1. PEP-II test chambers installation
SEY
GROOVE 1
GROOVE 2
FLAT 1
FLAT 2
COLLECTORS
ENERGY ANALYZER
THERMOCOUPLES
GROOVE CHAMBERS EXPERIMENT
SEY TEST STATION

2. SEY test station in PEP-II LER
0o position
45o position

3. Fin/Flat TiN chambers in PEP-II LER
Flat chamber
Fin chamber

4. Secondary Electron Yield Measurements at SLAC

5. SEY test chamber
19 March 2007

6. Grooved chambers

7. Collector signals vs PEP-II LER current Stainless steel chamber
Electron integrated energy distribution
Stainless steel chamber
Collector signal vs retarding grid field (10V = - 500V)
PEP-II LER current still raising (2.7A  4A)

8. Compare vacuum chamber e- currents
Measured e- current in grooved and TiN flat chambers << StSt chamber PEP-II LER current still raising (2.7A  4A)

10. Solenoid on and conditioning effect
14jan
17mar
18jan
19jan
External solenoid on, grooved/flat chambers (10A  Bz=20 Gauss)
Electron and photon conditioning in time on stainless steel chamber
3 days ROD starting next Monday, 1st sample transferring to laboratory for SEY and surface measurements after prolonged e- and ph dose.

11. Ready for INSTALLATION Coating of extruded Al chambers
Projects
ONGOING TESTS AT SLAC:
TEST in
LOCATION
Ready for INSTALLATION
Status
SEY TESTS
STRAIGHT
PEP-II LER PR12
November 2006
Ready
FINS RECTANG.
Coating of extruded Al chambers
ONGOING PROJECTS:
CLEARING ELECTRODES
BEND
PEP-II LER PR12
FY07-FY08
Design
FINS TRIANG.

12. Layout installation – in PEP-II
f 3.5”
f 1.73”
Proposed reduction
in chamber diameter
Chamber cross section
22”
~25”
59”
(D-BOX)
(D-BOX)
BEND
BEND
BEND
BEND
tapered chamber 1
spool chamber
Grooved chamber(?!)
Clearing electrode chamber
tapered chamber 2
D-BOX=diagnostic box, electron detection centered on BEND and 13.5” long

13. Test Chamber Assembly, 1.5M Long (59.00”)
Vacuum Tube, 3.75 OD x 3.51 ID
3.375” CFF, Rotatable
Vacuum Tube,
4.00 OD x 3.50 ID
Collector Port Flange
3.375” CFF, Non-Rotatable
Tube, 2.00” OD x 1.73” ID
Flange to Flange Length = 59.00”
1.33” CFF access port
Feedthrough,
Ceramtec # W
Mounted to 1.33” CFF

14. Test Chamber with Electrode
Electrode, Copper
0.063” x ~1.0” x 50.0”
(49.606” between
feedthrough centers)
Clearance between
Electrode and chamber
Varies between .070”
and .080”

15. LTOT Rpipe 1 t h3 h1 h2 LTAP Dimensions: LTOT630 mm LTAP115mm
Rpipe=44 mm
=60 deg
h1,h3,h3=5 mm
t=2 mm
2nd Geometry: 1 Ports 50 Ohm
1st Geometry: 2 Ports 50 Ohm
LTOT
Rpipe 1
David Alesini, Frascati, Feb 2007 t h3 h1
First discontinuity
LTAP h2

16. HFSS Results on Copper electrode stainless steel chamber
D.Alesini Frascati
A. Krasnykh, SLAC, Mar 2007
Longitudinal Impedance: power deposited to electrode ~10W with PEP-II beam, and ~2W for ILC DR beam.

17. Triangular groove chamber – (see Lanfa)

18. Single-bunch instability preliminary studies ongoing.
Cmad simulation code status
Tracking the beam in a MAD lattice for ILC DR, parallel code, interaction with cloud at each element in the ring and with different cloud distribution, single-bunch instability studies, threshold for SEY, dynamic aperture tune shift … CMAD [M. P.]
Single-bunch instability preliminary studies ongoing.
Electron cloud build-up (SEY, vacuum chamber, etc.) to be added.
ns=0.067
e- density 1e10 e/m3 macrop=100000
ILC DR
MAD deck to track beam with an electron cloud at each element of the ILC DR.
First results: 2 synchrotron oscillation periods (9min * 320 CPUs / turn) CMAD tracking, ILC DR beam at extraction, with average cloud density 1e10 e/m3 (below threshold).
Bottleneck => in ILC DR, beam aspect ratio reaches sx/sy=200, demanding Particle in Cell grid ratios num-gridx >> num-gridy, to correctly simulate Electric field.

20. Motivations and solutions summary
e-cloud observed at SPS and PS (CERN), PEP-II, KEKB, Dafne, CESR
concern for: ILC DR & CLIC, LHC, LHC+, SPS with PS2, KEKB, Dafne
best approach: avoid e-cloud build up
technological solutions:
- NEG non-evaporable getter coating (SPS, LHC 6km warm sections, RHIC, PEP-II, KEKB)
- TiN coating (Daphne wigglers, PEP-II, KEKB)
- grooves (PEP-II, SPS, CESR)
- “conventional” clearing electrodes (PEP-II, KEKB, DAFNE(?!), SPS)
- novel enamel clearing electrode (clearing electrode based on double layer of enamel coating, SPS)
slotted surface shielding beam fields (CERN)
air baking techniques (SPS, SLAC)

21. Global R&D program Ongoing: At KEKB
Secondary electron yield (SEY) in situ, ante-chamber and thin films coatings TiN and NEG.
Planning: clearing electrodes tests planned at KEKB in a wiggler magnet section
At SLAC
Conditioning and SEY of TiN and NEG samples in PEP-II beam line, groove chambers.
Planning: clearing electrodes and triangular grooves in bends with parameters close to ILC DR.
Planned:
At CERN: concern for the SPS and PS as LHC pre/injectors.
Planning: several mitigation techniques are under evaluation for the SPS and PS: increase chromaticity, scrubbing runs, smaller radii chambers, NEG coating, grooved surfaces, air baking and slots. Clearing electrodes on enamel substrate.
In Daphne, limitation on maximum positron current. Suspected electron cloud. Al chambers:
Planning: TiN film coatings in the wiggler Al chambers. (excluded by now clearing electrodes)
Cornell CesrTA:
> FY08, Electron cloud in wiggler sections with ILC DR parameters. Ultra-low emittancies. Fast Beam Ion instability.

22. Thanks !
To the contributors to this presentation M. Palmer (Cornell), S. De Santis (LBNL) F. Willeke (DESY), K. Suetsugu (KEK), K. Bane, P. Raimondi, L. Wang (SLAC), F. Zimmermann (CERN)
and to DR collaborators
D. Arnett, G. Collet, R. Kirby, N. Kurita, B. Mckee, M. Morrison, P. Raimondi, T. Raubenheimer, J. Seeman, L. Wang, G. Stupakov (SLAC), D. Rubin, D. Rice, L. Schachter, J. Codner, E. Tanke, J. Crittenden (Cornell), J. Gao (HIPEP), A. Markovic et al. (Rostock Univ.), M. Zisman, S. De Santis, C. Celata, M. Furman, J.L. Vay (LBNL), K. Ohmi, Y. Suetsugu (KEK), F. Willeke, R. Wanzenberg (DESY), J.M. Laurent, A. Rossi, E. Benedetto, F. Zimmermann, G. Rumolo, J.M. Jimenez, J-P. Delahaye (CERN), A. Wolski (Cockroft Uniiv.), B. Macek (LANL), C. Vaccarezza, S. Guiducci, R. Cimino (Frascati), et many other colleagues…

23. International Linear Collider R&D on electron cloud (SLAC)
M. Pivi, T. Raubenheimer, J. Seeman, T. Markiewicz, R. Kirby, F. King, B. McKee, M. Munro, D. Hoffman, G. Collet, L. Wang, A. Krasnykh, D. Arnett, (SLAC) M. Venturini, M. Furman, D. Plate (LBNL), D. Alesini (LNF Frascati) R. Macek (LANL)
19 March 2007