storage ring vacuum systems

BROOKHAVEN SCIENCE ASSOCIATES

SR Vacuum SystemsASAC Review, 7/17-

18/20081 of 21

Storage Ring Vacuum Systems

H. Hseuh, Vacuum GroupASAC Review of NSLS-II

July 17-18, 2008



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Outline

• Vacuum System Requirement and Layout

• Vacuum Chamber Design

• Prototype Chamber Fabrication

• Ray Tracing, Absorbers and Pressure Profiles

• Layout of Straight Sections for ID, Inj. and RF

• Development in Bellows, BPM Buttons, NEG Strip Support

• Development in In-situ Bake and Ozone Cleaning

• Summary



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Vacuum Chambers - Adequate Apertures and Low Impedance• Beam aperture – 25 mm (V) x 76 mm (H)• Chamber straightness - < 1 mm / 5 m• Smooth cross section changes: inclination angle < 10o

• Minimum steps or cavities < 1 mm• Mechanical stability: 1 fixed & 2 flexible invar supports at BPMs

P(avg) < 1 nTorr (> 50% H2, < 50% CO, CO2, CH4, …),

• Շ (beam-gas) > 40 hr (inelastic scattering)• Local pressure bumps ➾ bremsstrahlung radiation• Intercept BM photons at discrete absorbers

– To protect un-cooled flanges and bellows– Large ion pump and TSP (or NEG cartridge) at absorbers

• Two NEG strips in antechamber to provide linear pumping

Vacuum Requirements



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Cell Vacuum Chamber Layout

BM Beamline

ID Beamline

L.S.

S.S.

Absorbers/pumps

S2 - 3.6m

S3 - 3m

S4 – 3.3m

S5 – 3m

S6 – 3.7m

Aluminum Cell Chambers

S2 S3S4

S5

S6

Multipole chamber

Dipole chamber, 6o bend

Stainless chambers

S1

S1



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Extruded cross section

Machined at pole locations

Bended and machined

Extruded

3 mm wall

3.1 mm wall

Multipole ChamberDipole Chamber

At Quadrupole

At Sextupole

Cell Chamber Cross Sections and Analysis

Maxi. δ = 0.3 mm x2Max. S = 42 MPa

Maxi. δ = 0.27 mm x2Max. S = 64 MPa

Syield (A6063T5) = 145 MPaSstress (A6063T5) = 186 MPa



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End plate & bi-metal flanges

Aluminum Cell Chamber Fabrication

Extrusion ➾ bending ➾ machining ➾ cleaning ➾ welding ➾ assembly …. $ $$$$ $$$$$

V #1,2 V #3 V #4, 5, 6… APS APS BNL

Extrusions

Machining

Test extrusion with two vendors completed

Fabricate two S4 chambers by Sept

Machining by CS and by vendor started

Weld development by APS started

Bending of dipole extrusions starts soon

Machining End plate

End Assy

Welding at APS

L. Doom



18/20087 of 21

Ray Tracing of Photon Fans

To define photon fans and absorber locations

• ➾ To ensure adequate apertures for photon fans

• ➾ To protect un-cooled flanges and bellows

• ➾ To estimate power, density and ΔT for absorbers, and P profile

Damping Wiggler

Multipole

Dipole

Dipole

Multipole

Multipole

DW fan

DW absorber

Flange absorber

Stick absorber

Crotch absorber

DW fan: 32 kW x 2, ± 2.6 mrad

canted by ± 1.8 mrad

EPU fan: 6 kW x 2, ± 0.46/0.77 mrad

canted by ± 0.12 mrad?

IVU fan: 8 kW, ± 0.31 mrad

Dipole fan: 2.4 kW, 105 mrad

Damping Wiggler



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DW and BM Photon Fans at S1-S4 Region

Larger bellows and RF fingers to accommodate canted DW fan

S2 S3

S2S3

DW ABS > 15 kW

Vertical fan hitting Top/bottom wall

BM S3, S6 ~5EPU S1-S3 < 35IVU20 S1 160*DW S1 166 S2 280

S3 270

S4

Source Location P(W)

Large SR power intercepted here

Limited space for

pumping ports and multipoles

S3

S4BS4A

*on magnet shields

M. Ferreira



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P = 166 W

P = 274 W

P = 230 W

S1B

Simulation of DW vertical power using SPECTRA8

S2 S3

DW 1

P = 40 W

From DW1

From DW2

DW 2

ΔP < 0.3 W/cm2

h ~ 9 mmh = 10 - 25 mm

h = 15 - 25 mm

P = 6 W

DW fan profile

M. Ferreira

Power and density are not excessive for S2 and S3 chambersFlange absorbers may be added at S1A-S1B, S1B-S2, and S2-S3? to trim vertical fan effectively, still with reasonable impedance

+ 1.8 mrad

- 1.8 mrad

ΔP < 0.5 W/cm2

S1A



18/200810 of 21

Photon Absorbers (8-10 per cell)

Stick

< 12 W/mm2, Tmax ~ 200oC

< 3 W/mm2, Tmax ~ 68oC

P (kW) absorber 22

Pmax (W/mm2) 25

Smax (MPa) 303

Tmax (oC) 256

Damping Wiggler Absorber

BM Absorber Positions and Power

Crotch in dipoleCrotch Stick in multipole Flange

Absorber brazing development started



18/200811 of 21

Absorber Positioning vs. Aperture Requirement

-- ± 3% aperture

Δ ABS +X position

W. Guo



18/200812 of 21

Pressure Profile with and without DW

3 GeV, 0.5A, η = 1x10-

5

Pavg = 0.13 nT

Pavg = 0.25 nT

LS SS

Local ΔP w/ 15% DW fan ➾ bremsstrahlung radiation

Molflow Code(R. Kersevan/ESRF)

To be updated

E. Hu



18/200813 of 21

Layouts for Insertion Device Straights

ID Chamber Design:Chamber inner height ≈ magnet gap - 3 mm Extruded Al with NEG strips in antechamber Or extruded Al w/NEG coated

APS ID chamber

Limited space for stand-alone ID BPMs

h = 8 x 57 mm, 1mm wall

h = 7.5 mm, 1.25 mm wall

ESRF NEG coated chamber

9.3 m straight for 2 x 3.5 m DW

6.6 m straight for 2 x 2 m EPU



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Injection Straight

RF Straight

Bellows + transition

Layouts for Injection and RF Straights

Working closely with AP, Diag, Magnet and other systems on the layout of special

components



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inside fingers

M. Ferreira

outside fingers

Choice of RF Shielded Bellows

inconel springs

Be-Cu fingers

Inside fingers Outside fingers

(APS, LNLS) (Soleil, Diamond, etc)

Simple, reliable Lower impedance

$$ $$$

Outside fingers

Wider fingers

Fewer fingers

RF Bellows Requirements:Max mis-alignment: 2 mm; Max comp/extension: ± 12 mm;

Max angle deviation: 15 mrad

3D model for impedance simulation

Inside or outside fingers?

-20 -10 0 10 20 30 40 50 60 70-0.04

-0.03

-0.02

-0.01

0

0.01

0.02

0.03

0.04

s, mm

W,

V

loss = 10 mV/pC

Solid sleeve



18/200816 of 21

Impedance of Other Vacuum Components

Component # loss, V loss, V

RF Bellows 200 1e-2? 2

S4A pump port 30 1e-3 0.03

Stick absorber 120 2e-3 0.24

Gate valve 60 2e-3 0.12

Crotch absorber 60 TBD

Flange absorber ~ 50 0.2?

Multipole chamber with stick absorber and pumping

ports

S4A chamber with absorber and shielded pumping ports

A. Blednykh

GV RF shields

Work closely with AP on vacuum components impedance simulation and

approval

Flange absorber

S4A absorber and pump port

Dipole chamber with crotch absorber and pumping

ports



18/200817 of 21

Mounting of BPM Buttons/Flanges

7mm Ø 12 mm apart

w/ 44 mm Ø flange

Optimum design:

7 mm Ø buttons, 16 mm apart?

(O. Singh’s talk)

P. Cameron

Rectangular flange?Sealing reliability?

CD-2 Design

10mm Ø button /34 mm Ø flange /Helicoflex seal

50

16

25

2 12 mm wall may be too thin for bolts/inserts & sealing

15 mm wall?



18/200818 of 21

NEG strip supports

Riveted mounting every 10cm, with alumina insulators on carrier plates

Prototype to be tested on APS chambers for reliability and flexibility

L. Doom, K. Wilson

NEG support development using APS chambers

NEG strips in Antechamber



18/200819 of 21

M. Ferreira, F. Lincoln

T ~120oC achievable with foil heaters mounted at drift space (< 1 kW/m)

Need to optimize power, heater temp, non-magnetic, insulation, etc

Eliminate the needs of high P, hot water system, a major ES&H concern

In-situ Bake with External Heaters

APS chambers for bakeout development



18/200820 of 21

Process developed by T. Momose, KEK

Final cleaning prior to installation (after alignment…)

Extensive O3 monitoring to meet ES&H requirements

System being assembled for testing

K. WilsonOzone Cleaning Development

Flush chamber with < 500 ppm O3 in O2 to break and remove contaminants

Ozone system flow diagram



18/200821 of 21

Summary

• Cell vacuum chamber design is well advanced

• Test extrusion of both cross sections completed with two vendors

• Machining and weld development of prototype chambers are underway

• Ray tracing and absorber development continues

• Straight section layouts for ID, RF and Inj has started

• RF shielded bellows design has started

• Work with AP on vacuum component impedanace

• Work with Diag. on finalizing BPM button/feedthru design.

• NEG strip supports developed and is being tested

• Chamber bakeout with foil heaters is successful

• Ozone cleaning system developed and is ready for evaluation

storage ring vacuum systems

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