SπRIT: A time-projection chamber for symmetry-energy studies

Abstract

a b s t r a c tA time-projection chamber (TPC) called the SAMURAI Pion-Reconstruction and Ion-Tracker (SπRIT) has recently been constructed at Michigan State University as part of an international effort to constrain the symmetry-energy term in the nuclear Equation of State (EoS). The SπRIT TPC will be used in conjunction with the SAMURAI spectrometer at the Radioactive Isotope Beam Factory (RIBF) at RIKEN to measure yield ratios for pions and other light isospin multiplets produced in central collisions of neutron-rich heavy ions, such as 132 Sn þ 124 Sn. The SπRIT TPC can function both as a TPC detector and as an active target. It has a vertical drift length of 50 cm, parallel to the magnetic field. Gas multiplication is achieved through the use of a multi-wire anode plane. Image charges, produced in the 12096 pads, are read out with the recently developed Generic Electronics for TPCs.

Pion production in rare-isotope collisions

“…It is expected that new data will become available from experiments aimed at probing the symmetry energy at ρ≈2ρ 0 using neutron-rich and neutron deficient rare isotope beams [4,27]. It is, therefore, timely to try to understand the source of such discrepancies.…”

“…In anticipation of results from experiments recently performed with the SπRIT Time Projection Chamber described in Ref. [4], it is worthwhile to consider observables chosen to minimize systematic experimental uncertainties. For example, negative and positive pions are detected in different regions of phase space characterized by different detection efficiencies.…”

“…Clearly, it is incumbent upon nuclear physics to provide laboratory constraints on properties of dense nucleonic matter where such are feasible. Both astronomical observations and nuclear experiments are being designed to address these questions, putting the goal of a quantitative understanding of dense matter within scientific reach [2][3][4][5][6] This goal requires constraining the nuclear Equation of State (EoS) at densities above and below the saturation density (ρ 0 ≈0.16 nucleons/fm 3 ) that characterizes matter at the centers of atomic nuclei [2][3][4][5][6][7][8][9][10]. For low temperature systems, such as neutron stars, the EoS, (Eq.…”

A gating grid driver for time projection chambers

“…In the simulation, the gating grid is modeled by a capacitor of 26.5 nF, which matches the capacitance of the SπRIT TPC gating grid [9] in its operating environment, including cables between TPC and driver. Figure 6 shows SPICE simulations of the gating grid switching from the closed configuration to the open configuration and then back to closed configuration.…”

“…Chamber (SπRIT-TPC) [9], designed for use with the SAMURAI spectrometer at the Radioactive Ion Beam Factory (RIBF) at RIKEN, Japan [10] to illustrate the properties of the new gating grid driver.…”