High Beam Research Articles

High-peak-power long-wave infrared BaGa4Se7 optical parametric oscillator with 6.7-13.9 µm widely tunable range.

A high-peak-power, widely tunable range long-wave infrared optical parametric oscillator (OPO) based on the BaGa4Se7 (BGSe) crystal is demonstrated in this Letter. Pumped by a 1064 nm Nd:YAG laser, a high-peak-power of 0.15 MW was achieved at 9.8 µm with a pulse width of 5.0 ns. At 11.0 µm, a high beam quality of M2x = 4.1 and M2y = 3.3 was achieved. By rotating the BGSe crystal, a broad tuning range of 6.7-13.9 µm was realized. Furthermore, a theoretical analysis was conducted to elucidate the reasons behind the improvement in beam quality in the x-direction as the wavelength of the idler wave increases.

OSLD nanoDot characterization for carbon radiotherapy dosimetry

Objective. This study characterized optically-stimulated luminescent dosimeter (OSLD) nanoDots for use in a therapeutic carbon beam using the Imaging and Radiation Oncology Core (IROC) framework for remote output verification. Approach. The absorbed dose correction factors for OSLD (fading, linearity, beam quality, angularity, and depletion), as defined by AAPM TG 191, were characterized for carbon beams. For the various correction factors, the effect of linear energy transfer (LET) was examined by characterizing in both a low and high LET setting. Main results. Fading was not statistically different between reference photons and carbon, nor between low and high LET beams; thus, the standard IROC-defined exponential function could be used to characterize fading. Dose linearity was characterized with a linear fit; while low and high LET carbon linearity was different, these differences were small and could be rolled into the uncertainty budget if using a single linearity correction. A linear fit between beam quality and dose-averaged LET was determined. The OSLD response at various angles of incidence was not statistically different, thus a correction factor need not be applied. There was a difference in depletion between low and high LET irradiations in a primary carbon beam, but this difference was small over the standard five readings. The largest uncertainty associated with the use of OSLDs in carbon was because of the k Q correction factor, with an uncertainty of 6.0%. The overall uncertainty budget was 6.3% for standard irradiation conditions. Significance. OSLD nanoDot response was characterized in a therapeutic carbon beam. The uncertainty was larger than for traditional photon applications. These findings enable the use of OSLDs for carbon absorbed dose measurements, but with less accuracy than conventional OSLD audit programs.

Benchmarking Under- and Above-Canopy Laser Scanning Solutions for Deriving Stem Curve and Volume in Easy and Difficult Boreal Forest Conditions

The use of mobile laser scanning for mapping forests has scarcely been studied in difficult forest conditions. In this paper, we compare the accuracy of retrieving tree attributes, particularly diameter at breast height (DBH), stem curve, stem volume, and tree height, using six different laser scanning systems in a managed natural boreal forest. These compared systems operated both under the forest canopy on handheld and unmanned aerial vehicle (UAV) platforms and above the canopy from a helicopter. The complexity of the studied forest sites ranged from easy to difficult, and thus, this is the first study to compare the performance of several laser scanning systems for the direct measurement of stem curve in difficult forest conditions. To automatically detect tree stems and to calculate their attributes, we utilized our previously developed algorithm integrated with a novel bias compensation method to reduce the overestimation of stem diameter arising from finite laser beam divergence. The bias compensation method reduced the absolute value of the diameter bias by 55–99%. The most accurate laser scanning systems were equipped with a Velodyne VLP-16 sensor, which has a relatively low beam divergence, on a handheld or UAV platform. In easy plots, these systems found a root-mean-square error (RMSE) of below 10% for DBH and stem curve estimates and approximately 10% for stem volume. With the handheld system in difficult plots, the DBH and stem curve estimates had an RMSE under 10%, and the stem volume RMSE was below 20%. Even though bias compensation reduced the difference in bias and RMSE between laser scanners with high and low beam divergence, the RMSE remained higher for systems with a high beam divergence. The airborne laser scanner operating above the forest canopy provided tree attribute estimates close to the accuracy of the under-canopy laser scanners, but with a significantly lower completeness rate for stem detection, especially in difficult forest conditions.

Loss-tailoring single-mode high-power supersymmetric lasers.

Diode lasers with high beam quality and high power have many promising applications. However, high beam quality is always in conflict with high power. In this Letter, we theoretically and experimentally confirm the mode instability property of supersymmetric structures at higher operating currents. Meanwhile, we propose a loss-tailoring diode laser based on a supersymmetric structure, which enables the higher-order lateral modes to obtain higher losses, raises the excitation threshold of the higher-order lateral modes, and achieves a stable fundamental-lateral-mode output at higher current operation. The device obtained a quasi-single-lobe lateral far-field distribution with the full width at half maximum (FWHM) of 7.58° at 350 mA under room temperature, which is a 65% reduction compared to the traditional Fabry-Perot (FP) diode lasers. Moreover, the M2 of 2.181@350 mA has an improvement of about 37% over traditional FP and supersymmetric structure lasers.

Simulation of the reflection of a high energy laser beam at the sea surface for hazard and risk analyses

The application of a high energy laser beam in a maritime scenario necessitates a laser safety concept to prevent injury to personnel or uninvolved third parties from uncontrolled reflections of laser light from the sea surface. Therefore, it is crucial to have knowledge of the amount and direction of reflected laser energy, which varies statistically and depends largely on the dynamics of the wavy sea surface. These dynamics are primarily influenced by wind speed, wind direction, and fetch. An analytical model is presented for calculating the time-averaged spatial intensity distribution of the laser beam reflected at the dynamic sea surface. The model also identifies the hazard areas inside which laser intensities exceed a fixed exposure limit. Furthermore, as far as we know, our model is unique in its ability to calculate the probabilities of potentially eye-damaging glints for arbitrary observer positions, taking into account the slope statistics of gravity waves. This is a critical first step toward an extensive risk analysis. The simulation results are presented on a hemisphere of observer positions with fixed radii from the laser spot center. The advantage of the analytical model over our numeric (dynamic) model is its fast computation time. A comparison of the results of our new analytical model with those of the previous numerical model is presented.

High transmission efficiency collection system for laser-accelerated proton beams based on permanent magnet quadrupoles prefocusing

A new high transmission efficiency, easily tunable, and cost-effective beam collection system is proposed for laser-accelerated proton beams with large divergence angles and wide energy spectra. In previous experiments conducted at the compact laser plasma accelerator platform of Peking University, a beamline was initially constructed with a collection system based on an electromagnetic quadrupoles (EMQs) triplet. However, due to the limited acceptance angle, the EMQs exhibited a monoenergetic transmission efficiency of only 10% to 20% for laser accelerated proton beams. Permanent magnet quadrupoles (PMQs), known for their high magnetic field gradients, compact size, and lower expenses, are well suited for integration with other readily adjustable transmission elements like EMQs and solenoids, effectively enhancing the beam collection capabilities of the system. In this paper, we show that by introducing a pair of centimeter-sized PMQs in front of the EMQs for beam prefocusing, the beam’s transverse size is quickly compressed, enabling transmission of highly divergent protons. Experimental results demonstrate that the prefocusing by PMQs increased the system’s transmission efficiency by a factor of 2.44 to 6.01 compared to the original setup, while also enhancing the energy selection based on stronger chromatic effect. This method can be extended to 100 MeV high-energy proton beamlines and is crucial for applications of laser plasma accelerators. Published by the American Physical Society 2024

Gas mixing and double frequency operation of the permanent magnet quadrupole minimum-B electron cyclotron resonance ion source CUBE-ECRIS

CUBE-ECRIS is a recently commissioned permanent magnet electron cyclotron resonance (ECR) ion source developed at the university of Jyväskylä accelerator laboratory. The special features of the new ion source design include an unconventional quadrupole minimum-B magnetic field structure and a slit beam extraction system necessitated by the line-shaped plasma loss fluxes. Gas mixing and double frequency operation are widely used methods to optimize high charge state ion production of conventional ECR ion sources. The work presented here demonstrates the applicability of these methods for boosting the high charge state beam currents of argon, krypton and xenon extracted from CUBE-ECRIS. Oxygen and helium were used as mixing gases and microwave frequencies between 10 and 11 GHz were used for single and double frequency operation. Gas mixing has a strong impact on the high charge state beam currents. For example, the highest observed charge state increased from 15+ to 19+ for krypton and from 16+ to 23+ for xenon with oxygen gas mixing. Double frequency operation provides an additional performance improvement, for example the currents of argon 9+ and 11+ beams, produced with gas mixing, increased 30% and 100% in double frequency operation at the same total power.

Research and development activities to increase the performance of the CAPRICE ECRIS at GSI

At GSI the CAPRICE ECRIS is in operation to deliver high charge state ion beams from gaseous and metallic elements to the accelerator facility. A test campaign has been carried out at the ECR test bench to fulfill the demand for higher intensity and stability of high charge state ions and for mixed ion beams. The ion beam stability has been monitored by an Optical Emission Spectrometer (OES), which has been already used to check the plasma and the temperature of the resistively heated oven during metal ion beam operation, particularly for Ca ion beams. During the test campaign, it was investigated that the OES can be used for monitoring the stability of ion beams from gaseous elements and mixed ion beams, and the main achieved results are reported. The ion beams extracted from the ECRIS have been simulated with a particle tracking code in order to study and improve the beam matching into the RFQ. The preliminary results of the study together with possible modifications of the extraction column are presented.

Preface

Proceedings of the 20th International Conference on Ion Sources, Victoria, BC, Canada, 2023ICIS’23 was the 20th event in a biennial series of conferences that are dedicated to Ion Sources and their applications, and the first in-person conference of this series after the COVID 19 pandemic. The conference was hosted by TRIUMF (www.triumf.ca), Canada’s Particle Accelerator Centre in Victoria, BC, Canada, September 17 to September 22, 2023. The ICIS series covers the physics and technology of ion sources for scientific research and applications. With the conference being the main event within the ion sources community it offers a forum for exchanging of new ideas and establishing of collaborations.The conference was held at the Victoria Conference Centre in Victoria BC, Canada, with support from the adjacent Fairmont Empress hotel. The venue is located on the traditional, ancestral, and unceded territory of the Lkwungen People, also known as the Songhees and Esquimalt First Nations communities.The biennial conference series covers the physics and technology of ion sources for scientific research and applications. New developments and advancements have been presented and discussed. As in previous conferences of this series, all aspects of ion sources have been covered in the categories:• Fundamental processes in ion sources and plasmas• Production of high intensity ion beams• Production of highly charged ion beams• Negative ion sources• Ion sources for fusion• Radioactive ion sources, charge breeders and polarized beams• Beam formation, extraction, transport, and diagnostics• Applications of ion sources• Key technologies for ion sourcesThe conference was organized in a hybrid mode and a zoom link was made available to participants, who could not attend in person. A total of 178 participants have registered for the conference, of whom 20 were students and 23 attended from remote. Fifty contributions have been presented in plenary sessions of which 20 were invited by the international advisory committee. The remaining 30 have been selected by the Scientific advisory committee. 123 contributions have been presented at 2 poster sessions. The high level and interesting contributions triggered lively discussions during all sessions. Thank you to all who contributed to this.Additional events included a tour of the TRIUMF Laboratory on September 17 just before the conference, and a reception on the same evening. In the afternoon of Wednesday, September 20 delegates were able to enjoy the beautiful surrounding Vancouver Island by either participating in a whale watching tour or a nature hike along the shoreline. In the evening of this day the conference banquet was held in the Fairmont Empress hotel.Fifteen students participated in the student poster competition. Members of both the international advisory committee and the scientific program committee acted as judges. Thank you to all the students who have contributed and the judges. Three winners have been awarded.List of International advisory committee, Scientific program committee, Local organizing committee are available in this pdf.

Characterization of a broad beam ion source converted into a high intensity deuterium beam

Avalanche Energy is developing deuterium ion beams for the Orbitron fusion device. For these and similar projects, modification of off-the-shelf high current ion sources enables affordable and rapidly accessible alternatives to custom-built systems. We have successfully operated the Veeco MARK I broad beam source on deuterium to create multi-keV energy ions. Directing this beam through a small aperture required carefully designed optics. Once a narrower beam was created, a faraday cup was used to measure the beam current and profile while a Thomson Parabola was developed to help understand the beam species and energy composition.

Optimizing Ion Optical Design for Laser Ablation Source in Mass Spectrometry

The study focuses on optimizing a Laser Ablation Source (LAS) for use in mass spectrometry, particularly aiming to enhance transmission of ions and and determination of isotopic compositions in diverse matrices at TRIUMF’s Ion Trap for Atomic and Nuclear Science (TITAN). Critical variables affecting mass spectrometer resolution, such as ion kinetic energy distribution and ion transport are optimized through LAS. The paper explores the importance of consistent initial conditions, ion transport efficiency, and ion capture for accurate and reproducible measurements. Using SIMION software, we optimized ion optical design to tackle challenges like collimating ions travelling off-axis and mass filtering. A significant part of the study is dedicated to ion optic design to enable low abundance measurement of ions of interest (e.g., 10 ions of interest out of 1014 total ions). Techniques like high voltage switching and beam shaping were explored, and the final design aims for high transport efficiency and a 4 mm effective target scan area with maximum transport efficiency. The integration of LAS with a Multiple-Reflection Time-Of-Flight Mass Spectrometer (MR-TOF-MS) is expected to yield an analytical tool with high spatial resolution and transport efficiency for isotope abundance measurement.

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.

High intensity beam dynamics assessment and challenges for HL-LHC

The High Luminosity (HL-LHC) project aims to increase the integrated luminosity of CERN's Large Hadron Collider (LHC) by an order of magnitude compared to its initial design. This requires a large increase in bunch intensity and beam brightness compared to the first three LHC runs, and hence poses serious collective-effects challenges, related in particular to electron cloud, instabilities from beam-coupling impedance, and beam-beam effects. Here, we present the associated constraints and the mitigation measures proposed to achieve the baseline performance of the upgraded LHC machine. We also discuss the interplay of these mitigation measures with other aspects of the accelerator, such as optics, physical and dynamic apertures, the collimation system, and crab cavities. Additional potential sources of intensity limitations are also briefly discussed.

Design and beam dynamics simulation of an 8 MeV compact accelerator-driven neutron source

A compact accelerator-driven neutron source is proposed at Sino-French Institute of Nuclear Engineering and Technology, Sun Yat-Sen University, called Sun Yat-Sen University Proton Accelerator Facility (SYSU-PAFA). The proton accelerator is composed of a proton electron cyclotron resonance source, a four-vane radio frequency quadrupole (RFQ), and an alternative phase focusing drift tube linac (APF-DTL). It can accelerate 10 mA proton beam to 8 MeV. Due to the high current, beam matching is particularly important. In order to achieve beam matching between various components, beam transport sections are needed. The beam transport line is divided into three segments. The Low Energy Beam Transport (LEBT) ensures that the beam parameters are matched before entering the RFQ. The Medium Energy Beam Transport (MEBT) segment efficiently transfers the beam between the RFQ and DTL. The High Energy Beam Transport (HEBT) focuses on transporting the beam to the targets. The design goal of beam transport line is as short as possible while ensuring high efficiency of beam transportation. SYSU-PAFA has an overall transmission efficiency of 99%, with optimal transverse matching conditions between beam transport and RFQ or DTL accelerators. The efficient use of solenoids and magnets allows for a compact transmission section, resulting in a total length of 13.6 meters, shorter than most accelerators at the same beam energy. This paper will provide the detailed beam dynamics of the compact accelerator.

Application of Optical Emission Spectroscopy to Electron Cyclotron Resonance Ion Sources

Electron Cyclotron Resonance Ion Sources (ECRIS) are widely used for production of highly charged high intensity ion beams for research, medical and industrial applications.ECRIS performances, especially the charge state distribution and beam intensity, depend significantly on the electron energy distribution function that ranges from a few eV to hundreds of keV. Further improvements of ECRIS performances require a deeper and deeper understanding of the plasma heating mechanisms and ion generation by means of opportune plasma diagnostics. Amongst others, optical emission spectroscopy (OES) is the most remarkable for application in ECRIS: it is a non-invasive diagnostics able to operate also in high-voltage conditions and it requires small room for operation. OES has been already tested for plasma diagnostics in proton sources.This work presents the experimental set-up developed for the plasma diagnostics of the Advanced Ion Source for Hadrontherapy (AISHa), an ECRIS for medical applications, together with the strategy applied to relate plasma emission lines in the visible and near-infrared domain to plasma parameters for some ions of interest. Preliminary results and perspectives will be also discussed.

High beam current operation with beam diagnostics at LIPAc

The Linear International Fusion Materials Irradiation Facility Prototype Accelerator (LIPAc) is under commissioning in Rokkasho Fusion Institute in Japan and aims to accelerate 125 mA D+ at 9 MeV in Continuous Wave mode for validating the IFMIF accelerator design. To ensure a fine characterization and tuning of the machine many beam diagnostics are installed spanning from injector to the beam dump. The beam operations in 1.0 ms pulsed D+ at 5 MeV were successfully completed with a low power beam dump in 2019. Despite the challenges posed by the pandemic, the crucial transition to a new LINAC configuration was also finalized to enable operation in 1.0 ms — CW D+ at 5 MeV with the high-power beam dump. The 1st beam operation of the configuration was carried out in 2021. The experiences and challenges encountered during these beam campaigns are described in this paper.

Technological developments and accelerator improvements for the FRIB beam power ramp-up

The Facility for Rare Isotope Beams (FRIB) began operation with 1 kW beam power for scientific users in May 2022 upon completion of 8 years of project construction. The ramp-up to the ultimate beam power of 400 kW, planned over a 6-year period, will enable the facility to reach its full potential for scientific discovery in isotope science and applications. In December 2023, a record-high beam power of 10.4 kW uranium was delivered to the target. Technological developments and accelerator improvements are being made over the entire facility and are key to completion of the power ramp-up. Major technological developments entail the phased deployment of high-power beam-intercepting systems, including the charge strippers, the charge selection systems, the production target, and the beam dump, along with support systems, including non-conventional utilities (NCU) and remote handling facilities. Major accelerator improvements include renovations to aging legacy systems associated with experimental beam lines and system automation for improved operational efficiency and better machine availability. Experience must be gained to safely handle the increased radiological impacts associated with high beam power; extensive machine studies and advanced beam tuning procedures are needed to minimize uncontrolled beam losses for the desired operating conditions. This paper discusses the technological developments and accelerator improvements with emphasis on major R&D efforts.

The High Beam to Power Efficiency Investigation of Miniaturized Microwave Ion Source

A miniaturized 2.45 GHz microwave ion source (MIS) with plasma chamber of ϕ30 mm × 40 mm that has the ability to produce more than 20 mA CW hydrogen ion beam with 180 W microwave power has been built at Peking University (PKU) 5 years ago1. A hibrid discharge principle has been proposed on this kind of MIS2. Recently, under the structure of this MIS, factors such as input power, pressure, magnetic field configuration and the size of plasma chamber have been investigated. Based on this research, a more compact 2.45 GHz microwave ion source with inner diameter of 24 mm has been developed. A 32.5 mA hydrogen ion beam was obtained with only 100 W microwave power.

Ultra-highly sensitive dual gases detection based on photoacoustic spectroscopy by exploiting a long-wave, high-power, wide-tunable, single-longitudinal-mode solid-state laser.

Photoacoustic spectroscopy (PAS) as a highly sensitive and selective trace gas detection technique has extremely broad application in many fields. However, the laser sources currently used in PAS limit the sensing performance. Compared to diode laser and quantum cascade laser, the solid-state laser has the merits of high optical power, excellent beam quality, and wide tuning range. Here we present a long-wave, high-power, wide-tunable, single-longitudinal-mode solid-state laser used as light source in a PAS sensor for trace gas detection. The self-built solid-state laser had an emission wavelength of ~2 μm with Tm:YAP crystal as the gain material, with an excellent wavelength and optical power stability as well as a high beam quality. The wide wavelength tuning range of 9.44 nm covers the absorption spectra of water and ammonia, with a maximum optical power of ~130 mW, allowing dual gas detection with a single laser source. The solid-state laser was used as light source in three different photoacoustic detection techniques: standard PAS with microphone, and external- and intra-cavity quartz-enhanced photoacoustic spectroscopy (QEPAS), proving that solid-state laser is an attractive excitation source in photoacoustic spectroscopy.

The design and optimization methods towards 10 kW high beam quality fiber laser based on counter tandem pumping scheme

The design and optimization methods towards 10 kW high beam quality fiber laser based on counter tandem pumping scheme