CNGS HORN Mini-review induced by the break of the insulating glass disk

1. CNGS HORN Mini-review induced by the break of the insulating glass disk S. Rangod PH/DT1

2. Design evolution of the horn from WANF to CNGS (concerns only insulation and vapor tightness) Present design with a 19 mm thick glass disk and its apparent problems Preliminary proposal(s) for a new design Preliminary conclusions Summary S. Rangod PH/DT1

3. Generalities No vapor tightness asked The atmosphere inside the horn was directly in contact with ambient atmosphere of the cavern. Approximated section of the circular aperture: 130 cm2 Overall dimensions smaller than CNGS horn dimensions (reflector diam +/- equivalent to the diam of the CNGS horn) Horn was about 5 times less transparent to the beam than CNGS horn (bolted flanges, deflectors…) Voltage: 300 V maxi Design evolution of the hornWANF horn S. Rangod PH/DT1

4. Insulators (washers) Cooling lines Deflector 2 Bolted flanges Inner conductor 420 mm Deflector 1 Circular gap: 10 mm VAPOR Design evolution of the hornWANF horn Beam axis Water outlet Schematic view (principle) S. Rangod PH/DT1

5. Design evolution of the hornWANF horn & CNGS horn CNGS HORN WANF HORN S. Rangod PH/DT1

6. Reminder CNRS/Orsay was in charge of the complete development of the horns. Cern agreement necessary before manufacture. 1st horn delivered was not in conformity with the technical specifications (MoU) Vapor tightness strongly asked (reference to the WANF) Only mineral material allowed for insulation. Inner diameter of the outer conductor: Horn 700 mm Reflector 1100 mm Voltage: 500 V maxi Design evolution of the hornCNGS horns S. Rangod PH/DT1

7. Design evolution of the hornCNGS horns (CNRS solution for the glass disk assembly) Sliver 8 insulator rings (ARCLEX) mm 100 mm Sliver R370 mm S. Rangod PH/DT1

8. Main changes done on the design of the glass disc assembly to be in conformity with technical specifications (vapor tightness) Cross section larger and thickness increased from 15 mm to 19 mm 12 bolts instead of 8, placed on a diameter close the “C-shaped” seals Exchange of the standard bolts by “high grade” bolts M16 (A4 quality) The glass disc is now drilled with 20 holes (12 used to press the Tin/Ag seals + 8 for the clamping rods used to maintain the electrical connection plates) New high quality machining on the both polarity plates to accept the new dimensions of the glass disc Design evolution of the hornCNGS horns (CERN solution for the glass disk assembly) S. Rangod PH/DT1

9. Design evolution of the hornCNGS horns CERN design of the glass disk Viewable cracks S. Rangod PH/DT1

10. Design evolution of the hornCNGS horns (Comparison between CNRS and CERN glass disk assembly) CNRS Assembly CERN Assembly S. Rangod PH/DT1

11. Design evolution of the hornCNGS horns (CERN solution for the glass disk assembly) S. Rangod PH/DT1

12. Design evolution of the hornCNGS horns (CERN solution for the glass disk assembly) S. Rangod PH/DT1

13. Vérification de la force d’écrasement d’un joint métallique Garlock/Cefilac 175225 Caractéristiques du joint: HN200 tore : 6.1 mm Di: 734 De: 746.2 Revêtement d’étanchéïté : étain/Ag Revêtement interne : inconel 600 Ressort : Nimonic 90 Effort de serrage : Y2 = 100 N/mm pour e2 = 0.9 mm Calcul de la force totale transmise par 12 vis M16 A4/80 Longueur linéaire du joint : dia. moyen 739.5 soit : 2323 mm Force nécessaire pour e2 =0.9 mm : 232.300 N Couple de serrage : 156 N/m Force de serrage correspondante : 50.210 daN Soit pour 12 vis : 602.520 N Design evolution of the hornCNGS horns CERN design of the glass disk- Tightening calculationExtracted from the note S.R (04/10/2004) S. Rangod PH/DT1

14. Design evolution of the hornCNGS horns (CERN solution for the glass disk assembly) S. Rangod PH/DT1

15. Design evolution of the hornCNGS horns (ratio between the horn and the reflector) 1400 mm 1000 mm S. Rangod PH/DT1

16. Design evolution of the hornPrevious experience with a glass disk insulator(CERN horn prototype for NuFact project) Glass disk 670 mm S. Rangod PH/DT1

17. Design evolution of the hornPrevious experience with a glass disk insulator(CERN horn prototype for NuFact project)Detail of the glass disk Dimensions smaller than for CNGS horn Better ratio between overall dimensions and thickness Elastomere O-ring seals The annular pressure area is very limited Assembly with damping washers Only one row of drilled holes Assembly concept quite different (5 kV) 23 mm S. Rangod PH/DT1

18. 12 coaxial springs used during assembly phases Critical angular geometry 12 identical sectors Al2O3 (thickness 30 mm) For centering pins 6 necessary gaps to guarantee the contact on lateral faces Design evolution of the hornCNGS horns (Preliminary proposal 1) S. Rangod PH/DT1

19. Design evolution of the hornCNGS horns (Preliminary proposal 1- Cross section) 30 mm Electrical contact surfaces Al2O3 sector 60 mm Coaxial spring (s.steel) “ARCLEX” insulators (rings) Spacer ring S. Rangod PH/DT1

20. Design evolution of the hornCNGS horns (Preliminary proposal 1A) # 2.5 mm R Contact surface of the seals after clamping S. Rangod PH/DT1

21. Concern proposal 1 with the alternative solution 1A Advantages: Risk to break an element is very low Vapor tightness can be considered as correct, even without “Helicoflex”seals Mechanical characteristics of Al2O3 are better known and pieces can be precisely machined. Clamping for electrical contacts and for vapor tightness can be treated separately Disadvantages: All electrical connection plates must be re-designed Water tightness lost (risk of leak if dimensions of the water deflectors are not sufficient) Additional delay estimation: about 4 months Cost Design evolution of the hornCNGS horns Advantages/DisadvantagesComparison with the present solution (glass disc insulator) S. Rangod PH/DT1

22. Design evolution of the hornCNGS horns (Preliminary proposal 2) 15 mm Solution proposed after an open discussion with Piet Wertelaers PH/DT2 2 “Helicoflex” seals (lining silver) Glass disk insulator Reminder Slope 5.66 % S. Rangod PH/DT1

23. Advantages The glass disk is clamped between the 2 C-shaped seals in opposition, without any other contact with the connection plates. The flatness of the machined faces is less critical than previously, except for the seal grooves. The torque applied on the screws used for the clamping of the electrical contact surfaces can be dissociate of the torque applied on the screws used for the clamping of the seals. Water tightness Disadvantages Seals must be imperatively resistantto thecorrosion ( not a great experience in moist and high aggressive environment) Presently, no solution foreseen to empty the lower “chicane” Design evolution of the hornCNGS horns (Preliminary proposal 2) Advantages/DisadvantagesComparison with the present solution (glass disc insulator) S. Rangod PH/DT1

24. Mainly due to the limited choice of mineral material for the insulator, (glass, ceramics, mica/glass fiber composite, granite, marble…) several ways can be explored but not a lot. Because time is missing for long tests, the retained solution must preferably be already experienced (bad choices in high radioactive areas have a very high cost at a later stage). The ends of the inner conductor cannot be modified (monolith component of 6.5 m) Modifications on the extremity of the outer conductor lead to an extra delay not acceptable with the installation schedule. Overall dimensions of the horn cannot be increased Choice of the final solution must integrate the compulsory over cost and the additional extra delay CNGS hornsRemarks and preliminary conclusion S. Rangod PH/DT1