Session EI: Instrumentation II

BoxScore - A real-time beam-diagnosis program for CEAN x730 digitizer

BoxScore [1] is a C++ program for real-time beam diagnosis using a CAEN x730 series digitizer. The program has been implemented at the ATLAS in-flight system at Argonne National Laboratory for beam tuning and diagnosis, that isotopes can be selected online and the corresponding count rate can be deduced in real-time. We will present the functionalities and the program structure.

[1] T.L. Tang, Nucl. Instm. Methods Phys. Res. A, 1034, 166623 (2022)   

Progress Towards the EDM3 Instrument at the Facility for Rare Isotope Beams Part 2: Neutralization, Implantation, and Spectroscopy

Nuclear Schiff moments (NSMs) present a powerful probe into new physics through their connection to CP-symmetry violation. We are investigating the application of molecular matrix methods[1] to NSM searches of radioactive isotopes, particularly radium-225, which has an enhanced Schiff moment resulting from its octupole deformations[2]. These methods involve trapping polar molecules in a noble gas matrix, which is predicted to lock their orientation relative to the lattice vectors.

In this part of the contribution, we focus on the portion of the in-design FRIB EDM3 instrument that will neutralize the radioactive polar ions and implant them into a noble gas matrix, and the part that will be used to perform molecular spectroscopy. The ions will be neutralized using a vertical charge exchange cell. We plan to use an alkali metal-vapor based charge exchange cell[3]. After exiting the vertical charge exchange cell, the radium-monofluoride molecules will be co-deposited in a noble gas matrix.

Once the molecules are deposited, precise electromagnetic fields will be applied and laser spectroscopy will be used to perform nuclear Schiff moment measurements on the 225RaF[1].

[1] A.C. Vutha, M. Horbatsch, E.A. Hessels, Phys. Rev. A 98 (2018).

[2] V.V. Flambaum, V.G. Zelevinsky, Phys. Rev. C 68 (2003).

[3] A. Klose, K. Minamisono, et al, NiMA 678, 114 (2012).   

Development of a Triton Source at Florida State University

We are developing a unique triton beam capability that will allow one to perform nuclear physics experiments in regular kinematics at the John D Fox accelerator laboratory (Florida State University), in collaboration with the University of Tennessee Knoxville and Oak Ridge National Laboratory. We have installed a dedicated Multi-SNICS source to produce triton beams using Titanium tritide cathodes. We have also successfully loaded titanium cones with protium and deuterium to test titanium absorption of hydrogen; and the source's output in preparation for tritium loading. In this talk, I will discuss the loading technique, safety precautions, initial deuteron beam intensities, plans, and availability.   

Fast-timing measurements between LaBr3(Ce) detectors in the neutron-rich N = 20 region

Changes in nuclear shell structure can occur due to varying proton and neutron numbers inside the nucleus. Sensitive probes to those changes, so-called “nuclear shell evolution”, are nuclear transition rates, which depend in part on understanding the level lifetimes. The National Superconducting Cyclotron Laboratory (NSCL) conducted a β decay experiment in the neutron-rich N = 20 region where radioactive nuclei were implanted into a CeBr₃ scintillator coupled to a Position-Sensitive Photomultiplier Tube (PSMPT), which offered the ability to correlate the decays to the implanted ions using spatial and temporal techniques. 15 LaBr₃(Ce) detectors were used for γ radiation detection and to provide fast timing measurement, with time-difference spectra generated for β-delayed γ radiation following a decay event to measure half-lives. Corrections for the energy-dependent time-walk effects and validation results in the neutron-rich N = 20 region will be presented.

    

New Nuclear Targetry Group at SJSU

A new nuclear targetry lab has been established at San José State University. The last decade has seen a marked increase in the demand for well-made targets, driven by many thriving nuclear facilities, the advent of FRIB, and the closure of several legacy targetry labs. Focusing on thin film targets for low energy nuclear reaction studies, the SJSU targetry group are able to make and characterize nuclear targets for a variety of experimental applications. Current production techniques include physical vapor deposition via a resistive heating vacuum evaporator, cold rolling of ductile materials, and solvent casting for deuterated plastic targets. SJSU's target characterization capabilities includes optical microscopy for surface morphology, FTIR & XRD for elemental & chemical analysis, and α-energy loss for film thickness measurement. This talk will focus on introducing the different abilities currently available at SJSU by highlighting some recently produced targets for nuclear physics experiments, as well as planned radioactive targets.   

Characterization of Nonlinearity Scintillation Effects in HECTOR with GEANT4

It has been observed that NaI(Tl) detectors exhibit nonlinear behavior in light output for gamma-ray detection that varies with the total energy deposited and gamma-ray multiplicity. Understanding such changes in radiation detection can improve the energy resolution of the detector and ensure proper energy calibration. To understand such effects for the High EffiCiency TOtal absorption spectrometeR (HECTOR), GEANT4.10.5’s built-in scintillation function was used to model the scintillation of the NaI(Tl) crystals. The simulation was used to characterize the response of the detector to varying energies and multiplicities of gamma rays. Here, a comparison of the results to previously published results will be discussed in further detail.   

Simulations of the Multi-layer Active target for MoNA Experiments (MAME) with Garfield++

The study of neutron unbound systems via the invariant mass technique is the primary focus of the MoNA Collaboration, which built and operates the MOdular Neutron Array (MoNA) and the Large multi-Institutional Scintillator Array (LISA). Reaction cross-sections for producing neutron unbound systems from radioactive ion beams can be small, 0.1-1mb, and the use of a thick reaction target degrades the resolution of the measurement. As an upgrade to a pre-existing Si-Be segmented target, the Gas Electron Multiplier (GEM) technology is being investigated for its use in a Multi-layer Active target for MoNA Experiments (MAME) for the Collaboration’s research program at the Facility for Rare Isotope Beams with a possible expansion to missing mass capability. A GEM-based detector could allow for a higher degree of Be-foil segmentation. Performance studies are conducted using Garfield++ to understand electron transport within MAME including GEM configurations, electron position distribution, drift speed, signal generation, and simulation optimization. A Geant4 simulation is being developed to work in tandem with the Garfield++ simulation to model the detector response along with the physics of the reaction/decay process. Preliminary results from simulation studies will be discussed.

    

Detector Response Characterization at LANSCE for Spectrum Unfolding

Direct characterization of fast neutron spectra (> 1 MeV) is complicated due to the physics of neutron interactions and often relies on simulation or time-of-flight (TOF) techniques.  Spectrum unfolding allows fast neutron detectors, such as organic scintillators, to be used for characterizing spectra in fields where TOF techniques are not feasible.  Examples include nonproliferation/safeguards, nuclear emergency response, warhead verification, background characterization, and cross section measurements.

Spectrum unfolding requires the response of the detector to mono-energetic neutrons be well characterized.  Typically TOF measurements using a ²⁵²Cf source or an accelerator are used for characterization.  Recent work has shown characterization of several detector materials (deuterated and non-deuterated), sizes, and photomultipliers (PMT, SiPM) to be feasible with the neutron beam of LANSCE at LANL.  This work will be presented and compared to existing methods.  The beam at LANSCE allows detectors to be characterized in much less time and with better statistics, particularly at higher energies (> 10 MeV), than existing methods.  Future work will focus on characterizing additional materials, temperature dependence, and creating data sets for simulation validation.   

Experimental setup and preparation for the indirect measurement of 88Zr(n,γ) at DICER at LANSCE

A. Stamatopoulos¹, P. Koehler¹, A. Couture¹, B. DiGiovine², A. Matyskin³, V. Mocko³, G. Rusev³, J. Ullmann¹, C. Vermeulen³

 

 

Study of the 40Ar(n,2n)39Ar Reaction and First Detection of 42Ar with Accelerator Mass Spectrometry

ATLAS at Argonne National Laboratory, composed of an Electron Cyclotron Resonance ion source and a superconducting linear accelerator, hosts the sole Accelerator Mass Spectrometry (AMS) setup based on positive ion acceleration to a few MeV/u. A new multi-anode ionization chamber, MONICA, was built to enhance the ion identification for noble gases and medium to heavy mass isotopes. After undergoing commissioning at the University of Notre Dame, MONICA was used to study the ⁴⁰Ar(n,2n)³⁹Ar (t_1/2=268 y) reaction and, for the first time, detect ⁴²Ar (33 y) by AMS. The AMS detection of 39Ar leads to a first measurement of the ⁴⁰Ar(n,2n)³⁹Ar total reaction cross section at 14 MeV. These isotopes were explored as part of a proposed experiment to probe neutron-induced reactions in a high-density plasma at the National Ignition Facility.