In CERN's beam transfer lines, high-voltage generators have traditionally relied on thyratron switches;however, thyratrons present operational challenges and are also becoming increasingly hard to source. To addre...
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In CERN's beam transfer lines, high-voltage generators have traditionally relied on thyratron switches;however, thyratrons present operational challenges and are also becoming increasingly hard to source. To address this issue, there is a growing interest in adopting compact pulse generators made from commercially available off-the-shelf (COTS) components. Recent research has demonstrated that thyristors designed for rectifier applications, which are not specifically designed for fast rise times, can be activated in overvoltage mode-also referred to as impact-ionization mode. These devices achieve substantial improvements in their dU/dt and dI/dt characteristics. This activation method involves applying a substantial overvoltage between the thyristor's anode and cathode, along with a fast slew rate exceeding 1 kV/ns. The adoption of compact pulse generators built from COTS components opens up new opportunities for deploying this technology across multiple domains, including high-speed kicker generators in particle accelerators. In our methodology, we incorporated commercially available high-voltage components-SiC MOSFETs-that were triggered using a fast gate driver, which was custom-designed. The generated output pulse was then amplified and sharpened in a four-stage Marx generator composed of small, 1.2 kV rated D2PAK thyristors. This configuration yielded an output pulse with an amplitude of 11 kV and a 10-90% dU/dt of 13.3 kV/ns. The present study details the design of the Marx generator and the resulting pulses, along with the challenges faced in high-voltage measurements.
The yields of the reactions 11 B (γ, π − ) 11 C , 27 Al (γ, π + ) 27 Mg , 51 V (γ, π + ) 51 Ti and 51 V (γ, π − 2 n ) 49 Cr have been measured by activation analysis from threshold up to 750 MeV. The true and ...
The yields of the reactions 11 B (γ, π − ) 11 C , 27 Al (γ, π + ) 27 Mg , 51 V (γ, π + ) 51 Ti and 51 V (γ, π − 2 n ) 49 Cr have been measured by activation analysis from threshold up to 750 MeV. The true and integrated cross sections have been calculated. The experimental cross sections have been compared with predictions from a Fermi gas model. Fairly good agreement is obtained.
Electronic dc transport along a finite chain of scatterers that allow for elastic as well as inelastic processes is described within the Landauer-Büttiker approach. The transport channels in the chain are locally...
Electronic dc transport along a finite chain of scatterers that allow for elastic as well as inelastic processes is described within the Landauer-Büttiker approach. The transport channels in the chain are locally coupled via (current-conserving) side channels to electron reservoirs or heat baths that provide the phase randomization. Different choices for the parameters describing the inelastic coupling as well as the elastic (transmission and reflection) coefficients are compared. The scattering matrix of the chain is calculated with a recursive method. We show that the most general individual scatterer can be characterized by five parameters only, and that it can be represented by a subset of unitary 4×4 matrices. In order to demonstrate the influence of the inelastic-scattering parameters, we investigate the fluctuations of the chemical potential measured by a probe in front of an elastic scatterer. We find that—even in the noninvasive limit—the oscillations of the chemical potential with the distance between the two scatterers depend strongly on the choice of the scattering matrix representing the probe. Our results are discussed in the context of previous investigations.
Ultrasound imaging is a widely used imaging technique. The use of contrast agents has become an indispensible part of clinical ultrasound imaging, and molecular imaging via ultrasound has recently attracted significan...
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Ultrasound imaging is a widely used imaging technique. The use of contrast agents has become an indispensible part of clinical ultrasound imaging, and molecular imaging via ultrasound has recently attracted significant attention. We recently reported that "Bubble liposomes" (BLs) encapsulating US imaging gas liposomes were suitable for ultrasound imaging and gene delivery. The 12 amino acid AG73 peptide derived from the laminin alpha 1 chain is a ligand for syndecans, and syndecan-2 is highly expressed in blood vessels. In this study, we prepared AG73 peptide-modified BLs (AG73-BLs) and assessed their specific attachment and ultrasound imaging ability for blood vessels in vitro and in vivo. First, we assessed the specific attachment of AG73-BLs in vitro, using flow cytometry and microscopy. AG73-BLs showed specific attachment compared with non-labeled or control peptide-modified BLs. Next, we examined ultrasound imaging in tumor-bearing mice. When BLs were administered, contrast imaging of AG73-BLs was sustainable for up to 4 min, while contrast imaging of non-labeled BLs was not observed. Thus, it is suggested that AG73-BLs may become useful ultrasound contrast agents in the clinic for diagnosis based on ultrasound imaging. (C) 2012 Elsevier Ltd. All rights reserved.
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