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HQ - ramp rate effects

HQ - ramp rate effects. D.Tsirigkas , E. Todesco Acknowledgements : B. Auchmann , L.Fiscarelli. Context. HQ is very dependent on ramp rate (nominal = 13 A/s). Goal: investigate ramp rate effect. Measurements @CERN, SM18, 28/3 – 4/4. T = 1.9 K. Available measurements.

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HQ - ramp rate effects

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  1. HQ - ramp rate effects D.Tsirigkas, E. Todesco Acknowledgements: B. Auchmann, L.Fiscarelli

  2. Context • HQ is very dependent on ramp rate (nominal = 13 A/s) • Goal: investigate ramp rate effect • Measurements @CERN, SM18, 28/3 – 4/4 • T = 1.9 K

  3. Available measurements

  4. Variable minimum current

  5. Variable minimum current • If dI/dt is the same, TF is the same (I>5kA)

  6. Variable ramp rate • ±90A/s • ±60A/s • ±40A/s • ±20A/s

  7. Variable ramp rate (ramp up) • Ramp rate has an effect that persists at high currents

  8. Extrapolation to dI/dt=0 • For a specific current • - Plot TF vsdI/dt • - Extrapolate to • dI/dt = 0 • Repeat for different I’s

  9. Variable plateau

  10. Extrapolation to dI/dt=0

  11. Multipole analysis • Dependence on the ramp rate suggests an Eddy current effect. • Where does it come from? • Plot the difference |Δbn| vsn • |Δbn| • Solving for R ≈ 0.06 m • n

  12. Repeat for different currents • The data suggests that the effect comes from the coil – not the collar

  13. Conclusions • HQ has been tested at 1.9 T to investigate ramp rate effects • Strong dependence on the ramp rate that persists at high currents • The TF at dI/dt=0 has been approximated by extrapolation and by measurements at current plateaux • Analysis of the multipoles suggests that the ramp rate effect originates from the coil

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