The conference was primarily focused on the question of
using the
SLC to support a photon collider testbed. Such
a testbed would allow
all issues in achieving integrated luminosity, except
the high power
laser, to be demonstrated in a manner identical to what
would be
done at the NLC.
The laser and optics required for the test have been designed
at
the conceptual level. The only remaining issues
is the technical
details of how the laser and accelerator would be synchronized
at
the picosecond level.
Revival of the SLC has no showstoppers and is mainly a
question
of resources. It is somewhat hard to predict the
exact amount since
it is expected that problems will be uncovered during
recommissioning
that are unforeseen. Additionally there is a question
of how much
cannibalism of SLC systems will go on between now and
when a
decision is made to restart.
The SLD has been shut down but all cooling water and gas
flow
remains active. The liquid argon calorimeter is
still cold and full
of argon. The systems could be brought back on-line
but most of
the experts have gone on to other things and much of
the accumulated
expertise is gone. Marty estimates that reviving
the SLD would require
10's of full time people. Alternatives, to using
the full SLD were
considered. The luminosity monitors could be taken
as is and the front-end
electronics and readout system replaced. The space
around the IP
where the SVX used to sit could be replaced with a new
instrument package.
The SLD itself could be rolled out of the way leaving
the bare beam
pipe accessible. This would improve access to the
optics and
probably be helpful during the testing of the photon
collider optics but
would necessitate the addition of shielding and the construction
of
supports for the beamline components.
There was general consensus that such a test facility
would be an
important step on the road to a full photon collider
experiment at a
future LC. Currently, the community sees scenarios
in which a
photon collider would be an indispensible part of a future
physics
program. On the other hand, there are probably
scenarios in which
even if such a facility were available the luminosity
would be sent
to the e+e- experiments. Given this uncertainty
the community
would like the option for a photon collider to be retained.
This will
necessitate the inclusion of some accelerator options
like e-e- running
into the baseline. The decision to include these
options will probably
be made by the International Design Group as part of
the international
management structure. In the immediate future the
photon collider
working group should probably assist the Study on LHC/LC
Complementarity to clarify under what conditions the
community
would decide to devote luminosity to a photon collider
experiment.
A number of alternate scenarios for a photon collider
experiment
were discussed. If the Higgs were discovered a
dedicated low
energy photon collider Higgs factory could be constructed
with
significant cost savings if low emmittance polarized
rf guns could
be used. That would save the cost of damping rings
and a positron
source. Additionally, this scenario might be used
as part of a
staged turn-on of a future LC. The SLC might also
be turned into
a full fledged physics experiment. There are a
number of Standard
Model and Beyond Standard Model analyses that could be
done.
A baseline design and a suite of simulation tools will
be presented
at the photon2003 conference. If there is sufficient
interest this might
justify an SLC based photon collider facility on its
own merits.
The letter of intent for the photon collider test facility
is well advanced
and is intended to be submitted for the april 2003 EPAC
meeting.
The section on measuring photon collider luminosity will
be updated
to include background calculations and more detailed
scenarios
for the detector options will be included. Given
the current budget
situation at SLAC it will be difficult to fund this out
of the operating
budget. International participation would greatly
improve the
chances of this facility being approved.
Work will continue at LLNL on the high average power laser
and
the design of the optics to format it to match the NLC
bunch
structure. The opto-mechanical issues involved
with the
design of the beam pipe are mature and will not receive
further
attention until a test facility is approved.
For further details please see the relevent talks on the
website.