Effect of beam current on defect formation by high-temperature implantation of Mg ions into GaN

We evaluated the beam current dependence of defect formation during Mg ion implantation into GaN at a high temperature of 1100℃ with two beam currents. Photoluminescence spectra suggested that low-beam-current ion implantation reduced the vacancy concentration and activated Mg to a greater extent. Moreover, scanning transmission electron microscopy analysis showed that low-beam-current implantation reduced the density of Mg segregation defects with inactive Mg and increased the number of intrinsic dislocation loops, suggesting a decrease in the density of Ga and N vacancies. The formation of these defects depended on beam current, which is an important parameter for defect suppression.

A modular platform for automated cryo-FIB workflows

Lamella micromachining by focused ion beam milling at cryogenic temperature (cryo-FIB) has matured into a preparation method widely used for cellular cryo-electron tomography. Due to the limited ablation rates of low Ga+ ion beam currents required to maintain the structural integrity of vitreous specimens, common preparation protocols are time-consuming and labor intensive. The improved stability of new generation cryo-FIB instruments now enables automated operations. Here, we present an open-source software tool, SerialFIB, for creating automated and customizable cryo-FIB preparation protocols. The software encompasses a graphical user interface for easy execution of routine lamellae preparations, a scripting module compatible with available Python packages, and interfaces with 3-dimensional correlative light and electron microscopy (CLEM) tools. SerialFIB enables the streamlining of advanced cryo-FIB protocols such as multi-modal imaging, CLEM-guided lamella preparation and in situ lamella lift-out procedures. Our software therefore provides a foundation for further development of advanced cryogenic imaging and sample preparation protocols.

FCC-ee: the synthesis of a long history of e+e- circular colliders

The design of FCC-ee is relying on the accumulated experience of $$\mathrm {e^{+}e^{-}}$$ e + e - colliders that have been designed, constructed and operated in the past 40 years. FCC-ee will surpass the 26.7 km long Large Electron Positron collider LEP by a factor 4 in size. Like for LEP the large size is justified by the need to control the synchrotron radiation losses that for both machines reach a few percent per turn. To that end LEP had the first large super-conducting (SC) RF system with around 3.8 GV of accelerating voltage. LEP achieved for the first time very large beam-beam parameters of around 0.08, and it relied on transversely polarized beams to determine accurately the beam energy for the experiments. The DA$$\varPhi $$ Φ NE collider, together with PEP II and KEKB split the two beams into separate vacuum chambers to reach much higher Ampere-level beam currents. To overcome beam-beam lifetime and performance issues DA$$\varPhi $$ Φ NE used for the first time the Crab Waist concept for the interaction region (IR) optics. The B-factories, PEP-II and KEKB have verified the double-ring $$\mathrm {e^{+}e^{-}}$$ e + e - collider with multi-ampere stored currents for over 1000 bunches, small $$\beta ^*$$ β ∗ , top-up injection, and achieved then-highest luminosity. KEKB has applied 22-mrad crossing angle at the IP with crab crossing. Both machines inherited accelerator techniques from their predecessors, PEP and TRISTAN, which was a small-scale LEP. Currently the next generation SuperKEKB collider is starting up. It has already achieved some milestones required for FCC-ee such as small $$\beta ^*$$ β ∗ (0.8 mm) and virtual crab-waist scheme with a large Piwinski angle (>10).

A Modular Platform for Streamlining Automated Cryo-FIB Workflows

Lamella micromachining by focused ion beam milling at cryogenic temperature (cryo-FIB) has matured into a preparation method widely used for cellular cryo-electron tomography. Due to the limited ablation rates of low Ga+ ion beam currents required to maintain the structural integrity of vitreous specimens, current preparation protocols are time-consuming and labor intensive. The improved stability of new generation cryo-FIB instruments now enables automated operations. Here, we present an open-source software tool, SerialFIB, for creating automated and customizable cryo-FIB preparation protocols. The software encompasses a graphical user interface for easy execution of routine lamellae preparations, a scripting module compatible with available python packages, and interfaces with 3-dimensional correlative light and electron microscopy (CLEM) tools. The software enables the streamlining of advanced cryo-FIB protocols such as multi-modal imaging, CLEM guided preparation and in situ lamella lift-out procedures. Our software therefore provides a foundation for further development of advanced cryogenic imaging and sample preparation protocols.

Electron guiding in macroscopic borosilicate capillaries with large bending angles

This work presents experiments about the transmission of electrons with an energy of around 15 keV with beam currents up to 20 µA through macroscopic glass capillaries. A systematic study was conducted to experimentally investigate the transmission of electrons through borosilicate glass capillaries with curve angles of 90°, 180°, 270° and 360° for the first time. The focus of the work was to identify the conditions under which the injected electron current is transmitted through the capillary. It was also shown that the transmission process in the macroscopic capillaries can be optically observed by cathodoluminescence—the interaction of electrons with the capillary surface causes locally a blue glow. Different distinctive “glow states” were observed and are found to correlate with different states of electron transmission.

Current stability to improve AMS precision for cosmogenic 10Be applications

<p>With the present AMS <sup>10</sup>Be uncertainties (~2% best case scenario) and the increasing need for more precise cosmogenic <sup>10</sup>Be data it has become imperative to improve AMS measurements. Precision depends on counting statistics which in turn depend on ion beam current stability and sample longevity. The ion beam currents are dependent on the metal matrix in which BeO is dispersed; the matrix:BeO ratio; homogeneity of the mixture and the packing of the AMS cathode. We aim to understand the effect of cathode homogeneity in generating stable beam currents. We have performed a series of experiments using different metal matrices (Nb, Ag, Fe) in different forms (solid and in solution). The metals have been added to different stages of the sample precipitation process and both BeO and Be(OH)<sub>2</sub> have been pressed into AMS cathodes and analysed at SUERC. We will discuss results of these experiments and introduce an innovative use of polyoxometalates (molibdanate and niobate) to create a homogeneous compound that has the potential to generate stable ion beam currents from sputter ion sources.</p>

Electron Guiding in Macroscopic Borosilicate Capillaries With Large Bending Angles

This work presents experiments about the transmission of electrons with an energy of around 15 keV with beam currents up to 20 µA through macroscopic glass capillaries. A systematic study was conducted to experimentally investigate the transmission of electrons through borosilicate glass capillaries with curve angles of 90°, 180°, 270° and 360° for the first time. The focus of the work was to identify the conditions under which the injected electron current is transmitted through the capillary. It was also shown that the transmission process in the macroscopic capillaries can be optically observed by cathodoluminescence – the interaction of electrons with the capillary surface causes locally a blue glow. Different distinctive “glow states” were observed and are found to correlate with different states of electron transmission.

Material Sputtering with a Multi-Ion Species Plasma Focused Ion Beam

Focused ion beams are an essential tool for cross-sectional material analysis at the microscale, preparing TEM samples, and much more. New plasma ion sources allow for higher beam currents and options to use unconventional ion species, resulting in increased versatility over a broader range of substrate materials. In this paper, we present the results of a four-material study from five different ion species at varying beam energies. This, of course, is a small sampling of the enormous variety of potential specimen and ion species combinations. We show that milling rates and texturing artifacts are quite varied. Therefore, there is a need for a systematic exploration of how different ion species mill different materials. There is so much to be done that it should be a community effort. Here, we present a publicly available automation script used to both measure sputter rates and characterize texturing artifacts as well as a collaborative database to which anyone may contribute. We also put forth some ideas for new applications of focused ion beams with novel ion species.

Cyclotron-based production of 68Ga, [68Ga]GaCl3, and [68Ga]Ga-PSMA-11 from a liquid target

Purpose To optimize the direct production of 68Ga on a cyclotron, via the 68Zn(p,n)68Ga reaction using a liquid cyclotron target. We Investigated the yield of cyclotron-produced 68Ga, extraction of [68Ga]GaCl3 and subsequent [68Ga]Ga-PSMA-11 labeling using an automated synthesis module. Methods Irradiations of a 1.0 M solution of [68Zn]Zn(NO3)2 in dilute (0.2–0.3 M) HNO3 were conducted using GE PETtrace cyclotrons and GE 68Ga liquid targets. The proton beam energy was degraded to a nominal 14.3 MeV to minimize the co-production of 67Ga through the 68Zn(p,2n)67Ga reaction without unduly compromising 68Ga yields. We also evaluated the effects of varying beam times (50–75 min) and beam currents (27–40 μA). Crude 68Ga production was measured. The extraction of [68Ga]GaCl3 was performed using a 2 column solid phase method on the GE FASTlab Developer platform. Extracted [68Ga]GaCl3 was used to label [68Ga]Ga-PSMA-11 that was intended for clinical use. Results The decay corrected yield of 68Ga at EOB was typically > 3.7 GBq (100 mCi) for a 60 min beam, with irradiations of [68Zn]Zn(NO3)2 at 0.3 M HNO3. Target/chemistry performance was more consistent when compared with 0.2 M HNO3. Radionuclidic purity of 68Ga was typically > 99.8% at EOB and met the requirements specified in the European Pharmacopoeia (< 2% combined 66/67Ga) for a practical clinical product shelf-life. The activity yield of [68Ga]GaCl3 was typically > 50% (~ 1.85 GBq, 50 mCi); yields improved as processes were optimized. Labeling yields for [68Ga]Ga-PSMA-11 were near quantitative (~ 1.67 GBq, 45 mCi) at EOS. Cyclotron produced [68Ga]Ga-PSMA-11 underwent full quality control, stability and sterility testing, and was implemented for human use at the University of Michigan as an Investigational New Drug through the US FDA and also at the Royal Prince Alfred Hospital (RPA). Conclusion Direct cyclotron irradiation of a liquid target provides clinically relevant quantities of [68Ga]Ga-PSMA-11 and is a viable alternative to traditional 68Ge/68Ga generators.