12 June 2002 J.M.Maugain 1 HORN PROTOTYPE STATUS For the Neutrino Factory J.M.Maugain EP-TA3 For the Horn working group

12 June 2002 J.M.Maugain 2 Contents Goal Double horn Concept Main parameters & dimensions retained Main problems Main solutions 1, 2 & 3, 4 & 5 Mechanical design & construction at CERN Minimum lifetime Tests

12 June 2002 J.M.Maugain 3 Horn prototype constructed in the frame of the NUFACT Target-Collector activity Working Group Autin B. - Gilardoni S. - Grawer G - Haseroth H. - Maire G. Maugain J-M. - Ravn H. - Rangod S. - Sievers P. - Voelker F. Reference: CERN-NUFACT Note 80

12 June 2002 J.M.Maugain 4 Goal Verify the reliability of a 300kA-50Hz horn built according to the conventional technique of pulsed horns and providing a minimum lifetime of 2 x 10 8 pulses *. * Corresponding to 6 weeks of working operation at 50Hz

12 June 2002 J.M.Maugain 5 Proposed double horn 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.

12 June 2002 J.M.Maugain 6 Main Parameters Radius of the waist40 mm Peak current300 kA Repetition rate50 Hz Pulse length s Voltage on the horn4200 V rms current in the horn14.5 kA  ( CMS 19.5 kA)  ( ALEPH 5 kA) Power dissipation (by current)39 kW Skin depth1.25 mm

12 June 2002 J.M.Maugain 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

12 June 2002 J.M.Maugain 8 Main problems 1.Thermal losses and cooling requirements ( 39 kW mainly dissipated in the waist region ) 2.Pulsed electromagnetic forces and induced vibrations - resulting mechanical fatigue with thickness of the walls calculated for a minimum absorption. 3.Radiation resistance 4.Beam effects on mechanical strength of inner conductor 5.Current leads and busbars ( rms current in the horn 14.5 kA )

12 June 2002 J.M.Maugain 9 Main solutions 1 1a.Reduce power dissipation Short pulse ( s) High voltage capacitor discharge (6300 V) 1b.Improve water cooling system ( creation of an outer skin around inner conductor )  Standard cooling spray system of inner conductor is complemented with a low pressure annular water film flowing along inner conductor and an outer skin  Inner waist exchange surface is magnified by a factor 2  Spray cooling circuit is set apart for the waist zone Remark : Some sprayers are directly fed by the annular water film.

12 June 2002 J.M.Maugain 10 Water cooling circuit

12 June 2002 J.M.Maugain 11 Horn inner conductor waist Round shape thread inside the waist

12 June 2002 J.M.Maugain 12 Mean power dissipation in the horn by current (kW)39 Water flow needed with  W = 7°C (l/mn)81 Maximum allowable water flow in the horn (l/mn)90 Working water pressure (bar) Expected temperature increase on the neck ( 0 C)50 PwC1/PwC2 1 PwC1: Power extracted through the annular channel PwC2: Power extracted with showers from sprayers Remark : power dissipation due to beam has to be added Water cooling circuit

12 June 2002 J.M.Maugain 13 Main solutions 2 & 3 2.Adapt mechanical design to fit fatigue endurance limit ensuring expected life time ANSYS Finite Elements stress calculations and fatigue analysis (multi-axial stresses) remain to be done in static and dynamic. ( started but interrupted – budget restriction) CNGS study is used as basis for comparison (ref. Note EST-ME/ ) 3.Select appropriate (low cost) radiation resistant insulator materials Ceramic balls used as spacers between inner conductor and double skin to ensure concentricity Use of a glass disc insulator.

12 June 2002 J.M.Maugain 14 Main solutions 4 & 5 4.Current leads and busbars – no design yet but challenging figures (r.m.s current 14.5 kA, peak current 300 kA) 4.Evaluate beam effects on inner conductor - particle energy deposition ( adds to heating and induced thermal stresses) -neutron irradiation Calculations and studies done by S. Gilardoni

12 June 2002 J.M.Maugain 15 Mechanical design & construction at CERN 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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12 June 2002 J.M.Maugain 17 E.B. Welding Prototype has been 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 30 0 ). 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 to design and dimensions)

12 June 2002 J.M.Maugain 18 Longitudinal section Glass insulator disc Outer skin Inner skin Water outlet Electrical connections to the strip-lines Water inlets (circuit 2) Water inlets (circuit 2)

12 June 2002 J.M.Maugain 19 Construction of the horn at CERN Glass insulator disc

12 June 2002 J.M.Maugain 20 Construction of the horn at CERN Front side assembly

12 June 2002 J.M.Maugain 21 Construction of the horn at CERN Inner conductor

12 June 2002 J.M.Maugain 22 Construction of the horn at CERN Spherical blind holes for ceramic balls spacers

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12 June 2002 J.M.Maugain 25 Lifetime expected Fatigue is the major design issue. First static calculations give tensile stress of 15 Mpa ( in the most critical section of the waist considering only electroma- gnetic forces ). Considering that the limit of fatigue for 10 7 tractions is 100 Mpa, the survival of the prototype for 2 x 10 8 pulses* (required value) does not seem unrealistic. ANSYS calculation of stresses and fatigue analysis (multi-axial stresses) remain to be done

12 June 2002 J.M.Maugain 26 Tests possible without cost Check vibrational behaviour -30 kA / 1 Hz / 100 µ s (planned summer 2002) Vibration experimental tests (displacement capacitive sensor – W. Coosemans CERN/SU) 2 discharge circuits ready end of June Check magnetic field distribution - 30 kA / 1 Hz / ~ 2 ms ( in 2003 )

12 June 2002 J.M.Maugain 27 Tests possible with small cost Check heat load transfer - DC test at 5000A ( cancelled ) (only ~ 2% of total power dissipated in horn) –250 kA / 1 Hz / 6 ms (last quarter of 2002) using double pulse of CNGS horn capa banks with WANF transformer ratio 32  power dissipated in horn 7.5 kW (~ 19 % of total power dissipated in horn adapt old existing set of horn current leads (10.-kSF)

12 June 2002 J.M.Maugain 28 test conditions using CNGS power circuits 2 charging units at 4600V – 18A 2 x 4000 µ F capa banks Cycle 1.4s 1s charging time Recuperation 25%

12 June 2002 J.M.Maugain 29 Tests possible with moderate cost -300 kA / 1 Hz First fatigue test (2003) 1 charging unit 5 to 6 kV – 50A 2 spare CNGS thyristor switches improve current leads Final tests with high cost (unknown) -300 kA / 50 Hz final equipment needed - New charging unit and capacitors - New thyristor switches - New current leads and busbars