Beam Position Reconstruction for the g2p Experiment in Hall A at Jefferson Lab

TL;DR

This paper details the upgrade and calibration of beam position measurement systems for the g2p experiment at Jefferson Lab, ensuring precise beam tracking at low currents for accurate data analysis.

Contribution

Introduction of new beam position monitors, calibration methods, and data analysis techniques for improved beam position accuracy in low-current experiments.

Findings

Achieved 1-2 mm position accuracy at the target

Developed calibration procedures with super-harps

Validated beam position reconstruction event-by-event

Abstract

Beam-line equipment was upgraded for experiment E08-027 (g2p) in Hall A at Jefferson Lab. Two beam position monitors (BPMs) were necessary to measure the beam position and angle at the target. A new BPM receiver was designed and built to handle the low beam currents (50-100 nA) used for this experiment. Two new super-harps were installed for calibrating the BPMs. In addition to the existing fast raster system, a slow raster system was installed. Before and during the experiment, these new devices were tested and debugged, and their performance was also evaluated. In order to achieve the required accuracy (1-2 mm in position and 1-2 mrad in angle at the target location), the data of the BPMs and harps were carefully analyzed, as well as reconstructing the beam position and angle event by event at the target location. The calculated beam position will be used in the data analysis to accurately determine the kinematics for each event.