Material properties of relevance to cryogenic vacuum systems · 2019. 7. 17. · relevance to...

Material properties of

relevance to cryogenic

vacuum systems

Luisa Spallino, LNF-INFNBrussels, 26th July 2019

FCC WEEK 2019

FCC WEEK 2019, 26/7/2019 2L. Spallino, LNF-INFN

Work Package 4: Cryogenic beam

vacuum system

Task 4.4: Study vacuum stability at

cryogenic temperature

Research funded by EuroCirCol project

(Grant No. 654305) and supported by

MICA project funded by INFN-SNC5

• Introduction

• Strategy and experimental set-up at LNF

• Results

o TPD from LASE-Cu for temperature induced vacuum transients study

o Electron desorption studies: preliminary results

Outline



sawtooth

surface finishing

LASE-Cu

cooling channels

perforated

baffles

FCC-hh BSLHC BS

Introduction

R. Valizadeh et al. , Appl. Phys. Lett. (2014)

R. Valizadeh et al. , Appl. Surf. Sci. (2017)

Laser ablation and conditioning

Engineering the surface morphology


Introduction

LASE-Cu to mitigate e-cloud effects

Not only intrinsic properties of surface but

also the effects of:

Photons-surface interaction

Electrons-surface interaction

Temperature transients

Dipole cold bore at 1.9 K

Dia. 50/53 mm

Beam screen

5 - 20 K

Dia. 46.4/48.5 mm

Cooling tubes

Dia. 3.7/4.8 mm

Photons

Hole

pumping

Wall

pumpingDesorbed

molecules

Electrons

stripes

36

.8 m

m


Introduction

Working Pressure

(

R. Valizadeh et al. , Appl. Surf. Sci. (2017)

Engineering the surface morphology


What about the influence of the surface

features on vacuum stability?

Introduction

Low Temperature

Gas Adsorption Gas Desorption

SEY variation

Temperature variations/photons/electrons

Pressure variation

SEY, Mass Spectrometry, Thermal Programmed Desorption (TPD) and XPS (soon)

as useful techniques to quantitatively follow adsorption/desorption kinetics


Strategy and experimental set-up at LNF

Strategy and experimental set-up at LNF

Temperature Programmed Desorption

(TPD) and Mass Spectrometry

measurements

Equipment : QMS (Hiden HAL 101 Pic)

Secondary Electron Yield (SEY)

measurementsEquipment : Electron gun, Faraday cup

6004002000Ep(eV)

• LNF-cryogenic manipulator

• Sample at 15-300 K

Ultra high vacuum systems

main chamber

preparation

chamber

fast-entry lock


TPD from LASE-Cu for temperature

induced vacuum transients study

poly-CuComparative study of TPD from flat

poly-Cu and LASE-Cu samples

using different gases

(Ar, CH4, CO and H2 )



induced vacuum transients study: ArSingle TPD peak at ~30 K corresponding to the

desorption of a condensed thick Ar layer

Desorption temperature determined by the weak Ar-Ar

van der Waals interaction energiesAr on poly-Cu


L. Spallino, M. Angelucci, R. Larciprete, R.

Cimino,

Appl. Phys. Lett. 114, 153103 (2019)


induced vacuum transients study: Ar

L. Spallino, M. Angelucci, R. Larciprete, R.

Cimino,

Appl. Phys. Lett. 114, 153103 (2019)

Single TPD peak at ~30 K corresponding to the

desorption of a condensed thick Ar layer

Desorption temperature determined by the weak Ar-Ar

van der Waals interaction energies

TPD peak at ~30 K corresponding to the desorption of a condensed

thick Ar layer together with a broad TPD profiles, whose peak

temperatures and widths depend on the Ar dose

Ar on poly-Cu

Ar on LASE-Cu



induced vacuum transients study: Ar


TPD characteristics determined by the

sponge-like structural features of LASE-Cu5 mm

FCC WEEK 2019, 26/7/2019 L. Spallino, LNF-INFN 17

Conceptually identical to Ar resultsL. Spallino, M. Angelucci and R. Cimino, to be published


induced vacuum transients study: CH4

FCC WEEK 2019, 26/7/2019 L. Spallino, LNF-INFN 18

L. Spallino, M. Angelucci and R. Cimino, to be published


induced vacuum transients study: CO

Conceptually identical to Ar results


induced vacuum transients study: H2


TPD of 100 L H2 dosed on poly-Cu

and LASE-Cu samples held at

T~15-18 K

No TPD signal should be observed

by considering the H2 vapor suture

pressure curve!!!

The wide distribution of high energy

adsorption sites within the inner pore is

responsible for the H2 TPD signal from

LASE-Cu sample


Conceptually identical to Ar results


induced vacuum transients studySaturated vapour pressure from Honig and Hook (1960)

Further studies on this issue

and on electron/photon

stimulated desorption at low

T are necessary to completely

validate/optimize LASE-Cu.

L. Spallino, M. Angelucci and

R. Cimino, to be published


Electron desorption studies: preliminary results



The concept of the study:

SEY measurement of a condensed

gas layer induces electron

desorption

e-dose

Ar desorption on polycrystalline-Cu substrate as a test system


The mass spectrum shows the

sign of such electron desorption

SEY measurements, together

with mass spectrometry, ideal

to study ESD

Electron desorption studies: preliminary results

FOUNDAMENTAL TO MASS

SPECTRUM CALIBRATION

Tanks to the technical support of

DAФNE-L Team:

A. Grilli, M. Pietropaoli, A. Raco, V.

Tullio, V. Sciarra and G. Viviani

Thank you for your attention

Thanks to EuroCirCol project (Grant No. 654305) and

V. Baglin, P. Chiggiato, R. Kersevan, O. Malyshev, and

R. Valizadeh


Thanks to the low temperature team at LNF

Thanks to MICA supporting project funded by INFN-SNC5

M. Angelucci

R. Cimino

A. Liedl

R. LArciprete

Material properties of relevance to cryogenic vacuum systems · 2019. 7. 17. · relevance to...

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