WP4 Activity at LNF Marco Angelucci Roberto Cimino CERN 09102017 Beam Screen Temperature CERN 100917 Marco Angelucci 1 LHC SR Power 013 Wm FCC SR Power 40 Wm Working Pressure ID: 781457
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Slide1
Study of vacuum stability at cryogenic temperature
WP4 - Activity at LNF
Marco Angelucci
Roberto Cimino
CERN 09/10/2017
Slide2Beam Screen Temperature
CERN 10/09/17
Marco Angelucci1LHCSR Power = 0.13 W/m
FCCSR Power = 40 W/mWorking Pressure(<10-11)BS Temperature Range
Slide3Temperature
Find right working temperature is a fundamental point for vacuum stability.
Work near a gas desorption temperature could generate great pressure oscillations.CERN 10/09/17Marco Angelucci2
Study of adsorption/desorption behaviour near critical temperature is mandatory to understand vacuum stability
Study the behaviour of different surfaces
(treated sample)
Slide4Vacuum Stability
CERN 10/09/17
Marco Angelucci3Interaction With PhotonsInteraction With ElectronsDesorptionSecondary Electron EmissionPhotoelectron Emission
Electron CloudHeat Load
Interaction With Ions
Slide5LNF-Lab Now
CERN 10/09/17Marco Angelucci
4Two Different Ultra-High Vacuum Systems equipped with:
Low Energy Electron DiffractionSecondary Electron Yield SpectroscopySurface PreparationGas-Line
X-Ray/UV Photoemission
High Temperature Manipulator
Low Temperature Manipulator (
≈ 9 K)
Raman Spectroscopy
Scanning Tunneling Microscopy
New
Mass
Spectrometer
Slide6LNF-Lab Now
CERN 10/09/17
Marco Angelucci5Two Different Ultra-High Vacuum Systems equipped with:
Low Energy Electron DiffractionSecondary Electron Yield SpectroscopySurface PreparationGas-Line
X-Ray/UV Photoemission
High Temperature Manipulator
Low Temperature Manipulator (
≈ 9 K)
Raman Spectroscopy
Scanning Tunneling Microscopy
New
Mass
Spectrometer
Synchrotron beamlines (30-1000 eV)
Slide7Important
Results
CERN 10/09/17Marco Angelucci6
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 surfaceMeasure the desorption temperature of TF and SL with SEY and TPDMeasure Work Function (WF) variation
Slide8Important Tasks
CERN 10/09/17
Marco Angelucci7
Distinguish electron-induced from thermal desorption Study the contribution of reflected e- to Low-Energy SEYStudy the influence of the adsorbed gas in the Low-Energy SEY
Slide9Important 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 10/09/17Marco Angelucci8
Slide10LNF-Lab Activities
SEY of Clean metals
SEY of clean Cu with low contaminantsAdsorption and Desorption processes from different surfaces (clean Cu, Laser Treated sample)Interaction between electron and ArgonContribution of reflected Electrons to the Low-Energy SEY (Graphite, Cu, Cu with Argon)CERN 10/09/17Marco Angelucci9
Slide11LNF-Lab Activities
SEY of Clean metals
SEY of clean Cu with low contaminantsAdsorption and Desorption processes from different surfaces (clean Cu, Laser Treated sample)Interaction between electron and ArgonContribution of reflected Electrons to the Low-Energy SEY (Graphite, Cu, Cu with Argon)CERN 10/09/17Marco Angelucci10
Slide12Clean Metals
CERN 10/09/17Marco Angelucci
11Differences between “As Received” and Atomically Clean MetalsHigh-Energy SEY dependenceContaminants (as received)Materials (clean)General High SEY
Lower SEYCharacteristic CurvesL. A. Gonzalez et al: "The secondary electron yield of noble metal surfaces.” In print to AIP Advances
Slide13Clean Metals
CERN 10/09/17Marco Angelucci
12Differences between “As Received” and Atomically Clean Metalsin the Low-Energy rangeEvaluation of Work FunctionGeneral Behaviour in all clean metals
L. A. Gonzalez et al: "The secondary electron yield of noble metal surfaces.” In print to AIP Advances
Slide14LNF-Lab Activities
SEY of Clean metals
SEY of clean Cu with low contaminantsAdsorption and Desorption processes from different surfaces (clean Cu, Laser Treated sample)Interaction between electron and ArgonContribution of reflected Electrons to the Low-Energy SEY (Graphite, Cu, Cu with Argon)CERN 10/09/17Marco Angelucci13
Slide15Surface Modification
CERN 10/09/17Marco Angelucci
14Sub-Monolayer ContaminationsStrong Variations(SEY @10eV from 0.05 to 0.25)New characteristic structuresLow-Energy RangeLow Variations
(SEY Max from 1.4 to 1.3)Variation Dependence on Gas contaminant (?)High-Energy RangeInduced SEY variation by external contaminants L. A. Gonzalez et al: "The secondary electron yield of noble metal surfaces.” In print to AIP Advances
Slide16Surface Modification
CERN 10/09/17Marco Angelucci
15Induced SEY variation by external contaminants Sub-Monolayer ContaminationsHigh-Energy RangeStrong Variations
(SEY @10eV from 0.05 to 0.25)New characteristic structuresLow-Energy RangeLow Variations (SEY Max from 1.4 to 1.3)Variation Dependence on Gas contaminant (?)L. A. Gonzalez et al: "The secondary electron yield of noble metal surfaces.” In print to AIP Advances
Slide17LNF-Lab Activities
SEY of Clean metals
SEY of clean Cu with low contaminantsAdsorption and Desorption processes from different surfaces (clean Cu, Laser Treated sample) with ArgonInteraction between electron and ArgonContribution of reflected Electrons to the Low-Energy SEY (Graphite, Cu, Cu with Argon)CERN 10/09/17Marco Angelucci16
Slide18Argon Adsorption (SEY)
CERN 10/09/17Marco Angelucci
17Two different regionswith characteristic trends Low Energy(<50 eV)Thick Film (TF)
High Energy(>50 eV)Single Layer (SL)Adsorption process of Argon on Cu sample at 10 KGeneral behaviourMax dose160 LCu
Cu
Max dose
160 L
Δ
= 4.1
From 1.4 (10 K) to 5.5 (160 L)
(@900 eV)
Slide19Argon Desorption (SEY)
CERN 10/09/17Marco Angelucci
18AdsorptionDesorptionTFSL
Slide20Argon Desorption (TPD)
CERN 10/09/17Marco Angelucci
19Temperature Programmed Desorption (TPD) Characteristic desorption behaviourFirst desorption process around 20 K (P1)Second desorption process @ 30 K (P2)Other desorption after 50 KP1P2
Slide21Argon Desorption (TPD)
CERN 10/09/17Marco Angelucci
20Temperature Programmed Desorption (TPD) P1P2P1Correlation between P1 and SEY signals
Slide22Argon Results (Cu)
Berlin 30/05/17
Marco Angelucci21System returns to the original state with slight differences Possibility to follow formation of SL from TFPossibility to measure desorption temperature with SEY and TPDDesorption Process (Heating)
Formation of a Thick Film (TF) at high coverage (increasing of SEY)
Formation of a Single Layer (SL) on Cu at LT (characteristic peaks)
Adsorption Process (LT)
Slide23LNF-Lab Activities
SEY of Clean metals
SEY of clean Cu with low contaminantsAdsorption and Desorption processes from different surfaces (clean Cu, Laser Treated sample) with ArgonInteraction between electron and ArgonContribution of reflected Electrons to the Low-Energy SEY (Graphite, Cu, Cu with Argon)CERN 10/09/17Marco Angelucci22
Slide24Laser Treated Sample
CERN 10/09/17
Marco Angelucci23
Laser treated sample at 10 K
Strong Variation of SEY due to
the contamination
Slide25Laser Treated Sample
CERN 10/09/17
Marco Angelucci24
Laser treated sample Heated up to 300 K
Desorption
of contaminants
SEY returns to the initial value
Slide26Laser Treated Sample
CERN 10/09/17Marco Angelucci
25
Adsorption of contaminantsCooling Process
Modification of SEY
Additional contribution to Thermal Desorption
Slide27Laser Treated Sample
CERN 10/09/17
Marco Angelucci26Adsorption process of Argon (500 L) on Laser Treated sample at 10 KNo “significant” variation of SEYΔ = 0.05From 0.55 (10 K) to 0.6 (500 L)
(@900 eV)
Slide28Laser Treated Sample
CERN 10/09/17
Marco Angelucci27Desorption process from Laser Treated Sample with Argon (500 L)General behaviour between 30 and 100 KNo visible peak at 20 K (P1)Huge peak at 30 K (P2)
Temperature Programmed Desorption (TPD)
P1
P2
Slide29Laser Treated Sample
CERN 10/09/17
Marco Angelucci28Adsorption process of Argon (2000 L) on Laser Treated sample at 10 KNo “significant” variation of SEY
minor differences in the starting pointΔ = 0.1From 0.4 (10 K) to 0.5 (2000 L) (@900 eV)
Slide30Laser Treated Sample
CERN 10/09/17
Marco Angelucci29Desorption process from Laser Treated Sample with Argon (2000 L)General behaviour between 30 and 100 KVisible peak at 20 K (P1)Huge peak at 30 K (P2)
Temperature Programmed Desorption (TPD)
P1
P2
Slide31Laser Treated Sample
CERN 10/09/17Marco Angelucci
30
Temperature Programmed Desorption (TPD) P1P2P1P2
Slide32Laser Treated Sample
CERN 10/09/17Marco Angelucci
31CuLaserLaser500 L2000 L160 L
Temperature Programmed Desorption (TPD)
Slide33Laser Treated Sample
CERN 10/09/17Marco Angelucci
32P1 (@ 20 K) (10-7 mbar)P2 (@ 30 K) (10-7 mbar)Cu (160 L)0.10.45Laser Treated (500 L)0.0132Laser Treated (2000 L)0.18
7
Maximum pressure during desorption process
Slide34Argon Results (Laser Treated)
Berlin 30/05/17
Marco Angelucci33System returns to the original state with slight differences Differences with Cu in the range around 20 KDesorption Process (Heating)
Strong Variation during cooling process (contaminants)
No significant SEY variation during Argon Adsorption (up to 2000 L)
Adsorption Process (LT)
Slide35Important Tasks
Study the adsorption and desorption processes on “As Received” samples
Adsorption/Desorption processes with different gasesCERN 10/09/17Marco Angelucci34
Slide36LNF-Lab Activities
SEY of Clean metals
SEY of clean Cu with low contaminantsAdsorption and Desorption processes from different surfaces (clean Cu, Laser Treated sample) with Carbon-MonoxideInteraction between electron and ArgonContribution of reflected Electrons to the Low-Energy SEY (Graphite, Cu, Cu with Argon)CERN 10/09/17Marco Angelucci35
Slide37CO Adsorption (SEY)
CERN 10/09/17Marco Angelucci
36Two different regions High Energy(>50 eV)Low Energy(<50 eV)SEY @ 1000 eV decreases during deposition from 1.4 to 1.1
Formation of CO Thick Film (TF)Characteristic peak of TF at 65 eVAdsorption process of Carbon Monoxide on Cu sample at 10KGeneral behaviour
Slide38CO Adsorption (SEY)
CERN 10/09/17Marco Angelucci
37Two different regions High Energy(>50 eV)Low Energy(<50 eV)Characteristic peaks at different low energiesFormation of Argon Single Layer (SL)
Adsorption process of Argon on Cu sample at 10KLow Energy behaviour
Slide39CO Results (SEY)
CERN 10/09/17
Marco Angelucci38Formation of a TF with Low SEYAdsorption Process (10 K)
Characteristic peaks for SL in the Low Energy Region
Slide40LNF-Lab Activities
SEY of Clean metals
SEY of clean Cu with low contaminantsAdsorption and Desorption processes from different surfaces (clean Cu, Laser Treated sample)Interaction between electron and ArgonContribution of reflected Electrons to the Low-Energy SEY (Graphite, Cu, Cu with Argon)CERN 10/09/17Marco Angelucci39
Slide41Argon Adsorption II (SEY)
CERN 10/09/17Marco Angelucci
4010We can summarize the results observed forAr adsorption on Cu sample at 10 K
Slide42e--
Argon Interaction (SEY)CERN 10/09/17
Marco Angelucci4110Subsequent SEY scans on the Ar-dosed Cu sample
Slide43e
--Argon (SEY)
CERN 10/09/17Marco Angelucci42GAS ON: AdsorptionGAS OFF: e- DesorptionContinuous SEY scansSEY at 930 decreases as a function of time
SEY at 10 eV remains constante- bombardment induced different behaviour
Slide44e--Argon (SEY)
CERN 10/09/17
Marco Angelucci43SEY measured in different pointsNew Point presents different SEY spectra with the same features of SEY with large amount of Ar
Slide45e--Argon (SEY) II
CERN 10/09/17
Marco Angelucci44900 eV400 eVElectron Stimulated Desorption at different EnergiesStrong Interaction (desorption) with HE electrons
Slide46e--Argon (SEY) II
CERN 10/09/17
Marco Angelucci4510 eVElectron Stimulated Desorption at different EnergiesLow interaction (no desorption) with LE electrons
Slide47e--Argon (SEY)
CERN 10/09/17
Marco Angelucci46Continuous SEY scans (mass spec. signal)complete SEY scan
Study Electron Stimulated Desorption with Mass spectrometer
Slide48e
—
Argon results (SEY)CERN 10/09/17Marco Angelucci47Argon Thick film interacts with primary electrons and desorbsBeam-Layer Interaction
Slide49Beam Interaction
CERN 10/09/17Marco Angelucci
48Thermal DesorptionElectron beam dependence (size, energy …)
Non-Thermal Desorption
Slide50Important Tasks
Study the adsorption and desorption processes on “As Received” samples
Adsorption/Desorption processes with different gasesStudy the Electron Stimulated Desorption with different parametersCERN 10/09/17Marco Angelucci49
Slide51LNF-Lab Activities
SEY of Clean metals
SEY of clean Cu with low contaminantsAdsorption and Desorption processes from different surfaces (clean Cu, Laser Treated sample)Interaction between electron and ArgonContribution of reflected Electrons to the Low-Energy SEY (Graphite, Cu, Cu with Argon)CERN 10/09/17Marco Angelucci50
Slide52Low-Energy SEY
CERN 10/09/17Marco Angelucci
51CO
Ar10Different LE-SEY structuresdepending from adsorbed gasesStudy of reflected e- contribution
Slide53Low Energy SEY
CERN 10/09/17Marco Angelucci
52”Probabilistic model for the simulation of secondary electron emission” M. A. Furman and M. T. F. Pivi Phys. Rev. ST Accel. Beams 5, 124404 (2002)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 E
P (+ D)Rediffused electrons: number of electrons emitted between 50 eV and EP – D (if EP > 50 eV.)
Slide54Low Energy SEY
CERN 10/09/17Marco Angelucci
53abdd
SERSERSERSER
d
c
b
a
Evaluation of Reflected
(R)
and True Secondary (SE) electrons parts
Cimino
et al., PRL 93 (2004)
Slide55CERN 10/09/17
Marco Angelucci
54WfWf
WfEp= 2 eVEp= 6.5 eVEp= 20 eVEp= 130 eVEp= 310 eVPlotting all the data normalizing to UNITY the intensity of the EDC @ Ep< WfOrIntegrating the curves: (when Ep <50 eV)
0 to E
P
–
D (
True Secondary)
E
P
–
D
to
E
P
+
D (
Elastically Back.)
(
when Ep
> 50
eV
)
0 to
50 eV
(
True Secondary
)
50 eV to
E
P
–
D
(
Rediffused
)
E
P
–
D
to
E
P
+
D (
Elastically Back.)
D
Low Energy SEY
Slide56Low Energy SEY
CERN 10/09/17Marco Angelucci
55Clean Poly-Cu SEYEDCsReflected electrons in CopperPlotting all the data normalizing to UNITY the intensity of the EDC @ Ep< WfStructures in SEY are oscillations in the elastically backscattered components
Slide57Low Energy SEY
CERN 10/09/17Marco Angelucci
56Reflected electrons in CopperDifferent ContributionsSEYSecond.Redif.
Reflec
.
SEY
Second.
Redif
.
Reflec
.
Slide58Low Energy SEY
CERN 10/09/17Marco Angelucci
57Reflected electrons in CopperDifferent Contributions
SEYSecond.Redif.Reflec.
Slide59Low Energy SEY
CERN 10/09/17Marco Angelucci
58Reflected electrons in GraphiteSEYEDCsPlotting all the data normalizing to UNITY the intensity of the EDC @ Ep< WfStructures in SEY are oscillations in the elastically backscattered components
Slide60Low Energy SEY
CERN 10/09/17Marco Angelucci
59Reflected electrons in GraphiteDifferent ContributionsSEYSecond.Reflec.Redif.SEY
Second.Reflec.Redif.
Slide61Low Energy SEY
CERN 10/09/17Marco Angelucci
60Ar monolayerAr multilayerSEYEDCsSEYEDCs
Reflected electrons in Argon
Slide62Low Energy SEY
CERN 10/09/17Marco Angelucci
61... and: Bauer: “Surface microscopy with low
energy electrons” Springher 2014
Slide63Important Results I
CERN 10/09/17
Marco Angelucci62
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 surfaceMeasure Work Function (WF) variation
Slide64Important
Results II
CERN 10/09/17Marco Angelucci63
Measure the desorption temperature of TF and SL with SEY and TPDStudy the Electron Stimulated Desorption with mass spectrometer (quantify desorption)Study the contribution of reflected e- to Low-Energy SEYStudy the influence of the adsorbed gas in the Low-Energy SEY
Slide65Maintenance /Upgrades I
CERN 10/09/17
Marco Angelucci64
Non Standard chamber maintenance (open system)Implementations for Induced Desorption Studies
Standard chamber maintenance (
transfer)
Preparation chamber
Implemented data acquisition software
Slide66Future Activities
CERN 10/09/17Marco Angelucci
65Synchrotron BeamlinesXUV2: High Energy 60-1000 eV. XUV1: High Energy 30-150 eV.
Slide67Maintenance /Upgrades II
CERN 10/09/17
Marco Angelucci66
Connection (2/3 month)System optimization for experiment with electrons and photons
Alignment of Sychrotron beamlines
Preparation for connection with Experimental Chamber
Slide68Future Activities
CERN 10/09/17Marco Angelucci
67
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
Slide69e—cloud conference
CERN 10/09/17
Marco Angelucci68... Which will reconvene in Elba in June 2018
Slide70Argon Adsorption (SEY)
CERN 10/09/17Marco Angelucci
69Adsorption process of Argon on Cu sample at 10 KGeneral behaviourTwo different regionswith characteristic trends Low Energy(<50 eV)Thick Film (TF)
High Energy(>50 eV)Single Layer (SL)
Slide71Argon Adsorption (SEY)
CERN 10/09/17Marco Angelucci
70Two different regionswith characteristic trends Low Energy(<50 eV)Thick Film (TF)
High Energy(>50 eV)Single Layer (SL)
Slide72e--Argon (SEY) II
CERN 10/09/17
Marco Angelucci71
Slide73Laser Treated Sample
CERN 10/09/17Marco Angelucci
72
Slide74LNF-Lab Activities II
CERN 10/09/17Marco Angelucci
73Working Parameters:Basic Pressure ≤ 1x10-10 mbarElectron Beam Current < 1x10-7 Ampere (A) (Max Current @ max electron energy)Electron Beam Energy from 75 to 1000 eVSample Bias 75 VSingle Spectra Acquisition Time ≈ 120 secBeam Radius < 1.0 mm1 Langmuir (L) = 1 sec @ 1x10-6 mbar1 L = 1 Mono-Layer (ML) (with sticking coefficient = 1)Temperature range: form 10 to 300 K
Slide75LNF-lab Activities II
Why start with Atomically Sputtered clean Copper?
CERN 10/09/17Marco Angelucci74Electron Beams have not effect on a clean surface so any modification to the SEY can be attributed to atoms and molecules on surface.easy to single out contamination (sample pumping) from experimental.easy to eliminate spurious and otherwise occurring scrubbing effects from real non-clean surfaces.
Slide76LNF-lab Activities II
CERN 10/09/17Marco Angelucci
75Experimental Test with Atomically Sputtered CopperFirst observable changes (blu) after 0.02C/mm2 more than 6 h SEY measurementsMore significant changes (green) needs more than 60 h continuous measuringOur standard SEY lasts 120s!
Thanks to: Luis Gonzalezat P = 2x10-10 mbar
Slide77LNF-lab Activities II
Why Argon and Carbon-Monoxide?
CERN 10/09/17Marco Angelucci76Argon is a inert gas and it’s the best starting point to study SEY al Low TemperatureCarbon-Monoxide is a gas of great interest for accelerator physics
Slide78LNF-lab Activities II
CERN 10/09/17Marco Angelucci
77Reference Literature spectra of Argon and Carbon-Monoxide SEYJ. Cazaux et al.: Phys. Rev. B 71 (2005) 035419Argon
A. Kuzucan et al.: J. of Vacuum Sci. & Tech. A 30 (2012) 051401Carbon-Monoxide