Berkeley Lab
Bringing Science Solutions to the World

Nuclear Science Division

Inclusion, Diversity, Equity and Accountability Moments

APS Ethics Committee

In 2019, the American Physical Society (APS) formed an Ethics Committee (EC), charged to provide guidance on how the APS can promote ethical behavior by members, and police unethical behavior, including scientific ethics (fabrication, falsification or plagiarism) and interpersonal misbehavior – sexual harassment or bullying, for example. EC member and NSD Senior Scientist Spencer Klein discussed EC activities at a recent NSD staff meeting and summarizes those activities here.

Under the guidance of the APS Board, the committee works in several areas. They review APS statements on ethics and propose new ones, as appropriate. They provide ethics education, through presentations and workshops at APS meetings, and articles in different publications, such as Physics Today.

The EC develops policies and procedures for the APS to handle reports of misconduct. There are two categories: incidents at APS meetings, and everything else. For incidents at APS meetings, the APS will immediately (i.e., during the meeting) investigate and react as appropriate, and can remove the perpetrator from the meeting if needed.

Other complaints are dealt with in a longer, more involved process, starting with an initial review by the APS Ombudsperson (an outside lawyer), review by the EC, and then by the APS Board. Appeals are also possible. The APS also asks nominators (and, later, nominees) if nominees for APS committees, offices, prizes or fellowships are known to have committed misconduct. Positive answers are followed up and action may be taken.

For non-meeting complaints, the APS will not investigate, but will react to complaints which include an investigatory report by other agencies, such as the employer or other agency. The non-investigation policy can be problematic, since investigatory reports are usually private, and not available to would-be complainants or the APS.

Although many people think that the APS should conduct investigations when needed, there are real challenges in doing so. It would require significant resources, and could open the door to lawsuits. Incidents reported to the APS will likely have previously been investigated by one or more groups. Witnesses (especially victims of sexual harassment) may not want to tell their story many times, and not everyone will trust or cooperate with a U. S.-based organization. There is also some risk that different investigations reach different conclusions.

But, with outside investigatory reports generally unavailable, without its own investigation, the APS may be unable to act, even against pervasive behavior. And that is clearly extremely awkward. The EC is continuing to grapple with this.

Recent DEI topics @ NSD Staff Meetings

January 10, 2023 – Update on the Mental Health Initiative and WD&E Deadlines
January 24, 2023 – Effective Teams
February 7, 2023 – APS Ethics Committee
February 21, 2023 – Outreach Opportunities
March 7, 2023 – K-12 Stem Programs
March 21, 2023 – Women’s History Month and Transgender Day of Visibility
April 4, 2023 – Inclusion and Equity in Science Publications

Luminary Cards

To recognize their efforts in the area(s) of Inclusion, Diversity, Equity, and Accountability, the following people received a Luminary Card:

Spencer Klein

Applied Nuclear Physics Program Aiding Clean-up of Cold War-Era Radioactive Contamination through Radiological Mapping

From 1955–1988, low-level waste solutions from the processing of uranium and irradiated nuclear fuel were discharged into unlined earthen storage basins at the Savannah River Site (SRS) F-Area [1]. Over the decades, radioactive contaminants including uranium and iodine-129 (I-129) have leaked out of the basins and into the groundwater of the surrounding wetlands, and are now present at levels that exceed regulatory thresholds.

Figure 1: Hansell Gonzalez-Raymat of SRNL carries LBNL’s MiniPRISM radiation imager through the SRS F-Area wetlands.

In March 2023, scientists from NSD’s Applied Nuclear Physics (ANP) program returned to the SRS F-Area wetlands to conduct handheld gamma-ray surveys in order to map the intensity and spatial distribution of radioactive contaminants in the area. Using ANP’s Scene Data Fusion (SDF) radiological mapping technology (see, e.g., [2]), roughly 0.25 km2 of dense forested wetlands were surveyed. Several uranium hotspots (up to roughly five times higher than the SRS natural background) were identified, and more detailed analysis is ongoing both to refine the mapping results and to examine possible yearly variations compared to measurements from the team’s 2022 campaign. In Fig. 1, a Savannah River National Laboratory (SRNL) scientist can be seen carrying LBNL’s MiniPRISM radiation imager through the SRS-F Area wetlands. Fig. 2 shows SDF results, including a preliminary reconstruction of low energy gamma-ray intensities during one survey. In addition to the SDF mapping systems that are sensitive to uranium radioactivity, LBNL is exploring whether silicon drift detectors are a viable technology to map the I-129 in situ.  These efforts are part of the larger DOE-EM ALTEMIS project, which aims to develop long-term remediation and monitoring strategies for contaminated DOE legacy sites and have used the F-Area wetlands as a test bed.

Figure 2: Left: ground height estimation of a mapped area at the SRS F-Area. Right: preliminary reconstruction of low-energy gamma-ray intensities during a single survey. Hotspots are visible in the seepage areas towards the bottom of the map and are clearly distinguishable from low-activity areas.

Jayson Vavrek, Brian Quiter and Joanna Szornel collected the data in March 2023 with support from the Savannah River Site. Carol Eddy-Dilek (SRNL) and Haruko Murakami-Wainwright (MIT/LBNL) are Lead and Co-Lead of the DOE ALTEMIS project supporting this work. Zexuan Xu (LBNL EESA) is the LBNL PI.

[1] Biogeochemical gradients as a framework for understanding waste‐site evolution, M. Denham and K. Vangelas, Remediation Journal: The Journal of Environmental Cleanup Costs, Technologies & Techniques 19.1 (2008), DOI: 10.1002/rem.20188
[2] Free-moving quantitative gamma-ray imaging, D. Hellfeld et al., Scientific Reports 11 (2021), DOI: 10.1038/s41598-021-99588-z

Exploring Machine Learning at VENUS

In 2021, a collaboration of NSD scientists from the Applied Nuclear Physics, Low-Energy Nuclear Physics, and the 88” Cyclotron programs received funding through a DOE Office of Science FOA for “Data Analytics for Autonomous Optimization and Control of Accelerators and Detectors” to explore application of machine learning approaches to the operations of both the VENUS ion source [1] and the GRETA γ-ray detector array [2].

The primary goal of this project is to explore the best applications of existing machine learning approaches and techniques to optimize and automate operations of both devices.  Work has primarily been focused so far on the case of VENUS. The team has established a continuous logging system that has been used to populate a time-series database with relevant control and diagnostic parameters from the operation of the source for over a year.  The researchers, supported by a group of undergraduate researchers, are exploring the use of predictive neural networks and Bayesian optimization of the parameter space to tune the ion source.  

By providing training data, such as the parameter values that VENUS was operating at and the corresponding beam current produced, the team has begun to develop a neural network which is intended to predict the current for other parameter values and use it to optimize the source. Early indications, however, suggest that in order to do this successfully, the range of input parameters must be extended and the researchers are therefore installing environmental sensors at the ion source in order to measure additional parameters such as temperature and air pressure. 

In contrast, the use of Gaussian Process Regression (GPR) to map the parameter space and guide optimization of the VENUS tuning procedure has been very successful.  Using this approach, a probability map of the full parameter space is generated from just a few measurements at different parameter values. The probabilistic map can then be used to guess parameter values which are likely to provide a better beam current. By performing the procedure a few dozen times an optimal solution is iteratively approached within a few hours, a similar timescale that would be expected from a human operator.  The GPR approach has been shown to robustly produce a maximized beam current within a limited parameter space.  Fig. 1 shows the result of using GPR to explore a two-dimensional parameter space during a test run with VENUS.  The black circles represent measured observables, while the smooth distribution in the background shows the predictions from the GPR.  Work is ongoing to extend this effort and potentially identify useful operational settings for VENUS which have not been considered by human operators.  

Figure  1.  Two dimensional parameter space explored in a test run. Circles represent the measured data, the smooth distribution in the background shows the predictions from Gaussian Process Regression.

This project is led by Damon Todd from the Low Energy Nuclear Physics program, Marco Salathe from the Applied Nuclear Physics program and Heather Crawford, from the Low Energy Nuclear Physics program.

[1] Recent progress on the superconducting ion source VENUS, J.Y. Benitez et al., Review of Scientific Instruments 83, 02A311 (2012), DOI: 10.1063/1.3662119
[2] The GRETA Final Design Report, 2020.  Available online: GRETA_FDR.pdf

A New Dimension to the Jet-induced Mach Cone in the Subatomic QGP Droplets

Projectiles traveling at a speed greater than the velocity of sound generate Mach cones, such as the sonic boom originating from a supersonic aircraft. These kinds of Mach cones are also produced on the femtometer scale inside the droplets of quark-gluon plasma (QGP) by propagating jets in high-energy heavy-ion collisions at the Relativistic Heavy-ion Collider (RHIC) and Large Hadron Collider (LHC).  Inside the subatomic droplets of QGP, energetic jet partons propagate at the velocity of light and lose energy and momentum to the medium through strong interaction. The lost energy and momentum becomes a source of sound in the medium with sound velocity only a fraction of the velocity of light. This generates a sound wave in the form of a  Mach cone which will manifest itself in the final soft hadrons correlated with the energetic jets.  Study of this Mach cone structure in the final soft hadron distribution can shed light on the equation of state (EoS) and shear viscosity in the QGP medium.

Figure 1: 3D energy density distribution of a jet-induced Mach cone in Pb+Pb collisions at LHC (left) and soft hadron correlation in azimuthal angle and rapidity with respect to a photon-tagged jet from theoretical simulations (right). Arrowed lines represent jet partons, red and orange color represent energy density of the Mach cone, and green color represents the negative energy density of the diffusion wake.

In a recent article (Phys. Rev. Lett. 130 (2023) 5, 052301), Xin-Nian Wang from NSD’s Nuclear Theory program and his collaborators explored the 3D structure of the jet-induced Mach cone excitation in Pb+Pb collisions at LHC through theoretical simulations of the jet transport inside a hydrodynamically expanding QGP.  They found that the associated diffusion wake of the Mach cone produces a unique valley structure on top of the ridge from multiple parton scattering in soft hadron correlation with respect to photon-tagged jets in azimuthal angle and rapidity. The images in Fig. 1 show a 3D energy distribution of a jet-induced Mach cone and the soft hadron correlation.

This new dimension in the soft hadron and jet correlation in the rapidity direction opens up a new window to the study of jet-induced Mach cones. The unique structure should be easy to detect and will provide additional constraints on the equation of state and transport coefficients of the quark-gluon plasma as their study shows.

Inclusion, Diversity, Equity, and Accountability Moments

Colorblindness Inclusion in NSD

In September 2022, Jayson Vavrek, a postdoctoral researcher within the Applied Nuclear Physics program, gave a presentation at the NSD staff meeting about the need to consider the choice of colors when creating figures and other graphics so that we can better include those who are colorblind or are affected by another form of color vision deficiency (CVD). Measurements vary, but approximately 2–10% of men and 0.1–3% of women have some form of CVD, so a substantial proportion of your audience (roughly 5%) may have some difficulty perceiving color.

Jayson pointed out that although many popular scientific plotting packages have switched to colorblind-friendly default palettes in recent years, it is still important to consider how one’s plots and other graphics will be perceived by those with different abilities to see color. For example, here is a plot using matplotlib’s default color scheme, with the version on the right being adjusted to what a person with deuteranopia (or red-green colorblindness, the most common form of CVD) would see:

a plot using matplotlib’s default color scheme, with the version on the right being adjusted to what a person with deuteranopia (or red-green colorblindness, the most common form of CVD) would see

Instead of relying on color alone to convey meaning, one can also use text, symbols, and/or texture to signal the difference. In the above example, different line dashing styles would improve the differentiation between the lines. Another key takeaway is to use perceptually uniform colormaps instead of rainbow (or “jet”) colormaps, since they are more inclusive for viewers with CVD (and they can be misleading even for those without CVD!).

These days there are many technological solutions to help those without CVD to be more inclusive of those with CVD. There are specially designed color palettes (e.g., Color Brewer), and both desktop simulation tools (e.g., Color Oracle) and augmented reality mobile apps (e.g., Sim Daltonism) to allow one to see how a given plot or graphic will look under different types of CVD.

Coincidentally, on the very same day that Jayson gave his presentation, one of our colleagues within NSD had just alerted the IDEA Council that several signs and markings within the Laboratory make work harder for colleagues with CVD. In response, the IDEA Council initiated contact with Creative Services, Strategic Communications, and other offices and groups within LBL and has convened a working group to understand the existing policies for colorblindness inclusion at the lab, and to potentially craft new lab-wide recommendations for all staff to be aware of. The council will be informing the division of the progress on these recommendations so that we can continue to build a more safe and inclusive workplace at the lab.

Recent DEI topics @ NSD Staff Meetings

September 27, 2022 – Announcements, and Making colorblind-inclusive figures

October 11, 2022 – Disability Awareness Month

October 25, 2022 – DNP 2022 and Code of Conduct for APS meetings

November 8, 2022 – Native American Heritage Month, Veterans Day, and National Family Caregivers Month

November 22, 2022 – PIER plans for DOE proposals

December 20, 2022 – Winter Break 2022

Luminary Cards

To recognize their efforts in the area(s) of Inclusion, Diversity, Equity, and Accountability, the following people received a Luminary Card:

Alan Poon and multiple anonymous recipients

Scintillator Research Group moves to NSD

The LBNL Scintillator Research Group, formerly part of the Material Sciences Division, has joined the Nuclear Science Division. This move creates new opportunities for the development of novel radiation detection systems for a range of applications from basic science to nuclear security and medical imaging.

The detection of ionizing radiation underpins many applications that cover a large number of fields that span from the medical, to security inspection and non-destructive testing, to nuclear non-proliferation and emergency response, and to High Energy Physics. Many of these technologies rely on the capability of a group of materials, called scintillators, to efficiently convert the ionizing radiation into UV or visible light that can be more easily detected and analyzed. No single scintillator is, however, able to efficiently interact with all types of ionizing radiation, leading to the development of a large number of different materials tailored for each specific application. The discovery and the optimization of scintillators is still a thriving research field, as new needs arise.

The Scintillator Research Group at LBL has been active in inorganic scintillator research for over thirty years, building an almost unique laboratory in which all aspects of scintillator research can be tackled: from materials synthesis and growth into single crystals, to the characterization of their luminescence and scintillation properties. Over the past 15 years the Group discovered over 22 new scintillating materials. The Group is able to grow single crystals, Fig. 1, through a variety of methods (from Czochralski to Bridgman-Stokbarger and micro-Pulling Down) on both oxide- and halide-based scintillators. Optical, luminescence and scintillation properties of the obtained materials are investigated with a variety of methods (from photo- and radioluminescence both in steady state and time resolved (Fig. 2) manner, to pulse height spectra with gamma ray sources and thermally stimulated luminescence) in order to qualify these materials. 

Primary interests of the Group include the discovery of new scintillators, the optimization of scintillator properties through suitable chemical addition/modification of their composition, fundamental physic phenomena underlying the scintillation process itself including the role of defects, and synthesis strategies. Although the Group focus has been on inorganic scintillators, it recently expanded also to water-based liquid scintillators as well as organic/inorganic composites. 

The addition of the Scintillator Research Group strengthens NSD’s existing capabilities in radiation detector development and compliments the longstanding expertise in semiconductor development.

Federico Moretti and Weronika Wolszczak contributed to this article. Dr. Moretti is the PI of the Scintillator Research Group and Dr. Wolszczak is a Postdoctoral Researcher.

Figure 1: a polished piece of Cs2LiLaBr6:Ce (CLLB) single crystal grown by Bridgman Stockbarger.

Figure 2: Scintillation decay profile as a function of the temperature of a newly developed Tl2La0.95Ce0.05Cl5 single crystal measured with a table-top light-excited x-ray tube working at 40 kVp. The system has an instrument response function of about 100 ps. Measurements were performed in the 15-310 K. These scintillation decays allow to clarify how much charge carrier transport toward the luminescence centers is affected by the temperature. The curves have been shifted along the ordinate axis for clarity.