The Active Target Time Projection Chamber at NSCL

D Bazin,A Fritsch,L Carpenter,S Beceiro-Novo,J J Kolata,W Mittig,M Cortesi,W Lynch,Y Ayyad,T Ahn,N Watwood,J Bradt,E.C Simpson,K.J Cook,C Simenel,I.P Carter

doi:10.1051/epjconf/201716300004

Abstract

Reactions in inverse kinematics close to the Coulomb barrier offer unique opportunities to study exotic nuclei, but they are plagued by the difficulty to efficiently and precisely measure the characteristics of the emerging particles. The Active Target Time Projection Chamber (AT-TPC) offers an elegant solution to this dilemma. In this device, the detector gas of the time projection chamber is at the same time the target in which nuclear reactions take place. The use of this new paradigm offers several advantages over conventional inert target methods, the most significant being the ability to increase the luminosity of experiments without loss of resolution. The AT-TPC and some results obtained on resonant α scattering to explore the clustering properties of neutron-rich nuclei are presented, as well as fusion cross section results using a 10 Be radioactive beam. In addition, the first re-accelerated radioactive beam experiment using the fully commissioned ReA3 linac was conducted recently at the NSCL with the AT-TPC, where proton resonant scattering of a 4.6 MeV/u 46 Ar beam was used to measure the neutron single-particle strength in 47 Ar.

Highlights

Reactions close to the Coulomb barrier have been used with light beam probes such as protons, deuterons or alphas since the dawn of the first accelerators
The main reason lies with inverse kinematics where the light probe nuclei are at rest in a target and have much wider kinetic energy range after the reaction than in direct kinematics
Since the energy of the reaction products can be measured as they emerge from the reaction vertex, there is no loss of resolution regardless of the amount of material traversed by the incoming beam

Summary

Introduction

Reactions close to the Coulomb barrier have been used with light beam probes such as protons, deuterons or alphas since the dawn of the first accelerators. The concept of active target is an attempt at avoiding this compromise by turning the target into a detector medium where all the energy dissipated during the reaction can be measured and the location of each reaction vertex determined experimentally [1]. This is best done in a gas volume where the radioactive beam can react with the gas atomic nuclei as it slows down. A few examples of the results obtained are presented in the following, after a brief description of the detector and its associated technology

Detector

Fusion

Conclusion

Findings

Summary a