Optical Readout Time Projection Chamber (O-TPC) for a Study of Oxygen Formation in Stellar Helium Burning

Abstract

We are developing an Optical Readout Time Projection Chamber (O-TPC) detector for the study of the 12ag reaction that determines the ratio of carbon to oxygen in helium burning. This ratio is crucial for understanding the final fate of a progenitor star and the nucleosynthesis of elements prior to a Type II supernova; an oxygen rich star is predicted to collapse to a black hole, and a carbon rich star to a neutron star. Type Ia supernovae (SNeIa) are used as standard candles for measuring cosmological distances with the use of an empirical light curve-luminosity stretching factor. It is essential to understand helium burning that yields the carbon/oxygen white dwarf and thus the initial stage of SNeIa. The O-TPC is intended for use with high intensity photon beams extracted from the HIγS/TUNL facility at Duke University to study the 16 O(γ, α) 12 C reaction, and thus the direct reaction at energies as low as 0.7 MeV. We are conducting a systematical study of the best oxygen containing gas with light emitting admixture(s) for use in such an O-TPC. Preliminary results with CO 2 + TEA mixture were obtained.

Advances in thick GEM-like gaseous electron multipliers Part II: Low-pressure operation

“…heavy particles in nuclear reactions. We are currently investigating the application of THGEMs for the readout of a low pressure (~100Torr) TPC operating in an Oxygen-rich gas mixture, for the study of the O(γ,α)C reaction in cosmologically-relevant energy range [4]. Another example is in the detection of very lowenergy ions, recently proposed by us for track-structure studies in nanodosimetry applications.…”

Amplification and scintillation properties of oxygen-rich gas mixtures for optical-TPC applications

“…However, the use of CO 2 +N 2 is more favorable since it allows for the application of higher electric fields, resulting in higher multiplication factors and higher light. Taking into account the higher oxygen content of CO 2 , it is clear that CO 2 +N 2 is more suitable for the proposed experiment [1] than N 2 O+N 2 . Although…”

“…This work was motivated by the quest for an oxygen-rich gas mixture for the Optically read out Time Projection Chamber (O-TPC) "target-detector", designed to study the 16 O( γ , α ) 12 C reaction in the γ energy range of 7.9-10.0 MeV [1]. Its time-revised 12 C( α , γ ) 16 O reaction is a fundamental unknown in stellar evolution theory and our experiment will enable determining its cross-section in the alpha energy range of below 1.2 MeV.…”

“…Furthermore, the reaction products, alpha-particles and carbon ions, are expected to be measured and identified with close to 100% efficiency and with reliable background rejection. The experiment is also expected to yield the angular distribution of the reaction products, and thus a partial wave analysis of the reaction crosssections [1]. As the cross-section value is expected to be very low, the O-TPC gas-mixture, which constitutes the target volume, should be as dense as possible and contain the maximum possible fraction of oxygen.…”

“…Our goal is the application of an O-TPC detector for the measurement of cross-section of the 16 O( γ , α ) 12 C nuclear reaction [1] at a new generation of gamma-beam facilities such as HI γ S [18]. An O-TPC setup is well suited for such studies where the detector, with its countinggas also serving as interaction medium for the gamma-beam, is used to measure the signature of very rare reaction products.…”