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Elias Métral ( 25 + 5 min, 19 slides )

KICKER IMPEDANCE MEASUREMENTS AT THE CERN PS AND SPS. Elias Métral ( 25 + 5 min, 19 slides ). Introduction: Driving & detuning impedances and single wire measurement Measurements for a PS kicker by F. Caspers and T. Kroyer with 1 wire: Longitudinal impedance vs. transverse offset

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Elias Métral ( 25 + 5 min, 19 slides )

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  1. KICKER IMPEDANCE MEASUREMENTS AT THE CERN PS AND SPS Elias Métral (25 + 5 min, 19 slides) • Introduction: Driving & detuning impedances and single wire measurement • Measurements for a PS kicker by F. Caspers and T. Kroyer with • 1 wire: Longitudinal impedance vs. transverse offset • 2 wires (excited in opposite phase) • Measurements for a SPS kicker by F. Caspers and T. Kroyer with • 1 wire: Longitudinal impedance vs. transverse offset • 2 wires (excited in opposite phase) • Conclusion and future work

  2. INTRODUCTION (1/3) • Driving (=dipolar) and detuning (=quadrupolar) wakes from Burov-Danilov theory (PRL paper, Vol. 82, N. 11, 15 March 1999) Offset of the leading particle Offset of thetrailing particle Driving wake Detuning wake

  3. INTRODUCTION (2/3) • Measured longitudinal impedance vs. transverse offset, using a single displaced wire (in a symmetric structure)   The sum (or difference) of the driving and detuning impedances is measured with a single displaced wire  This explains why very different results are measured with the 2-wire method (which measures only the driving impedance) and the single-wire method (where >0, 0, or <0 impedances can be measured)

  4. INTRODUCTION (3/3) Longitudinal (classical) resistive-wall impedance (with a single wire) for a 2D rectangular metallic pipe of height 2b and width 2a • Example given by Tsutsui (CERN-SL-Note-2002-034 AP)  This explains why a zero impedance can be measured in the horizontal plane of a flat chamber, with a single wire

  5. PS KICKER  2 will be installed in the PS (SS 13 and 21)  It is the same type as the extraction kicker KFA 71 (but 4 times smaller)  The ferrite is split longitudinally in many cells Each cell is 24 mm long (19 mm of ferrite + 5 mm of Al)

  6. Measurements vs. Tsutsui (giving here only the driving) Tsutsui’s model Perfect conductor Im Re

  7. Comparison Tsutsui-Burov&Lebedev for the vertical driving impedance Measurements vs. Tsutsui Measurements vs. Burov-Lebedev

  8. MEASURED LONGITUDINAL IMPEDANCE (Re) VS. HORIZONTAL OFFSET 100 pictures (every 10 MHz until 1 GHz)

  9. MEASURED LONGITUDINAL IMPEDANCE (Im) VS. HORIZONTAL OFFSET 100 pictures (every 10 MHz until 1 GHz)

  10. MEASURED LONGITUDINAL IMPEDANCE (Re) VS. VERTICAL OFFSET 100 pictures (every 10 MHz until 1 GHz)

  11. MEASURED LONGITUDINAL IMPEDANCE (Im) VS. VERTICAL OFFSET 100 pictures (every 10 MHz until 1 GHz)

  12. Measured horizontal + vertical driving impedances (as when we sum the measured transverse impedances the detuning impedance disappears) Im Re

  13. Measured horizontal + vertical driving impedances: Comparison between the 1- and 2-wire measurement methods 1-wire 2-wire

  14. SPS (MKE) KICKER  1-wire method Driving + detuning impedance Driving + detuning impedance

  15. MEASURED LONGITUDINAL IMPEDANCE VS. TRANSVERSE OFFSET 100 pictures (from ~10 MHz until 1 GHz)

  16. 2-WIRE MEASUREMENT COMPARED TO 2D THEORY

  17. CONCLUSION FOR THE PS KICKER • More noise with the 2-wire measurement than with 1 wire • Possible errors in obtaining the transverse impedance from the parabolic fit (not symmetric, etc…) • Both the 1- and 2-wire methods seem in good agreement between ~ 400 MHz and 1 GHz for the real part of the sum of the transverse driving impedances

  18. CONCLUSION FOR THE SPS KICKER • The 1-wire method is not reliable (bad fits)  Re-measure? • With the 2-wire method, the measured vertical impedance for the SPS MKE kicker is very close to the 2D theoretical predictions! • We should re-do the measurements up to at least 2 GHz

  19. FUTURE WORK • Study the effect on the impedance of the finite length of the kicker using the electromagnetic code HFSS  Results to be published at EPAC06

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