118 July 2005“Mini-Review” on CNGS Horns
Introduction by K. Elsener 1
““Mini-Review” - IntroductionMini-Review” - Introduction
Function of focusing horns
“History” of CNGS horns
Milestones and set-backs
Modifications – examples
Installation / Schedule
Comments to this “Mini-Review”
N.B. This presentation is using slides presented by Ans Pardons to the workshop NBI2005, Fermilab 7-11 July 2005
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Introduction by K. Elsener 2
CNGS – function of focusing hornsCNGS – function of focusing horns
150 kA 180 kA
2.7 m
43.5 m
400Gev
6.5 ms
Electrical Pulse Timing
Beam Extraction = double pulse= 2.4x10E13 protons per pulse = 10.5µs (flat top el. pulse)
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0.35 m
35 GeV positively charged particles leaving the target
Magnetic Horn : Principle of focusing
inner conductor
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Introduction by K. Elsener 4
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Particles traverse inner conductor Particles traverse inner conductor -> it must be thin (e.g. 2 mm)-> it must be thin (e.g. 2 mm)
High current High current -> heating-> heatingBeam pulse (energy depos.) Beam pulse (energy depos.) -> heating-> heating
-> stresses ---> fatigue-> stresses ---> fatigue(1 year < 4 Mio. Pulses)(1 year < 4 Mio. Pulses)
Radiation + HumidityRadiation + Humidity -> corrosion-> corrosion
Building horns is a difficult business …Building horns is a difficult business …
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““History” of CNGS hornsHistory” of CNGS horns
T=24°C T=33°C
Design + fabrication of 2 horns + 1 reflector under responsibility LAL/Orsay - Paris
Some design studies, calculations, …Horn plates & outer conductor readyNon-conformity on location “spider grooves” inner conductor (repair started)Horn assembly startedStriplines & cooling circuit: not started
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MilestonesMilestones & Set-backs & Set-backs
Horn 1 delivered to CERN by LAL/Paris in April 2004
A number of 15+ points have to be corrected to guarantee the reliability (e.g: stirrups, frame, ceramic insulation on water outlets, glass disk, …) -- LAL team reluctant to discuss repairs.
Crisis meetingCERN / LAL 24 July 2004
LAL to concentrate on (a) reflector modifications (b) electric “fast coupling”
Repair, modifications & final assembly of horn taken over by CERN
Stripline + cooling circuit: design, fabrication & tests taken over by CERN
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Modifications - ExamplesModifications - Examples
Ex. 1: Link between outer conductors and drain pipe for cooling water evacuation
Helicoflex SS collar
Ceramic muff withTitanium flanges
TIG Weld (Al 6083)
Tin/Ag seal
SS bellow (316L)
Outer conductor
Drain pipe
Solution
ARCLEX insulators cannot be used in humid areas
Rejec
ted
Received from LAL
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Introduction by K. Elsener 9
Modifications - ExamplesModifications - Examples
Ex. 2: Modifications on the cooling water feed lines (normal + spare line)
Rejecte
d
Received from LAL
(to ceramic insulators) Brazed connection with ceramic
insulators broke (too much strain)
New smooth bellowsto avoid stress in ceramic insulators
Solution
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Horn Assembly - CERNHorn Assembly - CERN(with all modifications)(with all modifications)
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StriplineStripline
10kV
150kA
TRANSFO
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LAL Crisis – cont.LAL Crisis – cont.
24 July 2004:LAL to concentrate on (a) reflector modifications (b) electric “fast coupling”
10 Dec 2004:LAL to concentrate on electric “fast coupling”Reflector modifications takenback to CERN
Several months / many visits to LAL / many discussionsMis-understandings on engineering / production quality ?Non-communication ?
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Glass Disk EnigmaGlass Disk Enigma
Received from LAL
Glass plate broken Problem = conceptual
After modification
Crack discovered ~weeks after electrical tests
SolutionProblem
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CNGS Installation Planning
Horn & Reflector: Oct. 2005Striplines & Cooling: Nov. 2005
Installation / ScheduleInstallation / Schedule
CNGS Commissioning w/beam
Start: 29 May 2006
various scenarios can be imagined
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Comments to this “Mini-Review”Comments to this “Mini-Review”
Why hold this “Mini-Review” ?provide an opportunity to discuss possible solutions
Background:2002 – 2004: CNGS had yearly reviews
2005: no review foreseen15 June 2005: there appears to be a design problem
on horns (glass disk)
Goal (ambitious?):reach a consensus on the direction to take / the next steps
Main problems: Manpower / Time (not money)