The European Physical Journal D最新文献

{"title":"Measurement of the 2/1 error field from the passive coil used for runaway electron mitigation on J-TEXT tokamak","authors":"Hao Man,&nbsp;Song Zhou,&nbsp;Nengchao Wang,&nbsp;Junhui Yang,&nbsp;Zhengkang Ren,&nbsp;Shengnan Liu,&nbsp;Haonan Fang,&nbsp;Yangbo Li,&nbsp;Bo Rao,&nbsp;Yonghua Ding,&nbsp;J-TEXT Team","doi":"10.1140/epjd/s10053-026-01239-3","DOIUrl":"10.1140/epjd/s10053-026-01239-3","url":null,"abstract":"<p>In future tokamak reactors, passive coil (PC, or runaway electron mitigation coil, i.e., REMC) should be installed to passively induce currents during disruptions, generating magnetic perturbations that suppress runaway current. However, PC also induces currents during normal discharges, unavoidably introducing the <i>m</i>/<i>n</i> = 2/1 error field (PCEF, <span>({b}_{r,2/1}^{text{P}text{C}text{E}text{F}})</span>), where <i>m</i> and <i>n</i> are poloidal and toroidal mode number, respectively. This combination of PCEF and 2/1 intrinsic EF (IEF, <span>({b}_{r,2/1}^{text{I}text{E}text{F}})</span>) risks 2/1 field penetration and locked mode disruption. Based on J-TEXT tokamak and recently installed PC, this study measures <span>({b}_{r,2/1}^{text{I}text{E}text{F}})</span> and <span>({b}_{r,2/1}^{text{P}text{C}text{E}text{F}})</span> via a compass scan of the resonant magnetic perturbation (RMP) penetration threshold. Under typical discharge parameters, a loop voltage of ~ 2.79 V induces ~ 0.67 kA in the PC. At <i>r</i> = 0.2 m, <span>({b}_{r,2/1}^{text{P}text{C}text{E}text{F}})</span> is 1.45 G at 62.8°, and <span>({b}_{r,2/1}^{text{I}text{E}text{F}})</span> is 0.32 G at 296.5°. These EFs account for 14.2% and 3.1% of the 2/1 penetration threshold, respectively. Additionally, the radial profiles of both EFs are obtained under the EF radial attenuation law (<i>b</i>_<i>r​</i> ∝ <i>r</i>^<i>m</i>−1). Finally, based on J-TEXT discharge scenario, a further discussion suggests that the PC of J-TEXT can be connected throughout the entire discharge without inducing 2/1 field penetration, but it should still be capable of completely suppressing runaway current during disruptions. However, the calculated ratio <span>({b}_{r,2/1(text{c}text{a}text{l}text{c})}^{text{P}text{C}text{E}text{F}}/{b}_{r,2/1(text{c}text{a}text{l}text{c})}^{text{p}text{e}text{n}text{e}text{t}text{r}text{a}text{t}text{i}text{o}text{n}})</span> reaches 52% during <i>I</i>_p ramp-up phase in J-TEXT, it may be unacceptable for future reactors. Nevertheless, connecting the PC only after <i>I</i>_p flat-top is still feasible, as the ratio reduces significantly (e.g., 13% in J-TEXT).</p>","PeriodicalId":789,"journal":{"name":"The European Physical Journal D","volume":"80 8","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148783246","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Features of spectral-angular distribution of radiation by a train of electron bunches passing through the center of a conductive ball","authors":"Levon Grigoryan,&nbsp;Aram Saharian,&nbsp;Artak Mkrtchyan,&nbsp;Anush Sargsyan,&nbsp;Karen Aramyan,&nbsp;Mher Grigoryan,&nbsp;Jemma Markosyan,&nbsp;Hrant Khachatryan","doi":"10.1140/epjd/s10053-026-01238-4","DOIUrl":"10.1140/epjd/s10053-026-01238-4","url":null,"abstract":"<p>The spectral and angular distributions of radiation generated by a uniformly and rectilinearly moving charged particle or a train of charged particle bunches are studied. The bunches are assumed to pass through the center of a conductive-composite material ball. This work is based on exact analytic solutions of Maxwell’s equations. In the numerical analysis, a generalized Drude–Lorentz–Sommerfeld formula is used for the dielectric function of the ball material. Peaks in the emission spectrum of particles at certain “resonant frequencies” with wavelengths approximately equal to the radius of the ball are shown to be possible. The spectral density of radiated energy at these frequencies can be much greater than at adjacent frequencies. These peaks arise from the constructive superposition of electromagnetic field oscillations generated by a charged particle at the ball’s surface, accompanied by intense radiation. The peaks disappear when the ball is replaced by a plane-parallel plate made of the same material with a thickness equal to the ball’s diameter.</p>","PeriodicalId":789,"journal":{"name":"The European Physical Journal D","volume":"80 8","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148782527","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Low energy elastic scattering of hydrogen, deuterium, and tritium on helium isotopes","authors":"B. J. P. Jones,&nbsp;A. Negi,&nbsp;A. Semakin","doi":"10.1140/epjd/s10053-026-01237-5","DOIUrl":"10.1140/epjd/s10053-026-01237-5","url":null,"abstract":"<p>Motivated by the needs of atomic tritium sources for neutrino mass experiments and Doppler-free two-photon 1 S–2 S spectroscopy in atomic deuterium and tritium, we present calculations of energy-dependent elastic scattering cross sections of hydrogen isotopes (H, D, and T) on helium isotopes (³He and ⁴He) in the temperature range 1 mK to 300 K. The tritium-on-helium cross sections are found to be enhanced over their hydrogen-on-helium counterparts by a near-threshold resonant <i>s</i>-wave bound state at low energy, similar to one that has been predicted in the triplet T–T system. While the energy-dependent cross sections span a wide range at low energy due to this <i>s</i>-wave enhancement, they tend toward a common value at high energy where the scattering becomes effectively geometric in nature.</p>","PeriodicalId":789,"journal":{"name":"The European Physical Journal D","volume":"80 8","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjd/s10053-026-01237-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148782529","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Rydberg positronium injection of electrons and positrons into a levitated dipole trap","authors":"A. Deller","doi":"10.1140/epjd/s10053-026-01191-2","DOIUrl":"10.1140/epjd/s10053-026-01191-2","url":null,"abstract":"<p>A neutral-beam injection scheme for magnetically trapping electrons and positrons is proposed. Pulsed lasers excite positronium (Ps) to long-lived Rydberg states that drift at speeds of <span>(|vec {v}| sim 10^5)</span> <span>(textrm{m} , textrm{s}^{-1})</span> into the magnetic field of a levitated superconducting coil. The electric field experienced in the reference frame of the rapidly moving atoms is sufficient to ionize a significant portion of the loosely bound Ps. The released electrons and positrons are confined to the poloidal magnetic field lines that wrap around the coil. Rydberg positronium injection (RPI) does not perturb the confinement volume and ensures local charge symmetry. The technique provides equal, low temperatures for the electron and positron distributions, as well as smooth, inwardly peaked density profiles. The range of populated field lines depends on the Ps velocity distribution and the ionization threshold of the Rydberg state. Monte Carlo simulations are used to evaluate the <span>(e^+)</span> efficiency of RPI for the APEX (A Positron–Electron eXperiment) levitated dipole.</p>","PeriodicalId":789,"journal":{"name":"The European Physical Journal D","volume":"80 8","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjd/s10053-026-01191-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148782169","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Relative phase and position dependence of assisted electron-positron pair creation in the superposition of strong oscillating electric-field pulses","authors":"J. Braß,&nbsp;D. M. Müller,&nbsp;S. Villalba-Chávez,&nbsp;K. Krajewska,&nbsp;C. Müller","doi":"10.1140/epjd/s10053-026-01235-7","DOIUrl":"10.1140/epjd/s10053-026-01235-7","url":null,"abstract":"<p> Production of electron-positron pairs in the superposition of oscillating electric-field pulses with largely different frequencies is studied, focussing on the impact of relative phases between the pulses. Various field configurations are considered: (i) superpositions of two or three pulses of equal duration, and (ii) combinations of a long low-frequency with a short high-frequency pulse. By numerical calculations within a quantum kinetic framework we show that the relative phase and position of superimposed high-frequency modes can largely modify the momentum distributions of the produced pairs, leading to characteristic symmetry properties and to strongly enhanced pair yields by few orders of magnitude at specific momenta. While the impact of the relative phase on the total number of produced pairs is much smaller, it can still be sizable, causing enhancements by about 10–30% for the considered field parameters. Our results shed further light on the rich phenomenology of pair production in non-monochromatic field configurations.</p>","PeriodicalId":789,"journal":{"name":"The European Physical Journal D","volume":"80 8","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjd/s10053-026-01235-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148782170","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Determination of the refractive index of weakly absorbing materials in the GHz–THz range via tabletop Mach–Zehnder interferometer","authors":"V. Margaryan,&nbsp;P. Karataev,&nbsp;S. Khosrovyan,&nbsp;Yu. Cherepennikov,&nbsp;S. Noreyan,&nbsp;K. Hayrapetyan,&nbsp;R. Mirzoyan,&nbsp;D. Baghdasaryan,&nbsp;H. Samsonyan,&nbsp;V. Kocharyan","doi":"10.1140/epjd/s10053-026-01234-8","DOIUrl":"10.1140/epjd/s10053-026-01234-8","url":null,"abstract":"<div><p>In this study, we propose a method for measuring the refractive index of materials in the sub-terahertz frequency range based on phase-shift analysis using a coherent continuous-wave radiation source and a matrix detector. The spatial distribution of the phase shift across the beam cross section was reconstructed from interference patterns obtained with a Mach–Zehnder interferometer. Refractive indices were determined for wedge-shaped and plane-parallel samples made of Teflon and polymeric glass sample.</p><h3>Graphical abstract</h3><div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":789,"journal":{"name":"The European Physical Journal D","volume":"80 8","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148751811","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Strain-engineered intraband nonlinear optical response in ZnxCd1−xSe/ZnSe quantum dots","authors":"Prateek Uniyal,&nbsp;Saral Kumar Gupta,&nbsp;C. M. S. Negi","doi":"10.1140/epjd/s10053-026-01236-6","DOIUrl":"10.1140/epjd/s10053-026-01236-6","url":null,"abstract":"<p>We present a detailed theoretical investigation of the size and strain-dependent linear and nonlinear optical response of Zn_<i>x</i>Cd_1−<i>x</i>Se/ZnSe disk-shaped quantum dots (QDs). The complex valence–band structure of QDs was computed using 4 × 4 k.p Luttinger Hamiltonian. The results reveal a strong sensitivity of the optical response to both strain and QD height. Increasing the compressive strain from 4.15 to 5.46% produces a substantial enhancement in the linear and nonlinear absorption coefficients and a marked blue shift of the resonant transitions. For 5 nm QD, the peak linear absorption increases from 1.91 × 10³ to 1.02 × 10⁴ cm⁻¹, while the third-order absorption coefficient reaches − 5 × 10³ cm/GW, accompanied by a ~ 42 meV shift in peak energy. Energy band structure and dipole matrix element for the dominant optical transition were explored to explain the observed modification in the linear and nonlinear optical response with change in QD size and lattice strain. The strain-induced redistribution of valence–band states also governs the nonlinear refractive index. The nonlinear refractive index at 5.46% exhibits strong dispersive features with peak value increased to 3.6 × 10¹ cm²/GW, an order of magnitude greater than that of 4.15% strain. Our findings highlight strain engineering as an effective tool for tuning nonlinear optical behavior in II–VI QDs for ultrafast photonic applications.</p>","PeriodicalId":789,"journal":{"name":"The European Physical Journal D","volume":"80 8","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148751543","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A compact Ku-band relativistic transit-time oscillator with a double-gap buncher for microwave radiation","authors":"Ziyuan Chi,&nbsp;Tengfang Wang,&nbsp;Wei Zhang,&nbsp;Jinchuan Ju,&nbsp;Zihan Li,&nbsp;Jiyao Di","doi":"10.1140/epjd/s10053-026-01223-x","DOIUrl":"10.1140/epjd/s10053-026-01223-x","url":null,"abstract":"<div><p>Conventional multi-gap bunchers exhibit the problems of easy excitation of high-order modes and excessive axial size as the number of periods increases. Thus, this paper proposes a novel Ku-band coaxial transit-time oscillator with a double-gap buncher, aiming for compact design and high-efficiency performance in Ku-band high-power microwave sources. The double-gap buncher design can effectively suppress the excitation of high-order modes and ensure single-mode operation while greatly reducing the axial length of the buncher to achieve overall compactness. Furthermore, it combines the advantage of the low space-charge effect inherent in the coaxial structure to enhance the beam-wave interaction efficiency under a low guiding magnetic field. Finally, particle-in-cell simulation results demonstrate that under an acceleration voltage of 450 kV, a beam current of 7 kA, and a guiding magnetic field of 0.5 T, the TTO outputs an average power of 1.19 GW at 14.02 GHz, with a power conversion efficiency of 37.8%, and exhibits no high-order mode competition phenomena. The total axial length of the device is obviously shortened compared with the conventional three-gap buncher structure, which significantly enhances its compactness. This work provides a novel design concept for the miniaturization and engineering application of relativistic electron beam-driven microwave generators.</p><h3>Graphical abstract</h3>\u0000<div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":789,"journal":{"name":"The European Physical Journal D","volume":"80 8","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148751758","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Quartet bound states spectrum of the (2s^2 2p^2(^3P)3p) configuration in the neutral nitrogen","authors":"Adnan Yousif Hussein","doi":"10.1140/epjd/s10053-026-01226-8","DOIUrl":"10.1140/epjd/s10053-026-01226-8","url":null,"abstract":"<p>High-accuracy calculations of excitation energies and fine-structure splittings are reported for the <span>(2s^22p^2(^3P)3p;{}^4D^circ )</span>, <span>({}^4P^circ )</span> and <span>({}^4S^circ )</span> quartet bound states of neutral nitrogen. Extensive nonrelativistic configuration interaction (CI) calculations are performed using a combination of <i>a priori</i> selected CI and CI-by-parts (CIBP) techniques, enabling the systematic inclusion of electron correlation effects up to septuple excitation while keeping the effective CI dimensions computationally manageable. Near-full-CI convergence is achieved through careful control of CI space growth and basis set extrapolation. Relativistic corrections are evaluated within the framework of the Dirac–Coulomb–Breit Hamiltonian using relativistic CI calculations, which are added consistently to the nonrelativistic energies. The impact of the Breit interaction on excitation energies and fine-structure splittings is analyzed in detail. The calculated excitation energies are in excellent agreement with available experimental data, with residual deviations of only a few cm<span>(^{-1})</span>. Fine-structure splittings are reproduced to better than 1 cm<span>(^{-1})</span>, demonstrating the reliability of the combined correlation and relativistic treatment. The present results establish a robust and efficient computational framework for achieving spectroscopic accuracy in complex open-shell atomic systems.</p><p>Schematic representation of the computational strategy combining large-scale nonrelativistic CI (up to septuple excitations) with relativistic CI corrections (including Breit interaction) to achieve spectroscopic accuracy for the excited quartet states of neutral nitrogen, with calculated excitation energies and fine structure splitting’s compared against NIST experimental data.</p>","PeriodicalId":789,"journal":{"name":"The European Physical Journal D","volume":"80 8","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-08-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148751881","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An optical-fiber scanner for transverse profile measurement of low-intensity charged-particle beams","authors":"Artem Vukolov,&nbsp;Alexander Potylitsyn,&nbsp;Vladislav Lisov,&nbsp;Yury Cherepennikov,&nbsp;Mikhail Shevelev","doi":"10.1140/epjd/s10053-026-01231-x","DOIUrl":"10.1140/epjd/s10053-026-01231-x","url":null,"abstract":"<p>Traditional wire scanners for measuring low-intensity charged-particle beams face significant limitations due to X-ray background and technical challenges in signal detection. We propose a transverse-profile scanner based on optical-fiber technology, employing side-view detection of light yield from the fiber surface at <span>(90^{circ })</span> with respect to the beam trajectory. The method uses an objective (Tamron 70–300 mm f/4.5–6.3 Di III RXD) and a CMOS camera (QHY533C) to capture the 2D light distribution along the fiber. In this work, we tested and compared the light yield of two fiber types: a 1 mm thick polymethyl methacrylate fiber and a 1 mm thick wavelength-shifting fiber. Tests were conducted at the TPU microtron with a 5.7 MeV electron beam (macro-pulse duration: 0.5 <span>(upmu )</span>s, macro-pulse current: 360 <span>(upmu )</span>A). Comparative measurements with a wire scanner demonstrate that the fiber scanner reliably detects the beam and provides a qualitative 2D image of the light distribution suitable for low-intensity beams. Systematic effects—including convolution with the fiber diameter, optical defocus, camera point-spread function, and light transport along the fiber—limit the quantitative accuracy of the extracted beam size. The results confirm the feasibility of the technique as a simple and fast diagnostic for commissioning and low-intensity operation. Future work will focus on calibration and correction of these systematic contributions to enable absolute beam-profile monitoring.</p><p>Schematic of an optical-fiber scanner for transverse profile measurement of low-intensity charged-particle beams</p>","PeriodicalId":789,"journal":{"name":"The European Physical Journal D","volume":"80 8","pages":""},"PeriodicalIF":1.8,"publicationDate":"2026-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148751460","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}