Undergraduate Research at Jefferson Lab

Hodoscope Testing for Jefferson Lab's BigBite Electron Spectrometer

Student: Jonathan Fritz

School: Carnegie Mellon University

Mentored By: Douglas Higinbotham

Jefferson Lab's Hall A BigBite electron spectrometer aims to pinpoint the magnetic distribution of the neutron at four-current quantities ranging from 3.5 (GeV/c)² to 18.0 (GeV/c)² by registering the angle and momenta of scattered electrons. We upgraded the spectrometer's hodoscope by replacing 13 wide paddle scintillator bars with 90 curved and straight bars. The increase in bar count will drop the frequency of detection for each detector bar from 1 MHz to 100 kHz and allow the spectrometer to function in Jefferson Lab's new 12 GeV beam upgrade. Construction and installation of the hodoscope required initial testing of 200 photomultiplier tubes (PMTs) with cosmic rays, encasing PMTs in light-reducing and ventilation-controlling materials, attaching them scintillator bars, and testing them as a PMT-scintillator unit. The upgrade to the BigBite spectrometer will add more Q² values and minimize uncertainties on current Q² values of the neutron magnetic distribution.