Sti Geometry outside the TPC
Updated on Thu, 2016-02-04 11:47. Originally created by jwebb on 2016-01-07 17:28.
1) Is the outer field cage implemented in the Sti geometry model? Yes.
Few notes. Sensitive layer in the BTOF is the gas. Inclined sensors in BTOF may require division of the volume ala the pixel detector, in order to place them in different layers.
TOF trays are under the path
The (red) support structure BUND, its daughters are all aluminum.
The cross section isn't too uniform. 2-3x more material closer to the edge. But also closer to the active detectors. So let's just approximate this by uniformly spreading the mass out over the mother volume.
Except for the water pipe (negligible) it is all Al.
Start with TOF proper...
Volume = BRMD
Mass = 0.367702 [kg]
BRMD is not much in the way of mass.... well, except that we have ~30 of these suckers, so no... we cannot neglect the mass.
... so strategy here is to mix glass, supports and gas together for the sensitive volume. Maybe leave the front face on...
General Strategy for Representing the BTOF to Sti
We should keep in mind the use case here: improve projection of tracks to the active layers of the BTOF by using Sti to propagate tracks and store the track parameters (helix) at an appropriate position.
I would suggest that putting the detectors *themselves* into the model is not needed. We should be able to get good track propagation if we account for all of the material which is *in front of* the detectors.
This will significantly reduce the
Next would be the GMT detector...
Basically, the yellow box is hollow, and contains the GEM foils near the back. The bottom of the yellow box is 0.95mm of Al. Quite likely to be negligible.
So... here is the general layout of the BTOF detector... zoomed in on the top module. Shows (what I assume to be) the cable tray inside the radius of the detector.
Plot of number of radiation lengths vs phi (y-axis) and eta (x-axis) for the BTOF geometry. Left plot shows the full BTOF geometry, right plot shows the material budget for r < 210cm.
Next, plot radiation length in everything *except* the BRMD, BRM1 and GMTS volumes... i.e. taking out the material associated with active detectors, leaving support structures only.
3) Is there anything for the BEMC? No.
4) Action item from the 02/01/2016 OFFSOFT meeting: is there anything between BTOF trays and TPC outer field cage?
Plot below zooms in on the region of the TOFC and BTOF. The gap between TOHA (part of the outer field cage) and BTRA (the BTOF tray) is empty.
$ grep -i TOFC StRoot/StiTpc/*
StRoot/StiTpc/StiTpcDetectorBuilder.cxx: // {"TOFC","outer field cage - fill it with insulating gas already","HALL_1/CAVE_1/TPCE_1/TOFC_1/*","",""},
StRoot/StiTpc/StiTpcDetectorBuilder.cxx: {"TOFC","Inner Field Cage","HALL_1/CAVE_1/TPCE_1/TOFC_1","",""},
StRoot/StiTpc/StiTpcDetectorBuilder.cxx: {"TOFC","Inner Field Cage","HALL_1/CAVE_1/TpcRefSys_1/TPCE_1/TOFC_1","",""},
2) Is the GMT implemented in the BTOF geometry? Yes.Few notes. Sensitive layer in the BTOF is the gas. Inclined sensors in BTOF may require division of the volume ala the pixel detector, in order to place them in different layers.
TOF trays are under the path
BTOF_1/BTOH_1/BSEC_*/BTRA_1 BTOF_1/BTOH_1/BSE1_*/BTR1_1 BTOF_1/BTO1_2/BSEC_*/BTRA_1 BTOF_1/BTO1_2/BSE1_*/BTR1_1
Under BTRA and BTR1 we have BUND, a support structure, and BXTR (standard tray) and BXT1 (tray with GMT). Left shows the BTRA with the BUND structure visible. Center shows BUND hidden. Right shows with GMT.
The (red) support structure BUND, its daughters are all aluminum.
The cross section isn't too uniform. 2-3x more material closer to the edge. But also closer to the active detectors. So let's just approximate this by uniformly spreading the mass out over the mother volume.
Except for the water pipe (negligible) it is all Al.
Box with half widths:
dX = 1.01500
dY = 10.79500
dZ = 107.95000
Material is aluminum:
A=26.98 Z=13 rho=2.7 radlen=8.8751 intlen=38.8622
If we spread the mass out uniformly we get:
mass = 6.212914 [kg] / 9.462400E+3 [cm]^3
= 6.212914 [g] / 9.462400 [cm]^3
rho = 0.6565896601 [g]/[cm]^3
Alternatively, could preserve the denisiy and reduce dX -> 0.24683cm.
NOTE: There is a water pipe (green) which runs down the center. It accounts for 0.15 kg of the mass above. Propose to ignore.
Also, it looks like the BTOF trays are wrapped in an Al box, which presents ~1.9cm of material before (and after) the detectors.. and very thin sides which can be ignored. So we can simplify this to two planes, one before and one after the detectors, of (approx) 2.5cm and 1.9 cm of Al. Then we need to figure out how to represent the RPC detectors and GMT themselves...Start with TOF proper...
Volume = BRMD
Mass = 0.367702 [kg]
BRMD is not much in the way of mass.... well, except that we have ~30 of these suckers, so no... we cannot neglect the mass.
... so strategy here is to mix glass, supports and gas together for the sensitive volume. Maybe leave the front face on...
General Strategy for Representing the BTOF to Sti
We should keep in mind the use case here: improve projection of tracks to the active layers of the BTOF by using Sti to propagate tracks and store the track parameters (helix) at an appropriate position.
I would suggest that putting the detectors *themselves* into the model is not needed. We should be able to get good track propagation if we account for all of the material which is *in front of* the detectors.
This will significantly reduce the
Next would be the GMT detector...
Basically, the yellow box is hollow, and contains the GEM foils near the back. The bottom of the yellow box is 0.95mm of Al. Quite likely to be negligible.
So... here is the general layout of the BTOF detector... zoomed in on the top module. Shows (what I assume to be) the cable tray inside the radius of the detector.
Plot of number of radiation lengths vs phi (y-axis) and eta (x-axis) for the BTOF geometry. Left plot shows the full BTOF geometry, right plot shows the material budget for r < 210cm.
Next, plot radiation length in everything *except* the BRMD, BRM1 and GMTS volumes... i.e. taking out the material associated with active detectors, leaving support structures only.
3) Is there anything for the BEMC? No.
4) Action item from the 02/01/2016 OFFSOFT meeting: is there anything between BTOF trays and TPC outer field cage?
Plot below zooms in on the region of the TOFC and BTOF. The gap between TOHA (part of the outer field cage) and BTRA (the BTOF tray) is empty.
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