1 / 20

Damping materials* and WFMs # measurements

Damping materials* and WFMs # measurements. *G. De Michele 1,2,3 , A. Grudiev 1 ; # M. Dehler 2 , S. Bettoni 2 , G. De Michele 1,2,3 ; 1 CERN, 2 PSI, 3 EPFL. Motivations.

anika
Download Presentation

Damping materials* and WFMs # measurements

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Damping materials* and WFMs# measurements *G. De Michele1,2,3, A. Grudiev1 ; # M. Dehler2, S. Bettoni2, G. De Michele1,2,3 ; 1CERN, 2PSI, 3EPFL G. De Michele: HG2013, 3-6 June, ICTP Trieste

  2. Motivations The study of EM properties at microwave (μw) frequencies is full of academic importance (materials property research) μw communications and engineering (military, industrial, civil) Clock speeds of electronic devices at μw frequencies require knowledge of permittivity and permeability EM interference (EMI) and EM compatibility (EMC) Various fields of science and technology could profit: agriculture, food engineering, medical treatment, bioengineering High-quality design of the HOM dampers in CLIC accelerating structures (but also collimators, kickers) G. De Michele: HG2013, 3-6 June, ICTP Trieste

  3. Different techniques for materials characterization (1/2) • Non-resonant techniques: • Reflection method: open-circuited reflection; short-circuited reflection (S11) • Transmission/reflection methods: (S11,S12,S21,S22) • Resonator techniques: (the sample forms a resonator or a key part of resonator) • Dielectric resonator • Coaxial surface-wave resonator • Split resonator (dielectric sheet sample) • Resonant perturbation method: • The sample under test is introduced into the resonator and the EM properties are deduced from the changes in resonance frequency and quality factor of the cavity • Planar circuit methods (both resonant and non-resonant methods): • Stripline • Microstripe • Coplanar line G. De Michele: HG2013, 3-6 June, ICTP Trieste

  4. Different techniques for materials characterization (2/2) In a more general view we can split the techniques in two big families: • Non-resonant techniques : • possibility to measure EM properties in a wide range of frequencies • Resonator techniques: • Measurements possible at single or several discrete frequencies • Higher sensitivity and higher accuracy The presentation will focus on the non-resonant technique e.g. a coaxial line filled with the material under test (MUT). In the past waveguide method at CERN have been used and EM properties have been measured at some discrete frequency points. Measurements in a wide range of frequencies were done for the material AlN: R. Fandos, W. Wuensch, Estimation of the RF Characteristics of Absorbing Materials in Broad RF Frequency Ranges, CERN-OPEN-2008-019, CLIC-Note-766, 2008. G. De Michele: HG2013, 3-6 June, ICTP Trieste

  5. The Coaxial Technique Simulations Material properties AND Measurements The measurements system is simulated with 3D EM code using the material properties as free parameters From simulations one obtains the complex transmission parameter S21 as function of real(epsr) and imag(epsr) at a given frequency The possible solutions are calculated from the contour plots that result from the intersections between the 3D surfaces, obtained numerically, and the measurements (real and imag) G. De Michele: HG2013, 3-6 June, ICTP Trieste

  6. The Measurements Setup • The reflection method gave some limitations on the maximum measurable frequency range.For this reason transmission method has been evaluated • The setup consists on a SMA adapter filled by the material with a hollow coaxial shape. The dimensions of the samples are: • Length = 15.00±0.02mm • Outer diameter = 4.07±0.01mm • Inner diameter = 1.30±0.02mm • The samples were measured in two frequency ranges: from 2GHz to 10GHz and from 10GHz to 27GHz in order to have a better calibration • The calibrated planes are directly the 3.5mm adapters. No transition between the calibrated planes and the DUT reduces source of errors • The measured materials are CerasicB1, EkasicF, EkasicP G. De Michele: HG2013, 3-6 June, ICTP Trieste

  7. Results The data are filtered in order to delete multiple solutions. Below fits of the measurement with the Cole-Cole Model: G. De Michele: HG2013, 3-6 June, ICTP Trieste

  8. Error Analysis 1% 5% By mounting and dismounting the setup we found an error within 5% for the real part of the permittivity and 10% for the imaginary part Furthermore measurements on 4 different samples for EkasicP were performed. The magnitude and phase variation of S21 is within 5% and this gives a maximum variation of 6% for the real part of permittivity and 9% for imaginary part Repeated calibrations gave error within 1% G. De Michele: HG2013, 3-6 June, ICTP Trieste

  9. Remarks The reflection method has been deeply investigated as well; a transmission line model was also used in order to crosscheck the simulation results The air-gap correction has been investigated and an error of few percent has been found on final results (air-gap~20-30um) in the frequency range of interest Does not exist a unique setup: it depends on the frequency range of interest and on the MUT For details on reflection method, TL modeling and EM simulations please see: G. De Michele, A. Grudiev, EM Characterization of damping Materials for CLIC RF Accelerating Structures, CLIC Note 2013, to be published G. De Michele: HG2013, 3-6 June, ICTP Trieste

  10. WFM measurements at PSI Swiss FEL injector G. De Michele: HG2013, 3-6 June, ICTP Trieste X-band structure (common development of PSI, CERN, ELETTRA) in order to linearize the longitudinal phase space for high efficiency bunch compression Constant gradient design: 72 cells, active length 750 mm Long cells with large mean aperture of 9.1 mm: small transverse wake Wake field monitors to ensure optimum structure alignment Average gradient 40 MV/m with 29 MW input power Group velocity variation: 1.6-3.7% Fill time: 100 nsec Average Q: 7150 For details: M. Dehler et al., X-band structure with integrated alignment monitors, PRST 2009

  11. The x-band structure WFM upstream WFM downstream beam G. De Michele: HG2013, 3-6 June, ICTP Trieste

  12. Simulated output signalspectra Thereis a strong coupling to the beam in the region from 15.3 to 16.2GHz . Transversewakeimpedance Zt M. Dehler G. De Michele: HG2013, 3-6 June, ICTP Trieste

  13. Installation y x yaw z pitch 6390 roll beam 6392 6396 G. De Michele: HG2013, 3-6 June, ICTP Trieste

  14. Measurements • The structure was moved w.r.t. the beam by using the mechanical mover system in order to have a clear picture of the emittancedilution. • Signals were measured outside the tunnel with a LeCroy SDA816zi digital scope (18 GHz BW, 40 GS/sec). The measured attenuation of the connecting cable was 25 dB at 16 GHz. G. De Michele: HG2013, 3-6 June, ICTP Trieste

  15. Typical output from the WFMs Signalfrom the upstream WFM upstream Signalfrom the downstream WFM downstream G. De Michele: HG2013, 3-6 June, ICTP Trieste

  16. WFM monitors signals vs. horizontal and vertical offsets of the X-band structure • Averaged peak-to-peak over several hundreds measurements • Next time take the standard deviation of the peak and combine it with the noise floor • Next time take an external stable trigger • WFMs sensitivity: ≈10V/mm • A systematic study on shifts and tilts of the structure to be done G. De Michele: HG2013, 3-6 June, ICTP Trieste

  17. Emittance dilution vs. vertical shift • The quadratic fit gave a minimal emittance for a vertical offset y = -75 um (WFM predicts minimum at -100 um) • The same measurement was not possible in the horizontal plane since we lost the reference of the mechanical movers during the run S. Bettoni G. De Michele: HG2013, 3-6 June, ICTP Trieste

  18. Tilt (yaw) in the structure after alignment in horizontal plane The "hole" in the signal means that the 15.7GHz dipolar mode (that is strongly coupled to the beam in the central cell of the structure) is not excited i.e. the beam is passing in the center of the cell in the middle of the RF structure (cell 36). TILT OFFSET G. De Michele: HG2013, 3-6 June, ICTP Trieste

  19. Conclusions • We were able to align the structure to the golden orbit in the vertical plane. In the horizontal plane was not possible only because of the mechanical movers problem and available time • Even with a preliminary setup the alignment of the structure was much faster than measuring the emittance growth • With a dedicated RF front end we hope to see also bends, random misalignments in the structure • Next step will be the high power operation and in this phase effects of RF fields on beam emittance could be study as well if any • Comparison with Trieste WFMs measurements could be interesting as well G. De Michele: HG2013, 3-6 June, ICTP Trieste

  20. Background: Naples, Italy Thankyoufor yourattention G. De Michele: HG2013, 3-6 June, ICTP Trieste

More Related