Beam position reconstruction for the g2p experiment in Hall A at Jefferson lab

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.

The EMC Effect in A=3 Nuclei

“…The beam position in the frame of the u and v antennas are calculated by the taking the difference over the sum of the two wires in the u and v directions. The accuracy of the BPMs requires an absolute measurement of the electron beam's position to calibrate the BPMs [77,86]. The light gray symbols are the beam locations from harp measurements, while the colorful markings are measurements from the BPMs.…”

“…A triangle wave of 25 kHz controls the coils of the dipole magnets. The raster system begins ≈17 meters before the target chamber [86].The raster system's relative position can be seen in figure 3.3. Safety constraints administrated by the target group at JLab limited the minimum size of the raster spot for the MARATHON experiment to two millimeters by two millimeters.…”

The g$p\atop{2}$ Experiment: A Measurement of the Proton's Spin Structure Functions

“…The uncertainty in the calibration is due to uncertainty in the harp calibration constant, survey data and electronic pedestal value. Further details on the BPM calibration and reconstruction are found in Ref [117].…”

Beam Charge Measurement for the g2p/GEp experiments

“…A tungsten calorimeter [12] is located downstream of the BCMs and the two rasters [13] for calibrating the BCMs by measuring the beam induced temperature rise, as shown in Fig. 10.…”