3 rd INSTALLATION: chicane magnetic field tests PEP-II e+ ring 1 st and 2 nd Feb 2008 Electron cloud installation studies at SLAC ILC tests - SLAC Cherrill Spencer

ILC DR Workshop - KEK “Ecloud1” SEY test station in PEP-II SLAC Transfer system at 0 o PEP-II LER e+  Transfer system at 45 o 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 (0 o position) and out of this plane (45 o ). 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 installationXPS 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

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 Height=2mmHeight=1mm In this simulation the groove height is taken to be the effective total height from top to valley Lanfa Wang, SLAC

Simulation of electron cloud build up Groove height =1mm In the following simulations hg=1mm is the fixed height of the groove triangle (roundness reduces effective height). SEY= bunches per batch. Chamber cross section: 152x45 mm Other relevant parameters: E=450 GeV, B =2 T Grooves either on one or both sides of chamber

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)

munro16 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 geometry The real geometry: radius of tip=0.095mm radius of valley =0.14mm 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