Search Results (62)

The High-Intensity Heavy-Ion Accelerator Facility (HIAF) is a significant national science and technology infrastructure project, constructed by the Institute of Modern Physics, Chinese Academy of Sciences (IMP, CAS). It is designed to provide intense proton, heavy ion beams, and target-produced radioactive ion beams for nuclear physics and related research. Large-aperture, high-precision, room-temperature, and superconducting dipole magnets are extensively used to achieve high-intensity beams. However, for large-scale magnets (particularly superconducting magnets), the traditional Hall probe mapping measurement platform encounters several limitations: a long preparation time, high cost, low testing efficiency, and positional inaccuracies caused by repeated magnet disassembly. This paper presents a new magnetic field mapping measurement system incorporating ultrasonic motors operable in strong magnetic fields (≥7 T), enabling portable, highly efficient, and high-precision magnetic field measurements. After system integration and commissioning, the prototype dipole magnet for the high-precision spectrometer ring (SRing) was measured. The measurement system demonstrated superior accuracy and efficiency compared with traditional Hall probe mapping systems. On this basis, the magnetic field distribution and integral excitation curve of all 11 warm-iron superconducting dipole magnets and 3 anti-irradiation dipole magnets in the HIAF fragment separator (HFRS) were measured. Each magnet took less than 1 day to measure, and all magnetic field measurement results met the physical specifications. Full article

The ICARUS collaboration employed the 760-ton T600 detector in a successful three-year physics run at the underground LNGS laboratory. In 2021, ICARUS started its new operation at Fermilab, collecting a substantial amount of neutrino events from the Booster Neutrino Beam (BNB) and the neutrinos at the Main Injector (NuMI) beam off-axis. These were used to test the ICARUS event selection, reconstruction, and analysis algorithms. ICARUS successfully completed its commissioning phase in June 2022, moving then to data taking for neutrino oscillation physics, aiming at first to either confirm or refute the claim by the Neutrino-4 short-baseline reactor experiment. ICARUS will also perform measurements of neutrino cross sections in LAr with the NuMI beam and several Beyond Standard Model studies. After the first year of operations, ICARUS will search for evidence of sterile neutrinos jointly with the Short-Baseline Near Detector, within the Short-Baseline Neutrino program. In this work, preliminary results from the ICARUS data with the BNB and NuMI beams are presented, both in terms of the performance of all ICARUS subsystems and the capability to select and reconstruct neutrino events. Full article

The diagnosis of emergent conditions during pregnancy can be delayed due to insufficient knowledge of fetal radiation doses in different imaging modalities. The aim of this article is to investigate the ranges of fetal doses in most common diagnostic and interventional radiology procedures. Procedures were carried out on an anthropomorphic phantom, Tena, representing a pregnant woman in the 18th week of pregnancy with the fetus in breech position. Different clinical scenarios using computer tomography (CT), radiography, fluoroscopy and digital subtraction angiography were selected in three teaching hospitals. Measurements were performed using radiophotoluminescent glass dosimeters placed in dedicated holes in the fetal head and fetal body. Measured fetal doses were below 1 mGy when the fetus was not in the primary beam. The highest fetal doses, up to 47 mGy, were measured after a CT scan for polytrauma and up to 24 mGy after a CT scan of the abdomen and pelvis. Significant variability in fetal doses for the same procedure was found between different hospitals but within the same hospital also. All obtained results are below the threshold for deterministic effects given by the International Commission for Radiation Protection but can be reached with two or more imaging procedures employed. The variability in fetal doses for the same procedures highlights the need for the improved optimization of imaging protocols. Full article

The ultra-cold neutron (UCN) source being commissioned at North Carolina State University’s PULSTAR reactor is uniquely optimized for UCN production in the former graphite-filled thermal column outside of the reactor pool. The source utilizes a remote moderation design, which is particularly well suited to the PULSTAR reactor because of its high thermal and epithermal neutron leakage from the core face. This large non-equilibrium flux from the core is efficiently transported to the UCN source through the specially designed beam port in order to optimize UCN production at any given reactor power. The increased distance to the source from the core also greatly limits the heat load on the cryogenic system. A MCNP (Monte Carlo N-Particle) model of this system was developed and is in good agreement with gold foil activation measurements using a test configuration as well as with the real UCN source’s heavy water moderator. These results established a firm baseline for estimates of the cold neutron flux available for UCN production and prove that remote moderation in a thermal column port is a valuable option for future designs of cryogenic UCN sources. Full article

Progress in laser-driven proton acceleration requires increasing the proton maximum energy and laser-to-proton conversion efficiency while reducing the divergence of the proton beam. However, achieving all these qualities simultaneously has proven challenging experimentally, with the increase in beam energy often coming at the cost of beam quality. Numerical simulations suggest that coupling multi-PW laser pulses with ultrathin foils could offer a route for such simultaneous improvement. Yet, experimental investigations have been limited by the scarcity of such lasers and the need for very stringent temporal contrast conditions to prevent premature target expansion before the pulse maximum. Here, combining the newly commissioned Apollon laser facility that delivers high-power ultrashort (∼$24\mathrm{fs}$) pulses with a double plasma mirror scheme to enhance its temporal contrast, we demonstrate the generation of up to 35 MeV protons with only 5 J of laser energy. This approach also achieves improved laser-to-proton energy conversion efficiency, reduced beam divergence, and optimized spatial beam profile. Therefore, despite the laser energy losses induced by the plasma mirror, the proton beams produced by this method are enhanced on all accounts compared to those obtained under standard conditions. Particle-in-cell simulations reveal that this improvement mainly results from a better space–time synchronization of the maximum of the accelerating charge-separation field with the proton bunch. Full article

Beam position uncertainties along the beam trajectory arise from the accelerator, beamline, and scanning magnets (SMs). They can be monitored in real time, e.g., through strip ionization chambers (ICs), and treatments can be paused if needed. Delivery is more reliable and accurate if the beam position is projected from monitored nozzle parameters to the isocenter, allowing for accurate online corrections to be performed. Beam position projection algorithms are also used in post-delivery log file analyses. In this paper, we investigate the four potential algorithms that can be applied to all pencil beam scanning (PBS) nozzles. For some combinations of nozzle configurations and algorithms, however, the projection uses beam properties determined offline (e.g., through beam tuning or technical commissioning). The best algorithm minimizes either the total uncertainty (i.e., offline and online) or the total offline uncertainty in the projection. Four beam position algorithms are analyzed (A1–A4). Two nozzle lengths are used as examples: a large nozzle (1.5 m length) and a small nozzle (0.4 m length). Three nozzle configurations are considered: IC after SM, IC before SM, and ICs on both sides. Default uncertainties are selected for ion chamber measurements, nozzle entrance beam position and angle, and scanning magnet angle. The results for other uncertainties can be determined by scaling these results or repeating the error propagation. We show the propagation of errors from two locations and the SM angle to the isocenter for all the algorithms. The best choice of algorithm depends on the nozzle length and is A1 and A3 for the large and small nozzles, respectively. If the total offline uncertainty is to be minimized (a better choice if the offline uncertainty is not stable), the best choice of algorithm changes to A1 for the small nozzle for some hardware configurations. Reducing the nozzle length can help to reduce the gantry size and make proton therapy more accessible. This work is important for designing smaller nozzles and, consequently, smaller gantries. This work is also important for log file analyses. Full article

The beam position is the most important reference basis for the operation of synchrotron radiation light sources, particularly for commissioning the first-turn injection of fourth-generation light sources. To improve the accuracy of the beam position measurement, we analyzed methods for calculating the beam position, and a finite element calculation and the stretched wire calibration system were used to demonstrate the procedure. We proved the relationship between the coverage range, fitting order, scanning step size, and accuracy both theoretically and experimentally, which can provide a basis for selecting the appropriate fitting order for different operation stages of the accelerator. It was proved that the accuracy of beam position calculations using simplified polynomial coefficients is comparable to those without a simplified one, which can save resources for reading electronic processing. The testing results of a batch of beam position monitors (BPMs) were in good agreement with the finite element calculation results, and the small difference between the manufactured BPMs also proved that quality control was performed well, and it benefited from button sorting. Full article

The high peak current of the electron beam was found to be the key parameter for the THz SASE FEL at the Photo Injector Test facility at DESY in Zeuthen (PITZ). A multipurpose bunch compressor was implemented at PITZ to expand the parameter space of proof-of-principle studies on the tunable high-power accelerator-based THz source for pump-probe experiments at the European XFEL. The magnetic chicane, consisting of four rectangular dipole magnets, is designed with a bending angle of 19 degrees, due to limited space in the PITZ original beamline, to compress electron bunches with a beam momentum of 15–20 MeV/c and a charge up to 2 nC. The space charge effect and coherent synchrotron radiation are expected to drastically affect the bunch compressor performance for these parameters, thereby challenging the beam transport throughout the bunch compressor. A staged commissioning strategy was developed in order to achieve optimum bunch compressor operation. The first commissioning procedure establishes electron beam transport throughout the reference path and provides minimum beam momentum dispersion after the bunch compressor. This procedure yielded correlations between dipole magnet currents. As a result, the first bunch compression experiments were performed. Full article

Future electron accelerator applications such as X-ray free electron lasers and colliders are dependent on significantly increasing beam brightness. With the observation that linac beam manipulation’s best preservation of max brightness is at the cathode, we are incentivized to create an environment where we can study how to achieve the highest possible photogun brightness. In order to do so, we intend to extract beams from high-brightness photocathodes with the highest achievable accelerating gradients we can manage in a klystron-powered radiofrequency (RF) photogun. We utilize here cryogenic normal conducting cavities to achieve ultra-high gradients via limitation of breakdown rates (BDR). The low temperatures should also reduce cathode emittance by reducing the mean transverse energy (MTE) of electrons near the photoemission threshold. To this end, we have designed and produced a new CrYogenic Brightness-Optimized Radiofrequency Gun (CYBORG) for use in a new beamline at UCLA. We will introduce the enabling RF and photoemission physics as a primer for the new regime of high field low temperature cathodes we intend to enter. We further report the current status of the beamline commissioning, including the cooling of the photogun to 100 K, and producing 0.5 MW of RF feed power, which corresponds to cathode accelerating fields in the range of 80–90 MV/m. We further plan iterative improvements to both to 77 K and 1 MW corresponding to our ultimate goal >120 MV/m. Our discussion will include future beamline tests and the consideration of the initial realization of an ultra-high-gradient photoinjector concept. Full article

The purpose of this study is to evaluate RadCalc, an independent dose verification software, for patient-specific quality assurance (PSQA) in online adaptive planning with a magnetic resonance linear accelerator (MR-linac) of a 1.5 T. Version 7.1.4 of RadCalc to introduce the capability to establish a beam model that incorporates MR field characteristics. A total of six models were established, with one using manufacturer-provided data and the others differing in percentage depth dose (PDD) data sources. Overall, two models utilized PDD data from the treatment planning system (TPS), and three used commissioned PDD data from gantry angles of 0° and 270°. Simple tests on a virtual water phantom assessed dose-calculation accuracy, revealing percentage differences ranging from −0.5% to −20.6%. Excluding models with significant differences, clinical tests on 575 adaptive plans (prostate, liver, and breast) showed percentage differences of −0.51%, 1.12%, and 4.10%, respectively. The doses calculated using RadCalc demonstrated similar trends to those of the PSQA-based measurements. The newly released version of RadCalc enables beam modeling that considers the characteristics of the 1.5 T magnetic field. The accuracy of the software in calculating doses at 1.5 T magnetic fields has been verified, thereby making it a reliable and effective tool for PSQA in adaptive plans. Full article

An experimental platform for laser-driven ion (sub-MeV) acceleration and potential applications was commissioned at the HiLASE laser facility. The auxiliary beam of the Bivoj laser system operating at a GW level peak power (~10 J in 5–10 ns) and 1–10 Hz repetition rate enabled a stable production of high-current ion beams of multiple species (Al, Ti, Fe, Si, Cu, and Sn). The produced laser–plasma ion sources were fully characterized against the laser intensity on the target (10¹³–10¹⁵ W/cm²) by varying the laser energy, focal spot size, and pulse duration. The versatility and tuneability of such high-repetition-rate laser–plasma ion sources are of potential interest for user applications. Such a statistically accurate study was facilitated by the large amount of data acquired at the high repetition rate (1–10 Hz) provided by the Bivoj laser system. Full article

Presented here are the first results of commissioning of the S-Band hybrid photoinjector and laser systems at the new accelerator and light source facility, MITHRA, at UCLA. The radiation bunker and capabilities of the facility are described with motivation for detailed measurement of beam parameters explained. Following thorough characterization of the photoinjector, a 1.5 m linac is to be installed and experiments up to 30 MeV will begin. These will include experiments in basic plasma physics, space plasma, terahertz production in dielectric structures, and inverse Compton scattering and applications for the X-rays produced. Full article

To precisely measure atomic masses and select neutron-deficient isotopes produced by fusion evaporation reactions, an MRTOF-MS (multi-reflection time-of-flight mass spectrometer) at the SHANS (Spectrometer for Heavy Atom and Nuclear Structure) is being developed. One of the key parts, an RF ion trap system with the aim to provide brilliant ion pulses with a low energy spread and narrow pulse width for ion preparation prior to injection into the MRTOF mass analyzer, has been constructed and commissioned offline successfully. The principle, construction details and test results are reported. Pulsed beams of ${}^{39}$K${}^{1+}$, ${}^{85,87}$Rb${}^{1+}$ and ${}^{133}$Cs${}^{1+}$ ions have been tested and the amplitudes and frequencies of the RF signals, DC voltages, helium gas pressure and time parameters have been scanned. The corresponding time spreads have reached 0.252 µs, 0.394 µs and 0.450 µs, respectively. Full article

The ICARUS detector will search for LSND-like neutrino oscillations exposed at shallow depths to the FNAL BNB beam, acting as the far detector in the short-baseline neutrino (SBN) program. Cosmic background rejection is particularly important for the ICARUS detector due to its larger size and distance from neutrino production compared to the near detector SBND. In ICARUS, the neutrino signal over the cosmic background ratio is 40 times more unfavorable compared to SBND, partly due to an out-of-spill cosmic rate that is over three times higher. In this paper, we will illustrate techniques for reducing cosmogenic backgrounds in the ICARUS detector with initial commissioning data. Full article

The 476-ton active mass ICARUS T-600 Liquid Argon Time Projection Chamber (LArTPC) is a pioneering development that has become the template for neutrino and rare event detectors, including the massive next-generation international Deep Underground Neutrino Experiment. It began operation in 2010 at the underground Gran Sasso National Laboratories and was transported to Fermilab in the US in 2017. To ameliorate the impact of shallow-depth operation at Fermilab, the detector has been enhanced with the addition of a new high granularity light detection system inside the LAr volume along with an external cosmic ray tagging system. Currently in the final stages of commissioning, ICARUS is the largest LArTPC ever to operate in a neutrino beam. On this note, we describe the current status of the ICARUS detector and its achievements in this presentation, and review the plans for ongoing development of the analysis tools needed to fulfill its physics program. Full article