Vol.32,

In this study, a one-dimensional two-phase flow four-equation model was developed to simulate the water faucet problem. The performance of six different Krylov subspace methods, namely the generalized minimal residual (GMRES), transpose-free quasi-minimal residual, quasi-minimal residual, conjugate gradient squared, biconjugate gradient stabilized, and biconjugate gradient, were evaluated with and without the application of an incomplete LU (ILU) factorization preconditioner for solving the water faucet problem. The simulation results indicate that using the ILU preconditioner with the Krylov subspace methods produces better convergence performance than that without the ILU preconditioner. Only the GMRES demonstrated an acceptable convergence performance under the Krylov subspace methods without the preconditioner. The velocity and pressure distribution in the water faucet problem could be determined using the Krylov subspace methods with an ILU preconditioner, while GMRES could determine it without the need for a preconditioner. However, there are significant advantages of using an ILU preconditioner with the GMRES in terms of efficiency. The different Krylov subspace methods showed similar performance in terms of computational efficiency under the application of the ILU preconditioner.

433

To perform an integral simulation of a pool-type reactor using CFD code, a multi-physics coupled code MPC-LBE for an LBE-cooled reactor was proposed by integrating a point kinetics model and a fuel pin heat transfer model into self-developed CFD code. For code verification, a code-to-code comparison was employed to validate the CFD code. Furthermore, a typical BT transient benchmark on the LBE-cooled XADS reactor was selected for verification in terms of the integral or system performance. Based on the verification results, it was demonstrated that the MPC-LBE coupled code can perform thermal-hydraulics or safety analyses for analysis for processes involved in LBE-cooled pool-type reactors.

386

The nitrogen doping/infusion of 650 MHz cavities for the circular electron positron collider (CEPC) is investigated in this study. Two 650 MHz 1-cell cavities are first treated via buffered chemical polishing (BCP), followed by nitrogen doping. A "2/6" condition is adopted, similar to that for 1.3 GHz cavities of Linear Coherent Light Source II. The quality factor of both cavities improved to 7 × 10¹⁰ in low fields, i.e., higher than that obtained from the baseline test. One 650 MHz two-cell cavity is nitrogen infused at 165 °C for 48 h with a BCP surface base. The intrinsic quality factor (Q₀) reached 6 × 10¹⁰ at 22 MV/m in the vertical test, and the maximum gradient is 25 MV/m, which exceeds the specification of the CEPC (4 × 10¹⁰ at 22 MV/m).

386

Non-evaporable getter (NEG) films are an integral part of many particle accelerators. These films provide conductance-free evenly distributed pumping, a low thermal outgassing rate, and a low photon-and electron-stimulated desorption. These characteristics make it an ideal solution for resolving the non-uniform pressure distribution in conductance-limited narrow vacuum tubes. In this study, ternary Ti-Zr-V films were deposited on Si substrates and Ag-Cu (Ag 0.085 wt%) tubes with an inner diameter of 22 mm. All Ti-Zr-V films were prepared from an alloy target using the same DC magnetron sputtering parameters. The compositions and corresponding chemical bonding states were analyzed by X-ray photoelectron spectroscopy after activation at different temperatures. The test particle Monte Carlo (TPMC) method was used to measure the sticking probability of the Ti–Zr–V film based on pressure readings during gas injection. The results indicate that activation commences at temperatures as low as 150 °C and Ti⁰, Zr⁰, and V⁰ exist on the surface after annealing at 180 °C for 1 h. Ti-Zr-V films can be fully activated at 180 °C for 24 h. The CO sticking probability reaches 0.15, with a pumping capacity of 1 monolayer.

332

Single-particle resonances in the continuum are crucial for studies of exotic nuclei. In this study, the Green’s function approach is employed to search for single-particle resonances based on the relativistic-mean-field model. Taking ¹²⁰Sn as an example, we identify single-particle resonances and determine the energies and widths directly by probing the extrema of the Green’s functions. In contrast to the results found by exploring for the extremum of the density of states proposed in our recent study [Chin. Phys. C, 44:084105 (2020)], which has proven to be very successful, the same resonances as well as very close energies and widths are obtained. By comparing the Green’s functions plotted in different coordinate space sizes, we also found that the results very slightly depend on the space size. These findings demonstrate that the approach by exploring for the extremum of the Green’s function is also very reliable and effective for identifying resonant states, regardless of whether they are wide or narrow.

371

J. Adam，L. Adamczyk，J. R. Adams，J. K. Adkins，G. Agakishiev，M. M. Aggarwal，Z. Ahammed，I. Alekseev，D. M. Anderson，A. Aparin，E. C. Aschenauer，M. U. Ashraf，F. G. Atetalla，A. Attri，G. S. Averichev，V. Bairathi，K. Barish，A. Behera，R. Bellwied，A. Bhasin，J. Bielcik，J. Bielcikova，L. C. Bland，I. G. Bordyuzhin，J. D. Brandenburg，A. V. Brandin，J. Butterworth，H. Caines，M. Calderón de la Barca Sánchez，D. Cebra，I. Chakaberia，P. Chaloupka，B. K. Chan，F-H. Chang，Z. Chang，N. Chankova-Bunzarova，A. Chatterjee，D. Chen，J. Chen，J. H. Chen，X. Chen，Z. Chen，J. Cheng，M. Cherney，M. Chevalier，S. Choudhury，W. Christie，X. Chu，H. J. Crawford，M. Csanád，M. Daugherity，T. G. Dedovich，I. M. Deppner，A. A. Derevschikov，L. Didenko，X. Dong，J. L. Drachenberg，J. C. Dunlop，T. Edmonds，N. Elsey，J. Engelage，G. Eppley，S. Esumi，O. Evdokimov，A. Ewigleben，O. Eyser，R. Fatemi，S. Fazio，P. Federic，J. Fedorisin，C. J. Feng，Y. Feng，P. Filip，E. Finch，Y. Fisyak，A. Francisco，L. Fulek，C. A. Gagliardi，T. Galatyuk，F. Geurts，A. Gibson，K. Gopal，X. Gou，D. Grosnick，W. Guryn，A. I. Hamad，A. Hamed，S. Harabasz，J. W. Harris，S. He，W. He，X. H. He，Y. He，S. Heppelmann，S. Heppelmann，N. Herrmann，E. Hoffman，L. Holub，Y. Hong，S. Horvat，Y. Hu，H. Z. Huang，S. L. Huang，T. Huang，X. Huang，T. J. Humanic，P. Huo，G. Igo，D. Isenhower，W. W. Jacobs，C. Jena，A. Jentsch，Y. Ji，J. Jia，K. Jiang，S. Jowzaee，X. Ju，E. G. Judd，S. Kabana，M. L. Kabir，S. Kagamaster，D. Kalinkin，K. Kang，D. Kapukchyan，K. Kauder，H. W. Ke，D. Keane，A. Kechechyan，M. Kelsey，Y. V. Khyzhniak，D. P. Kikoła，C. Kim，B. Kimelman，D. Kincses，T. A. Kinghorn，I. Kisel，A. Kiselev，M. Kocan，L. Kochenda，L. K. Kosarzewski，L. Kramarik，P. Kravtsov，K. Krueger，N. Kulathunga Mudiyanselage，L. Kumar，S. Kumar，R. Kunnawalkam Elayavalli，J. H. Kwasizur，R. Lacey，S. Lan，J. M. Landgraf，J. Lauret，A. Lebedev，R. Lednicky，J. H. Lee，Y. H. Leung，C. Li，C. Li，W. Li，W. Li，X. Li，Y. Li，Y. Liang，R. Licenik，T. Lin，Y. Lin，M. A. Lisa，F. Liu，H. Liu，P. Liu，P. Liu，T. Liu，X. Liu，Y. Liu，Z. Liu，T. Ljubicic，W. J. Llope，R. S. Longacre，N. S. Lukow，S. Luo，X. Luo，G. L. Ma，L. Ma，R. Ma，Y. G. Ma，N. Magdy，R. Majka，D. Mallick，S. Margetis，C. Markert，H. S. Matis，J. A. Mazer，N. G. Minaev，S. Mioduszewski，B. Mohanty，I. Mooney，Z. Moravcova，D. A. Morozov，M. Nagy，J. D. Nam，Md. Nasim，K. Nayak，D. Neff，J. M. Nelson，D. B. Nemes，M. Nie，G. Nigmatkulov，T. Niida，L. V. Nogach，T. Nonaka，A. S. Nunes，G. Odyniec，A. Ogawa，S. Oh，V. A. Okorokov，B. S. Page，R. Pak，A. Pandav，Y. Panebratsev，B. Pawlik，D. Pawlowska，H. Pei，C. Perkins，L. Pinsky，R. L. Pintér，J. Pluta，J. Porter，M. Posik，N. K. Pruthi，M. Przybycien，J. Putschke，H. Qiu，A. Quintero，S. K. Radhakrishnan，S. Ramachandran，R. L. Ray，R. Reed，H. G. Ritter，O. V. Rogachevskiy，J. L. Romero，L. Ruan，J. Rusnak，N. R. Sahoo，H. Sako，S. Salur，J. Sandweiss，S. Sato，W. B. Schmidke，N. Schmitz，B. R. Schweid，F. Seck，J. Seger，M. Sergeeva，R. Seto，P. Seyboth，N. Shah，E. Shahaliev，P. V. Shanmuganathan，M. Shao，A. I. Sheikh，W. Q. Shen，S. S. Shi，Y. Shi，Q. Y. Shou，E. P. Sichtermann，R. Sikora，M. Simko，J. Singh，S. Singha，N. Smirnov，W. Solyst，P. Sorensen，H. M. Spinka，B. Srivastava，T. D. S. Stanislaus，M. Stefaniak，D. J. Stewart，M. Strikhanov，B. Stringfellow，A. A. P. Suaide，M. Sumbera，B. Summa，X. M. Sun，X. Sun，Y. Sun，Y. Sun，B. Surrow，D. N. Svirida，P. Szymanski，A. H. Tang，Z. Tang，A. Taranenko，T. Tarnowsky，J. H. Thomas，A. R. Timmins，D. Tlusty，M. Tokarev，C. A. Tomkiel，S. Trentalange，R. E. Tribble，P. Tribedy，S. K. Tripathy，O. D. Tsai，Z. Tu，T. Ullrich，D. G. Underwood，I. Upsal，G. Van Buren，J. Vanek，A. N. Vasiliev，I. Vassiliev，F. Videbæk，S. Vokal，S. A. Voloshin，F. Wang，G. Wang，J. S. Wang，P. Wang，Y. Wang，Y. Wang，Z. Wang，J. C. Webb，P. C. Weidenkaff，L. Wen，G. D. Westfall，H. Wieman，S. W. Wissink，R. Witt，Y. Wu，Z. G. Xiao，G. Xie，W. Xie，H. Xu，N. Xu，Q. H. Xu，Y. F. Xu，Y. Xu，Z. Xu，Z. Xu，C. Yang，Q. Yang，S. Yang，Y. Yang，Z. Yang，Z. Ye，Z. Ye，L. Yi，K. Yip，Y. Yu，H. Zbroszczyk，W. Zha，C. Zhang，D. Zhang，S. Zhang，S. Zhang，X. P. Zhang，Y. Zhang，Y. Zhang，Z. J. Zhang，Z. Zhang，Z. Zhang，J. Zhao，C. Zhong，C. Zhou，X. Zhu，Z. Zhu，M. Zurek，M. Zyzak

In 2018, the STAR collaboration collected data from 4496Ru+4496Ru and 4096Zr+4096Zr at sNN=200 GeV to search for the presence of the chiral magnetic effect in collisions of nuclei. The isobar collision species alternated frequently between 4496Ru+4496Ru and 4096Zr+4096Zr. In order to conduct blind analyses of studies related to the chiral magnetic effect in these isobar data, STAR developed a three-step blind analysis procedure. Analysts are initially provided a "reference sample" of data, comprised of a mix of events from the two species, the order of which respects time-dependent changes in run conditions. After tuning analysis codes and performing time-dependent quality assurance on the reference sample, analysts are provided a species-blind sample suitable for calculating efficiencies and corrections for individual ≈30-minute data-taking runs. For this sample, species-specific information is disguised, but individual output files contain data from a single isobar species. Only run-by-run corrections and code alteration subsequent to these corrections are allowed at this stage. Following these modifications, the "frozen" code is passed over the fully un-blind data, completing the blind analysis. As a check of the feasibility of the blind analysis procedure, analysts completed a "mock data challenge," analyzing data from Au+Au collisions at sNN=27 GeV, collected in 2018. The Au+Au data were prepared in the same manner intended for the isobar blind data. The details of the blind analysis procedure and results from the mock data challenge are presented.

469

Large-volume liquid scintillator detectors with ultra-low background levels have been widely used to study neutrino physics and search for dark matter. Event vertex and event time are not only useful for event selection but also essential for the reconstruction of event energy. In this study, four event vertex and event time reconstruction algorithms using charge and time information collected by photomultiplier tubes were analyzed comprehensively. The effects of photomultiplier tube properties were also investigated. The results indicate that the transit time spread is the main effect degrading the vertex reconstruction, while the effect of dark noise is limited. In addition, when the event is close to the detector boundary, the charge information provides better performance for vertex reconstruction than the time information.

462

The reaction dynamics of exotic nuclei near the drip line is one of the main research topics of current interest. Elastic scattering is a useful probe for investigating the size and surface diffuseness of exotic nuclei. The development of rare isotope accelerators offers opportunities for such studies. To date, many relevant measurements have been performed at accelerators using the projectile fragmentation technique, while the measurements at accelerators using isotope separator on-line (ISOL) systems are still quite scarce. In this work, we present the first proof-of-principle experiment with a post-accelerated ISOL beam at the Beijing Radioactive Ion Beam Facility (BRIF) by measuring the angular distribution of elastic scattering for the stable nucleus ²³Na from the doubly magic nucleus ⁴⁰Ca at energies above the Coulomb barrier. The angular distribution measured by a silicon strip detector array in a scattering chamber using the ISOL beam at BRIF is in good agreement with that measured by the high-precision Q3D magnetic spectrograph using the non-ISOL beam at nearly the same energy. This work provides useful background for making BRIF a powerful tool for the investigation of the reaction dynamics of exotic nuclei.

491

Helium bubbles, which are typical radiation microstructures observed in metals or alloys, are usually investigated using transmission electron microscopy (TEM). However, the investigation requires human inputs to locate and mark the bubbles in the acquired TEM images, rendering this task laborious and prone to error. In this paper, a machine learning method capable of automatically identifying and analyzing TEM images of helium bubbles is proposed, thereby improving the efficiency and reliability of the investigation. In the proposed technique, helium bubble clusters are first determined via the density-based spatial clustering of applications with noise algorithm after removing the background and noise pixels. For each helium bubble cluster, the number of helium bubbles is determined based on the cluster size depending on the specific image resolution. Finally, the helium bubble clusters are analyzed using a Gaussian mixture model, yielding the location and size information on the helium bubbles. In contrast to other approaches that require training using numerous annotated images to establish an accurate classifier, the parameters used in the established model are determined using a small number of TEM images. The results of the model formulated according to the proposed approach achieved a higher F1 score validated through some helium bubble images manually marked. Furthermore, the established model can identify bubble-like objects that humans cannot facilely identify. This computationally efficient method achieves object recognition for material structure identification that may be advantageous to scientific work.

557

Plastic scintillation detectors based on whole body β/γ contamination monitors are developed for use in radiation facilities. This microcontroller based multi-detector system uses 13 plastic scintillator detectors, with minimized dead detection zones, monitoring the whole body, and conforming to the contamination limit prescribed by the regulatory authority. This system has the features for monitoring hands, feet, head, and face β/γ using contamination monitors and portal exit monitors. It can detect gamma sources at a dose rate of 10 nGyh^-1. The system is calibrated using β sources ⁹⁰Sr/⁹⁰Y, ²⁰⁴Tl, and ³⁶Cl, and the efficiency is found to be 29 %, 22 %, and 18 %, respectively. The minimum detectable β/γ contamination is 0.15 Bqcm^-2, which is significantly less than the minimum detection objectives on head, face, hands, and feet.

455

As a proposed detector, the giant radio array for neutrino detection (GRAND) is primarily designed to discover and study the origin of ultra-high-energy cosmic rays, with ultra-high-energy neutrinos presenting the main method for detecting ultra-high-energy cosmic rays and their sources. The main principle is to detect radio emissions generated by ultra-high-energy neutrinos interacting with the atmosphere as they travel. GRAND is the largest neutrino detection array to be built in China. GRANDProto35, as the first stage of the GRAND experiment, is a coincidence array composed of radio antennas and a scintillation detector, the latter of which, as a traditional detector, is used to perform cross-validation with radio detection, thus verifying the radio detection efficiency and enabling study of the background exclusion method. This study focused on the implementation of the optimization simulation and experimental testing of the performance of the prototype scintillation detector used in GRANDProto35. A package based on GEANT4 was used to simulate the details of the scintillation detector, including the optical properties of its materials, the height of the light guide box, and position inhomogeneity. The surface of the scintillator and the reflective materials used in the detector were optimized, and the influence of light guide heights and position inhomogeneity on the energy and time resolutions of the detector were studied. According to the simulation study, the number of scintillator photoelectrons increased when changing from the polished surface to the ground surface, with the appropriate design height for the light guide box being 50 cm and the appropriate design area for the scintillator being 0.5 m². The performance of the detector was tested in detail through a coincidence experiment, and the test results showed that the number of photoelectrons collected in the detector was ∼84 with a time resolution of ∼1 ns, indicating good performance. The simulation results were consistent with those obtained from the tests, which also verified the reliability of the simulation software. These studies provided a full understanding of the performance of the scintillation detector and guidance for the subsequent operation and analysis of the GRANDProto35 experimental array.

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