Study of vacuum stability at cryogenic temperature - PowerPoint Presentation

Slide1

Study of vacuum stability at cryogenic temperature

WP4 - Activity at LNF

Marco Angelucci

Roberto Cimino

Berlin 30/05/2017Slide2

Beam Screen Temperature

Berlin 30/05/17

Marco Angelucci1LHCSR Power = 0.13 W/m

FCCSR Power = 40 W/mWorking Pressure(<10-11)BS Temperature RangeSlide3

Temperature

Find right working temperature is a fundamental point for vacuum stability.

Work near a gas desorption temperature could generate great pressure oscillations.Berlin 30/05/17Marco Angelucci2

Study of adsorption/desorption behaviour near critical temperature is mandatory to understand vacuum stability

Study the behaviour of different surfaces

(treated sample)Slide4

Vacuum Stability

Berlin 30/05/17

Marco Angelucci3Interaction With PhotonsInteraction With ElectronsDesorptionSecondary Electron EmissionPhotoelectron Emission

Electron CloudHeat Load

Interaction With IonsSlide5

LNF-Lab Now

Berlin 30/05/17Marco 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

SpectrometerSlide6

LNF-Lab Activities I

Adsorption process of Argon (

Ar) and Carbon-Monoxide (CO) on atomically sputtered Cu surface at low temperature (with SEY)Desorption process of Ar and CO from heated Cu sample (with SEY and TPD)Interaction between electrons and Ar films (SEY)Berlin 30/05/17Marco Angelucci5Slide7

LNF-Lab Activities I

Adsorption process of Argon (

Ar) and Carbon-Monoxide (CO) on atomically sputtered Cu surface at low temperature (with SEY)Desorption process of Ar and CO from heated Cu sample (with SEY and TPD)Interaction between electrons and Ar films (SEY)Berlin 30/05/17Marco Angelucci

6Slide8

Argon Adsorption (SEY)

Berlin 30/05/17Marco Angelucci

7Adsorption 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)Slide9

Argon Adsorption (SEY)

Berlin 30/05/17Marco Angelucci

8Two different regionswith characteristic trends Low Energy(<50 eV)Thick Film (TF)

High Energy(>50 eV)Single Layer (SL)Slide10

Argon Results I

Berlin 30/05/17

Marco Angelucci9Formation 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)Slide11

LNF-Lab Activities II

Study the adsorption process on “As received” and treated samples

Berlin 30/05/17Marco Angelucci10Slide12

LNF-Lab Activities I

Adsorption process of Argon (

Ar) and Carbon-Monoxide (CO) on atomically sputtered Cu surface at low temperature (with SEY)Desorption process of Ar and CO from heated Cu sample (with SEY and TPD)Interaction between electrons and Ar films (SEY)Berlin 30/05/17Marco Angelucci

11Slide13

Argon Desorption (SEY)

Berlin 30/05/17Marco Angelucci

12AdsorptionDesorptionTF

SLSlide14

Argon Desorption (SEY)

Berlin 30/05/17Marco Angelucci

13DesorptionTF @ 17 KSL @ 24 KDesorption TemperaturesSlide15

Argon Desorption (SEY)

Berlin 30/05/17Marco Angelucci

14Desorption process: Cu sample heated up to 100 KSample “Cleaned”SEY returns to the initial valueSlight differences due to possible residual impurities on the surfaceSlide16

Argon Desorption (TPD)

Berlin 30/05/17Marco Angelucci

15Test of Temperature Programmed Desorption (TPD) with Mass SpectrometerDifferent desorption process of TF from Manipulator (Peak 1) and TF/SL from sample (Peak 2 and 3)TF-Manip. @ 22 KTF-Sample @ 30 KSL-Sample @ 37 K

P1P2P3

ArSlide17

Argon Results

Berlin 30/05/17

Marco Angelucci16System 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)Slide18

Argon Results

Berlin 30/05/17Marco Angelucci

17Different Temperatures measured with TPD and SEYDesorption ProcessMore studies of desorption induced by electronsSlide19

LNF-Lab Activities II

Study the adsorption process on

Ar and CO on “As received” and treated samplesTest for TPD measurements with new mass spectrometerMeasure desorption with SEY and TPD at the same timeBerlin 30/05/17Marco Angelucci18Slide20

LNF-Lab Activities I

Adsorption process of Argon (

Ar) and Carbon-Monoxide (CO) on atomically sputtered Cu surface at low temperature (with SEY)Desorption process of Ar and CO from heated Cu sample (with SEY and TPD)Interaction between electrons and Ar films (SEY)Berlin 30/05/17Marco Angelucci19Slide21

Argon Adsorption II (SEY)

Berlin 30/05/17Marco Angelucci

2010We can summarize the results observed forAr adsorption on Cu sample at 10 KSlide22

e--

Argon Interaction (SEY)Berlin 30/05/17

Marco Angelucci2110Subsequent SEY scans on the Ar-dosed Cu sampleSlide23

e

--Argon (SEY)

Berlin 30/05/17Marco Angelucci22GAS ON: AdsorptionGAS OFF: e- DesorptionContinuous SEY scansSEY at 930 decreases as a function of time

SEY at 10 eV remains constante- bombardment induced different behaviourSlide24

e--Argon (SEY)

Berlin 30/05/17

Marco Angelucci23SEY measured in different pointsNew Point presents different SEY spectra with the same features of SEY with large amount of ArSlide25

Argon Results II (SEY)

Berlin 30/05/17

Marco Angelucci24Argon Thick film interacts with primary electrons and desorbsBeam-Layer InteractionSlide26

Beam Interaction

Berlin 30/05/17Marco Angelucci

25Thermal DesorptionElectron beam dependence (size, energy …)

Non-Thermal DesorptionSlide27

CO Adsorption (SEY)

Berlin 30/05/17Marco Angelucci

26Two 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 behaviourSlide28

CO Adsorption (SEY)

Berlin 30/05/17Marco Angelucci

27Two 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 behaviourSlide29

CO Results (SEY)

Berlin 30/05/17

Marco Angelucci28Formation of a TF with Low SEYAdsorption Process (10 K)

Characteristic peaks for SL in the Low Energy RegionSlide30

Low-Energy SEY

Berlin 30/05/17Marco Angelucci

29CO

Ar10Different LE-SEY structuresdepending from adsorbed gasesSlide31

Low Energy SEY

Berlin 30/05/17Marco Angelucci

30Secondary e-Reflected e-

Emitted electrons depends to e- primary energyCimino et al., PRL 93 (2004)Slide32

Low Energy SEY

Berlin 30/05/17Marco Angelucci

31Cimino et al., PRL 93 (2004)Different contributions to SEY Important contribution of reflected e- between 0 and 50 eVSlide33

Low-Energy SEY

Berlin 30/05/17Marco Angelucci

32CO

Ar10Different LE-SEY structuresdepending from adsorbed gasesStudy of reflected e- contributionSlide34

Important

Results

Berlin 30/05/17Marco Angelucci33

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) variationSlide35

Important Task

Berlin 30/05/17

Marco Angelucci34

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 SEYSlide36

Activities/Upgrades

Berlin 30/05/17Marco Angelucci

35

Different Gases adsorption (CO, CO2, CH4 ...) (pure and mixture) Electron desorption Thermal Programmed Desorption (TPD)Low-Energy SEYMeasurements on treated samples (received)

New gas line

Additional electron gun (Tests)

New High-resolution Mass Spectrometer (Mounted)

Maintenance of Electron Analayzer (Hardware and Software Tests)Slide37

e—cloud conference

Berlin 30/05/17

Marco Angelucci36... Which will reconvene in Elba in June 2018Slide38

LNF-Lab Activities II

Berlin 30/05/17Marco Angelucci

37Working 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 KSlide39

LNF-lab Activities II

Why start with Atomically Sputtered clean Copper?

Berlin 30/05/17Marco Angelucci38Electron 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.Slide40

LNF-lab Activities II

Berlin 30/05/17Marco Angelucci

39Experimental 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 mbarSlide41

LNF-lab Activities II

Why Argon and Carbon-Monoxide?

Berlin 30/05/17Marco Angelucci40Argon 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 Slide42

LNF-lab Activities II

Berlin 30/05/17Marco Angelucci

41Reference 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