Power Modulator using Inductive Energy Storage for Induction Synchrotron

1. Power Modulator using Inductive Energy Storage for Induction Synchrotron Eiki Hotta Kaoru Hashimoto, Kunihito Yamauchi, Masato Watanabe, Akitoshi Okino Tokyo Institute of Technology Acknowledgment SI Thyristors are provided by NGK Insulators Ltd.

2. Outline of Talk • Principle of Accelerating Voltage Generation • Testing Circuit: Operating Mode • POP Experimental Results • Summary

3. Induction Synchrotron Induction Accelerator Magnetic cores are used Necessary condition : ΔΦ=∫v(t)dt = 0 Main Ring Barrier Bucket Gap Acceleration Gap v v t t Non-symmetric output pulse waveform Super bunch Super bunch Voltage waveforms

4. Inductive Energy Storage E VL For Induction Synchrotron Only one switch - Simple circuit L R E VR Opening SW Normally used for Pulse Power System

5. Inductive Energy Storage Volt･second = = ET I(T) = I0 = ET/L Volt･second = = =- LI(T) = - ET ΔΦ=∫v(t)dt = 0 Opening switch with high-speed, high-hold-off voltage is required. E: Accelerating Voltage T: Accelerating Pulse Width

6. Circuit Analysis Laplace Transformation Laplace transformation after t = 0 At t = 0 =- ET Laplace transformation ￡ Final value theorem

7. Testing Circuitand its Operation 《Mode 1》 《Mode 3》 《Mode 2》 ON ON OFF ON Accelerating voltage generation Reset pulse generation Free wheeling of main current ON OFF OFF OFF V t E SI Thy (T335R-40): Peak hold off voltage 4000 V

8. Photo of Testing Circuit MOSFET Inductor Load Resister SI Thy

9. Output Voltage L = 2.6 mH 50 W V ★Accelerating voltage and reset pulse 　・Oscillation after the reset pulse ・Voltage drop in accelerating voltage

10. Suppression of Oscillation 50 W Increase the damping factor by connecting Rp Oscillation after reset pulse is suppressed

11. Cause of Voltage Drop V V Voltage drop in accelerating voltage Charge career density in SI Thy is low ⇒ Internal resistance of SI Thy is large 　 ⇒ ON voltage of SI-Thy is large By injecting charge, initial career density in SI-Thy is increased

12. Reduction of Voltage Drop Gate circuit By connecting a gate resistor, ON voltage of SI Thy is reduced and the flatness of the accelerating voltage is improved.

13. Experiment with Magnetic Core Only Modulator Modulator + Cable Modulator + Cable + Core 30 m Finemet 50 W Because of mismatch, a little dip in accelerating voltage and an oscillation after the reset pulse are observed.

14. Switching Loss of SI Thy. Larger L ⇒Lower current ⇒ Reduction of loss At DC power supply voltage of 250 V, L = 2.6 mH, pulse width = 900 ns, Switching loss is 5.2 mJ SI Thy：Junction temp. 125 ℃，Ambient temp. 25 ℃，Thermal Resistance0.055 ℃/W ⇒Maximum rep. rate will be about 400 kHz

15. Summary • Using anSI Thyristor as a high-voltage, high-speed opening switch, a power modulator using inductive energy storage for induction synchrotron was fabricated. • Generation of an accelerating voltage and a reset pulse has been confirmed. • The power modulator generates the reset pulse automatically according to the pulse width and height of accelerating voltage. • The estimated maximum repetition rate is 400 kHz under our experimental condition (250 V, 900 ns, L=2.6 mH) without forced cooling.