# Presentation: 949859

## Storage Ring Vacuum Systems

**H. Hseuh, Vacuum Group**
**ASAC Review of NSLS-II**
**  ****July 17-18, 2008**

## 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

## Vacuum Requirements

- Beam aperture – 25 mm (V) x 76 mm (H)
- Chamber straightness - < 1 mm / 5 m
- Smooth cross section changes: inclination angle < 10**o**
- Minimum steps or cavities < 1 mm
- Mechanical stability: 1 fixed & 2 flexible invar supports at BPMs

- P(avg) < 1 nTorr (> 50% H**2**, < 50% CO, CO**2**, CH**4**, ...),
- 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

## 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**

**S3**

**S4**

**S5**

**S6**

- Multipole chamber

- Dipole chamber, 6**o** bend

- Stainless chambers

**S1**

**S1**

## Cell Chamber Cross Sections and Analysis

- Extruded cross section

- Machined at pole locations

- Bended and machined

- Extruded

- 3 mm wall

- 3.1 mm wall

- Multipole Chamber

- Dipole Chamber

- At Quadrupole

- At Sextupole

- Maxi. δ = 0.3 mm x2
- Max. S = 42 MPa

- Maxi. δ = 0.27 mm x2
- Max. S = 64 MPa

**S**yield** (A6063T5) = 145 MPa**
**S**stress** (A6063T5) = 186 MPa **

## Aluminum Cell Chamber Fabrication 

- 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

## 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

## DW and BM Photon Fans at S1-S4 Region

- Larger bellows and RF fingers to accommodate canted DW fan

- S2

- S3

- S2

- S3

- DW ABS > 15 kW

- Vertical fan hitting Top/bottom wall

- BM        S3, S6	 ~5EPU       S1-S3 	< 35
- IVU20     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

- S4B

- S4A

- *on magnet shields

- M. Ferreira

## Simulation of DW vertical power using SPECTRA8

**P = 274 W**

**P = 230 W**

- S1B

- S2

- S3

- DW 1

**P = 40 W**

- From DW1

- From DW2

- DW 2

**Δ****P < 0.3 W/cm****2**

**h ~ 9 mm**

**h = 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 chambers
- Flange 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**

**Δ****P < 0.5 W/cm****2**

- S1A

## Photon Absorbers  (8-10 per cell)

- Stick

- < 12 W/mm**2**, T**max **~ 200**o**C

- < 3 W/mm**2**, T**max **~ 68**o**C

| P (kW) absorber | 22 |
| --- | --- |
| Pmax (W/mm2) | 25 |
| Smax (MPa) | 303 |
| Tmax (oC) | 256 |

- Damping Wiggler Absorber

- BM Absorber Positions and Power

- Crotch in dipole

- Crotch

- Stick in multipole

- Flange

- Absorber brazing development started

## --  ± 3% aperture

- Absorber Positioning vs. Aperture Requirement

**-****-****  **± 3% aperture
**Δ**       ABS **+X** position

- W. Guo

## Pressure Profile with and without DW

- 3 GeV, 0.5A, **η** = 1x10**-5**

- Pavg = 0.13 nT

- P**avg** = 0.25 nT

**LS**

**SS**

- Local ΔP w/ 15% DW fan ➾ bremsstrahlung radiation

- Molflow Code
- (R. Kersevan/ESRF)

- To be updated

- E. Hu

## 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

## Layouts for Injection and RF Straights

- Injection Straight

- RF Straight

- Bellows + transition

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

## Choice of RF Shielded Bellows

- 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?

- Solid sleeve

## 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

## 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?**

## 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

## In-situ Bake with External Heaters

- M. Ferreira, F. Lincoln

- T ~120**o**C 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

- APS chambers for bakeout development

## Ozone Cleaning Development

- Final cleaning prior to installation (after alignment...)
- Extensive O**3** monitoring to meet ES&H requirements
- System being assembled for testing

- K. Wilson

- Flush chamber with < 500 ppm O**3** in O**2** to break and remove contaminants

- Ozone system flow diagram

## 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