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Study of vacuum stability at cryogenic temperature

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Presentation on theme: "Study of vacuum stability at cryogenic temperature"— Presentation transcript:

1 Study of vacuum stability at cryogenic temperature
WP4 - Activity at LNF CERN 09/10/2017 Marco Angelucci Roberto Cimino

2 Beam Screen Temperature
Working Pressure (<10-11) BS Temperature Range LHC SR Power = 0.13 W/m FCC SR Power = 40 W/m CERN 10/09/17 Marco Angelucci

3 Study the behaviour of different surfaces (treated sample)
Temperature Find right working temperature is a fundamental point for vacuum stability. Work near a gas desorption temperature could generate great pressure oscillations. Study of adsorption/desorption behaviour near critical temperature is mandatory to understand vacuum stability Study the behaviour of different surfaces (treated sample) CERN 10/09/17 Marco Angelucci

4 Vacuum Stability Interaction With Electrons Desorption
Interaction With Photons Interaction With Electrons Photoelectron Emission Secondary Electron Emission Heat Load Electron Cloud Interaction With Ions Desorption CERN 10/09/17 Marco Angelucci

5 Scanning Tunneling Microscopy
LNF-Lab Now Two Different Ultra-High Vacuum Systems equipped with: X-Ray/UV Photoemission High Temperature Manipulator Low Energy Electron Diffraction Secondary Electron Yield Spectroscopy Surface Preparation Gas-Line Low Temperature Manipulator (≈ 9 K) New Mass Spectrometer Raman Spectroscopy Scanning Tunneling Microscopy CERN 10/09/17 Marco Angelucci

6 LNF-Lab Now Two Different Ultra-High Vacuum Systems equipped with:
X-Ray/UV Photoemission High Temperature Manipulator Low Energy Electron Diffraction Secondary Electron Yield Spectroscopy Surface Preparation Gas-Line Low Temperature Manipulator (≈ 9 K) New Mass Spectrometer Raman Spectroscopy Scanning Tunneling Microscopy Synchrotron beamlines ( eV) CERN 10/09/17 Marco Angelucci

7 Important Results Follow Adsorption process checking the High- Energy SEY (HE-SEY) Distinguish Single Layer (SL) from Thick Film (TF) formation by Low-Energy SEY (LE-SEY) Quantify the number of adsorbed layers on surface Measure the desorption temperature of TF and SL with SEY and TPD Measure Work Function (WF) variation CERN 10/09/17 Marco Angelucci

8 Important Tasks Distinguish electron-induced from thermal desorption
Study the contribution of reflected e- to Low- Energy SEY Study the influence of the adsorbed gas in the Low- Energy SEY CERN 10/09/17 Marco Angelucci

9 Important Tasks Study the adsorption and desorption processes on Laser treated samples (preliminary results) TPD measurements with new mass spectrometer (done) Measure desorption with SEY and TPD at the same time (data acquisition system improved) CERN 10/09/17 Marco Angelucci

10 LNF-Lab Activities SEY of Clean metals
SEY of clean Cu with low contaminants Adsorption and Desorption processes from different surfaces (clean Cu, Laser Treated sample) Interaction between electron and Argon Contribution of reflected Electrons to the Low-Energy SEY (Graphite, Cu, Cu with Argon) CERN 10/09/17 Marco Angelucci

11 LNF-Lab Activities SEY of Clean metals
SEY of clean Cu with low contaminants Adsorption and Desorption processes from different surfaces (clean Cu, Laser Treated sample) Interaction between electron and Argon Contribution of reflected Electrons to the Low-Energy SEY (Graphite, Cu, Cu with Argon) CERN 10/09/17 Marco Angelucci

12 Clean Metals High-Energy SEY dependence
Differences between “As Received” and Atomically Clean Metals High-Energy SEY dependence Contaminants (as received) Materials (clean) Lower SEY Characteristic Curves General High SEY L. A. Gonzalez et al: "The secondary electron yield of noble metal surfaces.” In print to AIP Advances CERN 10/09/17 Marco Angelucci

13 Clean Metals Differences between “As Received” and Atomically Clean Metals in the Low-Energy range General Behaviour in all clean metals Evaluation of Work Function L. A. Gonzalez et al: "The secondary electron yield of noble metal surfaces.” In print to AIP Advances CERN 10/09/17 Marco Angelucci

14 LNF-Lab Activities SEY of Clean metals
SEY of clean Cu with low contaminants Adsorption and Desorption processes from different surfaces (clean Cu, Laser Treated sample) Interaction between electron and Argon Contribution of reflected Electrons to the Low-Energy SEY (Graphite, Cu, Cu with Argon) CERN 10/09/17 Marco Angelucci

15 Sub-Monolayer Contaminations
Surface Modification Induced SEY variation by external contaminants Sub-Monolayer Contaminations High-Energy Range Low Variations (SEY Max from 1.4 to 1.3) Variation Dependence on Gas contaminant (?) Low-Energy Range Strong Variations from 0.05 to 0.25) New characteristic structures L. A. Gonzalez et al: "The secondary electron yield of noble metal surfaces.” In print to AIP Advances CERN 10/09/17 Marco Angelucci

16 Sub-Monolayer Contaminations
Surface Modification Induced SEY variation by external contaminants Sub-Monolayer Contaminations High-Energy Range Low Variations (SEY Max from 1.4 to 1.3) Variation Dependence on Gas contaminant (?) Low-Energy Range Strong Variations from 0.05 to 0.25) New characteristic structures L. A. Gonzalez et al: "The secondary electron yield of noble metal surfaces.” In print to AIP Advances CERN 10/09/17 Marco Angelucci

17 LNF-Lab Activities SEY of Clean metals
SEY of clean Cu with low contaminants Adsorption and Desorption processes from different surfaces (clean Cu, Laser Treated sample) with Argon Interaction between electron and Argon Contribution of reflected Electrons to the Low-Energy SEY (Graphite, Cu, Cu with Argon) CERN 10/09/17 Marco Angelucci

18 Argon Adsorption (SEY)
Adsorption process of Argon on Cu sample at 10 K General behaviour Max dose 160 L Max dose 160 L Two different regions with characteristic trends High Energy (>50 eV) Low Energy (<50 eV) Thick Film (TF) Single Layer (SL) Cu Cu Δ = 4.1 From 1.4 (10 K) to 5.5 (160 L) eV) CERN 10/09/17 Marco Angelucci

19 Argon Desorption (SEY)
Adsorption Desorption TF SL CERN 10/09/17 Marco Angelucci

20 Argon Desorption (TPD)
Temperature Programmed Desorption (TPD) P2 Characteristic desorption behaviour First desorption process around 20 K (P1) Second desorption 30 K (P2) Other desorption after 50 K P1 CERN 10/09/17 Marco Angelucci

21 Argon Desorption (TPD)
Temperature Programmed Desorption (TPD) P2 Correlation between P1 and SEY signals P1 P1 CERN 10/09/17 Marco Angelucci

22 Argon Results (Cu) Adsorption Process (LT)
Formation of a Thick Film (TF) at high coverage (increasing of SEY) Formation of a Single Layer (SL) on Cu at LT (characteristic peaks) Desorption Process (Heating) System returns to the original state with slight differences Possibility to follow formation of SL from TF Possibility to measure desorption temperature with SEY and TPD Berlin 30/05/17 Marco Angelucci

23 LNF-Lab Activities SEY of Clean metals
SEY of clean Cu with low contaminants Adsorption and Desorption processes from different surfaces (clean Cu, Laser Treated sample) with Argon Interaction between electron and Argon Contribution of reflected Electrons to the Low-Energy SEY (Graphite, Cu, Cu with Argon) CERN 10/09/17 Marco Angelucci

24 Strong Variation of SEY due to the contamination
Laser Treated Sample Laser treated sample at 10 K Strong Variation of SEY due to the contamination CERN 10/09/17 Marco Angelucci

25 Laser Treated Sample Laser treated sample Heated up to 300 K
Desorption of contaminants SEY returns to the initial value CERN 10/09/17 Marco Angelucci

26 Laser Treated Sample Cooling Process Adsorption of contaminants
Modification of SEY Additional contribution to Thermal Desorption CERN 10/09/17 Marco Angelucci

27 Laser Treated Sample Adsorption process of Argon (500 L) on Laser Treated sample at 10 K No “significant” variation of SEY Δ = 0.05 From 0.55 (10 K) to 0.6 (500 L) eV) CERN 10/09/17 Marco Angelucci

28 Laser Treated Sample Temperature Programmed Desorption (TPD)
Desorption process from Laser Treated Sample with Argon (500 L) P2 General behaviour between 30 and 100 K No visible peak at 20 K (P1) Huge peak at 30 K (P2) P1 CERN 10/09/17 Marco Angelucci

29 Laser Treated Sample Adsorption process of Argon (2000 L) on Laser Treated sample at 10 K minor differences in the starting point No “significant” variation of SEY Δ = 0.1 From 0.4 (10 K) to 0.5 (2000 L) eV) CERN 10/09/17 Marco Angelucci

30 Laser Treated Sample Temperature Programmed Desorption (TPD)
Desorption process from Laser Treated Sample with Argon (2000 L) P2 General behaviour between 30 and 100 K Visible peak at 20 K (P1) Huge peak at 30 K (P2) P1 CERN 10/09/17 Marco Angelucci

31 Temperature Programmed Desorption (TPD)
Laser Treated Sample Temperature Programmed Desorption (TPD) P2 P2 P1 P1 CERN 10/09/17 Marco Angelucci

32 Temperature Programmed Desorption (TPD)
Laser Treated Sample Temperature Programmed Desorption (TPD) Cu Laser Laser 160 L 500 L 2000 L CERN 10/09/17 Marco Angelucci

33 Maximum pressure during desorption process
Laser Treated Sample Maximum pressure during desorption process P1 20 K) (10-7 mbar) P2 30 K) Cu (160 L) 0.1 0.45 Laser Treated (500 L) 0.013 2 Laser Treated (2000 L) 0.18 7 CERN 10/09/17 Marco Angelucci

34 Argon Results (Laser Treated)
Adsorption Process (LT) Strong Variation during cooling process (contaminants) No significant SEY variation during Argon Adsorption (up to 2000 L) Desorption Process (Heating) System returns to the original state with slight differences Differences with Cu in the range around 20 K Berlin 30/05/17 Marco Angelucci

35 Important Tasks Study the adsorption and desorption processes on “As Received” samples Adsorption/Desorption processes with different gases CERN 10/09/17 Marco Angelucci

36 LNF-Lab Activities SEY of Clean metals
SEY of clean Cu with low contaminants Adsorption and Desorption processes from different surfaces (clean Cu, Laser Treated sample) with Carbon-Monoxide Interaction between electron and Argon Contribution of reflected Electrons to the Low-Energy SEY (Graphite, Cu, Cu with Argon) CERN 10/09/17 Marco Angelucci

37 Adsorption process of Carbon Monoxide on Cu sample at 10K
CO Adsorption (SEY) Adsorption process of Carbon Monoxide on Cu sample at 10K General behaviour Two different regions High Energy (>50 eV) Low Energy (<50 eV) eV decreases during deposition from 1.4 to 1.1 Formation of CO Thick Film (TF) Characteristic peak of TF at 65 eV CERN 10/09/17 Marco Angelucci

38 Adsorption process of Argon on Cu sample at 10K
CO Adsorption (SEY) Adsorption process of Argon on Cu sample at 10K Low Energy behaviour Two different regions High Energy (>50 eV) Low Energy (<50 eV) Characteristic peaks at different low energies Formation of Argon Single Layer (SL) CERN 10/09/17 Marco Angelucci

39 CO Results (SEY) Adsorption Process (10 K)
Formation of a TF with Low SEY Characteristic peaks for SL in the Low Energy Region CERN 10/09/17 Marco Angelucci

40 LNF-Lab Activities SEY of Clean metals
SEY of clean Cu with low contaminants Adsorption and Desorption processes from different surfaces (clean Cu, Laser Treated sample) Interaction between electron and Argon Contribution of reflected Electrons to the Low-Energy SEY (Graphite, Cu, Cu with Argon) CERN 10/09/17 Marco Angelucci

41 Argon Adsorption II (SEY)
We can summarize the results observed for Ar adsorption on Cu sample at 10 K 10 CERN 10/09/17 Marco Angelucci

42 e--Argon Interaction (SEY)
Subsequent SEY scans on the Ar-dosed Cu sample 10 CERN 10/09/17 Marco Angelucci

43 e--Argon (SEY) Continuous SEY scans
GAS ON: Adsorption GAS OFF: e- Desorption e- bombardment induced different behaviour SEY at 930 decreases as a function of time SEY at 10 eV remains constant CERN 10/09/17 Marco Angelucci

44 e--Argon (SEY) SEY measured in different points
New Point presents different SEY spectra with the same features of SEY with large amount of Ar CERN 10/09/17 Marco Angelucci

45 e--Argon (SEY) II Electron Stimulated Desorption at different Energies
900 eV 400 eV Strong Interaction (desorption) with HE electrons CERN 10/09/17 Marco Angelucci

46 e--Argon (SEY) II Electron Stimulated Desorption at different Energies
10 eV Low interaction (no desorption) with LE electrons CERN 10/09/17 Marco Angelucci

47 e--Argon (SEY) Continuous SEY scans (mass spec. signal)
Study Electron Stimulated Desorption with Mass spectrometer complete SEY scan CERN 10/09/17 Marco Angelucci

48 e—Argon results (SEY) Beam-Layer Interaction
Argon Thick film interacts with primary electrons and desorbs CERN 10/09/17 Marco Angelucci

49 Beam Interaction Thermal Desorption Non-Thermal Desorption
Electron beam dependence (size, energy …) CERN 10/09/17 Marco Angelucci

50 Important Tasks Study the adsorption and desorption processes on “As Received” samples Adsorption/Desorption processes with different gases Study the Electron Stimulated Desorption with different parameters CERN 10/09/17 Marco Angelucci

51 LNF-Lab Activities SEY of Clean metals
SEY of clean Cu with low contaminants Adsorption and Desorption processes from different surfaces (clean Cu, Laser Treated sample) Interaction between electron and Argon Contribution of reflected Electrons to the Low-Energy SEY (Graphite, Cu, Cu with Argon) CERN 10/09/17 Marco Angelucci

52 Low-Energy SEY Different LE-SEY structures
CO Ar 10 Different LE-SEY structures depending from adsorbed gases Study of reflected e- contribution CERN 10/09/17 Marco Angelucci

53 Low Energy SEY SEY: Total number of electrons emitted (TEE , TEY,...)
True secondaries: number of electrons emitted between 0-50 eV. (if EP > 50 eV.) Backscattered electrons (Reflected): number of electrons emitted at EP (+ D) Rediffused electrons: number of electrons emitted between 50 eV and EP – D (if EP > 50 eV.) ”Probabilistic model for the simulation of secondary electron emission” M. A. Furman and M. T. F. Pivi Phys. Rev. ST Accel. Beams 5, (2002) CERN 10/09/17 Marco Angelucci

54 Evaluation of Reflected (R) and True Secondary (SE) electrons parts
Low Energy SEY a b d SE R d a b c Evaluation of Reflected (R) and True Secondary (SE) electrons parts Cimino et al., PRL 93 (2004) CERN 10/09/17 Marco Angelucci

55 Low Energy SEY Ep= 2 eV Ep= 6.5 eV Wf
Plotting all the data normalizing to UNITY the intensity of the EDC @ Ep< Wf Or Integrating the curves: (when Ep <50 eV) 0 to EP – D (True Secondary) EP – D to EP + D (Elastically Back.) (when Ep > 50 eV) 0 to 50 eV (True Secondary) 50 eV to EP – D (Rediffused) Wf D Ep= 20 eV Ep= 130 eV Ep= 310 eV Wf CERN 10/09/17 Marco Angelucci

56 Reflected electrons in Copper
Low Energy SEY Reflected electrons in Copper Clean Poly-Cu Plotting all the data normalizing to UNITY the intensity of the EDC @ Ep< Wf SEY Structures in SEY are oscillations in the elastically backscattered components EDCs CERN 10/09/17 Marco Angelucci

57 Low Energy SEY Reflected electrons in Copper Different Contributions
Second. Second. Redif. Redif. Reflec. Reflec. CERN 10/09/17 Marco Angelucci

58 Low Energy SEY Reflected electrons in Copper Different Contributions
Second. Redif. Reflec. CERN 10/09/17 Marco Angelucci

59 Reflected electrons in Graphite
Low Energy SEY Reflected electrons in Graphite SEY Plotting all the data normalizing to UNITY the intensity of the EDC @ Ep< Wf Structures in SEY are oscillations in the elastically backscattered components EDCs CERN 10/09/17 Marco Angelucci

60 Low Energy SEY Reflected electrons in Graphite Different Contributions
Second. Second. Reflec. Redif. Redif. Reflec. CERN 10/09/17 Marco Angelucci

61 Reflected electrons in Argon
Low Energy SEY Reflected electrons in Argon Ar monolayer Ar multilayer SEY SEY EDCs EDCs CERN 10/09/17 Marco Angelucci

62 Low Energy SEY ... and: Bauer: “Surface microscopy with low energy electrons” Springher 2014 CERN 10/09/17 Marco Angelucci

63 Important Results I Follow Adsorption process checking the High- Energy SEY (HE-SEY) Distinguish Single Layer (SL) from Thick Film (TF) formation by Low-Energy SEY (LE-SEY) Quantify the number of adsorbed layers on surface Measure Work Function (WF) variation CERN 10/09/17 Marco Angelucci

64 Important Results II Measure the desorption temperature of TF and SL with SEY and TPD Study the Electron Stimulated Desorption with mass spectrometer (quantify desorption) Study the contribution of reflected e- to Low- Energy SEY Study the influence of the adsorbed gas in the Low- Energy SEY CERN 10/09/17 Marco Angelucci

65 Maintenance /Upgrades I
Standard chamber maintenance (transfer) Preparation chamber Implemented data acquisition software Non Standard chamber maintenance (open system) Implementations for Induced Desorption Studies CERN 10/09/17 Marco Angelucci

66 Synchrotron Beamlines
Future Activities Synchrotron Beamlines XUV2: High Energy eV. XUV1: High Energy eV. CERN 10/09/17 Marco Angelucci

67 Maintenance /Upgrades II
Alignment of Sychrotron beamlines Preparation for connection with Experimental Chamber Connection (2/3 month) System optimization for experiment with electrons and photons CERN 10/09/17 Marco Angelucci

68 Future Activities Different Gases adsorption (CO, CO2, CH4 ...) (pure and mixture) Electron Stimulated Desorption Measurements on treated samples (continue) Study of reflected electron on different systems Different studies with Synchrotron light CERN 10/09/17 Marco Angelucci

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