MKI Kicker Wire Measurements F Caspers T Kroyer

MKI Kicker Wire Measurements F. Caspers, T. Kroyer 1

Measurement Set-up u u Fully assembled MKI kicker with ceramic pipe 0. 5 mm copper wire placed in center of MKI Kicker Three measurement techniques were applied. u Ordinary transmission and reflection measurements without matching resi u Time domain gating used on the transmission and reflection data to remov u Resonator measurements. More tedious, but very high sensitivity at distinc 2

Resonator Measurement u u u u The TEM transmission line composed of the ceramic tube with copper strips an Capacitive coupling with low coupling coefficient k chosen, k = S 21/(1 -S 21) Typical resonance pattern. Loaded quality factor Q measured for each peak as well as S 21 L easily Line attenuation a can be In this case the coupling coefficient was a bit calculated from a = p/(Q 0*l) [Np/m] too high => errors in the range of a few % with Q 0 = QL * (1+k), valid for small k For too strong coupling, the unloaded Q factor can be obtained by correcting the measured Q factor knowing S 21 For too weak coupling the Q measurement gets impacted by noise An appropriate coupling coefficient between this two extremes was 3 chosen

Resonator Results u u u Attenuation evaluated at 36 resonance peaks below 1500 MHz Two distinct kicker Measured attenuation only slightly above the values calculated for the wire used resonances found at 390 and 770 MHz Wire attenuation calculated from with the wire resistivity r, the wire diameter d and the beam pipe diameter D Finite skin depth effect as well as field penetration through slots was accounted for. 4

Resonator Results - Details u u Apart from the two kicker resonances, the additional attenuation is rather low, The attenuation of the wire is much larger that this additional attenuation 5

Kicker Impedance per meter u The DC resistance R 0 of a wire of length L, resistivity r and diameter d is given u For skin depths d small compared to d the high frequency resistance This resistance is proportional to the line attenuation Comparing the measured kicker attenuation to the calculated wire attenuation u u All Data Detail 6

Comparison of Measurement Techniques u u u Power bilan; 0 d. B would be obtained for a lossless device Resonator measurement by far most reliable Good agreement between “Raw data” and “Resonator raw data” (blue) Wave power should add up to 0 d. B, otherwise the results are unphysical (activ Ripples in “Raw data” due to multiple reflections inside kicker Gated data too high at low frequencies; residue of gating process Fair agreement between corrected gated data and resonator data (red) 7

Resonances below 40 MHz Calibrated transmission data u u Z per meter Rather strong resonances at 2. 3 and 4. 8 MHz have been found The impedance was calculated using the log formula with the system impe 8

Imaginary Part of Z per meter u u Correction very sensitive on length of connectors, even dielectrics in the connectors play a role. . . Gated transmission data can be used, since wire attenuation does not impact No peaks at low frequency Phase correction performed according to measured line length visible like on the previous slide, since here gated data was used 9

Comparison with Previous Data Improvement: u Roughly factor 100 in real part of impedance and u The impedance of the entire MKI prototype was measured in 2000 (F. Caspers et a u About factor 20 in imaginary part 10