Publication:
Characterization of planar sensors bonded to RD53A readout chip for CMS phase 2 inner tracker system

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Authors
Guerrero Laos, Alvaro Javier
Embargoed Until
Advisor
Malik, Sudhir
College
College of Arts and Sciences - Sciences
Department
Department of Physics
Degree Level
M.S.
Publisher
Date
2021-06
Abstract
The HL-LHC conditions of instantaneous peak luminosities up to 7.5x10E34 cmE2 sE-1 and an integrated luminosity of the order of 300 fE-1/year would result in 1 MeV neutron equivalent fluence of 2.3x10E16 n_eq/cmE2 and a total ionizing dose (TID) of 12 MGy (1.2 Grad) close to the center of the CMS detector, where the Phase-2 Silicon Pixel Tracker will be installed during the long-shutdown between 2024-2026. The detector should survive the above radiation dose, handle the projected hit rates of 3 GHz/cmE2 at lowest radius, be able to separate and identify particles in extremely dense collision debris, deal with a pileup of 140-200 collisions per bunch crossing and have high spatial resolution. This translates into requiring a higher granular detector design, composed by thinner and smaller pixel sensors with higher radiation tolerance. The present work describes the characterization of four planar pixel sensors where one of them was submitted to radiation exposure of 1.3x10E16 n_eq/cmE2. They were bonded to RD53A readout chip. The pixel sizes are 50x50 square microns and 25x100 square microns pitch, with 150 micron thick. These sensors were tested at Fermilab Test Beam Facilities (FTBF) using a 120 GeV proton beam and a telescope of about 5 microns resolution to reconstruct the particle tracks. Monicelli and Chewie programs were used to get the hit efficiency, spatial resolution, cluster size and charge collection efficiency. Unirradiated sensors showed high hit efficiency and good resolution under conditions such as 15 C temperature and 80 V bias voltage. We saw that the radiation affects the hit eciency, however, it can be compensated by increasing the bias voltage. The resolution reached by irradiated sensor and size of 50 microns was approximately 12 microns using cluster size 2. In addition, its intrinsic spatial resolution was less than 10 microns. The resolution for all non-irradiated sensors was about 7 microns considering cluster size 2. The unirradiated sensors collected a expected 12000 electrons charge with a slight dependence of the rotation angle, in contrast, the radiation over a the sensor affected the collection efficiency because of the trapping. In general, the efficiency depends on the radiation stage and applied bias voltage. The rotation of the plane sensor with respect to the beam line helps to increase the resolution due to charge sharing between neighboring pixels at larger cluster sizes. The charge collection efficiency is proportional to bias voltage and rotation angle.

Las condiciones HL-LHC de luminosidades m aximas instant aneas de hasta 7.5x1034 cm-2s-1 y una luminosidad integrada del orden de 300 fb-1/año dar a como resultado una fluencia equivalente de neutrones de 1 MeV de 2,3x1016 neq=cm2 y una dosis ionizante total (TID) de 12 MGy (1,2 Grad) cerca del centro del Detector CMS, donde se instalar a el rastreador de pixeles de silicio en la Phase-2 durante el apagado prolongado entre 2024 y 2026. El detector debe sobrevivir a la dosis de radiaci on anterior, manejar las tasas de impacto proyectadas de 3 GHz/cm2 en el radio m as bajo, ser capaz de separar de identificar part culas en escombros de colisi on extremadamente densos, lidiar con una acumulación on de 140-200 colisiones por cruce de part culas y tener alta resoluci on espacial. Esto se traduce en la necesidad de un dise~no de detector granular, compuesto por sensores de pixeles m as delgados y peque~nos con mayor tolerancia a la radiaci on. El presente trabajo describe la caracterización on de cuatro sensores de pixeles planos donde uno de ellos fue sometido a una exposici on a radiaci on de 1.3x1016neq=cm2. Ellos fueron conectados al chip de lectura RD53A. Los tamaños de pixeles son 50x50 m2 y 25x100 m2, con 150 m de grosor. Estos sensores se testearon en Fermilab Test Beam Facilities (FTBF) utilizando un haz de protones de 120 GeV y un telescopio de aproximadamente 5 m de resoluci on para reconstruir las trayectorias de las part culas. Se utilizaron los programas de Monicelli y Chewie para obtener la eficiencia de impacto, la resoluci on espacial, el tama~no del cl uster y la eficiencia de recolecci on de carga. Los sensores no irradiados mostraron una alta eficiencia de impacto y una buena resoluci on en condiciones como temperatura de 15 C y un voltaje de polarizaci on de 80 V. Vimos que la radiaci on afecta la eficiencia del impacto, sin embargo, se puede compensar aumentando el voltaje de polarizaci on. La resoluci on alcanzada por el sensor irradiado y el tama~no de 50 m fue de aproximadamente 12 m usando el tama~no del cl uster 2. Adem as, su resoluci on espacial intri nseca fue de menos de 10 m. La resoluci on para todos los sensores no irradiados fue de aproximadamente 7 m considerando el tama~no de cl uster 2. Los sensores no irradiados recolectaron una carga esperada de 12000 electrones con una ligera dependencia del angulo de rotaci on, en contraste, la radiaci on sobre un sensor afect o la eficiencia de recolecci on debido al atrapamiento. En general, la eficiencia depende de la exposici on a la radiaci on y del voltaje de polarizaci on aplicado. La rotaci on del plano del sensor con respecto a la l nea del haz ayuda a aumentar la resoluci on debido al intercambio de carga entre pixeles vecinos en tamanos de cl uster m as grandes. La eficiencia de recolecci on de carga es proporcional al voltaje de polarizaci on y al angulo de rotaci on.
Keywords
CMS,
Sensor,
LHC,
Radiation,
Charged particle
Usage Rights
All Rights Reserved / restricted to Campus
Cite
Guerrero Laos, A. J. (2021). Characterization of planar sensors bonded to RD53A readout chip for CMS phase 2 inner tracker system [Thesis]. Retrieved from https://hdl.handle.net/20.500.11801/2807