sPHENIX MAPS tracker discussion

[Anthony Frawley <afrawley AT fsu.edu>]

Hi All,

Given that the MVTX/INTT will evidently not provide us with good enough extrapolation precision anyway, and since extending the Z coverage of the ladders sounds very hard, it makes sense to me to put the outer INTT layer at a radius that gives us full eta coverage. By this I mean that the outermost outer sub-layer should cover at least eta = 1 at Z = 10 cm.

Regarding the space charge distortion calibration, it seems to me that there are two options. They are not mutually exclusive.

1) Add a detector outside of the TPC that could be used to calibrate space charge distortion corrections. Even with such a detector, it may not be feasible to measure the track momentum well enough to interpolate precisely to each readout layer of the TPC. So the space points from such a detector would be used as part of an iterative correction/track fitting procedure aimed at a self-consistent track fit with a good chisquare (see 2.b below). The required acceptance and performance of the additional detector would need to be established from simulations that properly include space charge distortions.

2) Work on investigating algorithms that would combine:

a) The TPC position at or near the neutral point for space charge distortions in combination with the MVTX/INTT positions. This would improve the constraints on the trajectory over MVTX/INTT alone.

b) Iterative correction/tracking that uses information from simulations about the form of the space charge distortion, to correct the distortions to obtain a self-consistent track fit with a good chisquare. We would have to demonstrate that the procedure gave a unique set of track parameters, and gave adequate momentum resolution.

Cheers

Tony

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From: sPHENIX-MAPS-l <sphenix-maps-l-bounces AT lists.bnl.gov> on behalf of nouicer <rachid.nouicer AT bnl.gov>
Sent: Monday, October 29, 2018 10:07 PM
To: Mickey Chiu; sPHENIX-MVTX; sphenix-intt-l AT lists.bnl.gov; Sanghoon.Lim AT Colorado.EDU; Molly Taylor; sPHENIX-MVTX; Todoroki, Takahito; Christof Roland
Subject: [Sphenix-maps-l] Magic radii for INTT layers

 

Dear Mickey and Christof, 
 
> layer 2: 15.1183 and 15.6 
 
Right now, it will not fit. It requires some engineer work redesigns of the INTT mechanical supports.

See the attached file. 
Right now, the INTT maximum outer radials are 145.28/150.49 (mm)  corresponding to pseudorapidity 0.82/0.79. 

As I said before, more INTT outer radial increase, the acceptance in pseudorapidity will decrease dramatically. This implies that part of the TPC acceptance will not be covered by the INTT acceptance. 

I hope these inputs in the attached file will help.

Sincerely, 
Rachid  

On 10/27/2018 02:37 PM, Mickey Chiu wrote:

Hi Christof,

Yes, it seems this would fit.  But as Rachid mentioned, it will have a reduced eta acceptance.  It doesn’t seem easily possible to extend the active area by increasing the pitch in z of the strips since the half-ladder size is limited by the size of the wafer, not to mention the additional cost of a new mask.  At the moment the endcaps of the INTT are not designed, but they’re expected to be contain a substantial amount of material, and this part might be in edges of the acceptance, at eta ~ 1.0-1.1 .

Mickey

On Oct 26, 2018, at 9:21 AM, Christof Roland <christof.roland AT cern.ch> wrote:

Hi Mickey, 

I tested a INTT configuration with 2 layers, both with rphi resolution, i.e type 1 in Tony's nomenclature

with radii of:

layer 1: 12.676  and 13.179

layer 2: 15.1183 and 15.6

This gives the best performance for the extrapolation precision to the TPC I have seen so far. 

Would a configuration with layer positions in this ballpark be mechanically feasible?

If yes we will do more detailled studies with this setup file. 

Thanks for your input

Cheers

   Christof 

 

On 18. Oct 2018, at 16:39, Mickey Chiu <chiu AT bnl.gov> wrote:

Hi Tony,

After talking to Rachid yesterday, I was about to send out exactly something like this.  I think this is useful because we’ll actually simulate positions that are close to final, rather than choosing a random radius.  

My only comment would be that you do need to have some sort of support structure to hold the detector in place, as well as install it.  Right now our solution is a rail system, and the outer limit available for the INTT is 15.7 cm.  Thus, within the current design limitations, the outermost layer would be

   type 0  - 15.0846

   type 1 -  15.1183

According to what I see, we should be able to push out the rails by 0.5 cm (Dan Cacace disagrees a little).  So if we can push out the rails by 0.5 cm, you can pick the next step out in the radial location.

Mickey

On Oct 17, 2018, at 5:32 PM, Anthony Frawley <afrawley AT fsu.edu> wrote:

Hi All,

I made a little macro to estimate the best sensor radius to use in the tracking macro to get close packing of the ladders. It prints this out as a function of the number of ladders in a layer. If you want to play with it, the macro is at:

/sphenix/user/frawley/macros_newTPC_june6/macros/macros/g4simulations/calculate_optimum_ladder_radii.C

The output is as follows, where I have indicated the  number of ladders presently used for the default configuration with an arrow. The number in parenthesis after the arrow is the radius presently used for the default configuration in the tracking macro. The radii from my macro are within about 0.02 cm for those cases.

Ladder type 0 ladder_rphi 2.55 clearance rphi 0.0365
      nladders 17 sensor_radius 6.85152          <==== (macro: 6.876)
      nladders 18 sensor_radius 7.26318
      nladders 19 sensor_radius 7.67483
      nladders 20 sensor_radius 8.08649
      nladders 21 sensor_radius 8.49814
      nladders 22 sensor_radius 8.90979
      nladders 23 sensor_radius 9.32145
      nladders 24 sensor_radius 9.7331
      nladders 25 sensor_radius 10.1448
      nladders 26 sensor_radius 10.5564
      nladders 27 sensor_radius 10.9681
      nladders 28 sensor_radius 11.3797
      nladders 29 sensor_radius 11.7914
      nladders 30 sensor_radius 12.203
      nladders 31 sensor_radius 12.6147
      nladders 32 sensor_radius 13.0263
      nladders 33 sensor_radius 13.438
      nladders 34 sensor_radius 13.8496
      nladders 35 sensor_radius 14.2613
      nladders 36 sensor_radius 14.673
      nladders 37 sensor_radius 15.0846
      nladders 38 sensor_radius 15.4963
      nladders 39 sensor_radius 15.9079
      nladders 40 sensor_radius 16.3196
      nladders 41 sensor_radius 16.7312
      nladders 42 sensor_radius 17.1429
 Ladder type 1 ladder_rphi 3.8 clearance rphi 0.0365
      nladders 11 sensor_radius 6.56998
      nladders 12 sensor_radius 7.18058
      nladders 13 sensor_radius 7.79117
      nladders 14 sensor_radius 8.40177
      nladders 15 sensor_radius 9.01237       <======= (macro: 8.987)
      nladders 16 sensor_radius 9.62297
      nladders 17 sensor_radius 10.2336
      nladders 18 sensor_radius 10.8442       <======= (macro: 10.835)
      nladders 19 sensor_radius 11.4548
      nladders 20 sensor_radius 12.0654
      nladders 21 sensor_radius 12.676         <======= (macro: 12.676)
      nladders 22 sensor_radius 13.2866
      nladders 23 sensor_radius 13.8972
      nladders 24 sensor_radius 14.5078
      nladders 25 sensor_radius 15.1183
      nladders 26 sensor_radius 15.7289
      nladders 27 sensor_radius 16.3395
      nladders 28 sensor_radius 16.9501
      nladders 29 sensor_radius 17.5607
      nladders 30 sensor_radius 18.1713
      nladders 31 sensor_radius 18.7819
      nladders 32 sensor_radius 19.3925

Note that these are the radii that should be used for the inner sublayer of an overlapping pair of sublayers. The second overlapping layer should have the same number of ladders, and a radius larger by about 0.6 to 0.5 cm (decreasing a little as the layer radii increase).

Cheers

Tony

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                                               /                        /
 Rachid Nouicer                               /                        /
 Physicist, Brookhaven National Laboratory   /                        /
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