September 30 Meeting Minutes
Discussion about the conclusions (or the executive summary) section of the
detector r&d document:
The big point here is that we need engineering prototypes to get
the costing and design understood. Feeling among group atendees that
the fine-grained calorimeters do not need to be tested in a neutrino beam
first, many of them say we know how these detectors act in a charged
particle beam. Specifically, the challenge for the fine-grained
calorimeter concept is to get the signal out in a cost-effective
way. For RPC's this means, how do you interconnect different planes
cheaply? Probably the biggest single plane you could make comfortably
is 2mx5m, so it's 40 of these that need to get strung together cheaply
for one 20mx20m plane. (recall that handling a 4'x8' piece of plywood isn't
so easy). For the scintillator option, this means, how large an extrusion
can you make that won't leak? How long can the fiber be where the light
isn't attenuated by too much?
There was significant discussion on whether or not a water/scintillator
detector could use the extrusions that are used for making docks--these
extrusions are 2cmx2cm or 2.5cmx2.5cm and can be made "as long as you want
them to be", for MINOS they were made 8m long. They have
walls less than 1mm thick.
They are probably too fat for an off-axis detector, but then the problem
with making a prototype is that it would cost 100k$ for a factory to set
up a die to make the right size extrusion. (So then you have a problem
with getting the initital prototype funded...even if the final design
wouldn't be very expensive to implement).
Liquid argon TPC For this detector,
the engineering for small and 600ton units
is all done, what's really needed there is publications with physics
results--does this really see neutrinos as well as the monte carlo
says it does? Of course getting from 10m to 50m wires is important,
but again it's not the biggest unknown compared to just proving the
concept with a physics publication. There is good synergy with the
need for near detector physics measurements...
For any proposed detector, we should have in this r&d document a
set of technical benchmarks that should be reached before a large
detector is built. Ken Heller volunteered to write that list of
benchmarks (i.e. roadmap?) for liquid scintillator/water.
Editorial comment: I don't think we should discount the cosmic ray
studies, we really have to convince ourselves that these detectors
work on the surface and don't have higher levels of background than
we predict. Once we had cosmic ray studies for one type of fine-grained
calorimeter, for example, it might be possible to then extrapolate to
what the cosmic rays were like for other detectors...but I don't think
we're there yet.
Last modified: Mon Sep 30 17:10:13 CDT 2002