HORN PROTOTYPE STATUS

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• HORN PROTOTYPE STATUS
• For the Neutrino Factory
• J.M.Maugain EP-TA3
• For the Horn working group

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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

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• 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

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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

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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.

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Main Parameters

• Radius of the waist 40 mm
• Peak current 300 kA
• Repetition rate 50 Hz
• Pulse length 93 10-6 s
• Voltage on the horn 4200 V
• rms current in the horn 14.5 kA ? ( CMS 19.5 kA)
• 
  ? ( ALEPH 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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Main problems

• Thermal losses and cooling requirements
• ( 39 kW mainly dissipated in the waist
  region )
• Pulsed electromagnetic forces and induced
  vibrations
• - resulting mechanical fatigue
• with thickness of the walls calculated for
  a minimum absorption.
• Radiation resistance
• Beam effects on mechanical strength of inner
  conductor
• Current leads and busbars ( rms current in the
  horn 14.5 kA )

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Main solutions 1

• 1a. Reduce power dissipation
• Short pulse (93 10-6 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.

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Water cooling circuit
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Horn inner conductor waist
Round shape thread inside the waist
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Water cooling circuit

• Mean power dissipation in the horn by current
  (kW) 39
• Water flow needed with DQW 7C
  (l/mn) 81
• 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 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

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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/2001-008 )
• 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.

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Main solutions 4 5

• Current leads and busbars
• no design yet but challenging figures
• (r.m.s current 14.5 kA, peak current 300
  kA)
• 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

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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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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 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
  to design and dimensions)

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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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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

• Spherical blind holes for ceramic balls spacers

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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 107
  tractions is 100 Mpa, the
• survival of the prototype for 2 x 108 pulses
  (required value) does not
• seem unrealistic.
• ANSYS calculation of stresses and fatigue
  analysis (multi-axial
• stresses) remain to be done

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Tests possible without cost

• Check vibrational behaviour
• - 30 kA / 1 Hz / 100 µs
• (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 )

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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)

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• test conditions using CNGS power circuits
• 2 charging units at 4600V 18A
• 2 x 4000 µF capa banks
• Cycle 1.4s
• 1s charging time
• Recuperation 25

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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