A MAPS Based Micro-Vertex Detector for the STAR Experiment

For the 2014 heavy ion run of RHIC a new micro-vertex detector called the Heavy Flavor Tracker (HFT) was installed in the STAR experiment. The HFT consists of three detector subsystems with various silicon technologies arranged in 4 approximately concentric cylinders close to the STAR interaction point designed to improve the STAR detector's vertex resolution and extend its measurement capabilities in the heavy flavor domain. The two innermost HFT layers are placed at radii of 2.8 cm and 8 cm from the beam line. These layers are constructed with 400 high resolution sensors based on CMOS Monolithic Active Pixel Sensor (MAPS) technology arranged in 10-sensor ladders mounted on 10 thin carbon fiber sectors to cover a total silicon area of 0.16 m 2 . Each sensor of this PiXeL (\u201cPXL\u201d) sub-detector combines a pixel array of 928 rows and 960 columns with a 20.7 \u3bcm pixel pitch together with front-end electronics and zero-suppression circuitry in one silicon die providing a sensitive area of 3c3.8 cm 2 . This sensor architecture features 185.6 \u3bcs readout time and 170 mW/cm 2 power dissipation. This low power dissipation allows the PXL detector to be air-cooled, and with the sensors thinned down to 50 \u3bcm results in a global material budget of only 0.4% radiation length per layer. A novel mechanical approach to detector insertion allows us to effectively install and integrate the PXL sub-detector within a 12 hour period during an on-going multi-month data taking period. The detector requirements, architecture and design, as well as the performance after installation, are presented in this paper

The STAR Heavy Flavor Tracker (HFT): Focus on the MAPS based PXL detector

11The heavy quark hadrons are suggested as a clean probe for studying the early dynamic evolution of the dense and hot medium created in high-energy nuclear collisions. The Heavy Flavor Tracker (HFT) of the STAR experiment, designed to improve the vertex resolution and extend the measurement capabilities in the heavy flavor domain, was installed for the 2014 heavy ion run of RHIC. It is composed of three different silicon detectors arranged in four concentric cylinders close to the STAR interaction point. The two inner-most layers are based on CMOS monolithic active pixels (MAPS), featured for the first time in a collider experiment, while the two outer layers are based on pads and strips. The two innermost HFT layers are placed at a radius of 2.7 and 8 cm from the beam line and accommodate 400 ultra-thin (50 μm) high resolution MAPS sensors arranged in 10-sensor ladders to cover a total silicon area of 0.16 m2. Each sensor includes a pixel array of 928 rows and 960 columns with a 20.7 μm pixel pitch, providing a sensitive area of ∼ 3.8 cm2. The sensor features 185.6 μs readout time and 170 mW/cm2 power dissipation. The detector is air-cooled, allowing a global material budget as low as 0.39% X/X0 on the inner layer. A novel mechanical approach to detector insertion enables effective installation and integration of the pixel layers within an 8 hour shift during the on-going STAR run. After a detailed description of the design specifications and the technology implementation, the detector status and operations during the current 200 GeV Au+Au run will be presented in this paper, with a particular focus on calibration and general system operations aimed at stabilizing the running conditions. A preliminary estimation of the detector performance meeting the design requirements will be reported.openopenContin, Giacomo*; Anderssen, Eric; Greiner, Leo; Schambach, Joachim; Silber, Joseph; Stezelberger, Thorsten; Sun, Xiangming; Szelezniak, Michal; Vu, Chinh; Wieman, Howard; Woodmansee, SamContin, Giacomo; Anderssen, Eric; Greiner, Leo; Schambach, Joachim; Silber, Joseph; Stezelberger, Thorsten; Sun, Xiangming; Szelezniak, Michal; Vu, Chinh; Wieman, Howard; Woodmansee, Sa

The STAR Heavy Flavor Tracker (HFT): focus on the MAPS based PXL detector

International audienceThe heavy quark hadrons are suggested as a clean probe for studying the early dynamic evolution of the dense and hot medium created in high-energy nuclear collisions. The Heavy Flavor Tracker (HFT) of the STAR experiment, designed to improve the vertex resolution and extend the measurement capabilities in the heavy flavor domain, was installed for the 2014 heavy ion run of RHIC.It is composed of three different silicon detectors arranged in four concentric cylinders close to the STAR interaction point. The two inner-most layers are based on CMOS monolithic active pixels (MAPS), featured for the first time in a collider experiment, while the two outer layers are based on pads and strips. The two innermost HFT layers are placed at a radius of 2.7 and 8 cm from the beam line and accommodate 400 ultra-thin (50 μm ) high resolution MAPS sensors arranged in 10-sensor ladders to cover a total silicon area of 0.16 m 2 . Each sensor includes a pixel array of 928 rows and 960 columns with a 20.7 μm pixel pitch, providing a sensitive area of ∼ 3.8 cm 2 . The sensor features 185.6 μs readout time and 170 mW / cm 2 power dissipation. The detector is air-cooled, allowing a global material budget as low as 0.39% X / X 0 on the inner layer. A novel mechanical approach to detector insertion enables effective installation and integration of the pixel layers within an 8 hour shift during the on-going STAR run.After a detailed description of the design specifications and the technology implementation, the detector status and operations during the current 200 GeV Au+Au run will be presented in this paper, with a particular focus on calibration and general system operations aimed at stabilizing the running conditions. A preliminary estimation of the detector performance meeting the design requirements will be reported

The STAR Heavy Flavor Tracker (HFT)

The heavy quark hadrons are suggested as a clean probe for studying the early dynamic evolution of the dense and hot medium created in high-energy nuclear collisions. The Heavy Flavor Tracker (HFT) of the STAR experiment, designed to improve the vertex resolution and extend the measurement capabilities in the heavy flavor domain, was installed for the 2014 heavy ion run of RHIC. It is composed of three different silicon detectors arranged in four concentric cylinders close to the STAR interaction point. The two innermost layers are based on CMOS monolithic active pixels (MAPS), featured for the first time in a collider experiment, and the two outer layers are based on pads and strips. The two innermost HFT layers are placed at a radius of 2.8 and 8~cm from the beam line and accommodate 400 ultra-thin ($50 \mu m$) high resolution MAPS sensors arranged in 10-sensor ladders to cover a total silicon area of $0.16m^{2}$. Each sensor includes a pixel array of 928 rows and 960 columns with a $20.7\mu m$ pixel pitch, providing a sensitive area of $\sim 3.8 cm^{2}$. The sensor features $185.6 \mu s$ readout time and $170 mW/cm^{2}$ power dissipation, allowing it to be air cooled, which results in a global material budget of only 0.5% radiation length per layer in the run 14 detector. A novel mechanical approach to detector insertion enables effective installation and integration of the pixel layers within a 12 hour shift during the on-going STAR Run. After a detailed description of the design specifications and the technology implementation, the detector status and operations during the 200 GeV Au+Au RHIC run of 2014 will be presented in this paper. A preliminary estimation of the detector performance meeting the design requirements will be reported