1. Electron Cloud R&D for Future Linear Colliders
Mauro Pivi (SLAC)
CERN Geneva, 20 March, 2008
We acknowledge the support of the European Community-Research Infrastructure Activity under the FP6 "Structuring the European Research Area" programme (CARE, contract number RII3-CT ).

2. The electron-cloud effect (ECE) in a nutshell:
Beam residual gas ionization and photons produce primary e-
Number of electrons may increases/decreases due to surface secondary electron yield (SEY)
Bunch spacing determines the survival of the electrons
Especially strong effect and possible consequences:
Single- (head-tail) and coupled-bunch instability
Transverse beam size increase directly affecting the Luminosity
Vacuum pressure and excessive power deposition on the walls (LHC cryogenic system)
In summary: the ECE is a consequence of the strong coupling between the beam and its environment:
many ingredients: beam energy, bunch charge and spacing, secondary emission yield, chamber size and geometry, chromaticity, photoelectric yield, photon reflectivity, …
The electron cloud has been seen PSR, SPS, PEP-II, KEKB, DAFNE..

3. One of the main limitations to the future Colliders (ILC, LHC CLIC) performances and luminosity reach is the formation of an electron cloud and driven collective instabilities
Electron cloud effect occurs mainly in the Damping Ring of the Linear Collider, due to short bunch spacing

4. Simulation Efforts on LC
KEK: PEI and PEHTS codes K. Ohmi
LBNL: POSINST M. Furman, WARP J. L. Vay
CERN: ECLOUD, F. Zimmermann, D. Shulte, HEAD-TAIL, G. Rumolo, R. Thomas, E. Benedetto, FAKTOR2 codes W. Bruns (Berlin)
SLAC: CLOUDLAND L. Wang, POSINST and CMAD codes M. Pivi

5. Work done for the ILC Reference Design Report (RDR)
K. Ohmi KEK
Beam size growth from single-bunch instability driven by electron cloud in the 6.7 km positron ring (e- densities in e/m3) Instability threshold set tolerances on maximum allowed SEY.

6. Work done for the RDR
Tune shifts on the order of 0.01 are expected near threshold.
Simulations indicate that a peak secondary electron yield of ~1.2 results in a cloud density close to the instability threshold.
Based on this, the aim of ongoing experimental studies is to obtain a surface secondary electron yield of 1.1.
Simulations also indicate that techniques such as grooves in the chamber walls or clearing electrodes, besides coating, will be effective at suppressing the development of an electron cloud.

7. Work done for the RDR
M. Pivi, SLAC
Buildup of the electron cloud and the suppression effect of clearing electrodes in an arc bend of the 6.7 km ring.

8. Work done for the RDR
A clearing electrode bias potential of +100 V is sufficient to suppress the average (and central) cloud density by more than two orders of magnitude.
Techniques such as triangular or rectangular fins or clearing electrodes need further R&D studies and a full demonstration before being adopted.
Nonetheless, mitigation techniques appear to be sufficient to adopt a single 6.7 km ring as the baseline design for the positron damping ring.

9. e-cloud expectations in the positron DR
Average neutralization levels and single-bunch (SB) instability electron cloud density thresholds for various damping ring options in units of [1012 m-3]. The average density thresholds are for a ring modeled as a dipole region.
Circumference
6 km
Neutralization e [1012 m-3]
6.0
Simulated e in arcs max=1.4
8.0
SB: e threshold [1012 m-3]
1.0
Sim. e / SB threshold
Sections 6 km DR
E-cloud
SEY threshold
arcs dipole
expected
1.2
wigglers sections
Long straight sections
preventable
1.6
- Arcs and wiggler sections: aiming at SEY 1.1
Not an issue in straight sections, a coating (TiN, TZrV NEG) and solenoid or rectangular grooves would lower SEY < 1.6. Large chamber size.

10. The ECE plan Benchmark sim. Simulations Lab measurements
e- trapping mechanism in Quad
e- detector meas. in facilities
beam dynamics
e- cloud generation & equilibrium
single and multi-bunch instability
self-consistent 3D simulations
SEY meas. coatings + treatments
Coating durability under vacuum
Grooved surface design
Path
TiN
TiZrV
increase radius
electrodes
groove
other ?
Requirements
Demonstration I
groove and clearing electrode chambers in PEP-II , KEKB, SPS and CesrTA
Demonstration II
Installation coated samples in PEPII, SPS and KEKB Meas. SEY ex situ

11. ILC R&D Ecloud program
R&D at KEK. SEY measurements. Installation of dedicated chamber with clearing electrodes, coating and grooves in wigglers. Simulations of build-up and instabilities.
Y. Suetsugu, Fukuma, M. Pivi and L. Wang (SLAC), Kato
R&D at CERN. Laboratory SEY measurements. SPS tests in magnets with clearing electrodes on enamel substrate, chambers with carbon coatings, TiN and grooves. Simulations of build-up and instabilities.
E. Chapochnikova, G. Arduini, M. Jimenez, J.M. Laurent, F. Caspers, Mahner, E. Benedetto, D. Schulte, A. Rossi, G. Rumolo, R. Thomas, P. Chiggiato, T. Kroyer, M. Taborelli, F. Zimmermann, M. Pivi and L. Wang (SLAC), M. Venturini (LBNL)

12. ILC R&D Ecloud program
R&D at LANL. Electron trapping in quadrupole field – R. Macek et al.
R&D at Frascati. Characterization electron cloud in Dafne e+ ring – P . Raimondi, R. Cimino, T. Demma
R&D at SNS/BNL. Characterization of instability for long bunches. Simulations of build-up and instabilities.
S. Cousineau et al.
R&D at SLAC. Laboratory SEY measurements. Samples installed in beam line. Installation of grooved chambers. Installation of new chicane and diagnostics in magnets. Simulations of build-up and instabilities – M. Pivi, J. Ng, L. Wang, B. Smith, B. Kuekan, M. Munro, W. Wittmer, D. Arnett, J. Olszewski, Wallace, D. Kharakh, C. Spencer, T. Raubenheimer, J. Seeman, R. Kirby, F. Cooper, F. King

13. Secondary Electron Yield Measurements and Surface Analysis at SLAC
Secondary Electron Yield (SEY) and Surface characterization
R.Kirby, SLAC
XPS TiN/Al
Electron conditioning
TiZrV NEG sample (LBNL)
Rectangular groove SEY ~ 0.7!
flat surface
Rectangular and triangular grooves concept
rect. grooves

14. Why not an aluminum chamber?
Al as received
Electron conditioning (bombardment) effect on the SEY for aluminum. Laboratory measurements at SLAC and CERN agree very well. The electron conditioning is not completely effective to lowering the aluminum SEY as needed [SLAC-PUB-10894] Most of the Dafne ring is made of aluminum chambers.

15. Electron conditioning (scrubbing or processing) of thin films TiN, TiZrV. Laboratory measurements, SLAC.
Residual gas recontamination under vacuum
Based on laboratory measurements, the required conditioning dose in ILC DR would be achievable in hours of beam operation during commissioning.
Concerns about effective e- conditioning time and coatings durability in an accelerator environment …

16. Electron conditioning: issues
Electron conditioning “Asymptotic” behavior:
In an accelerator environment, the electron cloud itself is providing the conditioning of the vacuum chamber walls (in laboratory: conditioning is constant by fixed beam)
When the SEY decreases, the efficiency of the electron conditioning will decrease as well
Recontamination:
- Competing effect: residual gas recontamination  e- cloud reappears
PICTURE at the SEY threshold:
Two effects competing against each other
e- (asymptotic) Conditioning
SEY threshold
recontamination
(1) solution (LHC): running at higher current for a period of time
(2) key: combined photon/ions conditioning may keep SEY below threshold (?!)

17. Rectangular Grooves to Reduce SEY
Rectangular grooves can reduce the SEY without generating geometric wakefields.
The resistive wall impedance is roughly increased by the ratio to tip to floor.
Schematic of rectangular grooves
Without B field
Schematic of rectangular grooves
With B field
By=0.2T

18. Effect of triangular grooves on Impedance
Impedance enhancement factor for the triangular grooved surface with round tips. Note that this is valid for frequencies ω such that c/ ω >> W; for example, for W~3mm this means n<6e11 Hz.
ref. [L. Wang et al. FRPMS079, Proceedings of PAC07.]

19. Rectangular (!) groove design in field free region: Laboratory measurements, SLAC
M.P. and G. Stupakov, SLAC
5mm depth (PEP-II)
Same SEY results
Artificially increasing surface roughness.
1 mm
Special surface profile design, Cu OFHC. EDM wire cutting. Groove: 0.8mm depth, 0.35mm step, 0.05mm thickness.
Measured SEY reduction < 0.8.
More reduction depending geometry.
Triangular groove concept A. Krasnov LHC-Proj-Rep-617

20. Installed 5 chambers in PEP-II straight, January 2007:
R&D work at SLAC on mitigation techniques
Installed 5 chambers in PEP-II straight, January 2007:
Project “ECLOUD1”: a station with chamber that allows the insertion of samples directly into beam line to monitor the reduction of the SEY due to beam conditioning
Project “ECLOUD2”: 4 Grooved and Smooth chambers installed to measure performance in PEP-II beam environment

21. SLAC test chambers installation layout
ECLOUD1
ECLOUD2
SEY TEST STATION
GROOVE CHAMBERS EXPERIMENT
SEY
GROOVE 1
GROOVE 2
FLAT 1
FLAT 2
COLLECTORS
ENERGY ANALYZER
THERMOCOUPLES
ECLOUD1: SEY station can be used to expose samples to PEP-ii beam environment and then measure samples in lab setup (transport in Ultra-High Vacuum load-lock)
ECLOUD2: Grooved and Flat chambers installed to measure performance in PEP-ii beam environment

22. “ECLOUD1” SEY test station in PEP-II
2 samples facing beam pipe are irradiated by SR
PEP-II LER
e+ 
Transfer system at 0o
Isolation valves
Transfer system at 45o
ILC tests, M. Pivi et al. – SLAC
20 March, 2008
CERN

23. SEY TESTS TiN and NEG
Expose samples to PEP-II LER synchrotron radiation and electron conditioning. Then, measure Secondary Electron Yield (SEY) in laboratory Samples transferred under vacuum.
PEP-II LER side
20 mm
TiN/Al sample exposed to SR
Complementary to CERN and KEK studies

24. Results of Conditioning in PEP-II LER beam line
Before installation in beam line
After conditioning
e- dose > 40mC/mm**2
ILC tests, M. Pivi et al. – SLAC
SEY of Tin-samples measured before and after 2-months conditioning in the beam line samples inserted respectively in the synchrotron radiation fan plane (0o position) and out of this plane (45o).
Similar low SEY recently measured in situ in KEKB beam line S. Kato, Y. Suetsugu et al.
20 March, 2008
CERN

25. Surface analysis: Carbon content decrease
X-ray Photon Spectroscopy.
XPS Before installation
XPS After exposure in PEP-II LER for 2 months (e dose 40mC/mm^2)
LER#1
ILC tests, M. Pivi et al. – SLAC
Carbon content is strongly reduced after exposition to PEP-II LER  synchrotron radiation + electron + ion conditioning. This is a different result if compared to electron (only) conditioning in laboratory set-up where carbon crystals growth has been observed by many laboratories.
20 March, 2008
CERN

26. Surface analysis: Carbon content decrease
X-ray Photon Spectroscopy.
Carbon content is strongly reduced after exposition to PEP-II LER  synchrotron radiation + electron + ion conditioning. This is a different result if compared to electron (only) conditioning in laboratory set-up where carbon crystals growth has been observed by many laboratories.
20 March, 2008
CERN

27. SEY recontamination after long term exposure in vacuum environment
SEY below 1 if sample is left under vacuum following conditioning in PEP-II LER. Measured SEY after 162h and 1074h in laboratory setup. Average pressure 1.0e-9 torr, 10:1 H2:CO.

28. Results of NEG conditioning in PEP-II e+ beam line
NEG as received
After NEG heating
Attention: sample kept in vacuum ~1e-7 after heating. Also, although we took best precautions, the environment during sample transferring for measurements, may not have been perfectly CO CO2 or contaminants free.
After beam conditioning
March 2008
ILC tests – SLAC
20 March, 2008
CERN

29. Installed 5 chambers in PEP-II straight, January 2007:
R&D work at SLAC on mitigation techniques
Installed 5 chambers in PEP-II straight, January 2007:
Project “ECLOUD1”: a station with chamber that allows the insertion of samples directly into beam line to monitor the reduction of the SEY due to beam conditioning
Project “ECLOUD2”: 4 Grooved and Smooth chambers installed to measure performance in PEP-II beam environment

30. “ECLOUD2” groove chambers in PEP-II
FAN EVENTUALLY HITS “BOTTOM” OF SLOT FOR FULL SR STRIKE
LIGHT PASSES THRU SLOTS BETW FINS
BECAUSE FAN IS “THICKER” THAN FIN
FIN TIPS= I.D. OF CHAM
FAN HITS HERE FIRST
VIEW IS ROTATED 90 CCW FROM ACTUAL FAN ORIENTATION
Built Rectangular Groove (or “fin”) chambers by Aluminum extrusion, then TiN coated and installed in PEP-II LER straight sections for testing
p.30

31. Installation in PEP-II LER: Groove chambers
Flat chamber
Electron detectors
LER bend magnet upstream

32. Groove chambers in PEP-II straight
Performances in PEP-II beam environment. Straight field free regions.
Successfully measured electron signal in Groove chambers much lower than Smooth (or “flat”) chambers. All chambers with TiN coating.
CERN

33. Effect of external solenoid
Effect of external solenoid winding on measured electron cloud current in smooth an grooved chambers in PEP-II (10 A  Bz~20 Gauss).
CERN

34. R&D work at SLAC on mitigation techniques
New: Installation of an ILC chicane in PEP-II and multiple test chambers, in December 2007:
Project “ECLOUD3”: new chicane with ILC DR bend-type field, and test chambers including sections with
Aluminum
TiN coating
Grooves
Non-evaporable getter NEG coating
Installation plans that we had to stop due to US FY08 budget issues

35. Mitigations Tests SLAC: New ILC Chicane Installation
Verify efficiency of mitigation techniques in dipoles.
Installation of a new chicane in PEP-II with ILC DR-type bends, to test chambers with coatings (and chambers with grooves)
E-cloud diagnostics
PEP-II e+ beam line
ILC DR-type bends
Layout new chicane installation in PEP-II LER
PEP-II chamber with triangular grooves

36. Vacuum chambers Layout
Aluminum
TiN coating on Al
Groove
2 chambers: 135.3” and 31.2”.
4 analyzer electron cloud detectors, one at each magnet location

37. Chicane Assembly Layout
PEP-II
LER
HER

38. Layout of electron cloud tests in PEP-II
LER DIRECTION
PLAN VIEW
AISLE SIDE
Last bend of arc 1
ELEVATION VIEW
SEY station
Grooves/Smooth
New chicane

39. Dec 3, 2007
Chicane

40. Electron cloud installation studies at SLAC
ECLOUD3 INSTALLATION: magnetic field tests
PEP-II e+ ring
ECLOUD1 and 2
1.5% of the ring
ILC tests - SLAC

41. Electron detector #1 #2 #3
PEP-II positron beam line experimental chamber
Magnet iron plates

42. Latest installation: electron cloud chicane
Chicane magnetic field Off.
Electron cloud signal on collectors distributed along the horizontal axis. Aluminum section (above) and TiN coating (below) show a reduction of ~30 in favor of the coating.
Internal view of the special electron detectors allow measuring the e- horizontal distribution and electron energy.

43. Scan Chicane Magnetic field resonances in the electron cloud current (
PEP-II LER e+ beam current
Magnetic field scan (0 to 1.1kG - 1Gauss steps)
Central collectors electron signals
Work in progress LBNL/SLAC to simulate PEP-II case. See C. Celata talk.

44. Simulations results from C. Celata LBNL

45. Simulations results from C. Celata LBNL

48. R&D work plans for the ILC Engineering Design Report (EDR) – e- cloud Working Package 7
Achieving the objective of developing suppression techniques for the electron cloud will involve the following tasks:
Study coating techniques, test the conditioning in situ in PEP-II, KEKB, SPS and CesrTA.
Test clearing electrode concepts by installing chambers with clearing electrodes in existing machines and in magnetic field regions in KEKB, SPS, CesrTA and HCX (LBNL). Characterize the impedance, the generation of higher order modes, and the power deposited in the electrodes.
Test “groove” concepts by installing chambers with grooved or finned surfaces in existing machines, including bend and wiggler sections in PEP-II, KEKB, SPS and CesrTA. Characterize the impedance and HOMs.
20 March, 2008
CERN

49. Working Package 7 (e-cloud)
CERN
Fritz Caspers
Daniel Schulte
Frank Zimmermann
Cockcroft Institute
Oleg Malyshev
Ron Reid
Andy Wolski
Cornell
Jim Crittenden
Mark Palmer
DESY
Rainer Wanzenberg
FNAL
Panagiotis Spentzouris
INFN-LNF
David Alesini
Roberto Cimino
Alberto Clozza
Pantaleo Raimondi
KEK
John Flanagan
Hitoshi Fukuma
Ken-ichi Kanazawa
Kazuhito Ohmi
Kyo Shibata
Yusuke Suetsugu
Shigiri Kato
LANL
Bob Macek
LBNL
John Byrd
Christine Celata
Stefano de Santis
Art Molvik
Gregg Penn
Marco Venturini
Miguel Furman
Kiran Sonnad
Mike Zisman
PAL
Eun-San Kim
Rostock University
Aleksander Markovik
Gisela Poplau
SLAC
Karl Bane
Bob Kirby
Alexander Krasnykh
Mauro Pivi
Tor Raubenheimer
Tom Markiewicz
John Seeman
Lanfa Wang
Potential
Investigators
20 March, 2008
CERN

50. Example: WP 7 (e-cloud) The required input includes:
Experimental data from machines including CesrTA, PEP-II, KEKB, SPS and LHC. Data should include detailed comparison of electron cloud density in sections with mitigation techniques compared with the electron cloud density in sections without mitigating techniques.
The deliverables will include:
Technical specifications for techniques to be used to suppress build-up of electron cloud in the positron damping ring, consistent with aperture and impedance requirements.
Guidance for the design of the vacuum chamber material and geometry (Objective ), and for the technical designs for principal vacuum chamber components (Objective ).
20 March, 2008
CERN

51. WP 7 (e-cloud) ILC DR Challenge: 2 pm vertical emittance
If the electron cloud density is not reduced below the threshold level for beam instabilities, then the positron damping ring will be unable to provide a beam meeting the specifications for beam quality, stability and intensity; this will have a potentially significant impact on the luminosity of the ILC.
20 March, 2008
CERN

52. Test Facilities: CesrTA
Cesr-c is a wiggler-dominated electron-positron collider.
The proposed development of CESR into CesrTA would allow a unique opportunity for electron cloud studies at a dedicated test facility, operating in a parameter regime directly relevant for the ILC damping rings.
Requires relocation of wigglers to allow tuning for low natural emittance; upgrade of instrumentation for tuning for low vertical emittance; installation of instrumented test chambers in wigglers.
A range of other important studies will also be possible (e.g. low-emittance tuning, development of instrumentation for fast beam-size measurements of ultra-low emittance beams).
Presently, funding agencies are supporting CesrTA proposal.
20 March, 2008
CERN

53. Other Test Facilities KEKB and ATF DANE PEP-II (until April 2008)
Electron cloud
Fast ion instability
DANE
electron cloud
fast injection/extraction kickers
PEP-II (until April 2008)
SPS and LHC
20 March, 2008
CERN

54. R&D work plans for the EDR
From “Damping Rings EDPhase Gantt Links” document

55. Milestones to ILC EDR
The goal is to complete the following tasks by early 2010 as input for the Engineering Design Report (EDR)
o Test coating techniques and determine conditioning effectiveness in existing accelerator beam lines
o Characterize the efficiency of conditioning on TiN coatings with respect to NEG coatings.
o Characterize thin-film coating durability after long term exposure in an operating accelerator beam line: analyze PEP-II TiN-chambers after ~10 years operation.
o Need to experimentally characterize Photoemission in ILC DR parameters range to estimate initial seed of electrons
o Characterize the electron cloud build-up by simulations and measurements in existing accelerators
o Characterize the electron cloud in wigglers and quadrupoles
20 March, 2008

56. Milestones to EDR
o Characterize the electron cloud instability by measurements in existing facilities possibly also at CesrTA, KEKB operating at ultra-low emittances
o Characterize the ILC DR electron cloud instability by simulations
Evaluate the need for Additional Mitigation techniques (besides coating):
o Test clearing electrodes in magnetic field regions including wigglers at KEKB and CESR and dipoles at PEP-II and SPS
o Test triangular groove or slots in magnetic field regions including wigglers and dipoles PEP-II, KEKB and SPS
o Characterize the impedance and HOMs of mitigation techniques
o Use of antechambers
Recommendation of mitigation techniques to prevent the electron cloud in the ILC damping ring as input for the EDR
20 March, 2008

57. CesrTA Program I
CesrTA Program has been funded jointly by the US NSF and DOE
Dedicated DR R&D program starting in mid-2008
CesrTA Configuration:
12 damping wigglers located in zero
dispersion regions for ultra low
emittance operation (move 6 wigglers
from machine arcs to L0)
Diagnostic vacuum chambers
with EC suppression methods
Designated sections available for
installation of test devices
Precision instrumentation
Multi-bunch turn-by-turn BPM system
Fast X-ray beam profile monitors
4 ns bunch train operation
CESR-c Damping Wiggler
Courtesy of Mark Palmer, Cornell Univ.

58. Current focus is a 2 year program of ILC DR R&D
CesrTA Program II
Current focus is a 2 year program of ILC DR R&D
Reduction in scope from longer (3.5 year) program proposed to NSF/DOE in July
Maintain 3 core research areas:
Electron cloud studies
Low emittance program (revised target of 20 pm vertical emittance)
Development of a fast X-ray beam size monitor
Target bunch-by-bunch monitor capable of single-pass measurements for ILC DR
Integral to CesrTA program a ultra-low emittance measurements

59. CesrTA Parameters & Capabilities
Baseline Configuration
Parameters:
Baseline optics at 2 GeV for ultra low emittance studies
Energy flexibility will allow EC growth studies at 5 GeV as specified for the ILC DR
Parameter
Value
No. of Wigglers 12
Wiggler Field
2.1 T
Beam Energy
2.0 GeV
Energy Spread (DE/E)
8.6 x 10-4
Target Vertical Emittance
<20 pm
Horizontal Emittance
2.3 nm
Damping Time
47 ms
Bunch Spacing
4 ns
Bunch Length
9 mm
Multi-bunch turn-by-turn BPM
EC Measurements
1.2 x GeV
EC Measurements:
Multi-bunch turn-by-turn instrumentation has been commissioned
Measured vertical tune shift along a train generating the electron cloud and for witness bunches trailing the train at various intervals

60. CesrTA Summary CesrTA program presently ramping up R&D Targets:
Now through mid-2009
Complete low emittance machine reconfiguration and upgrades
Deploy and commission
instrumentation needed for low emittance program
Study EC growth studies in wigglers, dipoles, quadrupoles and drift regions
in CESR
Initial EC mitigation studies
Mid-2009 through April 1, 2010
Work towards progressively lower emittance operation
Complete EC mitigation studies
EC beam dynamics studies at the
lowest achievable emittances
Immediate focus:
Engineering preparation for machine reconfiguration
Preparation/testing of EC vacuum chambers, vacuum diagnostics, and beam instrumentation
Work on Data-Simulation Comparisons
Seeing qualitative agreement with shape of EC growth/decay
and vertical tune shift data from witness bunch studies
ECLOUD Simulation
CESR Dipole Region
Courtesy of Mark Palmer, Cornell Univ.

61. R&D program in the SPS CERN
Since beam scrubbing in the SPS is limited, the goal is to install a material with low SEY values from the start: not possible to bake vacuum chambers,
Laboratory SEY measurements
Simulations of electron cloud build-up and instabilities
Tests in the PS and SPS in magnets regions and instrumented chambers with:
Clearing electrodes on enamel substrate
Carbon coatings
TiN and coatings
Triangular grooves
E. Chapochnikova, G. Arduini, M. Jimenez, J.M. Laurent, F. Caspers, Mahner, E. Benedetto, D. Schulte, A. Rossi, G. Rumolo, R. Thomas, P. Chiggiato, T. Kroyer, M. Taborelli, F. Zimmermann, M. Pivi and L. Wang (SLAC), M. Venturini (LBNL)

62. Summary
Measured resonances similar as predicted by simulations: in the DR, the arc magnetic field can be tuned such as to seat at a resonance minimum, to reducing the electron cloud density by a factor ~2-3.
Rectangular groove very effective at further decreasing the electron cloud in field free.
Conditioning in PEP-II (with photons) decreases the SEY below 1 on TiN coating and very stably in time; SEY of NEG close to 1.
Looking forward to future tests at CERN, KEK and at CesrTA operating at ultralow emittancies.

63. T. Raubenheimer, J. Seeman,
Thanks! to F. Zimmermann, G. Arduini, E. Chapochnikova
and to:
M. Furman, M. Venturini, C. Celata, N. Kurita, G. Stupakov, K. Harkay, B. McKee, G. Collet, K. Jobe, K. Ohmi, A. Wolski, R. Macek, J. Ng, L. Wang, B. Smith, B. Kuekan, M. Munro, W. Wittmer, D. Arnett, J. Olszewski, Wallace, D. Kharakh, C. Spencer,
T. Raubenheimer, J. Seeman,
R. Kirby, F. Cooper, F. King
H. Braun, J. M. Laurent, N. Hilleret, M. Jimenez, F. Caspers, Mahner, E. Benedetto, D. Schulte, A. Rossi, G. Rumolo, R. Thomas, P. Chiggiato, M. Morvillo, M. Taborelli, A. Latina and many other colleagues ..