Beam Energy Research Articles

Towards Tests of an RFQ Cooler and Simulations

The cooling of secondary beams is important for accelerator-based nuclear physics. In the radiofrequency (RF) quadrupole cooler (RFQC), RF fields and ion-gas collisions may give a considerable increase or decrease of the beam transverse emittance and energy spread, depending on a delicate tuning of heating and cooling effects, dominated by the ion beam kinetic energy and the balance of collisions and confinement forces. An extra confinement may be added by a solenoid magnetic field, as in the RFQC prototype installed in the Eltrap machine. This provides a versatile test bench (distinct from a closed accelerator installation) for detailed studies of cooling dynamics and of several RFQC technical optimizations (for gas differential pumping and bias voltages). Modeling concepts and simulation results are summarized. The major RFQC parameters are reviewed, in particular for 133Cs+ collisions against He gas whose pressure pg ranges from 2 to 9 Pa in the reference case, with attention to the extraction, comparing triode/tetrode system, and to the bias voltages. Lower bias voltages request less pg , but provide less cooling of the energy spread.

Status of the MINERVA cryomodules and associated cryogenic system (MYRRHA phase 1)

MYRRHA at SCK CEN in Mol/Belgium will be a pre-industrial large-scale Accelerator Driven System for unparalleled research opportunities in spent nuclear fuel, nuclear medicine, and fundamental and applied physics. In 2018 the Belgian government released funding for MYRRHA’s first phase, MINERVA, for a staged implementation and operation. It covers the design, construction, and commissioning of the continuous-wave superconducting RF proton linac up to 100 MeV, as well as dedicated user target stations. The MINERVA proton linac will accommodate 30 identical cryomodules to boost the beam energy delivered by the normal-conducting frontend from 16.6 MeV to 100 MeV. Each cryomodule will contain two superconducting RF single-spoke cavities immersed in a superfluid Helium bath at 2 K. The design and architecture of the associated cryogenic system is derived from the stringent linac reliability requirements imposed by the future subcritical nuclear reactor. We present the architecture, design, and development status of the MINERVA cryomodules and associated cryogenic system towards the implementation phase of the project as part of a collaboration between ACS, CEA/DSBT, IJCLab, and SCK CEN. We also provide an overview of the initial outcomes of cryogenic and RF tests for the prototype MINERVA cryomodule, which are still ongoing at IJCLab.

Determination of impact parameter for CEE with digi-input neural networks

The impact parameter characterizes the centrality in nucleus-nucleus collision geometry. The determination of impact parameters in real experiments is usually based on the reconstructed particle attributes or the derived event-level observables. For the scheduled Cooler-storage-ring External-target Experiment (CEE), the low beam energy reduces correlation between the impact parameter and charged particle multiplicity, which decreases the validity of the explicit determination methods. This work investigates a few neural network-based models that directly take the digitized signals from the external Time-of-flight detectors as input. The model with the best performance shows a mean absolute error of 0.479 fm with simulated U-U collisions at 0.5 AGeV. The performances of the models implemented with digi inputs are compared with reference models with phase space inputs, showing the capability of neural networks to handle the original but potentially interrelated digitized signal information.

A state-selected continuous wave laser excitation method for determining CO2's rotational state distribution in a supersonic molecular beam.

State-resolved experiments can provide fundamental insight into the mechanisms behind chemical reactions. Here, we describe our methods for characterizing state-resolved experiments probing the outcome of the collision between CO2 molecules and surfaces. We create a molecular beam from a supersonic expansion that passes through an ultra-high vacuum system. The CO2 is vibrationally excited by a continuous wave infrared (IR) laser using rapid adiabatic passage. We attenuate the fractional excitation using a CO2 absorption cell in the IR beam path. We combine Monte Carlo simulations and molecular beam energy measurements to find the initial rotational state distribution of the molecular beam. We find that our pure CO2 beam from a 300K source has a rotational temperature of ∼26K.

Developing a penning ionization gauge ion source with a filament for a compact ion microbeam system

We present the development of a penning ionization gauge ion source with a filament (F-PIG) for producing submicron ion beams in a compact ion microbeam system. The conventional penning ionization gauge ion source (PIG) represents a viable choice for microbeam system due to its compact size and low power consumption. However, directly utilizing a PIG for generating submicron ion beam poses challenges, primarily from significant energy spread, causing substantial aberrations. Considering this, this study proposes a solving the generation of low-voltage discharge plasma, achieved using low-energy electrons from a filament by focusing on the development of F-PIG for this purpose. Experimental results demonstrate that the F-PIG exhibits considerable promise an ion source to forming submicron beam within a compact ion microbeams system. These findings indicate that F-PIG can effectively reduce the width of the beam energy spread, making it a valuable asset for microbeam applications.

Innovative Cesiation Deriving Incredible 145 mA Beam from J-PARC Cesiated RF-Driven H− Ion Source

In NIBS2022, the stable 8 hours operation of the J-PARC cesiated RF-driven H− ion source (IS) in a test-stand with a 69.9 keV 120 mA beam and a beam duty factor of 4 % (1 ms x 40 Hz) was reported. However, the Cesiation condition was produced after many times and rather large amount of Cs and H2Os injections. The fluctuation of the H− ion beam intensity (IH −) in a pulse and the transverse emittances were rather larger than those for the previous 65 keV 110 mA operation. The plasma electrode temperature (TPE) of 254 °C much higher than that not only for the usual J-PARC IS (about 70 °C) but also for the standard cesiated H− ion sources (180 ∼ 200 °C) suggested the existence of novel H2O mediated cesiation surviving against the high TPE. In this paper, the J-PARC IS improvements based upon a hypothesis of the best cesiation constituted of sub monolayer H2O (chemically bound with Mo) mediated cesiation and Cs half monolayer on remaining surface are presented. The innovative cesiation derived a 76.5 keV 145 mA beam stably with the small beam fluctuation and transverse emittances suitable for Radio Frequency Quadrupole LINACs of high energy LINACs. The measured results of the 145 mA / 83 mA beam, extraction electrode current and RF waveforms, parameter trends of an 8 hours 145 mA operation and the transverse emittances are presented. The optimum TPE was increased from 70 °C to 230 °C. Furthermore, the beam intensity for the J-PARC IS operation energy of 52.5 keV was increased from 72 mA to 83 mA, which was consistent with the 1.5 power perveance law on the beam energy compared with 145 mA for 76.5 keV.

First results of the cryogenics operation from the LHC physics Run 3 at the increased energy to 6.8 TeV

Back in 2018, LHC completed its Run 2 physics period. Consolidation, maintenance, and upgrade activities performed during the subsequent Long Shutdown 2 period (LS2), based on a data-driven approach, allowed for full potential availability of the LHC cryogenics infrastructure before tackling the 2021 magnet quench training campaign, preparing the whole machine for operation at the increased energy of 6.8 TeV. This paper will first give a summary of the main upgrades, consolidations and maintenance performed during the LS2. Magnet training of the machine to the increased energy of 6.8 TeV will be addressed. Results of the first year (2022) of Run 3 physics will be presented, achieving high cryogenic availability in a heavily sustained operational context of the accelerator (beams energy increase, induced heat load, peak & integrated luminosity). Helium inventory management aspects will be discussed, with a particular highlight on the necessary operational adjustments taken to cope with the present supply market evolution. Implementation of several operational modes for cryogenic plants will be presented, towards significant electrical power savings while maintaining nominal physics production at the highest availability rate.

Design improvements to the SNS ion source and diagnostics

The U.S. Spallation Neutron Source (SNS) is a state-of-the-art neutron scattering facility delivering the world’s most intense pulsed-neutron beams to a wide array of instruments which are used to conduct investigations in many fields of science and engineering. The accelerator system is fed by an RF-driven, multicusp, H− ion source which nominally provides pulsed beam currents of 50-60 mA (1ms, 60Hz). This report provides a discussion of ongoing design improvements to the SNS ion source and Low Energy Beam Transport (LEBT) as well as diagnostic upgrades undertaken since the previous ICIS conference. These improvements include (i) simple mechanical modifications to the source outlet aperture which resulted in dramatically increased extracted beam current and comparable or lower emittance at similar beam currents, (ii) design improvements to the LEBT chopper target which will enable full power beam-dumping during physics studies, (iii) refinement of the SNS Allison emittance scanner that has enabled the first reliable LEBT beam measurements at full beam power (65kV, 50-100mA, 1ms, 60Hz) on the SNS ion source test stand and (iv) the implementation of a thermal imaging camera for the monitoring the LEBT electrode temperatures. (v) The design of an advanced Cs system, capable of more efficient Cs utilization with significantly lower Cs losses from the source is also presented. Mechanical details, computational simulations and experimental results are discussed within the context of these improvements.

Permanent magnet ECR ion source and LEBT dipole for single-ended heavy ion ToF-ERDA facility

We present the status of the ion source and low energy beam transport prototyping for a single-ended heavy ion time-of-flight elastic recoil detection analysis equipment. The environmentally friendly concept is based on a permanent magnet ECR ion source and dipole magnet on a 500 kV platform without SF6 insulation, producing high charge state noble gas ion beams, e.g. 3–6 MeV argon. The ion fluxes of Ar6+–Ar12+ achieved with the CUBE-ECRIS permanent magnet minimum-B quadrupole ion source exceed 1-10 particle nA required for the low energy ToF-ERDA application. The CUBE-ECRIS can produce over 1 particle nA krypton and xenon beams up to charge states Kr19+ and Xe24+, which enables extending the scope of the ToF-ERDA application. The integration of an adjustable-field permanent magnet dipole into the CUBE-ECRIS test stand at the JYFL accelerator laboratory is described briefly.

A new proton injector based on PKU-type 2.45GHz PMECR ion source for BNCT facility

A first fully domestically Accelerator-based boron neutron capture therapy demonstration device(AB-BNCT) located in Yangtze River Delta region is being build recently. The project is held by “Xi’an Jiaotong University-Huzhou Neutron Science Laboratory” joint lab established by Xi’an Jiaotong University and Huzhou Industrial Group. The AB-BNCT facility requires a proton beam of 30 mA@40 keV at RFQ entrance, with its beam duty cycle between 0.5%-100%, and its normalized root mean square emittance less than 0.2 π.mm.mrad. Ion source group of Peking University (PKU) is in charge of the proton ion source and its low energy beam transportation section (LEBT). A PKU type compact permanent magnet 2.45 GHz ECR ion source (PKU-Type PMECR) and a two solenoid LEBT is under development for this purpose. So far, the PMECR ion source conditioning is complete and all parameters are better than required for this facility. The details will be presented in the present paper.

Recent advancements with the H− injector performance for the Spallation Neutron Source operation and upgrade

The Spallation Neutron Source (SNS) located at the Oak Ridge National Laboratory is an accelerator-based, pulsed neutron facility utilized for a broad range of scientific research and industrial applications. In the past 5 years, the facility has reliably been operated at its baseline design beam power of 1.4 MW, and it is currently undertaking an upgrade to double its power to 2.8 MW. A 65-keV H− injector, which comprises an rf-driven H− ion source and an electrostatic low energy beam transport, delivers the required high-current, time-structured H− beam to the accelerator. The H− injector can reliably provide 50-60 mA beam current at 6% duty-factor (1 ms, 60 Hz) for a 3-4 month service cycle. To ensure sufficient operational margins for the SNS routine operations and ongoing upgrade requirements, the injector system has been continuously improved on a R&D test stand. This paper presents the operational status and recent advancements with the injector system performance including the enhanced ion source beam output capability up to ∼110 mA, the improved ion source plasma ignition reliability using a 27.12-MHz RF system, and the upgraded LEBT beam chopper system etc.

Design of the RF waveguide network for the klystron-based CLIC main linac RF module

The klystron-based Compact Linear Collider (CLIC) was initially proposed with a low center-of-mass energy of 380 GeV, primarily due to potential cost-effectiveness. To enhance overall cost-efficiency, reliability, and stability, a novel RF module for klystron-based CLIC main linac has been designed and studied. This RF module utilizes two X-band klystrons to feed eight traveling wave accelerating structures, resulting in a beam energy increase of 138 MeV. A key innovation of the new RF module is the integration of double-height waveguides, which contributes to a 30% reduction in surface fields and a 40% decrease in RF loss. To meet the double-height requirement, a majority of the RF components responsible for transmitting the high RF power underwent a redesign. Two solutions, based on the choke mode flange and the L-shape waveguide, were proposed to facilitate the adjustment of the accelerating structures for beam-based alignment. Additionally, bent damping waveguides and HOM loads and a high order Magic-T, were designed for the accelerating structure named CLIC-K. The paper will comprehensively present and describe both the RF design and the integration of the klystron-based CLIC module.

Photonic entanglement with accelerated light

Accelerated light has been demonstrated with laser light and diffraction. Within the diffracting field it is possible to identify a portion that carries most of the beam energy, which propagates in a curved trajectory as it would have been accelerated by a gravitational field for instance. Here, we analyze the effects of this kind of acceleration over the entanglement between twin beams produced in spontaneous parametric down-conversion. Our results show that acceleration does not affect entanglement significantly, under ideal conditions. The optical scheme introduced can be useful in the understanding of processes in the boundary between gravitation and quantum physics.

Influence of Polymer Surface Roughness on the Fractions of Transmitted, Reflected and Absorbed Energy in Operation of Laser Transmission Welding

The study of energy fractions plays a fundamental role in laser joining operations: from their knowledge, it is possible to calculate the amount of laser beam energy that is effectively available during the formation of chemical and physical bonds, and how much energy is dissipated. This study examines semi-crystalline polymers of polyamide 6.6 (PA), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), and polypropylene (PP), semitransparent to light radiation, with the aim of studying the influence of surface roughness on the distribution of energy fractions, and in particular on the reflection portion. For this purpose, polymeric samples with different surface finishing were prepared and characterized by profilometric analysis. Subsequently, an experimental setup was implemented to directly measure the transmitted ratio, obtaining the reflected energy fraction from the Beer-Lambert law, and the absorbed ratio by energy balance. The results showed a decrease in the power transmitted by polymers subjected to surface treatment, due to an increase in the reflection fraction, a phenomenon particularly evident for PET, for which the reflection share increased from ~ 0.5% to ~ 15.3%, following P240 treatment. A lower influence was verified for PA and especially PTFE, due to a lower influence of the treatment on surface morphology. On the basis of the experimental results, it is hypothesised that roughening the lower section of the irradiated polymer could allow an increase in the total internal reflection fraction, favouring the joint at the interface point.Graphical

Theoretical and Numerical Investigation of the Effective Mechanical Properties of an Arc Star-Shaped Auxetic Honeycomb

Background: Auxetic honeycombs have attracted a lot of attention due to their excellent properties, including lightweight, and outstanding impact resistance and energy absorption. Methods: This study focuses on a new type of arc star-shaped honeycomb (ASSH) by replacing the tip angles of the classical star-shaped honeycomb (SSH) with curved edges. The theoretical expressions of the effective Poisson’s ratio and Young’s modulus are deduced by using the Timoshenko beam theory and energy method. Furthermore, the numerical model is also established through the Finite Element Method (FEM); then, both the analytical and computational approaches are adopted to conduct parametric analysis. Results: It was found that the effective mechanical properties obtained by theoretical analysis and the FEM are consistent with each other, and ASSH bears tunable effective Poisson’s ratio and Young’s modulus under varying geometric configurations. Conclusion: The present work may provide some guidance for the design and analysis of future auxetic honeycombs.

A study of polarity effect for various ionization chambers in kilovoltage x-ray beams.

Ionization chambers play an essential role in dosimetry measurements for kilovoltage (kV) x-ray beams. Despite their widespread use, there is limited data on the absolute values for the polarity correction factors across a range of commonly employed ionization chambers. This study aimed to investigate the polarity effects for five different ionization chambers in kV x-ray beams. Two plane-parallel chambers being the Advanced Markus and Roos and three cylindrical chambers; 3D PinPoint, Semiflex and Farmer chamber (PTW, Freiburg, Germany), were employed to measure the polarity correction factors. The kV x-ray beams were produced from an Xstrahl 300 unit (Xstrahl Ltd., UK). All measurements were acquired at 2cm depth in a PTW-MP1 water tank for beams between 60 kVp (HVL 1.29mm Al) and 300 kVp (HVL 3.08mm Cu), and field sizes of 2-10cm diameter for 30cm focus-source distance (FSD) and 4 × 4 cm2 - 20 × 20 cm2 for 50cm FSD. The ionization chambers were connected to a PTW-UNIDOS electrometer, and the polarity effect was determined using the AAPM TG-61 code of practice methodology. The study revealed significant polarity effects in ionization chambers, especially in those with smaller volumes. For the plane-parallel chambers, the Advanced Markus chamber exhibited a maximum polarity effect of 2.5%, whereas the Roos chamber showed 0.3% at 150 KVp with the 10cm circular diameter open-ended applicator. Among the cylindrical chambers at the same beam energy and applicator, the Pinpoint chamber exhibited a 3% polarity effect, followed by Semiflex with 1.7%, and Farmer with 0.4%. However, as the beam energy increased to 300 kVp, the polarity effect significantly increased reaching 8.5% for the Advanced Markus chamber and 13.5% for the PinPoint chamber at a 20 × 20 cm2 field size. Notably, the magnitude of the polarity effect increased with both the field size and beam energy, and was significantly influenced by the size of the chamber's sensitive volume. The findings demonstrate that ionization chambers can exhibit substantial polarity effects in kV x-ray beams, particularly for those chambers with smaller volumes. Therefore, it is important to account for polarity corrections when conducting relative dose measurements in kV x-ray beams to enhance the dosimetry accuracy and improve patient dose calculations.

Modeling compliant bistable mechanisms: An energy method based on the high-order smooth curvature model

This paper applies an energy method based on the high-order smooth curvature model to address the challenges of kinetostatically modeling the complicated nonlinear post-buckling behavior of inclined compliant beams. The proposed energy method is grounded in the principle of minimum strain energy, implying that the total strain energy is minimized at the equilibrium configuration. In this work, the high-order smooth curvature model is adopted to accurately model the bending strain energy of large deformation beams. Subsequently, the Lagrange multiplier method is employed to ascertain the minimum of strain energy while concurrently determining the corresponding tip loads. Additionally, the deformation shape and maximum stress are determined via the smooth curvature model. The proposed method is introduced for the first time in modeling compliant bistable mechanisms, and it is proven that the method can be used for modeling compliant beams with inclined angles ranging from 0 to 90 degrees. Following the modeling, finite element analysis and experimental tests are conducted to verify the accuracy of the proposed energy method. A comprehensive comparative analysis between proposed method and existing methods is conducted. The comparison results prove that the model is more computationally efficient without compromising modeling accuracy The proposed modeling method can not only be used for modeling compliant bistable mechanisms but also has extendable applications in modeling initially-curved compliant beams, contact-aid design problems, and distributed load problems.The present work not only advances the practical application of the proposed energy method but also lays the foundation for future research in modeling compliant mechanisms.

Simulation and experimental study of notched cantilever beam for improved vibration energy harvesting

This research paper addresses the design and analysis of a Notched Cantilever Beam Energy Harvester (NCBEH) aimed at enhancing vibration energy harvesting. The voltage output from Lead Zirconate Titanate (PZT) piezoelectric material is directly related to the strain it experiences. Therefore, numerical simulations using ANSYS were conducted to investigate the variations in natural frequency and stress–strain distribution with respect to slot length in a slotted cantilever beam. Additionally, a notch was introduced into the beam to further enhance strain distribution. The study found that, with precise PZT placement, an NCBEH with a 55 mm slot length can generate 15% more voltage output at lower natural frequencies compared to existing Piezoelectric Cantilever Beam Energy Harvesters (PCEH) [1]. Experimental tests were also conducted to compare the voltage output response of the NCBEH and the PCEH, with the results showing good agreement with the numerical simulation findings.

Impact of Electron Precipitation on Brown Dwarf Atmospheres and the Missing Auroral H3+ Emission

Recent observations have demonstrated that very low-mass stars and brown dwarfs are capable of sustaining strong magnetic fields despite their cool and neutral atmospheres. These kilogauss field strengths are inferred based on strong, highly circularly polarized gigahertz radio emission, a consequence of the electron cyclotron maser instability. Crucially, these observations imply the existence of energetic nonthermal electron populations, associated with strong current systems, as are found in the auroral regions of the magnetized planets of the solar system. Intense auroral electron precipitation will lead to electron collisions with the H2 gas that should generate the ion H3+ . With this motivation, we targeted a sample of ultracool dwarfs, known to exhibit signatures associated with aurorae, in search of the K-band emission features of H3+ using the Keck telescopes on Maunakea. From our sample of nine objects, we found no clear indication of H3+ emission features in our low-to-medium-resolution spectra (R ∼ 3600). We also modeled the impact of an auroral electron beam on a brown dwarf atmosphere, determining the depth at which energetic beams deposit their energy and drive particle impact ionization. We find that the H3+ nondetections can be explained by electron beams of typical energies ≳2–10 keV, which penetrate deeply enough that any H3+ produced is chemically destroyed before radiating energy through its infrared transitions. Strong electron beams could further explain the lack of UV auroral detections and suggest that most or nearly all of the precipitating auroral energy must ultimately emerge as thermal emissions deep in brown dwarf atmospheres.

Computational evaluation of the bucky components influence on the estimation of normalized glandular dose in digital mammography

The mean glandular dose (MGD) is the most suitable dosimetric quantity used in mammography to describe the absorbed dose by the breast, although it cannot be directly acquired. Studies have provided conversion factors widely implemented in international dosimetry protocols to estimate MGD, such as normalized glandular dose (DgN). Over time, the DgN estimation was refined by considering geometric models that approach a real clinical environment, such as new anode/filter combinations, compression plate and breast models. However, there is no detailed study of how the bucky (support plate, antiscatter grid and detector) can affect the DgN estimation. A modified PENELOPE Monte Carlo code was used for DgN estimation. The irradiation geometric model was built as a complete digital mammography system, considering a homogeneous breast and different typical bucky models in commercial mammography units. Simulations were carried out for mono and polyenergetic beams considering different imaging geometries. Studies with monoenergetic beams showed that the bucky presence affected DgN mainly for higher beam energies and thinner breasts. The breast support plate was the bucky component that most affected the DgN, followed by the antis-scatter grid and finally, the image detector. Studies with polyenergetic conventional (low-energy) spectra showed that the bucky exerted a minimal influence on DgN values (less than 1.0%). For high-energy spectra, mainly employed in modalities such as contrast-enhanced digital mammography, the DgN values were more affected by the bucky, increasing by 4.8% the DgN values for a 2 cm thick breast and a W/Cu 50 kV spectrum. Bucky inclusion in computer simulations is highly recommended mainly for thinner breasts and high-energy spectra. To simplify the simulations, we confirm that a homogeneous carbon fibre block support, with thickness between 3.9 and 4.1 mm, can be used as a good substitute for a complete bucky model.