm • Max diameter (electrical connection flange) 895 mm • Free waist aperture 56 mm • Waist outer diameter 80 mm • Average waist wall thickness 6 mm • Double skin thickness 2 mm S.Rangod

8. Dimensions comparison S.Rangod

9. Water cooling circuit1 • Mean power dissipation in the horn by current (kW) 39 • Water flow needed withDQW 150C (l/mn) 37 • Maximum allowable water flow in the horn (l/mn) 90 • Working water pressure (bar) 1-1.5 • Expected temperature increase on the neck (0C) 50 • PwC1/PwC2 y 1 PwC1: Power extracted through the annular channel PwC2: Power extracted with showers from sprayers S.Rangod

10. Water cooling circuit2 S.Rangod

11. Choice of the alloy • AA 6082-T6 / (AlMgSi1) is an acceptable compromise between the 4 main characteristics: • Mechanical properties • Welding abilities • Electrical properties • Resistance to corrosion S.Rangod

12. E.B. Welding1 • The prototype is entirely welded in the CERN workshop by Electron Beam Welding. • Advantages of EBW: Well adapted to thin wall thickness pieces. Less deformations due to the narrow smelting bath (total angle: about 300). Excellent homogeneity (vacuum). Short transition area. Minimum loss of initial mechanical characteristics (no more than 15% to 20%). • Disadvantages of EBW: Delay generally longer. Higher precision required for the junctions. Higher cost (between 20% and 50% more, according the design and dimensions) S.Rangod

13. EBW – CERN INSTALLATION Beam source Vacuum tank S.Rangod

14. Mechanical design • Main features: Staying in conventional mechanical technology Thickness of the walls calculated for a minimum absorption. Improvement of the cooling efficiency. Low cost radiation hardness insulation. • Highlights: Creation of a double skin. Sprayers directly feed by an annular low pressure water film. Cooling circuit shared out for the waist zone Inner waist exchange surface magnified by a factor 2 (round shape inner screw thread) Ceramic balls used as spacers between inner conductor and double skin to ensure the concentricity of the both components. Use of a glass disc insulator. S.Rangod

15. E.B. Welding2 S.Rangod

16. E.B. Welding 3 Magnification: x25 Magnification: x25 Magnification: x25 Under polarized light CERN/EST document S.Rangod

17. Longitudinal section Water inlets (circuit 2) Electrical connections to the strip-lines Outer skin Glass insulator disc Inner skin Water inlets (circuit 2) Water outlet S.Rangod

18. Inner conductor connection flange S.Rangod

19. Construction of the horn at CERN Drilling operation forradial holes S.Rangod

20. Construction of the horn at CERN Round shape thread inside the waist S.Rangod

21. Construction of the horn at CERN Punching of the outer skin S.Rangod

22. Construction of the horn at CERN • Glass insulator disc S.Rangod

23. Construction of the horn at CERN Front side assembly S.Rangod

24. Construction of the horn at CERN Inner conductor S.Rangod

25. Construction of the horn at CERN Inner and outer skins S.Rangod

26. Construction of the horn at CERN Spherical blind holes for ceramic balls spacers S.Rangod

27. Lifetime expected • Fatigue is the major design issue. Parallel study is going on ANSYS calculation of stresses and fatigue analysis (multi-axial stresses) First static calculations give tensile stress of 14.8 Mpa (in the most critical section of the waist). Considering that the limit of fatigue for 107 tractions is 100 Mpa, the survival of the prototype for 2 x 108 pulses* (required value) does not seem unrealistic. *Corresponding to 6 weeks of working operation at 50Hz S.Rangod

28. Tests foreseen • Step 1a: 30 kA / 1 Hz (May 2002) Vibration experimental tests (displacement capacitive sensor – W. Coosemans CERN/SU) • Step 1b: Magnetic measurements (May 2002) • Step 1c: 5000A Dc (July 2002) Heat load transfer test • Step 2: 300 kA / 1 Hz • Step 3: 300 kA / 50 Hz POSTPONED BUDGET RESTRICTIONS ! S.Rangod

29. Conclusions • Even, if phases of tests 2 and 3 are delayed or cancelled, step 1a, 1b and 1c allow by extrapolation to confirm important results about the reliability and the transfer of the heat load. • Nevertheless, a lot of questions are still without answers, in particular • Installation of the target in the waist • Horn exchange • Mechanical support frame • Etc … S.Rangod