To: Distribution 2 Apr 97

From: Martin Nordby

Subject: IR Engineering and Physics Meeting Minutes: 14 March 97

Hard-Copy Distribution:

Bob Bell	41		Nadine Kurita	18
Gordon Bowden	26		Harvey Lynch	41
Pat Burchat	95		Tom Mattison	17
Scott Debarger	17		James Osborn	LBL B71J
Hobey DeStaebler	17		Andy Ringwall	17
Jonathan Dorfan	17		John Seeman	17
Stan Ecklund	17		Mike Sullivan	17
John Hodgson	12		Uli Wienands	17
David Humphries	LBL 46-161		Mike Zisman	LBL B71J
Roy Kerth	LBL 50-340
David Kirkby	95
Jim Krebs	41

Electronic Distribution:

Curt Belser	Tom Elioff	Lew Keller	Natalie Roe	Dieter Walz
Lou Bertolini	Kay Fox	J. Langton	Ross Schlueter	Rick Wilkins
Adam Boyarski	David Fryberger	Georges London	Ben Smith	Fran Younger
Catherine Carr	Fred Goozen	Rainer Pitthan	Steve St Lorant	Ron Yourd
Al Constable	Alex Grillo	Joseph Rasonn	Joe Stieber
David Coupal	Keith Jobe	Jeff Richman	Jack Tanabe

Vertex Chamber RF Fingers

Nadine Kurita has developed the design of the RF fingers inside the bellows at the ends of the beryllium vacuum tube. The finger design is patterned after the HER Arc Bellows, with Glidcop shield fingers providing the RF shielding, and inconel leaf spring fingers providing the contact force. The fingers slide on a rhodium-plated Glidcop stub, and are mounted on the stainless steel flange which welds to the bellows. The flange is also welded to the stainless tube which is brazed to the beryllium chamber. The contact force on the shield fingers is 5 +/- 2 oz, with an axial travel of +/- 0.09 inches, X or Y offset of +/- 0.04 inches, and a maximum angular misalignment of 25 mrads.

H.O.M. resonance modelling by Eddie Lin indicates that up to 1000 W of beam power is trapped in the cavity of the Vertex Vacuum Chamber, between the first B1 masks. If the end pieces of stainless steel remain unplated, 85% of the power is deposited in these pieces, since their resistance is so much higher than that of beryllium. This suggests that all stainless steel parts must be gold plated after final welding.

Furthermore, an aluminum heat shunt will be epoxied to the outside of the stainless steel, to further improve conduction back to the water-cooled beryllium. For a 1000 W heat source, the distributed heat load is 1.8 W/cm^2 (for HEB and LEB I = 3 Amps). Given a water temperature of 20°C, the peak temperature at the Glidcop stub is 83°C, and the bellows flange temperature is 55°C.

For 2 Amp HEB on 2 Amp LEB, H.O.M. power is 240 W, and T(max) = 37°C, while the bellows flange temperature is 31°C.

Nadine is looking at the heat load these elevated temperatures will impose on the SVT inner carbon fiber cone, and report on this at the Vertex Vacuum Chamber Final Design Review.

IR-2 Alignment Concepts

Rick Wilkins discussed options for alignment of machine components in the IR-2 hall. A monument network has already been established on the walls of IR-2, both near floor elevation and at beamline height. He plans to install more targets, expecting that many lines-of-sight will be lost when components are installed.

The new shielding blocks in the tunnel mouths obstruct many lines-of-sight, and may pose a problem for HER alignment, and will definitely be a problem with BaBar in place. BaBar appears to obstruct all cross-over lines-of-site and, on the back end (north side) of BaBar, the DIRC S.O.B. provides a limited region where the Support Tube can be seen.

A liquid level system could provide vertical alignment of components, but it requires a constant elevation, can be physically big, and is costly.

Another option is to add two inverted pendela on either side of the IR hall. These are buried in what passes for bedrock, and are assumed to not change position with time. They can be surveyed before BaBar rolls on beamline, and provide a known offset across the IR hall. Used in conjunction with a geotheodolyte, which can give true bearing with respect to magnetic north, the alignment network could bridge the IR hall with reasonable accuracy.

These minutes, and agenda for future meetings, are available on the Web at:

http://www.slac.stanford.edu/accel/pepii/near-ir/home.html