arXiv subjects

Jonathan T. Morrell

Publications and source records attributed to Jonathan T. Morrell.

12 recordsLinked to original sources

arXiv2026

Characterizing Secondary Neutrons at BLIP for Isotope Production Applications

Fast secondary neutrons created at the Brookhaven Linac Isotope Producer (BLIP) facility following proton irradiation were characterized by the foil activation technique and compared with FLUKA Monte Carlo simulations. The FLUKA-simulated neutron flux was spectrally adjusted following the maximum entropy formalism using the International Reactor Dosimetry and Fusion File (IRDFF-II), with predictions agreeing with experimental measurements to within 9% following the adjustment procedure. A multitude of degrader configurations were simulated to assess the feasibility of improving the fast (En > 20 MeV) secondary neutron yield at the proposed neutron target position (N-slot). A configuration where the N-slot is closest to the proton degrader produced the highest fast neutron yield, with tungsten degraders achieving the best performance. Assuming the optimized target-degrader configuration proposed in this work, we discuss potential isotope production opportunities with secondary neutrons. In most cases the yields are in the order of several mCi.

physics.app-ph↗

arXiv2025

$\mathrm{^{117m}Sn}$ and $\mathrm{^{119m}Te}$ Production via Proton Bombardment on Natural Antimony and Implications for Modeling Charged Particle Reactions

$\mathrm{^{117m}Sn}$ and $\mathrm{^{119}Sb}$, the latter of which is produced via a $\mathrm{^{119m}Te}$ generator, are promising radionuclides for the targeted treatment of both osteoarthritis and small mass tumors via Auger therapy. Experiments were conducted at Lawrence Berkeley National Laboratory, Los Alamos National Laboratory, and Brookhaven National Laboratory to measure the $\mathrm{^{nat}Sb}$(p,x)$\mathrm{^{117m}Sn}$ and $\mathrm{^{nat}Sb}$(p,x)$\mathrm{^{119m}Te}$ cross sections for incident proton energies up to 200 MeV. Additional measurements for co-produced isotopes are included as well. In addition to this dataset, this paper investigates improvements for proton-induced reaction modeling capabilities through comparison of these experimental dataset against theoretical models in TALYS 1.95. Parameter adjustments affecting level density, optical model potential, and pre-equilibrium emission were explored, with a goodness-of-fit metric established by the largest independent cross section channels and cross-validated with remaining channels.

nucl-ex↗

arXiv2024

Measurement of Proton-Induced Reactions on Lanthanum from 55--200 MeV by Stacked-Foil Activation

Cerium-134 is an isotope desired for applications as a chemical analogue to the promising therapeutic radionuclide $^{225}$Ac, for use in bio-distribution assays as an in vivo generator of the short-lived positron-emitting isotope $^{134}$La. In the 50-100 MeV energy range relevant to the production of $^{134}$Ce by means of high-energy proton bombardment of lanthanum, existing cross section data are discrepant and have gaps at important energies. To address these deficiencies, a series of 17 $^{139}$La foils (99.919% natural abundance) were irradiated in two stacked-target experiments: one at the LANL's Isotope Production Facility with an incident proton energy of 100 MeV, and a second at BNL's Brookhaven Linac Isotope Producer with an incident proton energy of 200 MeV - a complete energy range spanning approximately 55-200 MeV. Cross sections are reported for 30 products of $^{139}$La(p,x) reactions (representing up to 55% of the total non-elastic cross section), in addition to 24 residual products measured in the $^{nat}$Cu and $^{nat}$Ti foils that were used as proton flux monitors. The measured production cross sections for $^{139}$La reactions were compared to literature data as well as default calculations from the nuclear reaction modeling codes TALYS, EMPIRE and ALICE, as well as the TENDL-2023 library. The default calculations typically exhibited poor predictive capability, due to the complexity of multiple interacting physics models in this energy range, and deficiencies in preequilibrium reaction modeling. Building upon previous efforts to evaluate proton-induced reactions in this energy range, a parameter adjustment procedure was performed upon the optical model and the two-component exciton model using the TALYS-2.0 code. This resulted in an improvement in $^{139}$La(p,x) cross sections for applications including isotope production, over default predictions.

nucl-ex↗

arXiv2022

Secondary Neutron Production from Thick Target Deuteron Breakup

Thick target deuteron breakup is a variable-energy accelerator-based source of high-energy neutrons, with applications in fundamental and applied nuclear science and engineering. However, the breakup mechanism remains poorly understood, and data on neutron yields from thick target breakup remains relatively scarce. In this work, the double-differential neutron yields from deuteron breakup have been measured on a thick beryllium target at $\epsilon_d=33$ and 40 MeV, using both time-of-flight and activation techniques. We have also introduced a simple hybrid model for the double-differential deuteron breakup cross section, applicable in the $\epsilon_d=10$--$100$ MeV energy range on light ($Z\leq 6$) targets. This model features four empirical parameters that have been fit to reproduce experimental breakup measurements on beryllium targets, using the method of least-squares. It was shown that these parameters extrapolate well to higher energies, and to other low-Z target materials. We also include optimization of the parameters that modify the Kalbach systematics for compound and pre-equilibrium reactions, in order to better reproduce the experimental data for beryllium targets at large angles.

nucl-ex↗

arXiv2021

Measurement and Modeling of Proton-Induced Reactions on Arsenic from 35 to 200 MeV

$^{72}$As is a promising positron emitter for diagnostic imaging that can be employed locally using a $^{72}$Se generator. However, current reaction pathways to $^{72}$Se have insufficient nuclear data for efficient production using regional 100-200 MeV high-intensity proton accelerators. In order to address this deficiency, stacked-target irradiations were performed at LBNL, LANL, and BNL to measure the production of the $^{72}$Se/$^{72}$As PET generator system via $^{75}$As(p,x) between 35 and 200 MeV. This work provides the most well-characterized excitation function for $^{75}$As(p,4n)$^{72}$Se starting from threshold. Additional focus was given to report the first measurements of $^{75}$As(p,x)$^{68}$Ge and bolster an already robust production capability for the highly valuable $^{68}$Ge/$^{68}$Ga PET generator. Thick target yield comparisons with prior established formation routes to both generators are made. In total, high-energy proton-induced cross sections are reported for 55 measured residual products from $^{75}$As, Cu, and Ti targets, where the latter two materials were present as monitor foils. These results were compared with literature data as well as the default theoretical calculations of the nuclear model codes TALYS, CoH, EMPIRE, and ALICE. Reaction modeling at these energies is typically unsatisfactory due to few prior published data and many interacting physics models. Therefore, a detailed assessment of the TALYS code was performed with simultaneous parameter adjustments applied according to a standardized procedure. Particular attention was paid to the formulation of the two-component exciton model in the transition between the compound and pre-equilibrium regions, with a linked investigation of level density models for nuclei off of stability and their impact on modeling predictive power.

nucl-ex↗

arXiv2021

Preparation and Characterization of Thin Arsenic Targets for Stacked-Target Experiments

Thin, uniform arsenic targets suitable for high-fidelity cross section measurements in stacked-target experiments were prepared by electrodeposition of arsenic on titanium backings from aqueous solutions. Electrolytic cells were constructed and capable of arsenic deposits ranging in mass from approximately 1$\unicode{x2013}$29 mg (0.32$\unicode{x2013}$7.2 mg/cm$^2$, 0.57$\unicode{x2013}$13 $\mu$m). Examination of electrodeposit surface morphology by scanning electron microscopy and microanalysis was performed to investigate the uniformity of produced targets. Brief studies of plating growth dynamics and structural properties through cyclic voltammetry were also undertaken. Alternative target fabrication approaches by vapor deposition and electrodeposition from a deep eutectic solvent were additionally conducted. We further introduce a non-destructive characterization method for thin targets by neutron activation, which is independent of neutron flux shape, environmental factors, and source geometry, while correcting for any potential scatter or absorption effects.

physics.ins-det↗

arXiv2021

Investigating High-Energy Proton-Induced Reactions on Spherical Nuclei: Implications for the Pre-Equilibrium Exciton Model

A number of accelerator-based isotope production facilities utilize 100- to 200-MeV proton beams due to the high production rates enabled by high-intensity beam capabilities and the greater diversity of isotope production brought on by the long range of high-energy protons. However, nuclear reaction modeling at these energies can be challenging because of the interplay between different reaction modes and a lack of existing guiding cross section data. A Tri-lab collaboration has been formed among the Lawrence Berkeley, Los Alamos, and Brookhaven National Laboratories to address these complexities by characterizing charged-particle nuclear reactions relevant to the production of established and novel radioisotopes. In the inaugural collaboration experiments, stacked-targets of niobium foils were irradiated at the Brookhaven Linac Isotope Producer (E$_p$=200 MeV) and the Los Alamos Isotope Production Facility (E$_p$=100 MeV) to measure $^{93}$Nb(p,x) cross sections between 50 and 200 MeV. The measured cross-section results were compared with literature data as well as the default calculations of the nuclear model codes TALYS, CoH, EMPIRE, and ALICE. We developed a standardized procedure that determines the reaction model parameters that best reproduce the most prominent reaction channels in a physically justifiable manner. The primary focus of the procedure was to determine the best parametrization for the pre-equilibrium two-component exciton model. This modeling study revealed a trend toward a relative decrease for internal transition rates at intermediate proton energies (E$_p$=20-60 MeV) in the current exciton model as compared to the default values. The results of this work are instrumental for the planning, execution, and analysis essential to isotope production.

nucl-ex↗

arXiv2020

An Integral Experiment on Polyethylene Using Radiative Capture in Indium Foils in a High Flux D-D Neutron Generator

The Department of Nuclear Engineering, University of California Berkeley built a D-D neutron generator called the High Flux Neutron Generator (HFNG). It operates in the range of 100-125 keV of accelerating voltage. The generator produces neutron current of about 10^8 per second. These neutrons have energies between 2.2-2.8 MeV. We report here the results of a measurement of the scattered vs unscattered neutron fluence on polyethylene determined via neutron activation of multiple natural indium foils from a D-D neutron generator. Both the angle-integrated spectrum and the angle differential results are consistent with the predictions of the Monte Carlo N-Particle Transport (MCNP) code, using the ENDF/B-VII.1. This supports shielding calculations in the fast energy region with high density polyethylene (HDPE). To the best of our knowledge no integral benchmark experiment has been performed on polyethylene using D(D,n)alpha neutron spectrum.

nucl-ex↗

arXiv2019

Proton-induced reactions on Fe, Cu, & Ti from threshold to 55 MeV

Theoretical models often differ significantly from measured data in their predictions of the magnitude of nuclear reactions that produce radionuclides for medical, research, and national security applications. In this paper, we compare a priori predictions from several state-of-the-art reaction modeling packages (CoH, EMPIRE, TALYS, and ALICE) to cross sections measured using the stacked-target activation method. The experiment was performed using the LBNL 88-Inch Cyclotron with beams of 25 and 55 MeV protons on a stack of iron, copper, and titanium foils. 34 excitation functions were measured for 4 < Ep < 55 MeV, including the first measurement of the independent cross sections for natFe(p,x) 49,51Cr, 51,52m,52g,56Mn, and 58m,58gCo. All of the models failed to reproduce the isomer-to-ground state ratio for reaction channels at compound and pre-compound energies, suggesting issues in modeling the deposition or distribution of angular momentum in these residual nuclei.

nucl-ex↗

arXiv2019

Measurement of $^{139}$La(p,x) Cross Sections from 35-60 MeV by Stacked-Target Activation

A stacked-target of natural lanthanum foils (99.9119% $^{139}$La) was irradiated using a 60 MeV proton beam at the LBNL 88-Inch Cyclotron. $^{139}$La(p,x) cross sections are reported between 35-60 MeV for nine radionuclides. The primary motivation for this measurement was the need to quantify the production of $^{134}$Ce. As a positron-emitting analogue of the promising medical radionuclide $^{225}$Ac, $^{134}$Ce is desirable for in vivo applications of bio-distribution assays for this emerging radio-pharmaceutical. The results of this measurement were compared to the nuclear model codes TALYS, EMPIRE and ALICE (using default parameters), which showed significant deviation from the measured values.

nucl-ex↗

arXiv2018

Design, construction, and characterization of a compact DD neutron generator designed for 40Ar/39Ar geochronology

A next-generation, high-flux DD neutron generator has been designed, commissioned, and characterized, and is now operational in a new facility at the University of California Berkeley. The generator, originally designed for 40Ar/39Ar dating of geological materials, has since served numerous additional applications, including medical isotope production studies, with others planned for the near future. In this work, we present an overview of the High Flux Neutron Generator (HFNG) which includes a variety of simulations, analytical models, and experimental validation of results. Extensive analysis was performed in order to characterize the neutron yield, flux, and energy distribution at specific locations where samples may be loaded for irradiation. A notable design feature of the HFNG is the possibility for sample irradiation internal to the cathode, just 8 mm away from the neutron production site, thus maximizing the neutron flux (n/cm2/s). The generator's maximum neutron flux at this irradiation position is 2.58e7 n/cm2/s +/- 5% (approximately 3e8 n/s total yield) as measured via activation of small natural indium foils. However, future development is aimed at achieving an order of magnitude increase in flux. Additionally, the deuterium ion beam optics were optimized by simulations for various extraction configurations in order to achieve a uniform neutron flux distribution and an acceptable heat load. Finally, experiments were performed in order to benchmark the modeling and characterization of the HFNG.

physics.acc-ph↗

arXiv2015

Performance of Several Solid State Photomultipliers with CLYC Scintillator

$Cs_2LiYCl_6:Ce^{3+}$ (CLYC) is an inorganic scintillator that has recently garnered attention for its ability to detect and discriminate between gammas and thermal neutrons. We investigate several important performance parameters of three different solid state photomultipliers (SSPMs) when reading out CLYC crystals: linearity, energy resolution, and pulse shape and discrimination ability. These performance parameters are assessed at a variety of temperatures between -20$^{\circ}$C and +50$^{\circ}$C.

physics.ins-det↗