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Carlo Baccigalupi PhD Student in TE-EPC-HPM

Carlo Baccigalupi PhD Student in TE-EPC-HPM. High-repeatability measurement of fast voltage pulses for the CLIC klystron modulators. The Measurement Problem. The Measurement Problem. 10 V pulses. Pulse to Pulse Repeatability (PPR) Definition. To be verified.

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Carlo Baccigalupi PhD Student in TE-EPC-HPM

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  1. Carlo BaccigalupiPhD Student in TE-EPC-HPM High-repeatability measurement of fast voltage pulses for the CLIC klystron modulators

  2. The Measurement Problem

  3. The Measurement Problem 10 V pulses

  4. Pulse to Pulse Repeatability (PPR)Definition To be verified

  5. 1st yearThe Reference Test-bed

  6. Reference Test-bed Requirements • REPEATABILITY: • According to standard ANSI/NCSL Z540-1-1994, Test Uncertainty Ratio should be at least 1:4 • To certify a repeatability of ±100 ppm, the reference system should be repeatable to better than ±25 ppm • SPEED and BANDWIDTH: • PPR to be verified over 5 MHz so • System bandwidth ≥ 5 MHz • System sampling rate > 10 MS/s • FULL SCALE: • Pulse Amplitude 10 V so • System Full Scale Range 0-10 V

  7. Reference Test-bed Requirements • No Acquisition boards with such characteristics are readily available on the market. • A direct acquisition is not possible!!!

  8. The Analogue Front-End Basic Idea • Full Scale spec of the acquisition system is relaxed (±2.5 V is a common range for Fully Differential ADCs). • Dynamic Range is improved. 10 V Vrail+ Amplify Translate 2.5 V Vrail- CLIPPING -2.5 V

  9. Key Consideration if the acquisition system has a suitable stability within the repetition period of the train of pulses (20 ms) the only factor that could affect PPR is noise (including quantization noise) => Repeatability specification is translated into system’s noise characterization

  10. Block Diagram

  11. Schematic

  12. Design and Prototyping process • Pspice simulations: • Bandwidth • Linearity • Noise (RTI) ≈ 5 MHz √ ≈ 1 ppm at 20 °C √ ≈ 3 ppm √ • Prototyping and Experimental evaluation: • Bandwidth • Linearity • Noise (RTI) > 5 MHz √ < 2 ppm at ≈ 20 °C √ ≈ 3.1 ppm √

  13. Preliminary Results • Front-end’s inputs shorted to ground • Fsampling = 15 MS/s (6 MHz Bandwidth) • 2100 samples (140 µs acquisition) for emulating the pulses

  14. Preliminary Results PPR < 25 ppm

  15. Future Work on Reference Test-bed • Improvements on Analogue Front-End • Noise shielding, Ground sensing, CMRR enhancing… • Statistical study on Maxima Distribution (Gumbel) • Complete Metrological Characterization of The Reference Test-bed …Expected to be finalized by June 2014

  16. Work Schedule Most of the requirements should be ready for March 2014

  17. Power Converter Acquisition System Requirements needed by March: • Acquisition System Sampling Rate? • Acquisition System Bandwidth? • Maximum Delay? • Acquisition System Pulse-to-Pulse Repeatability? …Thank you for your attention.

  18. Schematic

  19. Noise Setup

  20. Noise Acquisition ≈1.5 mVrms

  21. Bandwidth Setup

  22. Amplitude Bode Diagram > 5 MHz (-3 dB point)

  23. Linearity Setup

  24. Linearity Error Eppm < 2 ppm

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