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

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

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 18 March 2002 S.Rangod

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

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. 18 March 2002 S.Rangod

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 18 March 2002 S.Rangod

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 18 March 2002 S.Rangod

Dimensions comparison 18 March 2002 S.Rangod

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) 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 18 March 2002 S.Rangod

Water cooling circuit 2 18 March 2002 S.Rangod

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 18 March 2002 S.Rangod

E.B. Welding 1 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) 18 March 2002 S.Rangod

EBW – CERN INSTALLATION Beam source Vacuum tank 18 March 2002 S.Rangod

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. 18 March 2002 S.Rangod

E.B. Welding 2 18 March 2002 S.Rangod

E.B. Welding 3 Magnification: x25 Magnification: x25 Under polarized light CERN/EST document 18 March 2002 S.Rangod

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 18 March 2002 S.Rangod

Inner conductor connection flange 18 March 2002 S.Rangod

Construction of the horn at CERN Drilling operation for radial holes 18 March 2002 S.Rangod

Construction of the horn at CERN Round shape thread inside the waist 18 March 2002 S.Rangod

Construction of the horn at CERN Punching of the outer skin 18 March 2002 S.Rangod

Construction of the horn at CERN Glass insulator disc 18 March 2002 S.Rangod

Construction of the horn at CERN Front side assembly 18 March 2002 S.Rangod

Construction of the horn at CERN Inner conductor 18 March 2002 S.Rangod

Construction of the horn at CERN Inner and outer skins 18 March 2002 S.Rangod

Construction of the horn at CERN Spherical blind holes for ceramic balls spacers 18 March 2002 S.Rangod

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 18 March 2002 S.Rangod

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 ! 18 March 2002 S.Rangod

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