To: Distribution 2 Apr 97
From: Martin Nordby
Subject: IR Engineering and Physics Meeting Minutes: 14 March 97
|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|
|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
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: