State of ECR Plasma Test & Measurement of Ferrite Materials Permittivity Summer student meeting August 27, 2007 Ivan Pechenezhskiy, MIPT. Supervisor: Genfa Wu, TD/SRF Development Dept.

Brief Review of Plans & Results The ECR plasma cleaning test which was announced during the first presentation wasn’t carried out yet but... The ECR plasma cleaning test which was announced during the first presentation wasn’t carried out yet but...  Probe samples were contaminated with S particles and now they are ready to be analyzed after the plasma process  The test will be fulfilled in the next three weeks  I learned how to operate the SEM and EDX and now I’m able to do it without assistance [JSM-5900 in IB3, Fermilab] I familiarized with I familiarized with  The basics of the SRF cavities theory; the different types of SRF cavities processing which are used for the avoidance of quench, multipacting and field emission  SUPERFISH and FishPact programs // Probably, one simple task will be simulated by using these codes  The RF test technique giving information about cavity performance

Brief Review of Activities I took part in several RF cavity performance tests I took part in several RF cavity performance tests  A GCIB treated one-cell SRF cavity [in Fermilab]  An USC+HPR nine-cell SRF cavity [in Newman Lab, Cornell University] and others We continue to design the second sound setup We continue to design the second sound setup  The first experiment was unsuccessful due to big noise and crosstalk between the leads in the cable I have got experience working in Class 100 Clean Room I have got experience working in Class 100 Clean Room  We HPRed a cavity and attached it to the test stand in Newman Lab Clean Room

Non-SRF Cavity Activity The primary goal of this work is to measure dielectric constant of ferrite materials in wide frequency range The primary goal of this work is to measure dielectric constant of ferrite materials in wide frequency range  This data is required for a new kicker design  The frequency range is from ~300 kHz to ~20 MHz  Three types of ferrite material were investigated Results are represented in the notes Results are represented in the notes  TD , I. Terechkine “Method and setup for measurement of dielectric permittivity in wide frequency range”  TD , I. Pechenezhskiy, I. Terechkine “Dielectric permittivity of ferrite samples in the frequency range from 0.3 to 20 MHz”

Measurement Setup Simplified schematic of the measurement setupComposite sample capacitor C 1 (dimensions in mm) Having two expressions for two unknowns makes it possible to find both C 1 (and then dielectric constant of the material) and R 1

Dielectric Permittivity of Different Samples Permittivity of the samples is close to what was used while modeling the transition line-type kicker (  = 13), but using a value of permittivity  = 14 could be a better approximation. Capacitance with CMD10 ferrite as a dielectric. Blue dots represent a simplified method of capacitance calculation (C 2 << C 1 & R 2 << R 1 ) Permittivity of the different ferrite samples vs frequency

Thank You! Questions are welcome!

Appendix A: ECR Plasma Plasma cleaning Plasma cleaning  Plasma induces chemical reactions in reduced temperatures, promotes to transform the surface contaminants to gaseous phase to be effectively pumped away  Plasma also generates accelerated ions to bombard the surface Potential benefit of the ECR processing Potential benefit of the ECR processing  Reduce field emission  Applicable on equipped cavities (usual antennas, RF source, no internal parts but external magnet)  Potential new design for cryomodule recovery (build-in magnetic coil) ECR = Electron Cyclotron Resonance

Appendix B: RF Cavities RF accelerating cavities are microwave resonators with connecting tubes to allow particle beams to pass through for acceleration A nine-cell cavity The electric and magnetic fields in a single-cell cavity at TM 010 mode

Appendix C: Improvement of RF Cavities The main practical limitation on the accelerating gradient is the field emission due to The main practical limitation on the accelerating gradient is the field emission due to  Emitting sites (dusts, scratches)  Local enhancement of (surface roughness)  Absorbed surface contaminations Surface processing (not all techniques are shown) Surface processing (not all techniques are shown)  Chemical etching (BCP)  Electropolishing (EP)  High pressure rinsing (HPR)  Helium processing (HP)  High peak power processing (HPP )  Plasma cleaning DC discharge ECR … are usual techniques to remove the damage surface layers but after the such cleaning the following problems remain Not enough plane surface after etching Residues from chemical processing (EP, BCP) Water impurity (HPR) Clean room particles and assembly particulates further improvement to deactivate emitters

Appendix D: GCIB Principle scheme of Gas-Cluster Ion Technology The first RF test of a GCIB treated SRF cavity