GAMMA: GAMma Multiplicity Filter Array for the selection of angular momentum in heavy ion collision reactions

TL;DR

The paper presents the design, fabrication, and testing of a 50-element BaF2 gamma-multiplicity filter array for selecting angular momentum in heavy ion collision experiments, validated through simulations and experimental applications.

Contribution

It introduces a new gamma-multiplicity filter array optimized via GEANT3 simulations, with successful experimental validation in heavy ion reactions.

Findings

Effective angular momentum selection demonstrated in heavy ion reactions.

Successful correction of non-statistical events in fusion reactions.

Validated detector response and optimization through simulations and experiments.

Abstract

A 50 element BaF2 gamma-multiplicity filter has been designed, fabricated and installed successfully at the Variable Energy Cyclotron Centre (VECC), Kolkata for angular momentum selection in heavy ion collision reactions. A thorough GEANT3 Monte Carlo simulation was performed to optimize the individual detector shape and geometrical structure of the array. The detectors have been fabricated in-house from bare barium fluoride crystals (each measuring 5 cm in length and having cross-sectional area of 3.5 x 3.5 cm2). The basic detector properties have been studied using the lab standard -ray sources. The response function of the filter has been studied using GEANT3 for mapping the fold distribution of the filter onto the angular momentum space. The multiplicity filter has been used successfully to measure the high angular momentum of the compound nuclei populated in the reaction 20Ne (E = 145 & 160 MeV) + 93Nb, 27Al as well as low angular momentum events from the fission fragments of 252Cf spontaneous fission source. The filter has also been used successfully for correcting non-statistical events involved in the heavy ion fusion reaction.