Undergraduate Research at Jefferson Lab

Assembling and Assessing Hodoscope Arrays for the Hall A Neutron Polarimeter

Student: Carly Wever

School: Christopher Newport University

Mentored By: Brad Sawatzky

A comprehensive model of the internal structure of a neutron is still undeveloped. Hall A and Hall C of Jefferson Lab are in the midst of constructing a neutron polarimeter which will provide a way to measure the electromagnetic form factors (particularly, Gⁿ_E) within a neutron. The neutron contains one up-quark and two down-quarks whose electric charges cancel each other out (hence producing no outward charge). A neutron polarimeter measures the spin of the neutron which is connected to its internal structure. This gives insight into the electric and magnetic distribution and dynamics of the quarks and gluons within the neutron. The focus of this project was to deconstruct and verify the use of a plastic scintillator hodoscope in order to utilize its parts to create two hodoscope arrays. Initially, the old BigBite dE-E hodoscope had to be disassembled carefully. The scintillators retrieved were repaired as needed and a Data Acquisition System (DAQ) was established to test the disassembled paddles for gain matching and performance. From there, the scintillator panels were remounted into new test stands. It was found that the plastic scintillators were salvageable and useful towards designing two new arrays of detectors. The scintillators were in need of repair and cables had to meet specifications for the new detector. The cables were tested accordingly and the scintillators were found to produce signals, on average, at 1650V. The scintillators from the BigBite hodoscope have been repurposed and made into two arrays for an upcoming measurement of Gⁿ_E in Hall A (Experiment E12-17-004).