Status of Bartoszek Engineering’s effort on the Homestake proposal L. Bartoszek BARTOSZEK ENGINEERING 10/12/07
Summary • I have worked on this proposal since February of ’07 • To date, I have put in few hours, but my subcontractors have developed a very preliminary conceptual model of PMT support in the cavern • This talk summarizes what has happened and some concerns for the future
The charge: • BE’s original charge was to come up with a conceptual design of supports for PMTs in the cavern and a cable handling scheme • Most of the criteria came from Ken Lande • The main criteria was that any PMT be removable by a person standing at the top of the tank (in air) • No diving or draining of water was allowed
What we discovered • The mid-range CAD modelers that my subs and I are using are having real trouble handling solid models with hundreds of thousands of parts. • Modeling is only the first hurdle. • Making rendered images of the model is extremely taxing and challenging to the PCs we are using.
The concept • Ken suggested the segmentation of the PMTs into columns of 4 PMTs attached to panels • The panels are mounted on linear bearing rails (cheap ones), that allow the panels to be hoisted up. • Once the top panel is removed, the next is hoisted up until any panel can be accessed • This scheme is intended for the cylindrical walls • We do not have a working concept for the bottom PMTS • Top layer PMTs accessed through the top truss
View of wall panel from inside the cavern View of wall panel from the veto region
Close-up of back side of panel showing PMT support and panel guides Very conceptual bearing guides MiniBooNE style wire frames for PMT support
Conceptual design of the assembly of PMTs into panels Not all of the fastening details are worked out
The cavern showing a person for scale The top layer is turned off for clarity. The rails are shown for panel motion. This picture motivates the need for a different cavern design with a ledge at the top
Cutaway of cavern showing the liner and the PMTs mounted on the wall Top and bottom layers not shown
Close-up of rails, panels and the “clothes-line” movement system Cables are not shown. Cables are a really tough problem.
Cable issues • I have a sample of SNO cables from Ken • They are very stiff. It is doubtful they could be bent in the radius of curvature necessary to loop behind the PMT wall and allow the panels to be lifted easily • The location of connectors is a big deal • Ken has looked at the space required because of the cross-section of cables. I never got to the point of modeling the area of the cables. • I do not have a realistic cable handling scheme
Here is a cross-section of Super-K I do not know exactly how Super-K routes cables, but I do know that they do not require any PMT to be removable without draining. PMTs cannot move along the walls. Keeping the length of the cables for every PMT the same leads to enormous amounts of cable that have to be stored somewhere. I am not sure how Super-K does this.
SNO does not seem to be a useful model for cable routing because they have a lot more room around the sphere than we have in the veto region behind the PMT panels. PMTs are also not designed to be removable in SNO. I’ve been to SNO and the cleanliness of the experiment is truly mind boggling. I don’t think Super-K is held to the same cleanliness requirements. Is Homestake?
My concerns • The requirement to replace any PMT causes very tough problems with cables • The part count is much higher in a replacement scenario than in a non-replacement scenario • This means costs are much higher • How much higher? I don’t know. Lots higher. • Can we relax the requirement, or explore remote handling options with submersible ROVs (for example)?
The future • This experiment needs a solid engineering team to tackle the many challenges • The CAD problem is very challenging • For the immediate future (through 2008) I am completely swamped with work • I do not know if my work load is compatible with the Homestake schedule • I want to contribute, I am just trying to be realistic and honest.