MINUTES of ATLAS week LVL1 trigger meeting
==========================================
Salle Dirac, 40-S2-D01
Monday 13 September, 11:00-13:00


Agenda
======
- Rack layout in USA15.
- Proposed improvements in the barrel muon trigger design.
- Plans for tests of radiation tolerance of muon trigger electronics.


Minutes
=======

Rack Layout in USA15
--------------------
Murrough Landon introduced the topic showing drawings for the
proposed use of racks in USA15 Niveau 2. He proposed that the
calorimeter trigger should use Niveau 2 where a long row of
contiguous racks was available. This implied that the muon trigger,
CTP and TTC electronics would be on Niveau 1. There were no objections
to this proposal. It was asked if it would be possible to have the
larger holes (for cables between the cavern and USA15) 
on Niveau 2 rather than Niveau 1. Murrough agreed to follow up on this.

It was noted that the Technical Coordination group had been very
helpful in arranging modifications to the rack layout in USA15 to 
satisfy the requirements of the LVL1 trigger.

The following action items were identified:
- Nick, Philippe, Emilio/Stefano should discuss with Marzio about
  how/where/if to sum the signals from the PMs for the back sampling
  of the Tile calorimeter. These signals are needed to validate muon
  candidates in case of high "100 MeV" background conditions.
- Murrough to follow up with Mark Hatch concerning the possibility
  to have the larger (400 mm diameter) holes on Niveau 2 and also
  to check the cable lengths.
- Murrough to follow up concerning the cables for the Tile calorimeter;
  Nick to check with Eric Eisenhander to identify the appropriate
  contact person on this.
- Osamu (for the muon endcap trigger) to prepare:
  - a proposal for the use of rack space in USA15;
  - an estimate of the number and cross-section of cables from
    the cavern to USA15;
  - check the latency calculation with realistic cable paths.
- Emilio/Stefano (for the muon barrel trigger) to prepare the same
  information as above.
- Philippe et al (for the MUCTPI, CTP and TTC) to prepare the same
  information as above.
- Murrough (for the calorimeter trigger) to provide the same
  information as above (some of this already done).
- Nick to arrange video meeting on a timescale of about 1 month
  to follow up on the above points. It was suggested to hold this
  meeting shortly before the discussion with the LHCC referees
  which is scheduled for 19 October in the morning (regular progress
  review of LVL1 trigger).

Proposed improvements in the barrel muon trigger design
-------------------------------------------------------
Stefano Veneziano presented a number of proposed improvements to the 
design of the barrel muon trigger:
- Move the "pivot plane" to BM2.
- Optimization of the strip pitches in the RPCs.
- Choice between 90% versus 95% windows definition.
- New (larger) coincidence matrix size.
- Hardware modifications on PADs and CMA
- Integration of special chambers.

The optimization of the strip pitches is needed to avoid needing too 
big coincidence matrices in certain regions. With the revised scheme,
using a larger coincidence matrix size than in the TDR design,
it may be possible to provide a threshold setting lower than 6 GeV
and/or to increase the efficiency at the quoted threshold from 
90% to 95%.

The special chambers are being added to the detector simulation
which will allow proper assessment of the trigger acceptance
as a function of eta.

The proposed changes are still under evaluation and a firm proposal
will be made once simulation studies have been completed. The Steering
Group will then be asked to approve the changes. The cost of the coincidence
matrix is not expected to rise due to the changes (the chosen device
--- 0.25 micron CMOS Fujitsu gate array --- is big enough), but there may
be some changes in the cost for the rest of the system. This needs to
be evaluated.

Plans for tests of radiation tolerance of muon trigger electronics
------------------------------------------------------------------
It was agreed that Emilio/Stefano should discuss with Philippe about
radiation tolerance evaluation. It should be possible to irradiate
the PLL and other critical elements of the logic soon. It is also
planned to test the radiation tolerance of the Parroli link.