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Introduction of Flux Concentrator

Introduction of Flux Concentrator. Normal conducting magnet, resistive to radiation, Work at pulse mode to reduce input power, Magnetic flux is shifted into small central region to enhance the field. Release mechanic stress on coil. 1: Primary coil, 2: Core, 3: Radial slot,

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Introduction of Flux Concentrator

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  1. Introduction of Flux Concentrator • Normal conducting magnet, resistive to radiation, • Work at pulse mode to reduce input power, • Magnetic flux is shifted into small central region to enhance the field. • Release mechanic stress on coil. 1: Primary coil, 2: Core, 3: Radial slot, 4: Bore.

  2. Modeling Approach and Geometric Division Description of modeling approach Geometric division of flux concentrator

  3. Modeling of Flux Concentrator Coupling between coil and ring (i, j) Coupling between any two rings

  4. Geometry of Prototype Flux Concentrator

  5. Measurements of Transient Responses at room temperature • Two kinds of configurations: • Coil-Only Configuration • Flux Concentrator • Transient responses to be measured: • Voltage at the coil terminals, • Current flowing through the coil, • Magnetic field at the central axis of the coil assembly.

  6. Measurements at Low Temperature To improve field enhancement, the entire flux concentrator with coil is placed in a cooler. A reservoir is made on top of aluminum core. Liquid nitrogen flow into the reservoir to cool the whole structure. Temperature measurement • Temperature was measured using RTD sensor (100Ω Platinum). • Temperature is measured at two locations, one is on aluminum core, another on the coil. • Coil, 170ºK, • Aluminum core, 77ºK.

  7. Comparisons of Transient Responses (Before and After Cooling) With the same excitation voltage, coil current enhances about 20%, and magnetic field increases more than 50% after cooling by liquid nitrogen.

  8. Comparison of Transient Magnetic Field -- Flux Concentrator

  9. ILC OMD Design • Design requirements: • Peak on-axis magnetic field > 5 Tesla, • Pulse width = 5ms, • Pulse repetition rate = 5 Hz.

  10. Transient Responses and Field Profile Transient responses (1cm from the target) Distribution of on-axis magnetic field (4ms after pulse is applied.)

  11. Typical Operating Parameters Parameters of flux concentrator Parameters of DC coil

  12. Design of ILC AMD • Motivation: • Design an Adiabatic Matching Device (AMD) based on pulsed flux concentrator technique for ILC positron source. • Design requirements: • Peak on-axis magnetic field at target exit > 5 Tesla, • Pulse width = 5ms, • Pulse repetition rate = 5 Hz. • Design method: • Equivalent circuit model of pulsed flux concentrator.

  13. Geometric structure of ILC AMD based on flux concentrator Target Flux concentrator Coils (DC)

  14. Detailed geometric size of each copper disk and pancake coil in flux concentrator (FC) FC consists of 11 copper disks and pancake coils. The coils are serially connected together with one power source. The entire FC is cooled by liquid nitrogen (T=78ºk). Coil wire size is 0.4750.381cm in cross section.

  15. Geometric structure of DC coil DC coil is placed right after flux concentrator. It works at room temperature (T=293ºK). The coil is wound with gradually reduced layers to produce a tapered magnetic field. The wire size is 0.4750.381cm in cross section. Total number of turns is 135. Three layers One layer

  16. Design results of ILC AMD Transient response at target exit (Assuming source internal resistance is 0.07Ω.) Distribution of on-axis magnetic field (4ms after pulse is applied.) Target exit

  17. Typical operating parameters Parameters of flux concentrator Parameters of DC coil

  18. Comparison of designed AMD and ideal AMD Distribution of on-axis magnetic field Results from beam simulation Using the designed AMD, positron yield and polarization are very close to the results using ideal AMD.

  19. The effect of the fluctuation of B field in flux concentrator. Due to large time constant of the designed flux concentrator, there is no flat top in pulsed magnetic field during the pulse duration. To investigate the effect of such fluctuating field, magnetic field distributions at different time instant are applied in end to end simulation. The result of positron yield and polarization are compared here in the following table.

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