1. Overview of mechanical design & construction
HORN PROTOTYPE FOR
NUFACT PROJECT
Overview of mechanical design & construction
18 March 2002
S.Rangod
April 2002

2. Contents Goal Concept Main parameters & dimensions
Water cooling system
Material & Welding
Mechanical design
Construction phases (CERN workshop)
Minimum lifetime
Tests foreseen
Conclusions
18 March 2002
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
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S.Rangod

4. Goal
Verify the reliability of a 300kA-50Hz horn built according the conventional technique of pulsed horns and providing a minimum lifetime of one month.
18 March 2002
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.
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S.Rangod

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

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

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

10. Water cooling circuit 2
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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
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S.Rangod

12. E.B. Welding
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)
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S.Rangod

13. EBW – CERN INSTALLATION
Beam source
Vacuum tank
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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.
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15. E.B. Welding
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16. E.B. Welding 3 Magnification: x25 Magnification: x25
Under polarized light
CERN/EST document
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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
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S.Rangod

18. Inner conductor connection flange
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S.Rangod

19. Construction of the horn at CERN
Drilling operation for radial holes
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20. Construction of the horn at CERN
Round shape thread inside the waist
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21. Construction of the horn at CERN
Punching of the outer skin
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22. Construction of the horn at CERN
Glass insulator disc
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23. Construction of the horn at CERN
Front side assembly
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24. Construction of the horn at CERN
Inner conductor
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25. Construction of the horn at CERN
Inner and outer skins
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26. Construction of the horn at CERN
Spherical blind holes for ceramic balls spacers
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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
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S.Rangod

28. Tests foreseen POSTPONED BUDGET RESTRICTIONS !
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 !
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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 …
18 March 2002
S.Rangod