HORN PROTOTYPE FOR

1

• HORN PROTOTYPE FOR
• NUFACT PROJECT
• Overview of mechanical design construction

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Contents

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

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• 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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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.

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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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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

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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

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Dimensions comparison
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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
  

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Water cooling circuit 2
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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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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)

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EBW CERN INSTALLATION
Beam source
Vacuum tank
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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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E.B. Welding 2
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Magnification x25
Magnification x25
Magnification x25 Under polarized light
CERN/EST document
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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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Inner conductor connection flange
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Construction of the horn at CERN

• Drilling operation for radial holes

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Construction of the horn at CERN

• Round shape thread inside the waist

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Construction of the horn at CERN

• Punching of the outer skin

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Construction of the horn at CERN

• Glass insulator disc

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Construction of the horn at CERN

• Front side assembly

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Construction of the horn at CERN

• Inner conductor

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Construction of the horn at CERN

• Inner and outer skins

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Construction of the horn at CERN

• Spherical blind holes for ceramic balls spacers

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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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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 !
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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