DOI: 10.5281/zenodo.17180302
title: Smartpixels co-design datasets

description: The response of pixelated silicon sensors to incident charged particles (pions) was simulated using kinematic properties derived from fitted CMS Run‑2 tracks. Silvaco/Synopsis TCAD and a time-sliced version of PixelAV were used to simulate the initial electron-hole pairs produced in the active material of the pixel detector and subsequently calculate the induced signals. The pixel detector is taken to be a 21x13 array of pixels situated along a barrel layer (radius=30 mm) that is parallel to the beamline and centered around the interaction point. The detector is immersed in a 3.8T magnetic field parallel to the sensor X coordinate. Multiple sensor geometries, with varying pixel X-pitch, Y-pitch, and thickness (along Z), were studied in the smartpixels co-design program. Endcap sensor modules of the CMS detector that are perpendicular to the beamline and at around 250 mm from the nominal interaction point were also simulated for these geometries. The schematic diagrams (SP_coordinates.pdf and y-local_coordinate.pdf) illustrate some relevant geometric parameters of the simulation framework.In addition, four further datasets were produced: one for the baseline sensor (50x12.5x100 um^3) and the CMS Phase 2 sensor design (100x25x150 um^3), each simulated at two radiation levels in the barrel region, corresponding to integrated luminosities of 370 and 1100 1/fb. These irradiation levels map to fluences of 3.3 x 10^15 and 1.0 x 10^16 neq/cm^2 (1 MeV neutron equivalent), respectively. All datasets mentioned above consist of a flat pT dataset and a physical pT dataset variant. The flat pT corresponds to tracks that have a uniform distribution in transverse momentum in the 0 to 5 GeV range. The physical pT corresponds to tracks with a pT distribution similar to what is observed in CMS minimum-bias data.

The following tables summarize the datasets produced in this study, along with the folder names to locate the associated data:




Sl. No.
Sensor name
Pixel length [um]
Pixel width [um]
Pixel thickness [um]
Bias voltage [V]


1
S1
50
10
100
100


2
S2
50
12.5
100
100


3
S3
50
15
100
100


4
S4
50
20
100
100


5
S5
50
25
100
100


6
S6
100
25
100
100


7
S7
100
25
150
175




 




Sl. No.
Detector region
Simulated sensors
Angle between E and B (deg)
Irradiation level [1/fb]
Dataset name


1
Barrel
S1-S7
90
0
2s_LxWxT (physical pT)


2
Barrel
S1-S7
90
0
3s_LxWxT (flat pT)


3
Endcap
S1-S7
180
0
6s_LxWxT (physical pT)


4
Endcap
S1-S7
180
0
7s_LxWxT (flat pT)


5
Barrel
S1, S7
90
370, 1100
8s_LxWxT_Xfb (physical pT)


6
Barrel
S1, S7
90
370, 1100
9s_LxWxT_Xfb (flat pT)




 

Under the dataset name, L, W, and T refer to the length, width, and thickness of the sensor in consideration. If the thickness value is not present in the name, please consider a default 100 microns thickness. For datasets 8s and 9s, the suffix 'Xfb' corresponds to X level of irradiation in units of 1/fb.

Truth properties of each particle are saved in the labels files, which include columns x-entry, y-entry, z-entry, n_x, n_y, n_z, number_eh_pairs, y-local, pt, cotAlpha, cotBeta, y-midplane, x-midplane. The particle impact point on the sensor surface is described by (x-entry, y-entry), and the impact point at the sensor mid-plane (i.e., at Z=sensor thickness/2) of the sensor is (x-midplane, y-midplane). These impact points are in units of microns. The track direction is a unit vector given by (n_x, n_y, n_z). The number of electron-hole pairs created in the active silicon volume is number_eh_pairs. The y distance in mm between the center of the 21x13 pixel array and the center of a flat module is denoted by y-local (see included diagram). As illustrated in SP_coordinates.pdf, please note the differences between the barrel and endcap module coordinate systems. The particle transverse momentum in GeV is stored in the pt variable, with the sign indicating the sign of the particle charge. The angle of incidence in the x-z plane is described by cotAlpha, and the angle of incidence in the y-z plane (the bending plane of the magnetic field) is described by cotBeta.

The deposited charge per pixel per time slice is saved in the recon3D files. Reshaping each line as (20,13,21) gives the three-dimensional cluster in (time, y, x). Each slice in time corresponds to a window of 200 ps.