The China Spallation Neutron Source drift tube linac (DTL) is a high current intensity linear accelerator operated in pulsed mode. Beam loss is the most important cause of DTL performance degradation. Therefore, control of beam loss is very crucial to the linac's commission and routine operation. The beam loss in beam pulse width (∼several hundreds of microseconds) can be regarded as an instantaneous process, which may cause the local temperature of the drift tubes (DTs) to exceed the melting point or the thermal stress to exceed the material yield strength, resulting in permanent damage to the DTs. RF heating and beam loss are two major heat sources of the DTs during operation. First, temperature rise due to RF power dissipation is evaluated in this paper. Then, the thermomechanical response due to beam loss at different energies is investigated. It is found that the 3-MeV beam loss has the greatest stopping power and causes the largest temperature rise to the DTs. The maximum beam current loss for different working conditions is analyzed by both analytical method and ANSYS simulations, and the details will also be discussed in this paper.
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http://dx.doi.org/10.1063/5.0096462 | DOI Listing |
Beijing Da Xue Xue Bao Yi Xue Ban
February 2025
First Clinical Division, Peking University School and Hospital of Stomatology & National Center for Stomatology & National Clinical Research Center for Oral Diseases & National Enginee-ring Research Center of Oral Biomaterials and Digital Medical Devices, Beijing 100081, China.
Objective: To clarify the role of concentrated growth factors (CGF) in the treatment of periodontal cement defects using calcium phosphate cement (CPC) with self-curing properties.
Methods: Thirty-six intrabony defects were randomly divided into two groups. The experimental group received CGF+CPC treatment (=18), while the control group received CPC treatment alone (=18).
Beijing Da Xue Xue Bao Yi Xue Ban
February 2025
Department of Periodontology, Peking University School and Hospital of Stomatology & National Center for Stomatology & National Clinical Research Center for Oral Diseases & National Engineering Research Center of Oral Biomaterials and Digital Medical Devices, Beijing 100081, China.
Objective: To evaluate the clinical and radiographic efficacy of micro crestal flap-alveolar ridge preservation following extraction of mandibular molars with severe periodontitis compared with natural healing, and to preliminarily propose the surgical indication.
Methods: A retrospective analysis was conducted on clinical data from patients with mandibular molars with severe periodontitis either receiving micro crestal flap-alveolar ridge preservation (MCF-ARP group) or undergoing natural healing in department of periodontology, Peking University School and Hospital of Stomatology from September 2013 to June 2021. Cone-beam computed tomography scannings performed before/immediately after extraction (as baseline) and repeated before implantation (after the extraction socket healing) were used to measure the ridge width, height and volumetric changes of the sockets, and the proportion of guided bone regeneration (GBR) during implant therapy were compared between the two groups.
Nanomaterials (Basel)
January 2025
Key Laboratory of Optoelectronic Materials and Devices, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China.
Antimonide laser diodes, with their high performance above room temperature, exhibit significant potential for widespread applications in the mid-infrared spectral region. However, the laser's performance significantly degrades as the emission wavelength increases, primarily due to severe quantum-well hole leakage and significant non-radiative recombination. In this paper, we put up an active region with a high valence band offset and excellent crystalline quality with high luminescence to improve the laser's performance.
View Article and Find Full Text PDFNano Lett
January 2025
School of Chemical Sciences, University of Auckland, Auckland 1010, New Zealand.
Understanding metastable structural transitions under beam irradiation is essential for the phase engineering of nanomaterials. However, in situ studies of beam-induced structural transitions remain challenging. This work uses an electron beam in aberration-corrected high-angle annular dark-field scanning transmission electron microscopy to irradiate Au nanocrystals at room temperature.
View Article and Find Full Text PDFTzu Chi Med J
July 2024
Neuroscience Spine Center, Taichung Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Taichung, Taiwan.
Objectives: Minimally invasive surgery (MIS) has emerged as a promising alternative to conventional open techniques in the management of adolescent idiopathic scoliosis (AIS).
Materials And Methods: This study presents a case series of six patients who underwent MIS for AIS at a spine center, employing a synergistic blend of intraoperative fluoroscopy, cone-beam computed tomography scans, and three-dimensional navigation technology. The surgical procedures were meticulously guided, with a focus on ensuring safety and precision in posterior pedicle fixation.
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