1. Some input to the discussion for the design requirements of the GridPixel Tracker and L1thack trigger.
Here are some thoughts about possible detector layout which affect overall detector concept of the studies which we have to perform nearest future.
The first priority tasks I would split in 2 categories
The studies which we can perform with the existing TimePix set-up and which are clear now, such as:
Search and studies of the different gas mixtures
Text beam studies of the detector performance in different configurations with these mixtures in the magnetic filed.
……..
Another type of the activity is the work on the layout and on the detector module design which is indeed far away from to be clear now and which affects the work in all directions
Detector requirements and specifications.
This includes the detectors concept and requirements to its elements:
Physics and technological constrains on the detector performance.
Single Module design and limits/constrains coming from different type of technologies and electronics design.
And many issues
All this require a lot of conceptual and simulation work and we shell start discussions as soon as possible to make the plan how and what we want to address now and what we can leave for later stage. Even the choice of the priorities does not seem to be evident having in mind a present scale of our collaboration.

2. Introduction: Possible GridPixel Tracker layout
It is assumed that this detector will occupy the outer radii of the Inner Tracker and contains two layers interleaved with moderator or dense TR radiator h
Difficulties:
1. In the barrel region track angle very much depends on the angle
2. Lorentz displacement also changes the tack direction f

3. Possible GridPixel Tracker layout: turbine type

4. Possible GridPixel Tracker layout: turbine type
Basic Ideas:
Keep a reasonable projection angle of the track and its length on the pixel plane
Compensate a Lorenz Angle.
Maximize of the size of each module to minimize the dead areas, field distortion and allow effective inter chip communication.
angle optimization, size optimization, accuracy of Lorentz angle compensation….

5. Constrains on the module size.
Requirements:
The module area should be as large as geometry and parallax allow (depends also how well the L1 tack reconstruction algorithm can handle these issues.
Maximum area of the module (10 x 20 cm2 ?)
Allows to cover a reasonably large part of the aperture:
Minimizes of the dead areas
Minimizes the field distortions relative volume
Maximizes inter-chip processing communications
Minimizes simplifies of the number for service connections and simplifies design.
Allows significant overlap without increase of the material budget.
…….
Drawback:
Development of the post processing technique on the preassembled chip array
Do we have principal technological constrains on this approach apart of money issues?
Module
particle

6. Module constrains and questions to be answered-studied
Functionality:
Do we want to keep TR?
Track reconstruction: Pt> 1GeV?
L1 track trigger: Pt programmable but >10 GeV?
What are the requirements for the momentum accuracy at L1?
How the parallax and the Lorentz angle adjustment error is going to be treated?
Minimum pixel size?
Flexibility requirements (functional) ? ……
Gas requirements:
heavy (to maximize dE/dx),
fast,
low diffusion in the direction perpendicular to the magnetic filed,
minimum Lorentz angle
no ageing,
not aggressive
not electro negative
satisfying CERN safety requirements
3. Drift space
If we keep TR it should be at least ~16mm ( More BX overlapped)
Without TR other it can be <10 mm (higher drift velocity possible, almost 2 times less BXs overlap…) optimization still required.
Some other requirements/constrains/options???

7. Hot topics to follow up.
We shell define priorities as soon as possible (too many things to do).
We can keep TR and NO TR options a bit longer but it affects electronics design and at certain moment we shell choose.
We shell agree on the strategy how to maximize the size area of the module.
Which safety constrains on the gas components?
Other possible detector layouts?
Among many other things we desperately need detector simulation group. The detector and electronics concept depend on the results of the simulations
Shell we put as a goal an installation a sizable the detector prototype (almost production modules) with full or at least maximum functionality in the 2016 shutdown in the ID region and may be somewhere else? Do we agree on this?
How to acquire a more effectively working collaborators to the project?
Start preparation (talk to people, define the way, prepare proposal, find applications for the developments) to ask significant amount of money in EU funding
The list is not complete and please I would really ask all of you to put more questions to be answered to define priorities.

8. Test beam studies in 2011
Performance in a presence of a strong magnetic field
Objectives:
Studies of the gas mixtures
Performance studies with different gas gaps
Magnetic filed effects
TR studies in the magnetic field
B= 0 and B=1.5 T
Different gas options
Two drift spaces (16, ~10 (to be optimized)
Different angles to the magnetic filed.
Test of the Lorentz angle compensation B
L = 16 mm V0 V1
TR-Radiator
Beam
p, el
45o e-
Needs more detailed discussion of the test beam program.
Some MC simulations should be done in advance.

9. R&D summary Urgent (means NOW) feedback is required.
I must send it today!
VERY important if we want that ATLAS helps us!!!