Study of vacuum stability at cryogenic temperature WP4 - Activity at LNF Berlin 30/05/2017 Marco Angelucci Roberto Cimino

Beam Screen Temperature Working Pressure (<10-11) BS Temperature Range LHC SR Power = 0.13 W/m FCC SR Power = 40 W/m Berlin 30/05/17 Marco Angelucci

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) Berlin 30/05/17 Marco Angelucci

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 Berlin 30/05/17 Marco Angelucci

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 Berlin 30/05/17 Marco Angelucci

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 30/05/17 Marco Angelucci

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 30/05/17 Marco Angelucci

Argon Adsorption (SEY) Adsorption process of Argon on Cu sample at 10 K General behaviour Two different regions with characteristic trends Low Energy (<50 eV) Thick Film (TF) High Energy (>50 eV) Single Layer (SL) Berlin 30/05/17 Marco Angelucci

Argon Adsorption (SEY) Two different regions with characteristic trends Low Energy (<50 eV) Thick Film (TF) High Energy (>50 eV) Single Layer (SL) Berlin 30/05/17 Marco Angelucci

Argon Results I 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) Berlin 30/05/17 Marco Angelucci

LNF-Lab Activities II Study the adsorption process on “As received” and treated samples Berlin 30/05/17 Marco Angelucci

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 30/05/17 Marco Angelucci

Argon Desorption (SEY) Adsorption Desorption TF SL Berlin 30/05/17 Marco Angelucci

Argon Desorption (SEY) Temperatures TF @ 17 K SL @ 24 K Berlin 30/05/17 Marco Angelucci

Argon Desorption (SEY) Desorption process: Cu sample heated up to 100 K Sample “Cleaned” SEY returns to the initial value Slight differences due to possible residual impurities on the surface Berlin 30/05/17 Marco Angelucci

Argon Desorption (TPD) Test of Temperature Programmed Desorption (TPD) with Mass Spectrometer P1 P2 P3 Ar Different desorption process of TF from Manipulator (Peak 1) and TF/SL from sample (Peak 2 and 3) TF-Manip. @ 22 K TF-Sample @ 30 K SL-Sample @ 37 K Berlin 30/05/17 Marco Angelucci

Argon Results Adsorption Process (LT) Desorption 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) 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

Different Temperatures measured with TPD and SEY Argon Results Desorption Process Different Temperatures measured with TPD and SEY More studies of desorption induced by electrons Berlin 30/05/17 Marco Angelucci

LNF-Lab Activities II Study the adsorption process on Ar and CO on “As received” and treated samples Test for TPD measurements with new mass spectrometer Measure desorption with SEY and TPD at the same time Berlin 30/05/17 Marco Angelucci

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 30/05/17 Marco Angelucci

Argon Adsorption II (SEY) We can summarize the results observed for Ar adsorption on Cu sample at 10 K 10 Berlin 30/05/17 Marco Angelucci

e--Argon Interaction (SEY) Subsequent SEY scans on the Ar-dosed Cu sample 10 Berlin 30/05/17 Marco Angelucci

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 Berlin 30/05/17 Marco Angelucci

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 Berlin 30/05/17 Marco Angelucci

Argon Results II (SEY) Beam-Layer Interaction Argon Thick film interacts with primary electrons and desorbs Berlin 30/05/17 Marco Angelucci

Beam Interaction Thermal Desorption Non-Thermal Desorption Electron beam dependence (size, energy …) Berlin 30/05/17 Marco Angelucci

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) SEY @ 1000 eV decreases during deposition from 1.4 to 1.1 Formation of CO Thick Film (TF) Characteristic peak of TF at 65 eV Berlin 30/05/17 Marco Angelucci

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) Berlin 30/05/17 Marco Angelucci

CO Results (SEY) Adsorption Process (10 K) Formation of a TF with Low SEY Characteristic peaks for SL in the Low Energy Region Berlin 30/05/17 Marco Angelucci

Low-Energy SEY Different LE-SEY structures CO Ar 10 Different LE-SEY structures depending from adsorbed gases Berlin 30/05/17 Marco Angelucci

Emitted electrons depends to e- primary energy Low Energy SEY Secondary e- Reflected e- Cimino et al., PRL 93 (2004) Emitted electrons depends to e- primary energy Berlin 30/05/17 Marco Angelucci

Low Energy SEY Different contributions to SEY Important contribution of reflected e- between 0 and 50 eV Cimino et al., PRL 93 (2004) Berlin 30/05/17 Marco Angelucci

Low-Energy SEY Different LE-SEY structures CO Ar 10 Different LE-SEY structures depending from adsorbed gases Study of reflected e- contribution Berlin 30/05/17 Marco Angelucci

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 Berlin 30/05/17 Marco Angelucci

Important Task 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 Berlin 30/05/17 Marco Angelucci

Activities/Upgrades Different Gases adsorption (CO, CO2, CH4 ...) (pure and mixture) Electron desorption Thermal Programmed Desorption (TPD) Low-Energy SEY Measurements 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) Berlin 30/05/17 Marco Angelucci

... Which will reconvene in e—cloud conference ... Which will reconvene in Elba in June 2018 Berlin 30/05/17 Marco Angelucci