NEG thin film coatings: from the origin to the next ... · next-generation synchrotron-light sources Paolo Chiggiato CERN, Technology Department Vacuum, ... desorption yields after

4/6/2014 OLAV IV Taiwan - Paolo Chiggiato 1

NEG thin film coatings: from the origin to the

next-generation synchrotron-light sources

Paolo Chiggiato

CERN, Technology Department

Vacuum, Surfaces and Coatings


Outline

Historical perspective

TiZrV thin film coating for the LHC

MAX IV

Future developments

1

2

3

4


From NEG strips and SC-RF cavities to NEG thin-film coatings

• Cris Benvenuti and the very first Nb

coating team in 1983.

• The study was triggered by Emilio

Picasso, the former leader of the SC

cavities development then LEP

project leader.

• At that time only bulk Nb was

considered for SC-RF cavities.

• Cris Benvenuti first technical note about

linear pumping by NEG strips in June 1977.

• At that time, the study was not directly

motivated by the LEP.

• At that time, linear ion pumps had being

used.

Nadia

Circelli

1

Max

Hauer

Jacques

Genest Cris


NEG linear pumping and Nb coated SC-RF cavities: two technological

achievements for the LEP

Installation of a LEP2 cryomodule with Nb

coated RF cavities (1995)

First prototype of the LEP dipole beam pipe

with the St101 NEG strip in the antechamber

(1983).

1


The merging: first indirect trials

Cris Benvenuti, private communication:

• Cris had the first idea of coating the inner wall of vacuum chamber by NEG materials in

the early Eighties.

• He tried to sputter a St-101 strip in a LEP chamber (Al alloy AA 6060).

• The ultimate pressure after sputtering was excellent, but the re-activation impossible.

Cris Benvenuti et al. LEP2-Note-94-21

Copper coatings for the main couplers of the LEP2 superconducting RF cavities

Jordi Fraxedas (EU fellow) performed ESD measurements of Cu and Ti coated stainless-

steel RF coupler extensions. For Ti coating, he measured an abrupt decrease of the

desorption yields after heating at 350°C (2 hours).

This measurement was not considered as unexpected since the ‘activation’ of Ti bulk was

already known from previous experience in the ISR. The ‘activation’ had been recorded at

350°C (24h) for Ti experimental vacuum chambers.

1

4/6/2014 Document reference 6


Intertwisted Ti and Zr elemental wires

It became clear that NEG thin-film

coatings would have been used in the

LHC only if materials with lower activation

temperature could be found.

1

Stainless steel ≤ 350°C

Copper alloys ≤ 250°C

Aluminium alloys ≤ 200°C

Beryllium ≤ 200°C

In the 1962 edition of the Lafferty,

it is written that Ti-Zr alloys are known to

activate after heating at 300°C.

It was a common practice in vacuum

technology.

We looked for wires or rods made of Ti-Zr

alloys.

1995: Proposal for intertwisted Ti and Zr

wires.


January 1996: faster activation with Ti and Zr, one wire each 1

10-11

10-10

10-9

10-8

10-7

10-6

100 150 200 250 300 350 400 450

st.steel

Ti-Zr

Hf-Ti

Hf-Zr

P

[Tor

r N

2 e

q.]

2 Hours Heating Temperature [°C]

10-11

10-10

10-9

10-8

10-7

10-6

100 150 200 250 300 350 400 450

st.steelTiZrHf

P

[Tor

r N

2 e

q.]


10-11

10-10

10-9

10-8

10-7

10-6

100 150 200 250 300 350 400 450

st.steel

V

Nb

Ta

P

[Tor

r N

2 e

q.]


10-11

10-10

10-9

10-8

10-7

10-6

100 150 200 250 300 350 400 450

st.steel

Ti-Zr

Zr-V2

Ti-Nb

P

[Tor

r N

2 e

q.]


ESD

1 mA

500 V


December 1997: sometime wrong ideas give great results, TiZrV 1

01-1996: Ti-Zr

09-1997 Pd/TiZr

12-1997 TiZrV

During an informal meeting (V.

Rouzinov, J-M. Cazeneuve, F. Cicoira,

and myself) we decided to add a wire

of an element of the 5th group in Ti-Zr

braid. If positive, the result would have

been our Christmas present for Cris.

V was selected because it has the

largest O diffusivity, so it could have

increased the mobility of O in TiZr…

10-11

10-10

10-9

10-8

10-7

10-6

100 150 200 250 300 350 400 450

st.steel

Ti-Zr

Ti-Zr-V

P

[Tor

r N

2 e

q.]


10-7

10-6

10-5

10-4

10-3

10-2

10-1

100 150 200 250 300 350 400 450

H2

CH4

COCO

2

Eff

ect

ive

Deso

rpti

on Y

ield

[mol

ecu

les/

elect

ron]


R. Kersevan


IVC-1998 in Birmingham 1

+

= Presented at

EVC-1999

Lyon (France)

ESRF stainless steel undulator

vacuum chambers

&

change of EU regulation

in matter of RP

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100

101

102

103

104

105

106

Eff

ecti

ve d

esorp

tion

yie

ld

[mole

cule

s p

hoto

n-1]

Dose [mA h]

Activation

= 0,38 D-1

= 4,2 x 10-5 D

-0,38

Dose [photons m-1]

1019

1020

1021

1022

1023

1024

(2.3x10-3)

(6.1x10-6)

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&uact=8&docid=hf-ZHQiWAUsUPM&tbnid=mNZbfQp7fUy1nM:&ved=0CAYQjRw&url=http://physicsworld.com/cws/m/1814/265759/article/indepth/43350&ei=pFIvU5D6H4am0AW1zYDwAw&bvm=bv.62922401,d.d2k&psig=AFQjCNHO--zcE_8NxYwwuShPh5MIFj9_vQ&ust=1395696636514260

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&uact=8&docid=2k-JpuBWebfLCM&tbnid=fkUlWP8DchrXBM:&ved=0CAYQjRw&url=http://www.sitefinitysteve.com/donate&ei=3VIvU5_wFeam0QWfpIGIDQ&bvm=bv.62922401,d.d2k&psig=AFQjCNHYo8xsbcKwJc4xtZK8q1coPWwg5Q&ust=1395696725300605


An unexpected support after the IVC-1998 in Birmingham

‘The new alternative technology for flat screen displays, namely Field Emission

Displays require UHV to work. It could be possible to use NEGs to provide pumping

in the small space allowed in between the two panels.’

(see The Economist, September 12th-18th 1998, p.96-97)

1

A more systematic study started in 1998


Ti

Zr V

Quick activation: no + yes

(degrees)

30 40 50 60

TiZrV Substrate

2 (degrees)

30 40 50 60

TiZrV

Substrate

2

STM

100 nm

A. Prodromides, Ph.D Thesis No. 2652 (2002), Faculte´ Sciences de Base,

Section de Physique, EPFL; and references therein. CERN Library URL:

http://documents.cern.ch/cgibin/setlink?base=preprint&categ=cern&id=

cern-thesis-2002-042.


Optimization of the deposition parameters: the role of the substrate

temperature 1

300°C

250°C

200°C 1 m

100°C

150°C

350°C

10-3

10-2

10-1

100

101

10-7

10-6

10-5

10-4

10-3

1013

1014

1015

1016

Pum

ping

Spe

ed [

s-1 c

m-2

]

CO surface coverage [Torr cm2]

[molecules cm-2

]

coated at 300 °C

on rough Cu

coated at 300 °C

on smooth Cu

coated at 100 °C

on smooth Cu

C. Benvenuti, P. Chiggiato, P. Costa Pinto, A. Prodromides, V. Ruzinov,

Vacuum 71 (2003) 307.


1999-2000 After activation, TiZrV has a low SEY: a solution to ecloud in LHC

SEY after saturation with CO

1

B. Henrist, N. Hilleret, C. Scheuerlein, M. Taborelli, App. Surf. Sci. 172

(2001) 95.


Installation in accelerators: the production of undulator vacuum

chambers started in 1999 for the ESRF

1

EPAC 2000 and AVS-2000 Boston

ESRF: 10 chambers already inserted within two year

ELETTRA: 1 chamber installed (11/2000)

NSRRC: 1 prototype chamber coated, test in August 2002

DIAMOND: 1 prototype chamber coated (11/2000)

SOLEIL: under consideration By J

un

e 2

002

First chamber produced for other Institutes: PSI June 1999


Cross section of the TiZrV coated ESRF’s vacuum chamber (length=

5.5 m)

No effect on the machine global impedance was observed.

First ESRF Al-alloy vacuum chamber 1


SAES was the first industrial partner

(January 2001)

2000-2001: Licensing of ESRF and SAES Getters 1

ESRF was the first institute/firm to

be licensed by CERN (2000).

The support of Jean-Marc Filhol

was important.

Other licensees:

• DESY, GSI, LNLS

• VARIAN (now Agilent), FMB


First hypothetical application in the LHC: TiZrV in a beam

screen without holes

1

• The coating of a tight beam screen was inquired by L.

Evans, the LHC project leader.

• Heating would have been possible by 4 molybdenum

heaters isolated by alumina tubes.

• The main advantages would have been:

• No need for beam scrubbing in the LHC arcs.

• He leaks from the capillaries would have been less

critical.

• Possible heating of the beam pipe.

However:

- The pumping efficiency of TiZrV at 20 K was not confirmed.

- Pumping of CH4?

- The cryopumping of the cold bore would have been lost.

- It was too late to start a parallel study of integration.

- Additional costs for coating and cabling.

Management decision: Forget beam-screen and be ready for the coating of

experimental and long-straight section beam pipes.


2 TiZrV thin film coating for the LHC

• 6 Km of beam pipe

• About 1400 vacuum chambers

• Experimental vacuum chambers


In 2003 the team focused on the facility for the LSS series production 2

• The development and the construction of the coating

facilities started at the end of 2002.

• Pre-series of LSS standard chamber: November 2003

2013


The series production started in February 2004 1 The new set-up for the coating of the LSS chambers

Manifold and chambers on the bench

The solenoids

The cathodes

Slide prepared

for the

Department

Head


3mm wires of Ti, Zr and

V

The coating system 2


316LN st. steel: allows high T treatments without softening

OFE copper: high conductivity,

reliable brazing with st. steel

OFS copper: high conductivity, better mechanical performance than OFE at high temperature

L max = 7 m ID = 80 mm thickness = 2 mm

The LSS standard vacuum chamber 2

Courtesy of S. Atieh


The adhesion of the TiZrV film on copper was probed by high-pressure water

rinsing and/or ultra-sound agitation in deionized water.

October-November 2003: modification of surface treatment for copper tubes 2


Flake with copper

on one side and

NEG on the other





The coating team in September 2004 2


2004: Ultrathin heaters for vacuum chambers inserted into magnets 2


Functional quality control: XPS and pumping speed 2

Coupon samples for SEM and XPS 25-cm long vacuum chambers for

pumping speed measurement


0 50 100 150 200 250

Heating Temperature [ºC] - 1 hour duration

O 1

s p

eak a

rea (

A.U

.)O 1s peak area


Courtesy of M.Taborelli



10-3

10-2

10-1

100

1010

1011

1012

1013

1014

1015

1016

Cap

ture p

rob

ab

ilit

y

Q [molecules cm-2

]

CO


NEG coated chambers for the LHC

Production weeks

Num

ber

of

cham

be

rs

0

200

400

600

800

1000

1200

0 10 20 30 40 50 60 70

Mar 2004 Oct 2004

454 7m long

standard LSS chambers

Jun 2005 Jan 2006

650 chambers

MBXW, MQW, MBW, MCBW,

short LSS, experiments, etc

Series production 2

Courtesy of P. Costa Pinto


Series production 2

The LSS chamber was installed in the LHC tunnel in the summer 2006


Claudio Raggi, Master Degree Thesis, 2005

Activation in the LHC tunnel 2


NEG activation monitoring.

Installation of the bakeout heater and

control



Pressure profile during heating

180°C RGA + SVT

140°C Sec. Valves

250°C Flanges

150°C S.S.

230°C NEG


Courtesy of G. Bregliozzi


End of bakeout and NEG activation: acceptance test.

0

2 10-10

4 10-10

6 10-10

8 10-10

1 10-9

200 300 400 500 600 700

Mass 2

RG

A s

ign

al [A

]

Time [s]

Valve closed

Valve opened

TMP

RGA

St. Steel module

Valve

Beam pipe

Beam pipe

Experiments in the lab and a dedicated Monte Carlo simulation indicate that a good activation is obtained when the RGA H2 signal decreases by a factor of at least 3 when opening the valve.

H2

Sector A7R5



Average pressure, measured by BA gauges, 1 month after the end of bakeout: P ≈ 6x10-12 mbar N2 eq.

Ultimate pressures after activation and cooling 2



The ultimate pressure was limited by the outgassing of the uncoated st. steel module

With BA Gauge ON: QH2 ≈ 4.5 · 10-9 mbar /s

NEG Pumping Speed for H2 ≈260 /s

Degassing of the Stainless Steel Module:

P (N2 eq) ≈ 7 · 10-12 mbar N2 eq.

2



TiZrV coating during the Long Shutdown 1: assorted geometries 2



TiZrV coating during the Long Shutdown 1: assorted geometries 2



MolFlow+: ray-tracing, colour-coded pressure profile, and 2000 l/s NEG lump pump

2 New project: ELENA. NEG coating needed in 2015.

ELENA ring:

Calculation of the pressure profile

seen by the antiproton

beam along one dipole magnet

Courtesy of R. Kersevan

Vacuum, Surfaces & Coatings Group

Technology Department

3 NEG coatings in synchrotron radiation facilities

CERN

ESRF ELECTRA

SOLEIL DESY DIAMOND

MaxLab

BNL

LNLS

KEK

NSRRC

AS

ISA

ALBA

users

SESAME

ILSF

ANL

, in design/study


BPM location

Ion pump location

Crotch absorber location

Sector valve location

VC10 – straight section for IDs

VC1

VC2 VC3

VC4

VC5

VC6

VC7

VC8

VC9

One achromat Length 26 m

In each achromat: -> 10 BPMs -> 3 pumping ports (with ion pumps), -> 1 crotch absorber, -> 3 gate valves.

3 MAX IV in Lund

Courtesy of M. Grabski (MAX IV)


Distributed

cooling

Ribs

Cooling for

corrector

area

Cooling for

corrector area

Welded

bellows

Welded

bellows

Chamber

body

Inside diameter: 22

mm,

Total length: 2.5 m,

Bent part:

Arc length 1 m,

Bending angle 30,

Bending radius 19 m.

Bent part

3 MAX IV in Lund: the ‘standard’ vacuum chamber



3 MAX IV in Lund: the light-e beam bifurcation chambers (VC1 and VC2)

Ø25

5

7 Ø22

3

Ch

am

ber

exit

Ch

am

ber

en

tran

ce



3rd coating – 3+1 cathodes (9e-1 mbar, 240V, 0.28A, 68W)

360 Gauss

7th coating - 1 cathode (3.1e-1 mbar, 700V, 0.03A, 26W)

260 Gauss, diode

9th coating - 2 cathodes (2.7e-1 mbar, 775V, 0.06A, 47W)

360 Gauss, magnetron

VC2 with antechamber:

360 -> 270 Gauss – 1 cathode

12th coating - 1 cathode (3.6e-1 mbar, 650V, 0.04A, 26W)

3 MAX IV in Lund: the light-e beam bifurcation chambers (VC1 and VC2)

Courtesy of M. Grabski (MAX IV) and P. Costa Pinto


Courtesy of S. Marques Dos Santos

The standard coating of very small and asymmetric cross-section beam pipes:

• requires a significant amount of time for the optimization of the coating

parameters;

• the quality and uniformity of the film and its performance are unmeasurable;

In addition, at present, vacuum chambers are not designed to facilitate surface

treatments and coating.


4 Future developments

Ju

ly 1

999

CE

RN

qu

ota

tio

n f

or

ES

RF


4 Future developments: the electroforming way

Courtesy of L. Marques Antunes Ferreira











Acknowledgments

I warmly thank:

• Pedro Costa Pinto

• Giuseppe Bregliozzi

• Vincent Baglin

• Giulia Lanza

• Leonel Marques A. Ferreira

• Mauro Taborelli

• Marek Grabski

• Roberto Kersevan

for their help in the preparation of

this presentation;

• Cristoforo Benvenuti

• José Miguel Jimenez

for useful discussions.

Documents

NEG thin film coatings: from the origin to the next ... · next-generation synchrotron-light sources Paolo Chiggiato CERN, Technology Department Vacuum, ... desorption yields after