UIUC sPHENIX group successfully completes pre-production of EMCal absorber blocks

January 5, 2021

sPHENIX is an experiment at Brookhaven National Lab designed to study the microscopic properties of the quark gluon plasma with also some cold QCD potential. The experiment is scheduled to see first beam in 2023 and will take data through at least 2025, until the final preparations for the Electron Ion Collider will shut down RHIC. The UIUC Nuclear Physics group is in charge of building the absorber blocks for the sPHENIX electromagnetic calorimeter (EMCal). The blocks are shipped to our collaborators at BNL, where they are equipped with light guides and SiPMs and glued into sectors of 96 blocks each.

The technicians and students at NPL completed the pre-production stage of the project in late October 2020 by constructing 1,152 EMCal blocks. Since then the production stage is in full swing, with almost 4,000 blocks to be delivered to BNL. A block is made from an assembly of 2,668 scintillating fibers in a tungsten-epoxy matrix and is machined to high precision on all sides. While the fiber assemblies are prepared by undergrad students, the blocks are produced by our technician team at the Nuclear Physics Lab: Adam Wehe, Saad Altaf, several part-time technical helpers, and senior tech Eric Thorsland.

Each block is tested by undergrad students for light transmission, scintillation, dimensions, and density before sending it to BNL. As of the end of 2020, 60 UIUC undergrad students have worked with us on this project! The block testing and grading is coordinated by grad students (Anabel Romero Hernandez, Xiaoning Wang, Adin Hrnjic) and supervised by postdoc Tim Rinn. Research Assistant Professor Caroline Riedl is the corresponding level-3 manager with BNL and Associate Professor Anne Sickles is the PI.

The group tested several EMCal prototype blocks in a test beam at Fermilab in 2018. The analysis of the data was led by grad student Anabel Romero Hernandez and postdoc Tim Rinn. The findings from the test-beam data demonstrated that the energy resolution of the prototype satisfies the sPHENIX requirements for electron / hadron separation and they were published in:


(and accepted by IEEE TNS).