1. QD0 Prototype Magnetic Measurements Michele Modena, TE-MSC QD0 Workshop 2013, 29 January 2013

2. Michele Modena, TE-MSC “QD0 Prototype Field Quality Measurements”CLIC Workshop 2013 Outline: - The CLIC MDI and QD0 baseline design (for L* = 3.5 m optic) - The QD0 magnetic measurements campaign in 2012 - The 2013 magnetic measurement plan - Conclusions and Future activities on QD0

3. Michele Modena, TE-MSC “QD0 Prototype Field Quality Measurements”CLIC Workshop 2013 CLIC BDS/MDI layout with QD0s “embedded” in the 2 Experiments (SiD, ILD) End-Cups

4. Michele Modena, TE-MSC “QD0 Prototype Field Quality Measurements”CLIC Workshop 2013 Magnet design boundary conditions: -As much as possible compact design (to be compatible with an L* of 3.5 m, so minimizing the solid angle subtracted to the experiment Detector) -Compatible with magnet active stabilization (i.e. minimize magnet weight and vibration sources, ex. coil water cooling) -Presence of the post-collision line beam vacuum chamber (in its closer position at 35 mm from beam axis) QD0 study & design requirements QD0 Baseline ParameterValue Nominal target for field gradient575 T/m Magnetic length2.73 m Magnet aperture (required for beam)7.6 mm Magnet bore diameter 8.25 mm * * Including a 0.30 mm vacuum chamber thickness Good field region (GFR) radius1 mm Integrated field gradient error inside GFR< 0.1% Gradient adjustment+0 to -20%

5. Michele Modena, TE-MSC “QD0 Prototype Field Quality Measurements”CLIC Workshop 2013 QD0 in the MDI layout with L*=3.5 m layout (simplified view)

6. Michele Modena, TE-MSC “QD0 Prototype Field Quality Measurements”CLIC Workshop 2013 “Hybrid design” basic concept -Comparing to a “classical” quadrupole design, the presence of PM wedges compensate strongly the saturation of the poles  Max Gradient increase of a factor 1.5-1.68 Of course, tunability is the other most interesting aspects of this configuration. NI= 5000 A Grad [T/m] Sm 2 Co 17 550 Grad [T/m] Nd 2 Fe 14 B615 NI= 5000 A Grad [T/m] Sm 2 Co 17 531 Grad [T/m] Nd 2 Fe 14 B599 -The presence of the “ring” casing the PM blocks cause a reduction of ~ 4-5 % in gradient performance but has big advantages for the manufacturing and assembly technical aspects!

7. Michele Modena, TE-MSC “QD0 Prototype Field Quality Measurements”CLIC Workshop 2013 Evolution of the prototype design, conceptual design of the full size magnet Mode1st2nd3rd4th Freq [Hz] 190260310366

8. Michele Modena, TE-MSC “QD0 Prototype Field Quality Measurements”CLIC Workshop 2013 Final assembly of the prototype in Fall 2011:

9. Michele Modena, TE-MSC “QD0 Prototype Field Quality Measurements”CLIC Workshop 2013 Outline: - The CLIC MDI and QD0 baseline design (for L* = 3.5 m optic) - The QD0 magnetic measurements campaign in 2012 - The 2013 magnetic measurement plan - Conclusions and Future activities on QD0

10. Michele Modena, TE-MSC “QD0 Prototype Field Quality Measurements”CLIC Workshop 2013 The only available measuring system to perform the magnetic gradient and magnetic field quality measurements are the “stretched wire” and the “vibrating wire” systems. This is due to very small magnet aperture (Ø: 8.25 mm!) 1) The “stretched wire” is a well know, state-of-the-art measuring method for gradient and magnetic axis: - expected accuracy: 10 -3 2) The “vibrating wire” is a new CERN development (still in a prototype version!) but that is giving very good results in terms of easy, fast and magnet radius independency, field quality (multipoles or harmonics) magnetic measurements. - when utilized for harmonics measurement: expected accuracy : < ±3 units ( accuracy for measurements done at 3 mm and then extrapolated at 1 mm radius as specified in our case) - when utilized for magnetic axis measurement: expected resolution: 1 μm. The QD0 magnetic measurements campaign in 2012 Some References for the two measuring methods: 1) D. Zangrando, R.P. Walker: “A Stretched Wire System for Accurate Integrated Magnetic Field Measurements in Insertion Devices” at: http://oldweb.elettra.trieste.it/organisation/accelerator/docs/st_ m_96_01.pdf http://oldweb.elettra.trieste.it/organisation/accelerator/docs/st_ m_96_01.pdf 2) P Arpaia, M Buzio, J Garcia Perez, C Petrone, S Russenschuck and L Walckiers: “Measuring field multipoles in accelerator magnets with small-apertures by an oscillating wire moved on a circular trajectory” at: http://iopscience.iop.org/1748-0221/7/05/P05003http://iopscience.iop.org/1748-0221/7/05/P05003 Reference for the CLIC QD0 Magnet Measurements campaigns results: 1) P. Arpaia et al: “Magnetic Measurement of the Model Magnet QD0 (Nd 2 Fe 14 B), designed fort the CLICX Final Focus Beam Transport Line”, EDMS: 1184196 2) P. Arpaia et al: “Magnetic Measurement of the Model Magnet QD0 (Sm 2 Co 17 ), designed fort the CLICX Final Focus Beam Transport Line”, EDMS: 1262052

11. Michele Modena, TE-MSC “QD0 Prototype Field Quality Measurements”CLIC Workshop 2013 Two campaigns of measurements were done in 2012 with QD0 prototype in two different configuration: - In January 2012: the magnet equipped with the Nd 2 Fe 14 B blocks was measured with the “Vibrating wire system” (see after) - In August 2012: the same type of measurement was done for the configuration with Sm 2 Co 17 blocks. 1)Maximum achievable gradient: Here below the measurements of the MEASURED Gradients (red dots) (extrapolated from the INTEGRATED gradient effectively measured), plotted together with the COMPUTED Gradient (blue curves). The measured Gradient in the configuration with Sm 2 Co 17 blocks it is in very good agreement with the FEA computation. This is not the case for the Nd 2 Fe 14 B blocks were a difference of ~ -6% is noticeable. This could have 2 possible explanations: -The Permendur part saturate at lower level than expected.  to check that we re-compute the performances by FEA utilizing the exact permeability as measured on a production sample; this possible cause was then excluded. -The quality (magnetization module and/or direction) of the Nd 2 Fe 14 B PM blocks is not the expected one  we should get an answer on this possible cause measuring the PM blocks with a new measuring device (by Brockhaus Messtechnick GmbH) expected at the MM Section for late Spring 2013.

12. Michele Modena, TE-MSC “QD0 Prototype Field Quality Measurements”CLIC Workshop 2013 The 2 graphs show, for both QD0 configurations, the measured INTEGRATED Gradient in function of the magnet powering (total ampere-turn in the coils). A minimum hysteresis effect is visible. Due to the “hybrid” configuration, with a PM fix contribution at zero current, the hysteresis loop are not center to the axes intersection and is not necessary to perform negative current cycle to pre-cycle the magnet, but only to zero the current. From this point of view the gradient setting is more straightforward comparing to a classical EM magnet design. 2) Magnet cycles repeatability:

13. Michele Modena, TE-MSC “QD0 Prototype Field Quality Measurements”CLIC Workshop 2013 2) Magnet cycles repeatability: Nd 2 Fe 14 B Sm 2 Co 17

14. Michele Modena, TE-MSC “QD0 Prototype Field Quality Measurements”CLIC Workshop 2013 The below histograms provides for both QD0 configurations the magnetic harmonic content (multipoles) versus the magnet powering ; upper graph for Nd 2 Fe 14 B, lower graph for Sm 2 Co 17. For comparison: the first computed “permitted” mutipole at NI=5000A is : b6=1.4 units (integrated) for Nd 2 Fe 14 B and b6=0.7 units for Sm 2 Co 17. The concerned measured components are the one circled in red. 3) Magnetic Field Quality: IMPORTANT: remind that the measurements global accuracy is estimated at: ±3 units!

15. Michele Modena, TE-MSC “QD0 Prototype Field Quality Measurements”CLIC Workshop 2013 Outline: - The CLIC MDI and QD0 baseline design (for L* = 3.5 m optic) - The QD0 magnetic measurements campaign in 2012 - The 2013 magnetic measurement plan - Conclusions and Future activities on QD0

16. Michele Modena, TE-MSC “QD0 Prototype Field Quality Measurements”CLIC Workshop 2013 1) Investigation of the performance with Nd 2 Fe 14 B magnet configuration: In order to understand the discrepancy between computed and measured maximum gradient, we propose to perform an individual measurements of each inserts and compare their characteristics. Being each of the four PM inserts obtained by gluing 4 single PM wedged block with two different magnetization direction (see left figure below), we can only do an average measurements of each insert (no possible to easily detect which single blocks is not conform in magnetization module or direction). We can perform a relative measurement, comparing the magnetic moments (average magnetic flux density) of each insert. This measurement can be done with a special measuring device based on 3D pairs of Helmholtz coils. One of these system is under procuring from industry (Brockhaus Messtechnik GmbH, see right figure below) and the system is expected at CERN in March 2013. Depending by the results of these measurements, we could decide to eventual order some new set of insert to check the final performances of the quadrupole. The 2013 magnetic measurement plan 2) Cross-check of the harmonic measurement with a new “Rotating Coils” system: The new system (probe diam. Ø: 7.7 mm!) is actually under development (see figures below). (NOTE: All these new MM systems will be very proficient to projects like CLIC (we ask for them as one of the main new “client”) and a very good collaboration with MM Section is in place on these subjects; they develop/procure new tooling and methods and we provide good “test cases” !)

17. Michele Modena, TE-MSC “QD0 Prototype Field Quality Measurements”CLIC Workshop 2013 Outline: - The CLIC MDI and QD0 baseline design (for L* = 3.5 m optic) - The QD0 magnetic measurements campaign in 2012 - The 2013 magnetic measurement plan - Conclusions and Future activities on QD0

18. Michele Modena, TE-MSC “QD0 Prototype Field Quality Measurements”CLIC Workshop 2013 Magnetic Measurements Conclusions: 1) QD0 maximum Gradient measured in the configuration with Sm 2 Co 17 inserts is in very good agreement with the FEA computation. The measurements configuration with Nd 2 Fe 14 B inserts show a difference of -6% respect to the computed values. This effect is probably due to not correct magnetization (module and/or direction) of some of the Nd 2 Fe 14 B PM blocks. 2) Magnet cycling seems very precise and repeatable, a minimum hysteresis effect is present. 3) The measured magnetic field harmonics at the required (maximum) gradient are in the range of the required tolerances (10 units). 4) Considering the vibrating wire method measurement accuracy, the measured magnet field quality is in good agreement with the computation. The presence of normal and skew not permitted harmonics depends by the manufacturing tolerances of the Permendur part and by the PM inserts magnetization module and/or direction. 5) By the expected measurements with the 3D Helmholtz coils system, we expect better information on the PM blocks quality and their influence on the overall field quality. 6) The stability of the magnetic axis was confirmed inside ± 2.5μm all along the powering curve of the quadrupole. Future activities on QD0 prototype measurements & other: 1) PM blocks measurements by 3D Helmholtz coils system. 2) Measurements with a new dedicated rotating coils system under development. 3) Other measurements/activities could be eventually planned to better discriminate the contributions to the field quality by the quadrupolare structure in Permendur and by the PM inserts. 4) Other type of measurements to be eventually planned. 5) Manufacturing of a longer prototype is under evaluation/discussion. This will mainly depends by the evolution of the CLIC/MDI layout studies and R&D. As CERN we are strongly interest to proceed in this direction if useful, anyway this will be an activity planned for after the LHC “LS1”.

19. Acknowledgments: Thanks to: A.Vorozhtsov, E.Solodko, P. Thonet, C. Lopez for the magnet design, procurements of components and assembly Thanks to: C.Petrone, J.Garcia Perez, A. Bartalesi, M. Buzio for magnet measurements and data analysis Thank you for your attention