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 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

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

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

INTRODUCTION (3/3) Example given by Tsutsui (CERN-SL-Note-2002-034 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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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