1. Elias Métral (25 + 5 min, 19 slides)
KICKER IMPEDANCE MEASUREMENTS
AT THE CERN PS AND SPS
Elias Métral ( 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
Conclusion and future work
Elias Métral, CERN-GSI bi-lateral working meeting on Collective Effects – Coordination of Theory and Experiments, GSI, 30-31/03/06

2. Offset of the leading particle Offset of the trailing particle
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 the trailing particle
Driving wake
Detuning wake
Elias Métral, CERN-GSI bi-lateral working meeting on Collective Effects – Coordination of Theory and Experiments, GSI, 30-31/03/06

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)
Elias Métral, CERN-GSI bi-lateral working meeting on Collective Effects – Coordination of Theory and Experiments, GSI, 30-31/03/06

4. INTRODUCTION (3/3)
Example given by Tsutsui (CERN-SL-Note AP)
Longitudinal (classical) resistive-wall impedance (with a single wire) for a 2D rectangular metallic pipe of height 2b and width 2a
 This explains why a zero impedance can be measured in the horizontal plane of a flat chamber, with a single wire
Elias Métral, CERN-GSI bi-lateral working meeting on Collective Effects – Coordination of Theory and Experiments, GSI, 30-31/03/06

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)
Elias Métral, CERN-GSI bi-lateral working meeting on Collective Effects – Coordination of Theory and Experiments, GSI, 30-31/03/06

6. Measurements vs. Tsutsui (giving here only the driving)
Tsutsui’s model
Perfect conductor Im Re
Elias Métral, CERN-GSI bi-lateral working meeting on Collective Effects – Coordination of Theory and Experiments, GSI, 30-31/03/06

7. Comparison Tsutsui-Burov&Lebedev for the vertical driving impedance
Measurements vs. Tsutsui
Measurements vs. Burov-Lebedev
Elias Métral, CERN-GSI bi-lateral working meeting on Collective Effects – Coordination of Theory and Experiments, GSI, 30-31/03/06

8. MEASURED LONGITUDINAL IMPEDANCE (Re) VS. HORIZONTAL OFFSET
100 pictures (every 10 MHz until 1 GHz)
Elias Métral, CERN-GSI bi-lateral working meeting on Collective Effects – Coordination of Theory and Experiments, GSI, 30-31/03/06

9. MEASURED LONGITUDINAL IMPEDANCE (Im) VS. HORIZONTAL OFFSET
100 pictures (every 10 MHz until 1 GHz)
Elias Métral, CERN-GSI bi-lateral working meeting on Collective Effects – Coordination of Theory and Experiments, GSI, 30-31/03/06

10. MEASURED LONGITUDINAL IMPEDANCE (Re) VS. VERTICAL OFFSET
100 pictures (every 10 MHz until 1 GHz)
Elias Métral, CERN-GSI bi-lateral working meeting on Collective Effects – Coordination of Theory and Experiments, GSI, 30-31/03/06

11. MEASURED LONGITUDINAL IMPEDANCE (Im) VS. VERTICAL OFFSET
100 pictures (every 10 MHz until 1 GHz)
Elias Métral, CERN-GSI bi-lateral working meeting on Collective Effects – Coordination of Theory and Experiments, GSI, 30-31/03/06

12. Measured horizontal + vertical driving impedances (as when we sum the measured transverse impedances the detuning impedance disappears) Im Re
Elias Métral, CERN-GSI bi-lateral working meeting on Collective Effects – Coordination of Theory and Experiments, GSI, 30-31/03/06

13. Measured horizontal + vertical driving impedances: Comparison between the 1- and 2-wire measurement methods
1-wire
2-wire
Elias Métral, CERN-GSI bi-lateral working meeting on Collective Effects – Coordination of Theory and Experiments, GSI, 30-31/03/06

14. SPS (MKE) KICKER  1-wire method
Driving + detuning impedance
Driving + detuning impedance
Elias Métral, CERN-GSI bi-lateral working meeting on Collective Effects – Coordination of Theory and Experiments, GSI, 30-31/03/06

15. MEASURED LONGITUDINAL IMPEDANCE VS. TRANSVERSE OFFSET
100 pictures (from ~10 MHz until 1 GHz)
Elias Métral, CERN-GSI bi-lateral working meeting on Collective Effects – Coordination of Theory and Experiments, GSI, 30-31/03/06

16. 2-WIRE MEASUREMENT COMPARED TO 2D THEORY
Elias Métral, CERN-GSI bi-lateral working meeting on Collective Effects – Coordination of Theory and Experiments, GSI, 30-31/03/06

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
Elias Métral, CERN-GSI bi-lateral working meeting on Collective Effects – Coordination of Theory and Experiments, GSI, 30-31/03/06

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
Elias Métral, CERN-GSI bi-lateral working meeting on Collective Effects – Coordination of Theory and Experiments, GSI, 30-31/03/06

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
Elias Métral, CERN-GSI bi-lateral working meeting on Collective Effects – Coordination of Theory and Experiments, GSI, 30-31/03/06