To: Distribution 26 August 96

From: Martin Nordby

Subject: Minutes of the IR Engineering and Physics Meeting of 23 Aug 96

Hard-Copy Distribution:

Bob Bell41Jim Krebs 41
Lou BertoliniLLNL L-287 David Kirkby95
Gordon Bowden26Harvey Lynch 41
Pat Burchat95Tom Mattison 17
David Coward95James Osborn LBL B71J
Scott Debarger17Eric Reuter 18
Hobey DeStaebler17Andy Ringwall 17
Jonathan Dorfan17Knut Skarpaas VIII 18
Stan Ecklund17John Seeman 17
Alex Grillo95 Mike Sullivan17
John Hodgson12 Uli Wienands17
Hank HsiehLBL B71JMike Zisman LBL B71J
David HumphriesLBL 46-161 Lowell Klaisner17
Roy KerthLBL 50-340 Burl Skaggs

Electronic Distribution:

Catherine CarrNadine Kurita Natalie RoeRick Wilkins
David CoupalGeorges London Ross SchlueterFran Younger
Fred GoozenJoseph Rasonn Joe Stieber
Rick IversonJeff Richman Jack Tanabe

Q2/4/5 Raft Analysis

Scott Debarger reported preliminary results of an FEA analysis of the Q2/4/5 Raft. The Raft deflects 0.007 inches under its own weight, and 0.75 inches when loaded with magnets (although the Q2 magnet weight was not included). The peak deflection occurs on the in-board end of the Raft, at the connection to the Support Tube. The Raft design includes half-cones around the Q2 magnet and chamber, and mounts under the in-board ends of Q4 and Q5.

The regions which largely contribute to deflection are the joints between the half-cones, and the two flaring regions: one between the cone and the "canoe-shaped" piece under Q4, and one between the canoe and the two structural tubes around Q5. Furthermore, these rectangular tubes twist due to the force couple applied by the Q5 magnet and the supports to ground.

The results of this analysis show that the Raft is considerably flimsier than the rough preparatory analysis suggested. To stiffen up the Raft, the half-cones on the cantilever section will be made full-cones (although this complicates installation and servicing of the Q2 magnet and chamber). Also, cross-members will be added under Q5 to reduce twisting. Finally, it may be necessary to add a gusset on the vertical plane under the cones to increase the stiffness of the cantilever (this would require opening up a radial gap in the shielding plug).

Next Steps:

--Finish post-processing results of FEA model to understand sources of deflection.

--Stiffen Raft as described above.

--Re-run static gravitational analysis, and modal analysis.

--Run model with earthquake loading scenario, where the in-board support is transferred to the EQ bracket mounted to the IFR door.

Q2 Shielding Plug Removal

Ed Hadjena showed the latest thoughts for the plug removal equipment on the Backward end. The Plug is mounted on cam followers, and is driven by a lead screw. Outside the SOB, the rails are supported on structural tubing which are mounted to the front face of the Raft Piers. This portion of track is remove-able, so it can be pulled away from the beamline (transverse motion) during operation, allowing clearance for expected relative motion between the Raft and the Detector in an earthquake. The supports for the move-able rails are curved to fit around the flared portion of the Q2/4/5 Raft. These supports will most likely hold the out-board end of the fixed piece of track, to structurally isolate it from the SOB.

To remove the Plug, the remove-able rails are swung or slid into place. The plug and SOB shield cylinder are then pulled back until the entire cylinder is clear of the SOB. At this point it overhangs the front one-third of Q5. (It was not clear if the cylinder would interfere with services near the front of Q5, but Scott Debarger is looking into this ).

The shield cylinder is disconnected from the plug and removed. Finally, the plug is withdrawn to the end of its stroke, and pulled away with the crane. The lead screw is automatically disengaged as the plug is removed.

While this process is fairly automated, there was concern that it could still take quite some time to remove the plug to gain access to the face of the Drift Chamber.

Q2/4/5 Raft Base Piers

Martin Nordby presented layouts for the Forward and Backward Piers for the IR-2 hall. The Forward Pier replaces the A-Frame base for the Q2/4/5 Raft, which included a post through the foot of the Forward IFR Doors. The Pier includes a cantilevered section which reaches off the front of the pier to support the in-board mount for the Q2/4/5 Raft.

The Forward Pier also includes two access-ways cut through it. One is a walkway, while one is for existing cable trays, which run along the wall under the tunnel mouth. Both piers provide support for all machine components in the IR-2 hall, and support overhead cable trays which are extensions to those in the tunnel. These reach in to the in-board face of Q5, then turn down, to pick up machine cables coming from Q2 and Q4.

There was considerable discussion about the location of these cable trays, since they may impede access to the inside of the SOB on the back side, and could reduce the working volume for the Forward Calorimeter removal fixtures on the Forward end. Martin will look at re-locating the trays to gain back access, while still providing safe routing for the air-cooled D.C. magnet cables.

Regarding impact on the F-Cal removal equipment, Jim Krebs will look into this.

BaBar Platforms and Walkways

Jim Krebs showed the latest thinking regarding the platforms, racks, and walkways surrounding BaBar. There will be two platforms for equipment and racks, 3/4 up each side of the detector, between the doors. These will be accessed by stairs which descend to walkways on either side of the detector, 6 risers off the floor, and running the length of the IR hall. The east walkway ties into platforms coming out of each tunnel, with stairs dropping down to the floor located where the shielding wall keys into the wall of the building. Since both the detector and the shielding wall move during an earthquake, there is ample clearance between them and fixed objects.

The main cable tray run starts at the west-side platform, crosses over the top of the detector, down to the east platform, then down to the ground. It then exits through the shielding wall. The secondary cable run begins at the base of the North Pier (Backward end), and runs across the floor to another penetration in the shielding wall. These cable trays contain Drift Chamber cables coming out of the Q2/4/5 Raft.

Floor space is very limited, but there must be room available to store the Q2 Plug removal, as well as F-Cal removal gantry. Jim will work on putting all this in.

Phase I HER Beampipe

Martin Nordby presented a first-pass for a mechanical design of the interaction region for HER commissioning. The intent of this design is to substantially reproduce the expected backgrounds to gain a first-look at this before full HER/LER commissioning. However, this must be done "on the cheap," since time and money are in short supply. To do this, Martin, Mike Sullivan, and Tom Mattison have put together a beamline which uses as many standard HER straight-section components as possible. The region starts at the Q4 Chamber, and includes two borrowed (rented?) gate valves from the LER, two standard straight-section quad chambers with BPM's, and a standard Pump Tee, modified to include a S.R. mask. At either end of the region, custom transition chambers will make the shape change from octagonal Q4 Chamber to 3.5 inch I.D. round chamber. Finally, an aluminum chamber will bridge the (X,Y,Z) = (0,0,0) region. This is 0.125 inch thick, with copper cooling channels epoxied on to the outside.

There was discussion about how well the geometry simulated the expected backgrounds. While the S.R. mask produced the expected S.R. backgrounds, there were not comparable surfaces near the "I.P." to produce the expected lost-particle backgrounds. This had been partially addressed by kinking the beamline near (0,0,0), but it looks like adding more of a kink would help this.

Next Steps:

--Add more kink to the beamline at z = +0.5 m (Martin Nordby, Mike Sullivan).

--Look into adding a bump across from the S.R. mask at z = -1.0 m (Martin Nordby, Tom Mattison).

--Put cooling tubes off the horizontal plane for all chambers (Martin Nordby).

--Run Monte Carlo simulation to look at effects of above changes (David Kirkby?).

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