Comments on Hall D civil day 2

[Elton Smith <elton@jlab.org>]

Dear collaborators,

The following issues came up during discussion yesterday at the civil
design review

1. We need to provide guidance for the length of the 10" pipe extending
beyond the walls and the flanges on either end of the beam pipe that
connects the tagger building and the collimator hut.
- Do we need more than 6" extending beyond the wall?
- What do we suggest for the type of flange?

2. EP104 - In the counting room layout space is added to accomodate the
UPS for the computers. Does the space in the racks include space for the
UPS's already? Are we double counting in the present layout?

3. In the list of power supplies there is a quadrupole in Hall D. What is
this needed for? Or... is this a mis-identified duplicate item for the
quadrupole upstream of the tagger magnet? (The tagger quadrupole is listed
separately).

4. We need to provide guidance for the rail types in Hall D. On how many
points are we supporting the weight of the downstream detectors down to
the rails? Are the rails embedded in the concrete?

5. We need to provide guidance on the hole penetration in the steel in the
photon beam dump so that the beam is dumped deep inside the steel.
- Given possible settlements of up to 2", I suggest a relatively large
size hole (e.g.  6" pipe) and design an insert at a later time when
precise positions are surveyed. This also provides flexibility for using a
composite material for beam dump proper.

Quick summary of the results of the value engineering (VE) workshop:
--------------------------------------------------------------
We also had the closeout of the value engineering workshop yesterday
afternoon (following the design review). The team provided numerous
suggestions which included both cost increases as well as savings. The
major savings, interestingly, were simply confirmations of suggestions
provided by JLab during the meetings.

There were two interesting "out-of-the-box" suggestions which were
offered:

1) put the counting house above Hall D. This would essentially save on the
cost of the counting house roof. The costs for the slab foundation for the
counting room would be used to construct a relatively thick roof/ceiling
radiation barrier between the new hall and counting room. Part of the
savings would also be used to install an elevator for handicap access to
the counting room. My opinion: it deserves some merit except for the fact
that it completely changes the design.

2) Mirror the Hall and truck ramp north/south, but leave the counting room
on the north. This places the beamline farther from the counting room, so
the open staging area between the roll-up door and the detector is also
between the detector and the counting house. The reason for this
suggestion is that the grade levels between north and south are different
by about 2 feet. This does not sound like much, but when translated into
the effort in stacking shielding and building retaining walls the impact
is significant. My opinion: The VE team did not have time to consider
impacts on our experiment and this is not a workable solution.  However
they did identify the difference in grade levels between north and south
and the significant impact it has on cost, so this may help in finding a
way of lowering the cost of the nominal design by taking this into
account.


Elton Smith
Jefferson Lab
elton@jlab.org
(757) 269-7625