NSLS-II ASAC Review, 10/9-11/06 H-C. Hseuh,…, SR Vacuum Systems Storage Ring Vacuum Systems H-C....

NSLS-II ASAC Review, 10/9-11/06 H-C. Hseuh,…, SR Vacuum Systems

Storage Ring Vacuum Systems

H-C. Hseuh, C. Foerster, J. Hu, G. Mahler, S. Pjerov, S. Sharma, J. Skaritka, C. Stelmach, …

October 10, 2006


OutlineDesign Principles

Vacuum Cell Layout

Cell Chambers and Material - Al

Chamber Cross Sections and Analysis

Vacuum Pumping and Pressure Profiles

Front End Vacuum

Summary


Low Pressure of < 1 nTorr (» 50% H2)

• Low outgassing and desorption after in-situ bake and pre-conditioning

• Intercept photons at discrete absorbers– Located absorbers far away from the source

• Lower power density and simpler cooling

• High effective pumping speed (IP + TSP) at absorber locations

Low Impedance:• Beam channel with smooth cross sections

– Minimize no. of tapers, steps, gaps – low Z– Minimize no. of holes, slots for pumps and bellows – low Z/n

• Inner wall surface finish to ~ μm

Design Principles

Adequate Apertures for Beam and Exit Photons• BSC - 25mm x 70mm• Chamber cross section precision to ~1 mm• Chamber temperature stability « 1oC


30 standard cells of ~ 19m eachLSS: 15 x 5m and 15 x 8mIsolatable with 60 gate valves

Vacuum Cell Layout

4m3m3m 5m

4m

Cell chamber material: extruded aluminum 6063-T5

NSLS and APS experience; fabrication cost

thermal/electrical conductivity; ease of in-situ baking

60 bending chambers of 6o each, 3m long

90 multipole chambers of 3 different lengths/types

> 20 day-one LSS chambers of various types

extruded Al with same cross sections as cell chambers

Absorber locations FE


Specifics Al SST CuInitial PSD rate High Low Average

Mechanical strength

Acceptable

Excellent Good

Thermal expansion Large Small Small

Thermal conductivity

Excellent Poor Excellent

Weldability Good Excellent Good

Beam impedance Low High Low

Bi-metal flanges Yes No Yes

Cooling channels Extrusion Brazed Brazed

Fabrication cost Low Average Expensive

Ease of in-situ bake Good Poor Good

Radiation shielding Poor Average Excellent

AL-6063 (T5) Extrusion for the Cell Chamber

Comparison of chamber materials


Material ($): Aluminum 6063-T5 billets, ~ 350mm diameter

Extrusion ($): only a few available (interested) vendors in the US

(due to the large cross sections and required dimensional precision)

➱ > 1 yr to develop the correct parameters for each type

before production can start

Stretching: to straighten and eliminate the waviness of inner surface

Roll Bending ($): to obtain the correct curvature for bending chambers

Machining ($$$): ports for beam lines, BPMs, absorbers, pumps, ….

profiles at multipole, transitions, …

Cleaning ($): to remove surface contaminants and reduce oxide layer

Welding ($$): photon exit ports, SS-Al bi-metal flanges, etc.

Assembly ($$$): BPMs, NEG strips, pumps, gauges, absorbers, ….

Fabrication Steps for Cell Aluminum Chambers

(G. Goeppner/E. Trakhtenberg, APS, ANL)


Bending chamber, ~ 3m long

3-D Models of Cell Chambers

Special Bending chamber for IR lines

Bending magnet/girder

#3 Multipole magnets/girder

Multipole chamber #3, ~ 5m long


3mm wall

BSC: 25 x 70 mm2

Dipole extruded cross sections

Chamber cross sections


Multipole chamber extruded cross section

@ sextupole

@ quadrupole

After Machining

3.9mm

3.2mm

BSC: 25 x 70 mm2

Chamber cross sections – cont’d


SM = 172 MPa

(Localized)

von Mises stress at sextupole location

SY = 144 MPa for Al 6063-T5

SM (D) = 54 MPa

SM (Q) = 100 MPaChien Pai, C-AD


DM = 0.6mm x 2

Deflection at sextupole location

DM (Dipole) = 0.36mm x 2

DM (Quad) = 0.57mm x 2Chien Pai, C-AD


UHV Pumping and Pressure Profiles

Pavg < 1 nTorrIn-situ baking of entire cells at 120 C x 40 hrs

To reduce thermal outgassing to < 1x10-12 Torr.l/s/cm2

Total ring thermal gas load of < 1x10-5 Torr.l/s

Pressure will be dominated by photon stimulated desorption (PSD)

# photons from BM ~ 1x10+21/s ≈ 7x10-5 Torr.l/s Assuming η (PSD) = 2x10-6 mol/hv for Cu after ∫hv > 1024/m

# photons from each 7m DW ~ 6x10+20/s

with 15% intercepted by the ring absorber ➱ 7x10-6 Torr.l/s

NEG strips ~ 1,400 m @ > 100 l/s/m for active gases

Reside in ante-chambers as in APS

Pump thru the photon slots ( C = ~ 200 l/s/m)

Ion pumps and TSP of ~ 500 l/s at absorbers

5 IP/TSP per cell + 2 for each ID location


PSD Yield versus Photon Dosagemeasured at NSLS U9A & X28 beam lines

C. Foerster, et.al, J. Vac Sci. Technol. A14, 1273(1996).

C. Foerster, et.al, J. Vac Sci. Technol. A19, 1652(2001).

CuAl

~ 100A.hr at NSLS


Pressure Profiles (BM only) with Various Pumping Schemes

By E. Hu & F. MakahlehUsing Molflow and VacCal codes

Pavg ~ 1.5 nTorr

Pavg ~ 0.3± 0.1 nTorr

Distributed NEG strips are critical to achieve low Pavg!

Prelim

inar

y


Pressure Profiles with and w/o Damping Wiggler Radiation

By E. Hu & F. Makahleh

Pavg ~ 0.27 nTorr

Pavg ~ 0.3 nTorr

AbsorberIP/TSP

Prelim

inar

y


Beam Line Front End Vacuum

Typical layout of Day 1 front end w/o beam line.

Pressure of a few nTorr to protect the UHV SR vacuum from HV beam line with window or differential pumpingEntire FE to be bakeable to 200 C (all metal, UHV material, etc)IP/TSP combination (same as SR) at high heat load components

PS: photon shutter

BS: Bremsstrahlung beam stop

IP/TSP: ion pump/titanium sublimation pump

GV: gate valveGV B

S

PS

IP/TSP

Front end design depends on type of radiation source (BM or ID) base on experience at NSLS and APSDetails are being developed with the beam line determination

Front End Vacuum Systems


IP/TSP

GV

BPM

BPM

SS x 2

COPM

PS

IP/TSP

GV

FV

BDA

PM: photon mask; CO: collimator; PS: photon shutter; BDA: beam defining aperture; SS: safety shutter

Typical layout of hard/soft x-ray beam line front end.

GV: gate valve; FV: fast valve;

IP/TSP: ion pump and titanium sublimation pump

IP/TSP


Detail layout of cell and ID chambers, absorbers and pumps

Detail design of cell chambers and absorbers

Fabricate or acquire (from APS?) a few prototype cell chambers

Learn and develop expertise in NSLS-2 chamber fabrication

Establish formal collaboration with APS colleagues

Work with potential extrusion vendors ASAP

Refine the fabrication technique to meet the specifications

Perform mechanical and vacuum evaluation on prototype chambers

Dimensional precision, support, alignment

NEG strip supports and installation

Vacuum performance

In-situ baking, NEG activation

Major Goals for FY07 and FY08:


Summary

Preliminary layout of cell chambers is progressing well

Improvements are made together with the lattice

Stress and deflection of chambers at multipole locations are acceptable

Detail chamber design can be started

Ray tracing of SR fan continues to optimize the absorber design

Simulation of the pressure profiles has started.

Including the PSD gas load from ID devices.

To be refined with the final chamber/absorber design

Pressure of < 1 nTorr is achievable with present pumping scheme

Need to collaborate with APS colleagues on chamber fabrication

Need to work with extrusion vendors soon

NSLS-II ASAC Review, 10/9-11/06 H-C. Hseuh,…, SR Vacuum Systems Storage Ring Vacuum Systems H-C....

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Transcript of NSLS-II ASAC Review, 10/9-11/06 H-C. Hseuh,…, SR Vacuum Systems Storage Ring Vacuum Systems H-C....