Comments on Beam Monitoring System Review
                            Dec 10, 2001

                    from Jim Hylen
                        ------------------------

1. Overall Remarks -

   Four major advances have taken place in the last year.
The PIC technology has been selected, prototype PIC chambers
have been built and tested, measurements have
been made of where saturation sets in, and the SWIC electronics
has been understood.

The PIC technology appears very robust (eliminating such
features of the LIC design as using rad-soft materials and having
the detector wall also serve as the pressure vessel wall).  It appears
to be a good choice for both the muon and hadron monitors.

The latest round of beam tests demonstrates that the chamber response
is linear with intensity for the muon monitors, and for
the hadron monitors for normal beam running, and for
target-out running at low intensity.  The hadron monitor response
would enter the saturation region in a target-out full beam intensity
situation, but such a run is not required for the physics.

The roles of the two monitoring systems seems reasonably laid out.

The goal for the muon monitor system of 1% stability is explicit,
and that stability was demonstrated for a single channel over a
modest time period, as well as a calibration scheme to track it.
Pad to pad variation was presented as 2%, with no scheme to
absolutely calibrate it presented.  The role presented does not require
absolute calibration, just stability, so this looks fine.

For the hadron monitor system, the system requirement was
stated in terms of a position measurement.  This was not translated
into a requirement on chamber response calibration, but is presumably
much looser than the 1% desired for the muon chamber, and is
on an absolute calibration pad to pad rather than a stability requirement.
The probable pad variation in response from construction variations
was presented as about 5% for the hadron monitor.  No scheme to
calibrate the hadron monitor pads was presented.

The most serious R&D issue remaining is to measure
the hadron chamber response to neutrons, and a test is planned.

My opinion is that the PIC design for muon monitoring is ready
to proceed to engineering design.  The hadron monitor requires
some more work to sharpen up the requirements and match them
to a calibration (or just QA?) scheme.



2. Itemized suggestions, questions and concerns

(1) In the tests done so far, the chamber center was in the beam
but the readout wires were outside the beam spot.  In actual
operation, the readout wire routing will be in the beam, so it
would be interesting to see what signal the beam might induce
on that wire and whether mitigation would be needed.

(2) The dynamic range issue needs to be clarified.  The current
document shows (1) a factor of 40 eaten up by variation between pads,
which may not leave enough room for variation in running conditions,
and (2) pads which would fall below Albert's specification of 10 pC mininum
for low intensity running.  (I believe all is fixable, just not integrated
yet).

(3) I would like to see the hadron monitors be replaceable.  I suggest
the cost-effective way to do that is to have a few small-profile rows
sitting in trays or racks, where a single row
could separately be extracted out the side into a small coffin.

(4) A calculation of how hot a hadron monitor pad gets from
beam heating with gas convection to the surrounding box then gas
convection to the (100def F?) surrounding air should be done -
not to great accuracy, but to get order of magnitude.  It is not
obvious that gas temperature will not affect chamber response
in DC running.  This would not affect the primary role of the chamber
for commissioning.

(5) As discussed in the general comments, a propagation of
specification of position accuracy to chamber response calibration
should be incorporated in the hadron monitor specification document.
I think this is needed before the calibration requirement can be
understood for the hadron monitor.