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TQM-HQM Status R. Bossert, F. Nobrega

TQM-HQM Status R. Bossert, F. Nobrega. CM-13 LARP Collaboration Meeting November 4-6, 2009. Introduction & Motivation. Fermilab has implemented the “Magnetic Mirror” design for both dipoles and quadrupoles, as an efficient way to optimize and/or “pre-test” Nb 3 Sn coils.

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TQM-HQM Status R. Bossert, F. Nobrega

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  1. TQM-HQM StatusR. Bossert, F. Nobrega CM-13LARP Collaboration MeetingNovember 4-6, 2009

  2. Introduction & Motivation Fermilab has implemented the “Magnetic Mirror” design for both dipoles and quadrupoles, as an efficient way to optimize and/or “pre-test” Nb3Sn coils. It is an efficient way to optimize Nb3Sn quadrupole coils with 90-120 mm apertures. Based on positive experiences gained using dipole and quadrupole mirror structures to test coils of 1m, 2m and 4m long we can: test individual coils under operating conditions similar to those of the real magnet reduce the turnaround time, material and labor costs scale-up Nb3Sn coil technology Quadrupole mirrors offer even greater benefits due to larger number of coils in quadrupoles with respect to dipoles. TQM-HQM Mirror Status Rodger Bossert CM-13 November 4, 2009

  3. Mirror Design The quadrupole mirror designs TQM (for 90-mm TQ coils) and HQM (for 120-mm HQ coils) are based on the mechanical structure of the LARP technology quadrupole collar (TQC) series. Three coils, stainless steel collar blocks and preload control spacers were replaced by the magnetic mirror blocks and spacers. TQC TQM HQM TQM-HQM Mirror Status Rodger Bossert CM-13 November 4, 2009

  4. Field Distribution Mirror vs. quadrupole models: similar field distribution => maximum field in both cross-sections is reached in the inner-layer pole turns small differences can be noticed in the coil midplane turns => smaller azimuthal component of Lorentz force and eddy current losses in the midplane turns in the mirror configuration.

  5. Short Sample Limit The estimated magnet quench currents based on the “reference” current density of 2800 A/mm^2 at 4.5 K and 1.9 K are shown below. This SSL is based on the mirror magnetic features and the presentation by Paolo Ferracin, “TQ Performance Overview” on Sept. 8, 2008 at the TQ discussion teleconference. The maximum field point in both cases is located in the outer layer pole turn of the magnet return end. SSL in TQS, TQC and TQM structures compared. 5

  6. Lorentz Forces and Coil Stress At quench current the azimuthal Lorentz force in the mirror is ~30% lower than in the quadrupole model => lower coil prestress needed. The coil stress after assembly of 120-130 MPa provides the coil compression up to 14 kA in TQM (SSL) and up to 17 kA in HQM (85% SSL). 300 K 4 K 4 K, 14 kA, 17 kA 90 mm 120 mm

  7. Assembly and Instrumentation Transverse coil preload and support is provided by stainless steel skin. Axial preload and support is provided through end bolts in the end plates. Instrumentation: VT, SG, strip heater, temperature sensors Quench antenna.

  8. TQ Mirror Shim System • Specific size of vertical shims based on desired preload and measured coil size. • Shim system shown based on measured size of coil 19. TQM-HQM Mirror Status Rodger Bossert CM-13 November 4, 2009 8

  9. TQM01-03 Goals Three quadrupole mirror models TQM01-03 were assembled and tested from January-August 2009. TQM01 and TQM02: TQ coils previously tested in TQC quadrupole models Primary goal: Verify the quadrupole mirror design concept Verify assembly procedure Compare coil quench performance with TQ models TQM02 was also equipped with midplane strip heaters to study Nb3Sn coil thermal performance. TQM03: New TQ coil made of improved Nb3Sn strand, RRP 108/127 Primary goal: Study quench performance and instability at 1.9-4.5K TQM03 was tested twice, using different coil prestress in each test.

  10. Magnet Specific Features * * ** * 125 mm thick insulation ** 150 mm thick insulation Azimuthal Preload at Inner Poles 10

  11. Training: excellent consistency of coil training in mirror and quadrupole models. some degradation of quench current at T>2.2 K after quenching in superfluid He Ramp rate dependence: good correlation at dI/dt<100 A/s at higher dI/dt – more optimistic data in mirror due to lower AC losses in midplane turns. (mirror not device to examine dI/dt >100 A/s) TQM and TQ Comparison

  12. Standard training behavior for all three mirror models at 4.5 K. Iq reduction and erratic quench behavior for TQM01-02 with coils made of RRP-54/61 at 1.9K Short training and Iq increase for TQM03 with new coil made of more stable RRP-108/127 at 1.9K TQM01: coil #19, RRP-54/61, 95% of its SSL (higher than TQ02 models) TQM03 coil #34 made of RRP-108/127 reached 97/99% of its SSL. Training

  13. Ramp Rate Dependence Regular ramp rate dependences for all coils at 4.5 K. Reduction of Iq at low ramp rates and unusual increase of the quench current at 200-275 A/s for the coil made of RRP-54/61 at 1.9 K Regular ramp rate dependences for coil made of RRP-108/127 at 1.9 K.

  14. Temperature Dependence TQM01 was only quenched once at 1.9K. TQM02 shows unstable quench behavior at temperatures below 2.5-3 K. transition temperature to the unstable range reduces with the current ramp rate increase. TQM03 shows stable quench performance at all tested temperatures some degradation of quench current at T>2.2 K after quenching in superfluid He

  15. Latest Results on Conductor Work Going from the baseline 54/61 conductor with 74 m filaments To a standard 108/127 design with 52 m filaments Confirmed by Magneto Optical Imaging in Superconductor Science and Technology , 22 (2009), 095008 (13pp). 108/127 54/61 1. Improved the current stability of the ROUND strand, but did not solve the problem of subelement merging in cables. Increasing the spacing between the filaments 2. Dramatically reduced merging too. E. Barzi 15

  16. Cable in Mirrors at 4.2K TQM03 TQM01, TQM02 E. Barzi 16

  17. TQ Mirror Plans • TQM03c features: • Same as TQM03, TQM03b but with another preload increase (200MPa?) • TQM04 features (coil #TQ35): • New, unused coil with 108/127 strand. • Return to S-2 glass sleeve for cable insulation. • Cable has 25 um thick stainless steel core. HQ Mirror Plans • All structural parts are available for an HQ mirror. Assembly can begin mid-November. Choices for coil are HQ02 (54/61 strand) and HQ03 (108/127 strand) 17

  18. Possible Future Mirror Tests • Further TQ mirrors could include: • 132/169 strand • Alternative Potting Materials • Further alternate insulation tests LQ mirror could be built, using 108/127 coil. Most parts are at Fermilab, the balance could be ready by end of calendar year. Additional HQ mirrors. 18

  19. Conclusions A quadrupole mirror structure to test single 90-120 mm quadrupole coils has been developed and successfully tested at Fermilab. Two mirror models have been assembled and tested using regular LARP 90 mm TQ coils previously tested in TQ quadrupole models. A new TQ coil made of the optimized Nb3Sn RRP-108/127 strand demonstrated improved quench performance and stability at all tested temperatures from 1.9 to 4.5 K confirmed by TQS03 test results Future tests: Tests at higher preloads. 90 mm TQ coils made of Nb3Sn cable with SS core, advanced Nb3Sn strands and/or coil impregnation materials. The developed mirror structure is available for 120-mm HQ coils and 4-m long LARP 90-mm quadrupole coils

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