MDI meeting minutes


1. Surface assembly - presented by Andrei

About the shaft: Norbert thinks that additional
shaft is needed for servicing. The current thinking
is that there is only one big shaft per experiment
which contains elevators, stairs, and pipes.
CFS people thinks this is technically possible.

Surface assembly building: CMS is 23m by 140m when
it is the longest. The capacity of the crane depends
on the assembly scheme (pure-CMS or modified-CMS).
The modified CMS scheme (GLD case) is 400t. Plus
smaller cranes.

IR hall: CMS hall is 32(W)x72(L)x35(H). The lagest
among three concepts is GLD's 25x55x35. So far, we
may be able to maneuver for assembly inside this
volume (more study needed).

E-hut: Where should it be? De we need an alcove?
How big is it? It should probably fit in the shaft
so that it can be lowered as a whole (when the
detector assembly is mostly completed). The control
room should be on surface. It also depends on
push-pull or not where E-hut may have to move
together with the detector. E-hut volume is
probably dominated by power-supplies - may not
be much smaller than in the past.

Gas system, cooling, etc. should be doubled between
the surface and below? CMS experience is optimistic-
not much more cost.

Andrei suggested that the CMS-style and modified CMS
style assembly are sent to CFS for costing. The real
costing should be possible after decision on 1IR
vs 2IR, merging of detector concepts. Phil
expressed concern that things are proceeding to
details too fast. Andrei points out that for the
CCR, costing is needed. Shall we ask each concept
to work out pure and modified CMS assembly? It
would take too much time and effort. For now,
we will go ahead with costing of two schemes for
GLD case. However, we should keep in mind that
the comparison of the two schemes depends on
concepts and sites.

Cost optimization: One way to proceed may be to
get paramerized costings of the exp. hall and
cranes etc. and we (detector people) will do the
design optimization. However, this has been tried
recently, but CFS people prefers to do the costing

Tom read Witold's comments: Witold asked CMS
people, and their feeling now is overwhelmingly
for surface assembly. Underground assembly
is much more stressful then on surface. Space,
access, and safety issues (ventillation). 50%
more time underground. Disconnecting and
re-connecting at patch panels were not a problem.
Why then CMS is not much ahead of ATLAS?
1. ATLAS got the priority due to its scheduleing.
2. CMS site had worse ground condition.

The CCR text was checked. It does not specify
the details of surface assembly (CMS or modified
CMS). It looks fine. The purpose of CCR is
mainly schedule, not cost saving. This is class-1.

Details are still to be worked out. The MDI panel
is comfortable with the idea of surface assembly.

2. Low-P option - presented by Wolfgang

Low-P option reduces number of bunch by 1/2,
squeeze bunches to recover the luminosity.
This increases beam background, and beam energy
bias due to beamstrahlung. Energy bias will be
about x3 larger. This will affect precision
measurements of top mass, Higgs mass etc. Nearly
all background (pair or not) will increase by
x2 or more. Thus, when the background is a
limiting factor, it could also reduce usable
luminosity. The most vulnerable detector element
is the vertex detector whose design limit of
occupancy is exceeded by the Low-P option.
(even though the limit is not a sharp line)

On the 1/2 luminosity option: MDI panel agrees
that 1/2 luminosity option is essentially different
from the 14mradx2 option or even the push-pull
option, in that it will fundamentally reduces the
physics capability of the machine. The discussion
should be done within WWS.

3. Leakage fields - presented by Sugimoto

Sugimoto-san showed compensation coil scheme
of controlling leakage field. The requirement
from beam optics is less than 50 gauss at 10m
from IP. With two compensating coils per side
at 10m from IP and at the hall wall, it is
shown that GLD yoke size can be reduced
substantially (~4000t of iron).
For the pure CMS style assembly,
there is 15cm gap between the large rings.
This could cause leakage of radiation.
Can it be engineered so that there is not
such large gaps? For that matter, there is
no such design for the modified CMS style

4. reports- Yamamoto

HY reported that we may be asked to write the
MDI section of DCR. Wolfgang will contact Ties
about how to proceed. Also, the MDI panel will
be working with the local MDI conveners of the
Beijing workshop. The local contact is Gao Ji.