The vacuum system for 3 GeV ring

ALERT workshop, 16th September 2016, Trieste, ItalyMarek Grabski

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16th September 2016

Trieste, Italy

MAX IV 3 GeV ring vacuum system

Advanced Low Emittance Rings Technology (ALERT)2016 Workshop

On behalf of the vacuum team

Marek Grabski, Max IV laboratory


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Contents

• Machine and vacuum system layout,

• NEG-coating R&D at CERN,

• Installation procedure,

• Vacuum commisioning status.


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MAX IV layout

https://www.maxlab.lu.se/maxiv

3 GeV ring (528 m)

Linac (300 m)Short pulse

facility

1.5 GeV ring (96 m)Conventional

design

Small aperture,all NEG-coated

Max IV - Synchrotron light source facility in Lund, Sweden.

Commissioning started:

August 2015Commissioning started:

September 2016


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3 GeV ring layout

100 MHz RF cavities

Landau cavities

InjectionEmittance measurement

Circumference 528 m, 20 achromats, 19 straight sections for IDs

2 In vacuum undulators (2 m long)

• NanoMAX IVU18

• BioMAX IVU18

2 EPU (4 m long, min gap 11 mm)

• VERITAS EPU48

• HIPPIE EPU53

1 In vac. Wiggler (2.4 m long)

• BALDER IVW50

Installed Insertion Devices:

Legend:

• Dk: Dipole kicker (S1)

• Mk: Multipole kicker (L)

• LK: Longitudinal kicker (S2)

• VP: Vertical pinger (S2)

L=long straight, S=short straight,


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U2, VC4

Min. clearance with the iron 0.5 mm, min. clearance with the coils 2 mm.

Ø22

(ID)

Dipole

3 GeV magnet layoutOne achromat

Beam direction

Photon beam

Corrector25mm

Chamber ID 22mm

Magnet apertures Ø25mm

Sextupole

Ø25

- Total length ~26 m, - 4.5 m straight section (L)


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Standard vacuum chamber geometryOne achromat

Beam direction

VC5

Distributed cooling

Ribs

Cooling for corrector

Cooling for corrector

Welded bellows

Welded bellows

Chamber body

Material: OFS copper

Inside diameter: 22 mm, Total length: 2.5 m,

Bent part Arc length: 1 m, Bending angle: 30, Bending radius: 19 m.

NEG-coated.

Bent part

VC5 chamber


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Vacuum achromat layout

Penning gauge (S2)

Extractor gauge (S1)

In each achromat:

10 BPMs,

3 pumping ports (with ion pumps) and 1 pump in FE,

1 crotch absorber,

3 gate valves.

One achromat

Beam direction

VC1VC2

VC3

VC4VC5

VC6

VC7

VC8VC9

VC10

One achromatLength: ~26m


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NEG coating development

• NEG-coating of vacuum chambers by magnetron sputtering was developed at CERN for warm LHC sections, 6 km of vacuum pipe was coated.

• NEG-coating is used widely in many light sources -mainly for ID chambers.

• At SOLEIL 56% of storage ring is NEG coated. • In MAX II since 2007 three dipole chambers were

replaced by NEG-coated vacuum chambers.

LHC warm sections

‘NEG thin film coatings: from the origin to the next-generation synchrotron-light sources’,

Paolo Chiggiato, CERN (presented at OLAV’14)


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NEG-coating R&D at CERN

1. Define and perform initial surface treatment of OFS copper substrate.

2. Validate compatibility of NEG-coating (adhesion, thickness, activation

behavior):

a). on etched OFS copper.

b). on wire-eroded surfaces and used brazing alloys.

To validate the coating feasibility 3 main stages of NEG (Ti, Zr, V) coating

validation by magnetron sputtering in collaboration with CERN were undertaken.

(R&D duration ~2 years).

3. NEG-coating validation of compact vacuum chamber geometries:

a). Coating and testing of small diameter, bent tubes.

b). Establish coating procedure/technology and coat chambers

of complex geometry.


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NEG-coating series production

1. Standard bent vacuum chambers (VC4) - 1.50 and 30 bends,

2. Straight vacuum (VC10) chambers,

3. Special vacuum chambers.

30

2.8 m (VC4)

2 m (VC10B)

Electron beam

Photon beamVC2

BPM

17.2 mm

Ø22

Ø22 mm

One achromatBeam direction

3 GeV - 1 achromat (~26m)

VC4VC2

Industry (70% length wise)

Collaboration with ESRF (15%)

Collaboration with CERN (15%)

Main vacuum chamber types:

VC10

Photon beam


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Installation procedure

Installation of NEG-coated ring

Ring installation was tested and

rehearsed by installing and activating

1 mockup achromat in summer 2014.

Actual installation started in

November 2014, ended June 2015


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• Assembly insitu (above magnets), • Pumpdown and testing, • Lifting,

• Baking/activation for 20 h,


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• Lowering to the bottom magnet half, • Installation of final equipment (supports,

BPM cables),

• closing magnet blocks.


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Coating non-conformitiesAll the chambers were inspected at site before installtion.

Peeling-off at RF fingers and Cu endpiece

Observed peeling-off:At RF fingers Cu-Be insert and Cu end piece. RF fingers and Cu end were not shielded properly during coating. Solution: new pieces ordered and replaced (without coating).

Uncoated areas:Few cm^2 uncoated, in complex chambers.

Uncoated areas

Peeling-offPeeling-off at the edge

of stainless VC. Chamber not aproved for

installation.

Severe peeling-off


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Commissioning progress

Commissioning started in August 2015

0

20

40

60

80

100

120

1-A

ug-

20

15

31

-Au

g-2

01

5

1-O

ct-2

01

5

31

-Oct

-20

15

1-D

ec-2

01

5

31

-Dec

-20

15

31

-Jan

-20

16

1-M

ar-2

01

6

1-A

pr-

20

16

1-M

ay-2

01

6

1-J

un

-20

16

1-J

ul-

20

16

1-A

ug-

20

16

Do

se [

Ah

]

Date

Accumulated beam dose

reached: 112 Ah.

March 2016 shutdown:

- 2 in-vacuum undulators,

August 2016 shutdown:

- 2 EPU chambers (8x36mm),

- In-vacum wiggler.

Average base pressure:

Gauges 2e-10 mbar,

Ion pumps in 8e-11 mbar range.

2nd shutdown

1st shutdown


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Pressure vs beam current, dose

Beam direction

1E-10

3E-10

5E-10

7E-10

9E-10

1E-09

1E-09

2E-09

0

20

40

60

80

10

0

12

0

14

0

16

0

18

0

20

0

P av[m

bar

]

I [mA]

@dose=16 Ah

@dose=95 Ah

Pressures at dose 16 Ah and 95 Ah, during beam ramp up.

(presure recorded by extractor gauge at not NEG coated crotch

absorber in S1)


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Pressure in one achromat vs beam current

Beam direction

Pressures at dose 95 Ah, during beam ramp up, recorded at different positions along achromat (L, S1, S2)

1E-11

1E-10

1E-09

1E-08

1E-07

0

20

40

60

80

10

0

12

0

14

0

16

0

18

0

20

0

P av [m

bar

]

Beam Current [mA]

Legend:• Pressure at S1 (ion pump)• Pressure at S1 (extractor gauge)• Pressure at S2 (penning gauge)• Pressure at S2 (ion pump) • Pressure at L (ion pump)

* Pressure at L (Ion pump) probably due to electric effect


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Pressure vs beam current, dose

Beam direction

1E-12

1E-11

1E-10

1E-09

0.1 1 10 100 1000

No

mra

lized

aver

age

pre

ssu

rePa

v/I [

mb

ar/m

A]

Accumulated Dose [A∙h]

Y=(3.08e-10)*x^(-0.68)

Y=(1.64e-10)*x^(-0.75)

Normalized average pressure vs beam dose,

recorded in S1 uncoated crotch absorber, and S2 NEG-coated

Legend:• Pressure at S1

(extractor gauge)• Pressure at S2

(penning gauge)


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Lifetime evolution

1

10

100

1000

10000

0.1 1 10 100 1000

I∙τ

[mA∙h

]

Dose [A∙h]

Normalized lifetime vs accumulated doseI∙τ [mA∙h] vs Dose [Ah]

Beam lifetime up to 6 Ah,

Maximum stored beam

current 180 mA


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H2 (2)85.33%

He (4)0.12%

C (12)0.78%

(14)0.33%

(15)1.17%

CH4 (16)2.16%

OH (17)0.05%

H2O (18)0.10%

F (19)0.08%

CO (28)9.39% O2 (32)

0.01%

Cl (35)0.03%

Cl (36)0.00%

Ar (40)0.01%

CO2 (44)0.42%

Residual gas spectrumResidual gas spectrum at 140 mA beam current

* Mass 16 and 19 is most likely due to intrinsic degassing of the

gas spectrometer.

Main residual gasses:Hydrogen 85.33 %, Carbon monoxide 9.39 %Carbon dioxide 0.42 %Methane 1.17 %


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Scraper measurementsMean lifetime vs vertical scraper distance from the beam center

(Done at beam dose 40 Ah)Total average pressure along the beam path

(contribution from all gasses based on the RGA spectra)

*Scraper measurements and calculations done by Jens Sundberg, Thanks!

At 50 mA:P_Torr = 3.3e-09 torrT_elastic= 104.69 hT_inelastic= 88.47 hT_Touschek= 16.62 h

y = 0.0363x + 1.5052R² = 0.9849

0

1

2

3

4

5

6

0 20 40 60 80 100

Pre

ssu

re [

e-9

To

rr]

Beam current [mA]

Scraper position from beam center, y (mm)

Mean

lif

eti

me, T

(h

)


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Problems

• RF cavity (S2) venting due to broken high power feedthrough

during conditioining (with closed valves). Now cavity is removed

from the ring and dummy chamber placed as could not be run with

high power anymore. Now awaits conditioning outside the ring.

Electron beam

Photon beam

Hot spot

• Hot spots in proximity of crotch absorber (S1), mis-positioning of

the crotch chamber,


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Future plans and development

Development needed:

• Coating of 8 mm aperture, long, bend chambers,

• Effective thin layer in-situ baking system without the need of removing the

vacuum chamber from the final location for re-activation,

• Handling of flexible delicate small vacuum pipes,

• Study new materials possible for chamber manufacturing,

• New methods of manufacturing (electroforming).

Preliminary Studies Towards a Diffraction-Limited Storage Ring- Pedro F. Tavares, September 2014

Vacuum system constraints:

• Vacuum chamber outer diameter 10 mm,

• Compact vacuum system design,

• Very low impedance flange/bellow

assemblies,

• Distributed pumping.


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Thank you for your attention

Acknowledgments:

Jonny Ahlbäck, Eshraq Al-Dmour, Michael Gilg, Pedro F. Tavares (MAX IV),

CERN, PKAB, ALBA, ESRF, BINP, Solaris and MAX IV staff

Documents

The vacuum system for 3 GeV ring