1. LHC OPERATION AND SUPPORT
CERN, internal review of superconductors and magnet laboratories,
19th May 2009
LHC OPERATION AND SUPPORT
E. Todesco
Magnets, Superconductors and Cryostats Group
Technology Department, CERN
Acknowledgements: A. Siemko, W. Venturini Delsolaro, L. Walckiers,

2. MAGNETIC MEASUREMENTS AND POWER TEST
General strategy: CERN should have the possibility of testing during the whole LHC life any magnet of the machine
Magnets that today cannot be tested at CERN: the triplet MQXA and MQXB, and the separation dipoles
No equipment for magnetic measurements is available
The LHC MQXA made by KEK
LHC separation dipole made by BNL

3. MAGNETIC MEASUREMENTS AND POWER TEST
SM18 has been designed to test a large number of dipoles and quadrupoles during the production (12 test benches)
During operation, we do not expect that we need such a high rate, therefore we should rather diversify than focusing on keeping 12 benches, but …
remember the 3-4 incident experience, where testing rate has become critical for operation

4. SPECIAL NEEDS FOR OPERATION: FiDEL
Throughout the life of the machine we will probably need to have additional magnetic measurements to have a better understanding of the magnetic model
Example: in Tevatron a campaign of measurements was started at the end of the 90s to improve the knowledge of the magnets, triggered by the RUN II, i.e., by a substantial machine upgrade
The LHC upgrades will probably need more and more magnetic measurements, as new beam physics will point out new directions
b3 decay in Tevatron dipoles, From J. Annala, et al, TD (2004) pg. 38

5. SPECIAL NEEDS FOR OPERATION: FiDEL
Main features of the magnetic model needs
Flexibility: being able to measure every type of magnet
Speed: being able to measure with high rates (~10 Hz) for decay and snapback
Calibration: being able to measure the absolute values of transfer functions (for instance, for the squeeze) – even for correctors (limited knowledge of the TF of correctors can be an issue)
Capability of using the LHC control software LSA to steer tracking tests (dipole vs quadrupole, dipole vs correctors)

6. SPECIAL NEEDS FOR OPERATION: FiDEL
Proposed program of additional measurements: tracking
MB—MCS (b3 compensation during snapback – already done, but residual b3 of ~0.3 units – critical for ramp – more test needed)
MQ—MQT (tracking the tune)
MQ—MS (Q’ tracking?)
N. Sammut, b3 correction in tracking test – FiDeL meeting, winter

7. SPECIAL NEEDS FOR OPERATION: FiDEL
Proposed program of additional measurements
MQM/MQY transfer functions at low current (beta-beating at injection - done for MQM)
MCBX hysteresis: separation, collision, crossing angle (for collision)
MQT, MS hysteresis small loops around zero current (tune and chromaticity)
W. Venturini Delsolaro – MQM transfer function – FiDeL meeting, May 2009

8. SPECIAL NEEDS FOR OPERATION: FiDEL
Proposed program of additional measurements
Validation of influence of powering cycles and pre-cycles
Any other issue with powering history

9. SPECIAL NEEDS FOR OPERATION: POWER TESTS AND PROTECTION
Proposed program of additional test
assistance to the calibration of BLM (energy to quench vs. operating current), dedicated tests with heaters in the magnet cold bore
magnet protection, experiment on specific cases with high splice resistance, possibly interconnects on bus-bars with controlled faults, to decide on critical thresholds for operation