Ans Pardons (with input from Jean-Marc Cravero) CERN CNGS Horn Experience (issues since NBI2010) Ans...
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Transcript of Ans Pardons (with input from Jean-Marc Cravero) CERN CNGS Horn Experience (issues since NBI2010) Ans...
Ans Pardons(with input from Jean-Marc Cravero)
CERN
CNGS Horn Experience (issues since NBI2010)
Ans Pardons, CERN 1NBI2012
Outline
• Introduction – CNGS Horns– Memorable Moments– Electrical Properties– Power Convertor Circuit
• CNGS horns operation issues 2010-2012– Exit Inductances– Thyristor– Capacitor Banks
• Summary
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Introduction: CNGS horns
• 150/180kA, 0.3Hz avg.(20Hz inst.)
• Water-cooled• Design lifetime:
20 106 double pulses
CERN
Gran Sasso
3Ans Pardons, CERN
Introduction: CNGS horns
Ans Pardons, CERN 4
Underground:
150/180kA
7.7kV, 9.4kA (horn)6.3kV, 5.6kA(refl)
Water cooling &Demineralisation (20m)
High Voltage cables (1km, 12 per horn)
On the surface
HORN/REFLECTOR
POWER CONVERTORS
TRANSFORMERSX16(H) x32 (R)
Jan-06 Jul-06 Dec-06 Jun-07 Dec-07 Jun-08 Dec-08 Jun-09 Dec-09 Jun-10 Dec-10 Jun-11 Dec-11 Jun-120.0E+00
2.0E+06
4.0E+06
6.0E+06
8.0E+06
1.0E+07
1.2E+07
Introduction: Memorable Moments
Reflector outlet water leak
Broken stripline cable
Water conductivity issues
Electronics radiation damage
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Inductances&
thyristors broke
Capacitors
measured
Double pulses
Introduction: Memorable Moments
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• 2006: water outlet leak– Badly designed brazed &
machined ceramic assembly– All brazed ceramics in horns
replaced
• 2007: broken stripline cable– Insufficiently restrained &
brazing-weakened cables– Replaced with restrained &
(more) rigid solution of Ag-plated copper plates
Introduction: Electrical Properties
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Converter Circuit Diagram
Ans Pardons, CERN 8
1st
2nd
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• History– Recuperated from WANF, no
documentation at the time– Found later from manu-
facturer’s documentation:Under-dimensioned for CNGS
– Replaced with new, correctly dimensioned inductances all OK
• Failure detailsMechanical fatigueInsulating foil degradation Short circuit at the exit of the
power converters
Exit Inductance Failure: mid 2011
10
Thyristor Issues: Mid 2011
Thyristor firing board
InductanceFor pulse 1- Pulse 2
Thyristor stack for pulse 1 – pulse 2• At each inductance failure– The output of the converter
is in short-circuit, leading to the destruction of the thyristor stacks
• Additional observation– Sometimes pulse 1&2 fired
at the same time due to the EM susceptibility of the thyristor firing board
– Problem solved with filter added on the board and additional EM shielding
Capacitor Banks Issue: Early 2012
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• History– New capacitors installed in 2006,
24 capacitor cans per horn– Designed for 20 million pulses at
10kV • Performance
– During machine stop early 2012, measured capacitance value found to be at ˜50% (horn) and 90% (reflector) of nominal
– At this moment, only 10 million pulses and max. 7kV
life time issue
Capacitor Banks Issue: Early 2012
Ans Pardons, CERN 12
• Solution– For 1st half of 2012: 7 spare cans
(original design) were installed horn up to 84% ok until new
– In June 2012: 24 new cans installed in the horn converter (new design from manufacturer)
– No degradation observed since• Reason for premature wear-???
– Unknown (awaiting tests results from manufacturer)
Summary• 2006-2010: Many mechanical issues, lots of repair &
re-design work done, many lessons learnt(and in parallel: enhancement of other systems) This seems to have paid off:
no mechanical or cooling issues in 2010-2012• 2010-2012: Electrical issues found and solved• Lessons learnt:
– Double check when recuperating existing equipment Do look the gift horse in the mouth!
– Capacitor banks have to be measured on a regular basis to detect life time issues (early).
– EM compatibility is always a tricky issue when dealing with kA current pulses
Ans Pardons, CERN 13