Veto Scintillating Detector Design Testing

As a part of the upgrades from PRad I, the new PRad II will have the addition of an extremely low angle Veto Scintillating Detector. This detector will consist of 4 actuating panels of scintillating material.These panels will be able to be brought in to cover extremely low angles for calibration. While the beam is running, the panels will retract and allow for differentiation between e-p and e-e events at these low angles. The ability to separate at these low angles will improve statistics for the proton radius measurement in a region that was previously unable to be separated in PRad I.

Currently, there are two potential designs prepared for this detector. The difference between the two is the thickness of the scintillating panels. The panels can either be 5mm thick or 3mm thick. The preference would be to use as little material as possible to lower multiple scattering effects, and minimize energy losses in this detector. However, it is currently being checked if the signal from the 3mm panels will be good enough to use during the experiment. See details for this project below.

Scintillating Panel Thickness Testing

In order to check the responses of the two scintillator thicknesses (3mm and 5mm) there will modules with one of each thickness constructed in Youri Sharabian's lab and then tested in the black box he has in his lab. The simultaneous testing will allow for direct comparisons to be made. The scintillator modules were set up so that the 3mm and 5mm paddles are directly in line with one another vertically while the light guides and components are not above each other. This allows for a DAQ trigger to be set to save only events where both modules experience an event in coincidence with each other. This means that the events are from the same particle which means passing through each module and their responses can be used to see the performance of each module. Ideally, the thinner 3mm module is to be used in the actual construction of the Veto Scintillator due to it introducing the least amount amount of material possible into the experiment. GEANT4 simulations have shown that the 3mm thickness should be adequate for the needs of PRad II, but a real hardware test is needed for final confirmation.

Originally, Aruni, Buddhiman, and Erik were provided with scrap scintillating material to practice gluing the larger surfaces without bubbles or any other issues. This also allowed us to check the transparency of the UV-activated glue we intend to use for the test and it seems to be good enough for the test especially since any effects could be expected to be equal in each module. The testing modules have since been constructed and wrapped with reflective material. Youri manufactured two holding units for holding the PMT and light guide of the module together under a small amount of pressure from a stiff foam. These holding units allow for the test to be set up and stable. Armen Stepanyan of the Fast Electronics Group also terminated the PMT dividers to the HV and LEMO connections needed for the test. Sergey Boyarinov was asked by Youri to set up the DAQ for two scintillator thickness test.

Contributors

• Aruni Nadeeshani (Mississippi State University)
• Buddhiman Tamang (Mississippi State University)
• Erik Wrightson (Mississippi State University)
• Youri Sharabian (Hall B, JLab)
• Armen Stepanyan (Fast Electronics Group, JLab)
• Sergey Boyarinov (Hall B, JLab)