Atmospheric Microwave plasma torches for advanced cleaning (Giovanni Terenziani - 30') Speaker: Giovanni Terenziani - Legnaro National Laboratories - INFN | Duration: 30 min. Abstract During the last years of research in the plasma field, more and more importance has been focused on Atmospheric Plasma sources. One of the biggest and most important possible application is to use them like a ultra-cleaning device. In fact experiments on Uranium or Thorium contaminated samples have shown that an Atmospheric Plasma surface treatments can decrease significantly the amount of contaminant species without adding any unwanted contamination. These experiments have been taken during the creation of an ultra-cleaning protocol for the C.U.O.R.E. experiment. This kind of results can also open great possibilities in the field of superconductivity physics. In fact devices like Atmospheric Plasma torches could be used in the future to clean the inside surface of resonant cavities used in the particle accelerators. During my work at Legnaro National Laboratories in the National Institute of Nuclear Physics I’ve developed an Atmospheric Plasma Semi-Metallic Torch. The principal aim of this device was to lower the content of radioactive contaminant in some Copper samples. The experimental results were encouraging and the study in this field seems to be very fruitful. One of the possible improvement that we took into account was the possibility of increase the ionized species population by adding to the carrier gas different miscellaneous of various gases or liquid. In particular it’s been noticed, from the literature, the strong effect produced by the O+ and O++ particles. Because of this, we thought that adding water vapor in the gas carrier flux can provide good improvement in the O+ and O++ population. So we reach what we called “The Burning Water Configuration”. The main idea was to introduce a water vapor flux, produced by a vapor generator, directly into the plasma in order to “burn” the biggest quantity of the water possible. Problems with pressure and temperature of the vapor was solved. In fact the condensation of the water on the quartz tube walls, even in the plasma region, could decrease the quantity of “burned” vapor. Increasing then the working temperature and decreasing the flux we reached a minimum in the condensation regime and the plasma with vapor has been obtained. A new development of this plasma source, for treating cavities, can be the creation of a bended plasma. This can be obtained by using a particular angular tube placed by the end of the plasma torch. This, with the help of a turbulent flux regime, can guide the plasma through the bended tube without hitting walls, avoiding in this case the melting of the tubes. With the possibility to bend the plasma flame we can be able to reach the most difficult part of the inner cavities surface. This should ensure more flexibility of operation to the whole system referring also to any other application field.

1. Atmospheric Microwave Plasma Torches for Advanced Cleaning Giovanni Terenziani FabrizioStivanello Antonio Alessandro Rossi

3. Cleaning Experiments

5. Cut Off

6. Plasma BendingFinal Considerations

8. Electron density: 1021 – 1026 m-3

9. Inelastic collision create reactive species

10. (elastic one heat heavy particle)

11. Te >> Th

12. Electron density: <1019 m-3

13. Inelastic collision induce the plasma chemistry

15. Types of Atmospheric Plasmas DC and low frequency discharge RF waves Microwaves discharge Industrial sources Arc torch Corona and DBD (pulsed DC) ICP (Inductivelycoupled plasma) IST (pulsed) Laboratorydevelopment Microplasma APPJ, cold plasma torch, hollow cathode, microplasma CCμP TIA (torche à injection axiale), MTD (Microwave torch discharge), MPJ (Microwave plasma jet), MPT (Microwave plasma torch)

16. Types of Atmospheric Plasmas DC and low frequency discharge RF waves Microwaves discharge Industrial sources Arc torch Corona and DBD (pulsed DC) ICP (Inductivelycoupled plasma) IST (pulsed) Laboratorydevelopment Microplasma APPJ, cold plasma torch, hollow cathode, microplasma CCμP TIA (torche à injection axiale), MTD (Microwave torch discharge), MPJ (Microwave plasma jet), MPT (Microwave plasma torch)

17. Semi Metallic Plasma Torch

19. Microwave equipment (wave guide, tuning system, circulator)

20. An ignition system

22. Plasma Flame Compressed Air gas is used Plasma flame: 15 cm long Wave Guide 3 cm thick

23. Cleaning Trials – Metallized Alumina BEFORE AFTER

24. Ultra-Cleaning Results on Copper Po210 Before AP After AP

25. Improvements – Vapor Added Vapor Generator characterized by: Operative pressure from 4 to 6 bar / from 58 to 87 psi Vapor temperature from 155 to 160° C Vapor capacity 62 g/min. max.

26. Improvements – Vapor Added A narrowing it’s been created in the glass injector Analumina capillary it’s been placed at the end of the vapor injector Vapor Inlet a b Air Inlet Alumina Capillary

28. Improvements – Vapor Added

31. Plasma Flames with and without Cut-Off 17 cm 10 cm

32. Improvements – Plasma Bending Pyrex Glass

34. Possible Applications – Cavities Treatment? 1.5 GHz Cavity Bended Quartz Tube

36. Enhancement of O+ and O++is possible by adding water vapor

37. Application in the RF Superconductivity Physics for surface treatment of cavities

39. Microwave Source – The Magnetron Supplyconnectors Cooling Fins Antenna

40. Microwave Source – The Magnetron Antenna Anodic Cavities Cathode emitting e-

41. Microwave Equipment Circulator: protects Magnetron from back-scattered wave 3-Stub Tuner: used to determine the right position of E field maximum

42. Microwave Equipment Wave Guide Hole for the quartz tube ( Position of max E field)

43. Analysis of I-V Curve with double LP To evaluate the electron temperature we track a parallel to x axisand the intercept with the interpolation of the curve in the concavity changing point gives the value of 2kTe/e So kTe/e ≈ 9.65 eV Te = 11400 K ???????

44. Primary electrons measure? Double Probe Double Probe ruled by primary e-

45. Our Results