Evidence for fireballs in bipolar HiPIMS plasmas

Abstract Using laser Thomson scattering (LTS) and 2D optical imaging, a fireball-like discharge is detected during the positive pulse period of bipolar voltage waveforms, for a circular planar unbalanced magnetron with W target operating in argon. These reverse discharges, excited for positive pulse voltages V pp from 200 to 300 V, sit primarily on the discharge centreline. Their establishment is delayed relative to the initiation of the positive pulse, with the delay time shortening with increased V pp: they are clearly attached to the target (anode in this phase) and have lifetimes extending to the end of the positive pulse. LTS measurements of the electron temperature T e show dramatic electron heating (T e rises from 1 up to 3 eV) both on the discharge centre line and above the racetrack during the fireball event. This is consistent with greater light intensities from the broad band optical imaging of the discharge. In the fireball phase, the LTS measurements also show greatly reduced election densities (by a factor of 5) in the magnetic trap (directly above the racetrack) compared to the unipolar pulse case. The existence of such anodic fireballs is quite possibly an unwanted effect in bipolar HiPIMS.</jats:p

Rapid single step atmospheric pressure plasma jet deposition of a SERS active surface

A helium gas atmospheric pressure plasma jet (APPJ) is used to prepare a silver-based SERS substrate. The Raman enhancement from substrates created using APPJ compares well with two commercially available silver-based SERS substrates and an in-house prepared physical deposition of pre-synthesised silver nanoparticles. An aqueous solution of rudimentary silver salt was required as an ink to deposit zero valent silver in a single step with no post processing. An array of 16 × 16 silver ‘islands’ are printed on borosilicate glass, each island taking 5 seconds to print with a power of < 14 W to sustain the plasma. The SERS response was assessed using 4-mercaptobenzoic acid and rhodamine 6G as model analytes, with a calculated detection limit of 1 × 10−6 M. Also demonstrated is the removal of analyte from the surface after Raman measurement by exposure to helium APPJ doped with oxygen followed by hydrogen to restore zero baseline. This regeneration takes less than 10 seconds and allows for replicate measurements using the same SERS substrate

Emerging ethical issues raised by highly portable MRI research in remote and resource-limited international settings

Smaller, more affordable, and more portable MRI brain scanners offer exciting opportunities to address unmet research needs and long-standing health inequities in remote and resource-limited international settings. Field-based neuroimaging research in low- and middle-income countries (LMICs) can improve local capacity to conduct both structural and functional neuroscience studies, expand knowledge of brain injury and neuropsychiatric and neurodevelopmental disorders, and ultimately improve the timeliness and quality of clinical diagnosis and treatment around the globe. Facilitating MRI research in remote settings can also diversify reference databases in neuroscience, improve understanding of brain development and degeneration across the lifespan in diverse populations, and help to create reliable measurements of infant and child development. These deeper understandings can lead to new strategies for collaborating with communities to mitigate and hopefully overcome challenges that negatively impact brain development and quality of life. Despite the potential importance of research using highly portable MRI in remote and resource-limited settings, there is little analysis of the attendant ethical, legal, and social issues (ELSI). To begin addressing this gap, this paper presents findings from the first phase of an envisioned multi-staged and iterative approach for creating ethical and legal guidance in a complex global landscape. Section 1 provides a brief introduction to the emerging technology for field-based MRI research. Section 2 presents our methodology for generating plausible use cases for MRI research in remote and resource-limited settings and identifying associated ELSI issues. Section 3 analyzes core ELSI issues in designing and conducting field-based MRI research in remote, resource-limited settings and offers recommendations. We argue that a guiding principle for field-based MRI research in these contexts should be including local communities and research participants throughout the research process in order to create sustained local value. Section 4 presents a recommended path for the next phase of work that could further adapt these use cases, address ethical and legal issues, and co-develop guidance in partnership with local communities