1. 1 18 July 2005 “Mini-Review” on CNGS Horns Introduction by K. Elsener 1 “Mini-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

2. 2 18 July 2005 “Mini-Review” on CNGS Horns Introduction by K. Elsener 2 CNGS – 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)

3. 3 18 July 2005 “Mini-Review” on CNGS Horns Introduction by K. Elsener 3 0.35 m 35 GeV positively charged particles leaving the target Magnetic Horn : Principle of focusing inner conductor

4. 4 18 July 2005 “Mini-Review” on CNGS Horns Introduction by K. Elsener 4

5. 5 18 July 2005 “Mini-Review” on CNGS Horns Introduction by K. Elsener 5 Particles traverse inner conductor -> it must be thin (e.g. 2 mm) High current -> heating Beam pulse (energy depos.) -> heating -> stresses ---> fatigue (1 year corrosion Building horns is a difficult business …

6. 6 18 July 2005 “Mini-Review” on CNGS Horns Introduction by K. Elsener 6 “History” 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 ready Non-conformity on location “spider grooves” inner conductor (repair started) Horn assembly started Striplines & cooling circuit: not started

7. 7 18 July 2005 “Mini-Review” on CNGS Horns Introduction by K. Elsener 7 Milestones & 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 meeting CERN / 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

8. 8 18 July 2005 “Mini-Review” on CNGS Horns Introduction by K. Elsener 8 Modifications - Examples Ex. 1: Link between outer conductors and drain pipe for cooling water evacuation Helicoflex SS collar Ceramic muff with Titanium flanges TIG Weld (Al 6083) Tin/Ag seal SS bellow (316L) Outer conductor Drain pipe Solution ARCLEX insulators cannot be used in humid areas Rejected Received from LAL

9. 9 18 July 2005 “Mini-Review” on CNGS Horns Introduction by K. Elsener 9 Modifications - Examples Ex. 2: Modifications on the cooling water feed lines (normal + spare line) Rejected Received from LAL (to ceramic insulators) Brazed connection with ceramic insulators broke (too much strain) New smooth bellows to avoid stress in ceramic insulators Solution

10. 10 18 July 2005 “Mini-Review” on CNGS Horns Introduction by K. Elsener 10 Horn Assembly - CERN (with all modifications)

11. 11 18 July 2005 “Mini-Review” on CNGS Horns Introduction by K. Elsener 11 Stripline 10kV 150kA TRANSFO

12. 12 18 July 2005 “Mini-Review” on CNGS Horns Introduction by K. Elsener 12 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 taken back to CERN Several months / many visits to LAL / many discussions Mis-understandings on engineering / production quality ? Non-communication ?

13. 13 18 July 2005 “Mini-Review” on CNGS Horns Introduction by K. Elsener 13 Glass Disk Enigma Received from LAL Glass plate broken Problem = conceptual After modification Crack discovered ~weeks after electrical tests Solution Problem

14. 14 18 July 2005 “Mini-Review” on CNGS Horns Introduction by K. Elsener 14 CNGS Installation Planning Horn & Reflector: Oct. 2005 Striplines & Cooling: Nov. 2005 Installation / Schedule CNGS Commissioning w/beam Start: 29 May 2006 various scenarios can be imagined

15. 15 18 July 2005 “Mini-Review” on CNGS Horns Introduction by K. Elsener 15 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 foreseen 15 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)