2023 CAP Congress / Congrès de l'ACP 2023

(G*) Laser Calibration Studies Using the ALPHA-g Detector

Jun 20, 2023, 4:30 PM

15m

UNB Kinesiology (Rm. 201 (max. 98))

Oral Competition (Graduate Student) / Compétition orale (Étudiant(e) du 2e ou 3e cycle) Symposia Day (DNP - DPN) - Precision Physics and Tests of Fundamental Symmetries | Physique de précision et tests des symétries fondamentales (DNP) T4-6 Precision Physics and Tests of Fundamental Symmetries | Physique de précision et tests des symétries fondamentales (DPN)

Speaker

Pooja Woosaree (Dep. of Phys. and Astronomy University of Calgary (CA))

Description

ALPHA-g has completed a successful run in 2022 in the pursuit of measuring the gravitational mass of antihydrogen. This apparatus was designed to test whether antimatter follows Einstein’s Weak Equivalence Principle (WEP), where the acceleration due to gravity that a body experiences is independent of its structure or composition. A measurement of the gravitational mass of antimatter has never been done before, as previous experiments used charged particles, which meant the experiments were dominated by electromagnetic forces. The ALPHA-g apparatus uses electrically neutral antihydrogen atoms produced in a vertical Penning-Malmberg trap and trapped in a magnetic minimum trap. By measuring the antihydrogen annihilation positions after a controlled magnetic release of the atoms the gravitational mass of antihydrogen can be determined. Annihilation positions are reconstructed using a radial time projection chamber (rTPC) surrounding the trapping volume. To accurately determine vertical annihilation positions, precise detector calibrations are needed.
A laser calibration system was developed and used to gather drift time data in the rTPC, which results in vertical position information, and can be used to monitor changes in pressure, temperature, and magnetic field. In particular, we can calculate the Lorentz angle which is then used in reconstruction to accurately determine the annihilation positions. Simulations are also required to determine the expected drift time and Lorentz angle. Using Geant4 and Garfield++ toolkits, we can simulate these observables from electrons drifting through the gas portion of the ALPHA-g detector. In this talk I will discuss the laser calibration system for the rTPC and the results of the drift time and Lorentz angle data taken over the course of the 2022 run period. I will further discuss how these results are used in the reconstruction of antihydrogen annihilations by comparing with simulation, and how this calibration will be implemented in future ALPHA-g measurements.