Active Target for α-Particle Condensation Studies in 16O

Abstract

An active target has been developed for studying the Hoyle like states in 16O. It is a position and time sensitive detector system based on the Low-Pressure Multy-Wire Proportional Chamber (LPMWPC) technique and Si detectors. The few Torr pressure of methyl ((OCH3)2CH2) serves as a working gas for the LPMWPC operation, and the oxygen atoms of the methyl molecules serve as an experimental target. The main advantage of this new target-detector system is a high sensitivity to the low-energy, highly ionizing particles, produced after photodisintegration of 16O, and the insensitivity to the γ-rays and low ionizing particles, which allows one to detect only the products of the nuclear reaction, which are studied. The threshold energies for detection of α particles and 12C nuclei are about 50 keV and 100 keV, respectively. Temporal and positional resolution of the LPMWPC modules was investigated with the use of the α-particle source. This paper discusses the architecture of the active target and the test results of the prototype MWPC detector. This installation has been constructed to study the cluster states at 15.1 MeV in 16O using the proton beams from the Yerevan proton cyclotron and the Compton backscattered photon beams of the ELI-NP facility.