Undergraduate Research at Jefferson Lab

The Upgraded Hall A BigBite Spectrometer

Student: Josh McMullen

School: Northern Michigan University

Mentored By: Douglas Higinbotham

The recent 12 GeV upgrade of the Continuous Electron Beam Accelerator Facility (CEBAF) has ushered in a new era of nuclear physics research at Thomas Jefferson National Accelerator Facility (Jefferson Lab). The recently upgraded BigBite apparatus will be used as the electron arm in Jefferson Lab's upcoming Hall A form factor experiments. BigBite is a non-focusing, magnetic spectrometer responsible for particle tracking, particle discrimination, and generating precise timing signal information in regards to the scattered electrons. The detector package has received significant modifications and updates in preparation for maintaining efficiency despite experimental factors associated with an increased electron beam energy of 12 GeV. Significant modifications include the replacement of Multi-Wire Drift Chambers (MWDC) with the more efficient gas electron multiplier (GEM) detectors as well as alterations made to the gas ring imaging (GRINCH) Cherenkov chamber. This document will provide an updated technical report on the BigBite spectrometer by detailing the changes made to the detector package and discussing the significant role the apparatus continues to play in Hall A form factor research.