1. Author CERN – Geneva – CH Jacques.Dutour 14th International Magnetic Measurement Workshop 26-29 September 2005, Geneva, Switzerland 1 / 16 MQW magnets: results from the measuring campaign (double aperture resistive quadrupoles for LHC) Didier Cornuet Jacques Dutour Miguel Silva

2. Author CERN – Geneva – CH Jacques.Dutour 14th International Magnetic Measurement Workshop 26-29 September 2005, Geneva, Switzerland 2 / 16 Topics to be presented: - ‘MQW magnet’ characteristics - Characteristics of the measurements - Measuring sequences - Results from the analysis of the measurements - Conclusions

3. Author CERN – Geneva – CH Jacques.Dutour 14th International Magnetic Measurement Workshop 26-29 September 2005, Geneva, Switzerland 3 / 16 -Quadrupole magnet: 48 installed,4 reserve), 6 MQW quadrupoles replace 1 superconducting quadrupole. - In cleaning insertions of LHC. - Normal conducting (high radiation levels) - Two apertures in a common yoke (space constraints in the tunnel). - Two different power connections : DF (MQWA) and FF (MQWB). - Precision between pole profiles: 1x10 -4 m (over a length of 3.1m) MQW magnet characteristics:

4. Author CERN – Geneva – CH Jacques.Dutour 14th International Magnetic Measurement Workshop 26-29 September 2005, Geneva, Switzerland 4 / 16 Characteristics of the measurements -120 measurements MQWA,90 measurements in MQWB 114 measurements in central position. - “Harmonic Coil” technique (using 5 coils in radial configuration) -“ Mole” (0.75 m) displaced manually with extension shafts (carbon fiber tube ) in 5 positions along the magnet. - 3 measurements (forwards and backwards) in each position for all the measuring currents. - DF measuring currents: 40A, 200A, 710A (nominal) and 810A - FF measuring currents: 40A, 200A and 600A (nominal) - ‘Integrated field gradient’ measurement errors: ± 2 ‰ at 40A (Gm.Lm) ± 1,5 ‰ at 200A ± 1 ‰ at 600A - Sextupolar component: ± 2 units - Other harmonics: ± 10 %

5. Author CERN – Geneva – CH Jacques.Dutour 14th International Magnetic Measurement Workshop 26-29 September 2005, Geneva, Switzerland 5 / 16 Magnetic field lines DF configurationFF configuration - High saturation in some regions of the yoke, due to FF configuration, changes the quadrupole and sextupole components of the DF configuration. The values measured in DF1 at 40A, no longer correspond to real magnetic field values (2 nd measuring sequence) Measuring sequences

6. Author CERN – Geneva – CH Jacques.Dutour 14th International Magnetic Measurement Workshop 26-29 September 2005, Geneva, Switzerland 6 / 16 Measuring sequences Influence of the FF configuration: the measuring sequence had to be changed. The magnets could be remeasured or we could introduce a correction in the measured values: -5 cycles not enough to fully magnetize (change ∫Gdl at low current). -Start measurements at high currents and then at low currents (remanent field stabilized, less change of ∫Gdl at low currents). - Change demagnetization cycles (-Imax/3 => -2/3 Imax). -FF mode before DF mode because of change ∫Gdl and sextupole components even after demagnetization (memory of FF mode).

7. Author CERN – Geneva – CH Jacques.Dutour 14th International Magnetic Measurement Workshop 26-29 September 2005, Geneva, Switzerland 7 / 16 Improved demagnetization cycle Measuring sequences

8. Author CERN – Geneva – CH Jacques.Dutour 14th International Magnetic Measurement Workshop 26-29 September 2005, Geneva, Switzerland 8 / 16 Analysis of the measurements Harmonic coefficients MQWA: nominal current

9. Author CERN – Geneva – CH Jacques.Dutour 14th International Magnetic Measurement Workshop 26-29 September 2005, Geneva, Switzerland 9 / 16 Analysis of the measurements Harmonic coefficients MQWA: nominal current R 2 =0.6924R 2 =0.7843

10. Author CERN – Geneva – CH Jacques.Dutour 14th International Magnetic Measurement Workshop 26-29 September 2005, Geneva, Switzerland 10 / 16 Analysis of the measurements Harmonic coefficients MQWB: nominal current

11. Author CERN – Geneva – CH Jacques.Dutour 14th International Magnetic Measurement Workshop 26-29 September 2005, Geneva, Switzerland 11 / 16 Analysis of the measurements Magnetic length MQWA: MQWB:

12. Author CERN – Geneva – CH Jacques.Dutour 14th International Magnetic Measurement Workshop 26-29 September 2005, Geneva, Switzerland 12 / 16 Main field gradient MQWA: MQWB: Analysis of the measurements

13. Author CERN – Geneva – CH Jacques.Dutour 14th International Magnetic Measurement Workshop 26-29 September 2005, Geneva, Switzerland 13 / 16 Analysis of the measurements Main field gradient

14. Author CERN – Geneva – CH Jacques.Dutour 14th International Magnetic Measurement Workshop 26-29 September 2005, Geneva, Switzerland 14 / 16 Analysis of the measurements Magnetic centre drift In horizontal plane MQWA: - magnetic centres get further from each other MQWB: - magnetic centres get closer to each other

15. Author CERN – Geneva – CH Jacques.Dutour 14th International Magnetic Measurement Workshop 26-29 September 2005, Geneva, Switzerland 15 / 16 Analysis of the measurements Main field direction Average values: AP1 = 0.03 mrad ; AP2 = -0.08 mrad Values are within the expected precision: ± 2 mrad

16. Author CERN – Geneva – CH Jacques.Dutour 14th International Magnetic Measurement Workshop 26-29 September 2005, Geneva, Switzerland 16 / 16 Conclusions - The measured values are correct, within our expected errors: there’s no need of corrections (MQW magnets in cluster of 5, average improved). - Each improvement made to get a better precision of the measurements, resulted in a longer time needed for the same measurements. -If 10 magnets were measured only in ‘FF configuration’ and the other 42 magnets only in ‘DF configuration’ the measurement campaign time would have been much reduced, but the flexibility for the selection of the magnets would have been lost.