| Paper |
Title |
Page |
| WEPP056 |
Aperture Restriction Localisation in the LHC Arcs using an RF Mole and the LHC Beam Position Measurement System
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2644 |
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- O. R. Jones, J. Albertone, S. Bartolome-Jimenez, C. Boccard, T. Bogey, P. B. Borowiec, E. Calvo, F. Caspers, M. Gasior, J. L. Gonzalez, B. Jenninger, L. K. Jensen, T. Kroyer, S. Weisz
CERN, Geneva
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Ensuring that the two 27km beam pipes of the LHC do not contain aperture restrictions is of utmost importance. Most of the ring is composed of continuous cryostats, so any intervention to remove aperture restrictions when the machine is at its operating temperature of 1.9K will require a substantial amount of time. On warming-up the first cooled sector, several of the sliding contacts which provide electrical continuity for the image current between successive sections of the vacuum chamber were found to have buckled into the beam pipe. This led to a search for a technique to verify the integrity of a complete LHC arc (~3km) before any subsequent cool-down. In this paper the successful results from using a polycarbonate ball fitted with a 40MHz RF transmitter will be presented. Propulsion of the ball is achieved by sucking filtered air through the entire arc, while its progress is traced every 54m via the LHC beam position measurement system which is auto-triggered by the RF transmitter on passage of the ball. Reflectometry at frequencies in the 4-8 GHz range can cover the gaps between beam position monitors and could therefore be used to localise a ball blocked by an obstacle.
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| WEPD001 |
The Quality Control of the LHC Continuous Cryostat Interconnections
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2398 |
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- F. F. Bertinelli, D. Bozzini, P. Cruikshank, P. Fessia, W. Maan, A. Poncet, S. Russenschuck, F. Savary, Z. Sulek, J.-P. G. Tock, D. Tommasini, L. R. Williams
CERN, Geneva
- P. B. Borowiec, A. Kotarba, S. Olek
HNINP, Kraków
- A. Grimaud
ALL43, Saint-Genis-Pouilly
- L. Vaudaux
IEG, St-Genis-Pouilly
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The interconnections between the Large Hadron Collider (LHC) magnets have required some 40 000 TIG welded joints and 65 000 electrical splices. At the level of single joints and splices, non-destructive techniques find limited application: quality control is based on the qualification of the process and of operators, on the recording of production parameters, and on production samples. Visual inspection and process audits were the main techniques used. At the level of an extended chain of joints and splices - from a 53.5 m half-cell to a complete 2.7 km sector - quality control is based on vacuum leak tests, electrical tests and RF microwave reflectometry that progressively validated the work performed. Subsequent sector pressure tests, cryogenic circuits flushing with high pressure helium and cool-downs revealed a few unseen or new defects. The nature of defects is analyzed and classified according to their origin. Methods for defect localization are described. This paper presents an overview of the quality control techniques used and critically evaluates their effectiveness in progressively identifying defects, seeking lessons applicable to similar large, complex projects.
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