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NEG COATING RESULTS AND TRENDS

R. Kersevan, Vacuum Group, Tech.Serv.Division, ESRF, Grenoble

ALBA-MaxLab Workshop on Vacuum Systems for Synchrotron Radiation Light Sources, Barcelona, 12-13 Sept 2005

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Status of NEG-Coated ID Chambers for RUN 05-4 (18/8 – 17/10/2005):

NEG-COATED CHAMBERS:

10 mm ALU CV5073: 11x

15 mm ALU CV5073: 2x

15 mm ALU CV2093: 4x

10 mm SS CV5175: 1x

Total NEG-coated length, m: 79.5

•NO ADVERSE EFFECT ON RESISTIVE-WALL IMPEDANCE*

•LONG-TERM STABILITY (>5 YRS) ESTABLISHED

•PROGRAM OF UPGRADE OF REMAINING (6+1) 15-19mm CHAMBERS (SSNEG/Al)

UNDERWAY

*T. Perron, “Single Bunch-Related Impedance Measurements on the ESRF Storage Ring", PhD thesis, November 2005, Université Joseph Fourier, Grenoble

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Cross-Sections of NEG-Coated ID Chambers:

“10mm” SS CV5175 (50x8mm2 version) 1 left in the ring (ID28), obsolete design

“15mm”extruded-Al CV5073/2093 (2x CV5073 + 4x CV2093)

“10mm”extruded-Al CV5073(11x CV5073)

(CV2093 version under design)

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“Pump-less”Quadrupole-Type Vacuum Chambers:

Fact: The ESRF has in excess of 700 lumped pumps installed around the ring

Q: “Does the vacuum engineer of a state-of-the-art SR light source need all those expensive, appendage pumps and the related power supplies and cabling?”

A: “If we believe the results of 5+ years of machine operation at the ESRF (and Elettra), the answer might be ‘NO’ ”

• Proven fact: pump-less chambers, characterized by extremely low conductances, have been operated without major effects on the operation of the 6 GeV light source for over 5 years.

• Long-term issues settled: no need for re-activation unless vented. One chamber activated 6 times (vented 4), and still good

• Why? Because the NEG-coating technology has removed the need for appendage pumps, by reducing drastically the SR-induced gas load

• CV3 chamber of cell 6: 3.53 m long, 3 pumping ports, 2x GP200 + 1x 45 l/s SIP installed; SS with OFH Cu absorber (brazing, eb-welding)

• Two types tested: Soleil extrusion and “Esrf-2” extrusion• Prototypes coated in-house and installed in Cell 6• Vacuum and bremsstrahlung conditioning followed closely• Both the Soleil-type and the ESRF-2 type have been successful

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CV3-Type Vacuum Chambers,3530 mm long:

Standard CV3 chamber: 2xNEG + 1 SIP

Hi-temp brazing of Cu absorber ; precision eb-welding of SS parts

ESRF-2 extrusion: 30x20mm2 (HxV)

chamber NO pumps, only NEG-coating

Soleil-type CV3:

Al extrusion 70x35mm2; NO pumps, only NEG-

coating

GP20045 l/s StarCell

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Vacuum and Bremsstrahlung Measurements of NEG-Coated Vacuum Chambers on cell 6/ID6:

• Each new NEG-coated CV5000 is pre-installed and pre-conditioned on ID6, where its bremsstrahlung level can be measured precisely (dedicated hutch). Very effective way (the only way) of characterizing vacuum inside the ID chamber

• The conditionings of Soleil- and ESRF-2-type CV3 chambers have been monitored on ID6’s hutch

Extra gauges, measuring along the

chamber

RUN 05-1 RUN 05-3

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Vacuum Conditioning of a Standard ESRF-type CV3 Chambers:

RUN 05-4: new CV3

RUN 02-1: new CV3

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Comparison of Standard and Pump-less CV3s Conclusions:

• Comparable, if not better, pressures (PEN4)

• Comparably low, if not better, bremsstrahlung levels (not discussed in detail here)

• Much easier fabrication, lower cost

• NEG-coated types allow much smaller quadrupole and sextupole openings, ideal for advanced machine, with demanding lattices

• No need for many appendage pumps, and all that goes with them (cabling, power supplies, control software, etc…). Only places where ion-pumps would be needed is at (crotch) absorbers

What is needed:A new project which dares implementing the pump-less concept on a

global scale

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ESRF: R&D and Chamber Production:

• A second NEG-coating tower is being commissioned now, and production of NEG-coated chambers for some of Soleil’s in-air IDs is underway

• New tower is equipped with 2m-long (1.9m effective length) solenoid, with increased field (first system has 1m-long, 80cm-effective length)

• New tower has movable upper fixation point, allowing easier handling of short chambers (Soleil, SLS)

• Still some open issues concerning quality of NEG coating: had to reject a couple of chambers (10mm extruded alu ESRF CV5073)

• Chemical stripping of NEG film seems to be the cause of some failures

• Testing Soleil’s quadrupole chambers (1556mm long, with pumping ports) on D31

• Lower limit on the size/cross-section of ‘coatable’ chambers seems to have been reached: the 57x8mm2 “10mm” cross-section: no way to coat smaller chambers, unless new technology is discovered

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Many thanks to…:

-The “NEG-Coating Team” –

E. Burtin (software)F.Demarcq, I. Parat (deposition and assembly)

M.Hahn, R.Kersevan (supervision, planning, R@D)D. Cognie, F. Bodart (mechanical set-up)

V.Marion (Soleil contract)

G. Debut (measurements on D31, D15)

B. Plan (Mech.Engineering Group) (design of tools and chambers)

The constant support and encouragement of the present (P.Elleaume) and past (JM. Filhol) machine directors is gratefully

acknowledged