3rd INSTALLATION: chicane magnetic field tests

PEP-II e+ ring

1st and 2nd

Feb 2008

Electron cloud installation studies at SLAC

ILC tests - SLAC

Cherrill Spencer

ILC DR Workshop - KEK

““Ecloud1” SEY test station in PEP-II SLACEcloud1” SEY test station in PEP-II SLAC““Ecloud1” SEY test station in PEP-II SLACEcloud1” SEY test station in PEP-II SLAC

Transfer system at 0o

PEP-II LER e+

Transfer system at 45o

2 samples facing beam pipe are irradiated by SR

Isolation valves

ILC tests, M. Pivi et al. – SLAC

ILC DR Workshop - KEK

Results of TiN conditioning in PEP-II e+ beam line

SEY of Tin-samples measured before and after 2-months conditioning in the beam line. 2 samples inserted respectively in the synchrotron radiation fan plane (0o position) and out of this plane (45o).

ILC tests, M. Pivi et al. – SLAC

Before installation in beam line

After beam conditioning

e- dose >

40mC/mm**2

Similar low SEY recently measured in situ in KEKB beam line S. Kato, Y. Suetsugu et al.

LER#1

XPS Before installation XPS After exposure in PEP-II LER for 2 months (e dose 40mC/mm^2)

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.

Surface analysis: Carbon content decrease

TiN samples: X-ray Photon Spectroscopy.

ILC tests, M. Pivi et al. – SLAC

Results of NEG conditioning in PEP-II e+ beam line

ILC tests – SLAC

NEG as received

After beam conditioning

March 2008

After NEG heating

KEK, Feb 2008

Clearing electrodes in KEKB magnetic free region

Y. Suetsugu, KEK

Y. Suetsugu, KEK

11 March, 2008 SPS meeting. Mauro Pivi SLAC

Gianluigi Arduini, Elena Chapochnikova, Paolo Chiggiato, Miguel Jimenez, Mauro Taborelli (CERN) Mauro Pivi, Lanfa Wang, Frank Cooper, Munro Morrison (SLAC)Marco Venturini, Miguel Furman (LBNL)

SPS Groove Chamber Tests Collaborators

Secondary electron yield (SEY) estimate: SPS Groove

0 100 200 300 400 500 600 7000

0.2

0.4

0.6

0.8

1

1.2

1.4

Energy (eV)

SE

Y

0=1.20,B=2 Tesla,R

tip=0.13mm,H=2mm

Grooved SurfaceFlat Surface

0 200 400 600 8000

0.2

0.4

0.6

0.8

1

1.2

1.4

Energy (eV)

SE

Y

Grooved SurfaceFlat Surface

0=1.20,B=2 Tesla,R

tip=0.13mm,H=1mm

Height=2mm Height=1mm

In this simulation the groove height is taken to be the effective total height from top to valley

Lanfa Wang, SLAC

Marco Venturini, LBNL

electron cloud build-up as a function of time for 1mm deep grooves with angle alpha =80 deg, for various choices of the groove tip radius. Groove on bottom and top sides. In these simulations hg=1mm is the height of the groove triangle.

Simulation of electron cloud build up

•Max. e-cloud linear density vs. groove tip radius (SEY=1.3)•For flat surfaces the max. linear density is ~ 1.5 nC/m). •In the SPS tests, grooves on top and bottom side. •In these simulations hg=1mm is the height of the groove triangle.

Marco Venturini, LBNL

Simulation of electron cloud build up

• Roundness of tips and valley is important• Manufacture Tolerances on roundness are

rather tight for 1mm grooves

• Few more work on simulations:– In the SPS, would it be more realistic to assume

initial SEY=1.5 (?!), since no photon scrubbing. – Define tolerance roundness to obtain SEY<1– For small 1mm groove important to consider the

effective groove height (after roundness)

munro 16

TRIANGULAR GROOVE CHAMBER MFG

January , 2008

Requirements

Triangular Grooves

Groove Width 0.35 mm

Groove Depth 1 mm

Overall Depth 2 mm

Groove Length 0.5 M

Taper Angle 20 degrees

Radius at Top & Bottom 0

Basic Problems

• Very small grooves are difficult to fab

• Sharp radii at base & top of grooves unattainable by normal mfg methods

• Mfg options are to either have grooves as part of vac chamber, or fab grooves as separate item & then attach to vac chamber.

Mfg Options• Extrusion: Very small radii at top & bottom of

grooves are difficult to mfg• Machining: Mill multiple slots in solid material• Metal Folding: Form multiple folds• EDM: Small radii are beyond normal tolerances • Brazed-up Assembly: Use individual razor type

foil blades• Isostatic Pressing or Metal Injection Molding:

Uses powdered metal & binders which would probably would not be suitable for vacuum usage. Also have difficulty in forming small radii

Groove Options Manufactured

Series of aluminum extrusions fabricated

• Grooves all around chamber (2 different groove profiles)

• Grooves at top & bottom of chamber

• Separate linear extrusion for insertion into existing stainless vacuum chamber

Cost Considerations

• Assuming long sections required, the extrusion approach is by far the least expensive.

• Limited to aluminum material

• Copper may be possible, but could not find vender

Aluminum triangular grooves by ALMAG.Original design for the SPS: 2mm depth, limited by the groove sharpness.SLAC 2008

Aluminum triangular groove:

depth 1.9mm, angle 20deg, radius top 0.095mm, radius valley 0.140mm

With final geometryThe real geometry:

radius of tip=0.095mm

radius of valley =0.14mm

0 100 200 300 400 500 600 7000.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

Energy (eV)

SE

Y

0=1.50,Height=1.9mm, =200

Flat surfacer=0.14mm,B=2 Teslar=0.14mm,B=0.2Teslar=0.09mm,B=2 Teslar=0.09mm,B=0.2Teslaaverage,B=2 Tesla

Lanfa Wang, SLAC

Manufacturing Options depth 1mm: Metal Folding

Metal Folding: Form multiple folds. [EMEGA Company, USA]

Manufacturing Options depth 1mm: Razor Blades

Brazed-up Assembly: Use individual razor type foil blades

Manufacturing Options depth 1mm: Razor Blades