Low-energy Accelerator Research Articles

Optimized beam shaping assembly for a 2.1-MeV proton-accelerator-based neutron source for boron neutron capture therapy

Boron Neutron Capture Therapy (BNCT) is facing a new era where different projects based on accelerators instead of reactors are under development. The new facilities can be placed at hospitals and will increase the number of clinical trials. The therapeutic effect of BNCT can be improved if a optimized epithermal neutron spectrum is obtained, for which the beam shape assembly is a key ingredient. In this paper we propose an optimal beam shaping assembly suited for an affordable low energy accelerator. The beam obtained with the device proposed accomplishes all the IAEA recommendations for proton energies between 2.0 and 2.1 MeV. In addition, there is an overall improvement of the figures of merit with respect to BNCT facilities and previous proposals of new accelerator-based facilities.

Low-Energy Acceleration of Binarized Convolutional Neural Networks Using a Spin Hall Effect Based Logic-in-Memory Architecture

Deep Learning (DL) offers the advantages of high accuracy performance at tasks such as image recognition, learning of complex intelligent behaviors, and large-scale information retrieval problems such as intelligent web search. To attain the benefits of DL, the high computational and energy-consumption demands imposed by the underlying processing, interconnect, and memory devices on which software-based DL executes can benefit substantially from innovative hardware implementations. Logic-in-Memory (LIM) architectures offer potential approaches to attaining such throughput goals within area and energy constraints starting with the lowest layers of the hardware stack. In this paper, we develop a Spintronic Logic-in-Memory (S-LIM) XNOR neural network (S-LIM XNN) which can perform binary convolution with reconfigurable in-memory logic without supplementing distinct logic circuits for computation within the memory module itself. Results indicate that the proposed S-LIM XNN designs achieve 1.2-fold energy reduction, 1.26-fold throughput increase, and 1.4-fold accuracy improvement compared to the state-of-the-art binarized convolutional neural network hardware. Design considerations, architectural approaches, and the impact of process variation on the proposed hybrid spin-CMOS design are identified and assessed, including comparisons and recommendations for future directions with respect to LIM approaches for neuromorphic computing.

Imaging and dosimetric characteristics of 67 Cu

In recent years the use of beta-emitting radiopharmaceuticals for cancer therapy has expanded rapidly following development of therapeutics for neuroendocrine tumors, prostate cancer, and other oncologic malignancies. One emerging beta-emitting radioisotope of interest for therapy is 67Cu (t1/2: 2.6 d) due to its chemical equivalency with the widely-established positron-emitting isotope 64Cu (t1/2: 12.7 h). In this work we evaluate both the imaging and dosimetric characteristics of 67Cu, as well as producing the first report of SPECT/CT imaging using 67Cu. To this end, 67Cu was produced by photon-induced reactions on isotopically-enriched 68Zn at the Low-Energy Accelerator Facility (LEAF) of Argonne National Laboratory, followed by bulk separation of metallic 68Zn by sublimation and radiochemical purification by column chromatography. Gamma spectrometry was performed by efficiency-calibrated high-purity germanium (HPGe) analysis to verify absolute activity calibration and establish radionuclidic purity. Absolute activity measurements corroborated manufacturer-recommended dose-calibrator settings and no radionuclidic impurities were observed. Using the Clinical Trials Network anthropomorphic chest phantom, SPECT/CT images were acquired. Medium energy (ME) SPECT collimation was found to provide the best image quality from the primary 185 keV gamma emission of 67Cu. Reconstructed images of 67Cu were similar in quality to images acquired using 177Lu. Recovery coefficients were calculated and compared against quantitative images of 99mTc, 177Lu, and 64Cu within the same anthropomorphic chest phantom. Production and clinical imaging of 67Cu appears feasible, and future studies investigating the therapeutic efficacy of 67Cu-based radiopharmaceuticals are warranted.

Nuclear Physics. The Societal Impact – A project for Greece?

Answers to some of the most important questions that our world is facing out, will come from interdisciplinary efforts in medicine, energy and climate. These are involving contributions from fundamental research and in particular from nuclear physics and associated techniques. From the different types of radiation used in hospitals to Magnetic Resonance Imaging (MRI), nuclear physics and its associated technologies that is accelerators and superconducting magnets are omnipresent. The development of new radioisotope production techniques, therapy of certain cancers with ions and hadron therapy or high field MRI are among the subjects undergoing rapid development. Furthermore, archaeometry and many other societal applications are also benefited from the techniques of nuclear physics. My presentation in the 6th workshop of the Hellenic Institute of Nuclear Physics (HINP) was focused on the links between fundamental research and society and was partially inspired by an article I have published in 2020 on this subject [1]. In the last part of my presentation, I have brushed up the situation concerning the construction of low energy accelerator facilities worldwide. The construction of new accelerator installations is going through a flourishing period in particular in Europe with the construction of new accelerators dedicated to fundamental research in Nuclear Physics, to neutron production and to societal applications. This favourable climate could motivate the Hellenic nuclear physics community to design a new accelerator facility dedicated to fundamental research, neutron production and to the multiple applications of nuclear physics techniques to societal problems. Its construction could benefit from European funds and technical contributions from many European countries like France or Italy.

Широкоапертурные низкоэнергетичные ускорители электронов АО «НИИЭФА» на основе высоковольтного тлеющего разряда

Широкоапертурные низкоэнергетичные ускорители электронов АО «НИИЭФА» на основе высоковольтного тлеющего разряда

Measurement and simulation of gamma-ray background in a low energy accelerator facility

The γ-ray background in the indoor environment has been measured up to 3 MeV to evaluate the feasibility of studying low cross-section (nanobarn to picobarn range) astrophysical reactions at the Facility for Research in Experimental Nuclear Astrophysics (FRENA), Saha Institute of Nuclear Physics, Kolkata. An n-type coaxial HPGe detector with 20% relative efficiency has been placed at different locations in the accelerator and beam halls for the measurement. The measured activity has been compared with that at two laboratories (with standard brick walls) with and without passive and active radiation shieldings. As the halls at FRENA are well shielded by concrete, the contribution of the shielding in indoor γ-ray background has been delineated by simulation using a 4π-geometry model.

Simulation Study for Beam Extraction with an Electrostatic Einzel Lens for Low Energy Accelerator Mass Spectrometry

Radiocarbon dating using a compact or low energy accelerator mass spectrometer has been rapidly developing in recent times. A gaseous ion source was designed and simulated to reduce sample preparation times. Then, a simulation study for low-energy accelerator mass spectrometry using the designed ion source for low energy beam transport was conducted to analyze beam separation optimization. Based on our simulation results, the use of an electrostatic Einzel lens led to an enhancement in beam focusing and separation. The ion beam trajectories were calculated using a SIMION program. These simulation results for ion beam extraction are presented in this paper.

Data Orchestration in Deep Learning Accelerators

This Synthesis Lecture focuses on techniques for efficient data orchestration within DNN accelerators. The End of Moore's Law, coupled with the increasing growth in deep learning and other AI applications has led to the emergence of custom Deep Neural Network (DNN) accelerators for energy-efficient inference on edge devices. Modern DNNs have millions of hyper parameters and involve billions of computations; this necessitates extensive data movement from memory to on-chip processing engines. It is well known that the cost of data movement today surpasses the cost of the actual computation; therefore, DNN accelerators require careful orchestration of data across on-chip compute, network, and memory elements to minimize the number of accesses to external DRAM. The book covers DNN dataflows, data reuse, buffer hierarchies, networks-on-chip, and automated design-space exploration. It concludes with data orchestration challenges with compressed and sparse DNNs and future trends. The target audience is students, engineers, and researchers interested in designing high-performance and low-energy accelerators for DNN inference.

DESIGN AND BEAM COMMISSIONING OF THE LEAF-RFQ

An 81.25 MHz continuous wave (CW) radio frequency quadrupole (RFQ) accelerator has been designed and fabricated for the Low Energy Accelerator Facility (LEAF) by the Institute of Modern Physics (IMP) of the Chinese Academy of Science (CAS). The operation frequency is 81.25 MHz and the inter-vane voltage is a constant of 70 kV. It took about 44 hours continuous conditioning to reach RF power of 75 kW which is 1.1 time of the maximum designed value, and the successful CW acceleration of 150 eµA He+ beam to the designed energy of 0.5 MeV/u was already done. The results of the low power test, the RF conditioning and the beam acceleration will be reported in this paper.

Characterization of the new hybrid low-energy accelerator facility in Mexico

In 2013, a new accelerator mass spectrometry (AMS) facility was inaugurated in Mexico. Since then a substantial number of precise measurements of low concentrations of radioactive isotopes (14C, 10Be, 26Al and Pu) have been made. This paper describes the extension to the isotope separator installed at the end of 2017. It takes advantage of the 1MV High Voltage Engineering Europa (HVEE) tandem accelerator with the multicathode ion source (MCIS) and the fine-tuned injection system which delivers low-energy beams into a multipurpose scattering chamber. The MCIS allows for a quick and smooth change of the ion species to be accelerated. The ability to automatically tune all the optics in the injection system produces an accelerator laboratory that can change the beam species, intensities and energies in a few seconds. The careful and detailed study of the high-energy analyzing magnet using well-known proton resonances in 12C and 28Si, allowed for a calibration of the terminal voltage and beam energy. Stable ion beams with energies as low as 300 keV and as high as 8 MeV, from H to Fe, and with intensities in the range 109-1015 particles per second, were produced as listed.

Development and beam commissioning of a continuous-wave four-vane heavy ion radio-frequency quadrupole accelerator based on stable operation

Abstract A continuous-wave (CW) heavy ion radio frequency quadrupole (RFQ) accelerator was developed for the Low Energy Accelerator Facility (LEAF) at IMP. The RFQ accelerator is the most effective accelerator for accelerating the low energy high intensity beam, but there are challenges achieving the stable CW operation. This paper presents the development of the LEAF RFQ based on the stable CW operation. In the beam dynamics design, a multi-harmonic buncher is utilized to reduce the longitudinal emittance and the constant-voltage design is applied for low RF power loss. In the radio frequency (RF) design, the constant-voltage four-vane RFQ is selected to reduce the power dissipation. The π -mode stabilizing loop (PISL) is employed to reduce the admixture of the dipole field. In order to ensure the stability of the cavity structure, the multi-physics of the cavity are analysed. The resonant frequency sensitivities of the cooling water temperature are studied to tune the cavity frequency during operation. Through low power test and tuning, the resonance frequency and field distributions are optimized. The beam commissioning ( 4He 1 + , 14N 2 + and 86Kr 13 + ) and some radiation experiments have been performed. The entire processes of the LEAF RFQ development, such as, beam dynamics design, RF design, multi-physics analysis, low power test, high power conditioning, beam commissioning and some radiation experiments, will be detailed presented in this paper. The results of testing and commissioning indicate that the development of the LEAF RFQ has succeeded. And the design scheme for RFQ with stable CW operation in this work can be applied to other future CW RFQs.

Effect of Hagedorn states on isothermal compressibility of hadronic matter formed in heavy-ion collisions: From NICA to LHC energies

In this work, we have studied the isothermal compressibility ($\kappa_T$) as a function of temperature, baryon chemical potential and centre-of-mass energy ($\sqrt{s_{NN}}$) using hadron resonance gas (HRG) and excluded-volume hadron resonance gas (EV-HRG) models. A mass cut-off dependence of isothermal compressibility has been studied for a physical resonance gas. Further, we study the effect of heavier resonances ($>$ 2 GeV) on the isothermal compressibility by considering the Hagedorn mass spectrum, ${\rho}(m)\sim{\exp(bm)}/{(m^2+m_0^2)^{5/4}}$. Here, the parameters, $b$ and $m_0$ are extracted after comparing the results of recent lattice QCD simulations at finite baryonic chemical potential. We find a significant difference between the results obtained in EV-HRG and HRG models at a higher temperatures and higher baryochemical potentials. The inclusion of the Hagedorn mass spectrum in the partition function for hadron gas has a large effect at a higher temperature. A higher mass cut-off in the Hagedorn mass spectrum takes the isothermal compressibility to a minimum value, which occurs near the Hagedorn temperature ($T_H$). We show explicitly that at the future low energy accelerator facilities like FAIR (CBM), Darmstadt and NICA, Dubna the created matter would be incompressible compared to the high energy facilities like RHIC and LHC.

Accelerator Mass Spectrometry of 237Np, 239Pu and 240Pu for environmental studies at the Centro Nacional de Aceleradores

Low-energy Accelerator Mass Spectrometry (AMS) systems (i.e. working with 1 MV terminal voltages and below) have demonstrated in the past their capability for the ultra-trace analyses of 236U and 239,240Pu in different field studies. The situation for 237Np has been different, mostly due to the constraints imposed by the lack of a Np isotopic tracer. Here, it is presented a comprehensive study on the performance of the 1 MV AMS system at the Centro Nacional de Aceleradores (CNA) for: i) the determination of 237Np using 242Pu as the AMS normalisation isotope and, ii) the efficient analysis of 239Pu, 240Pu and 237Np when they coexist in the same cathode with traces of natural uranium. Working procedures to analyse 237Np and 239Pu on one hand, and 240Pu on the other, are developed in order to meet competitive 238U suppression factors and counting efficiencies for every radionuclide. It is demonstrated that the sputtering-process-based temporal trend in the 237Np/242Pu AMS ratios show a coherent behaviour between the different studied matrixes, demonstrating the reliability of the necessary standard correction procedure in AMS. It is proved that 237Np and 239Pu concentrations at the 1 fg level and 240Pu concentrations at the 0.1 fg level can be quantified in samples containing 238U traces. The technique is applied to the 239,240Pu and 237Np analysis of a seawater reference sample supplied by the International Atomic Energy Agency (IAEA): IAEA-443.

Design and Construction the RF Ion Source for Compact Accelerator with 30 keV Energy

In constructing the low energy accelerator for plant modification the most important part is the ion source. In the conventional cold cathodes and hot filament ion source methods the filament continuously burns out over time, has a shorter lifespan and requires venting of the ion source to atmosphere. Henceforth the Radio frequency (RF) antenna ion source or “non-thermionic ion source” with 13.6 MHz was used in the accelerator as well as it being easy to generate varie the plasma souce and stability. This ion source can produce a particle beam of about ~30 to 40 mA current. The ion particle was extracted by the first zero voltage extraction rod electrode method focusing the ion beam of 0-30 kV with the second rod electrode after which the third rod electrode has zero voltage. In calculating and designing this system via the Simion8.0 Program, the result showed that the Ar+ ion beam with 30 keV can be focused with 1 cm diameter beam at the distance of 10 cm of the drift space.

Inelastic dark matter at the LHC lifetime frontier: ATLAS, CMS, LHCb, CODEX-b, FASER, and MATHUSLA

Visible signals from the decays of light long-lived hidden sector particles have been extensively searched for at beam dump, fixed-target, and collider experiments. If such hidden sectors couple to the Standard Model through mediators heavier than $\sim 10$ GeV, their production at low-energy accelerators is kinematically suppressed, leaving open significant pockets of viable parameter space. We investigate this scenario in models of inelastic dark matter, which give rise to visible signals at various existing and proposed LHC experiments, such as ATLAS, CMS, LHCb, CODEX-b, FASER, and MATHUSLA. These experiments can leverage the large center of mass energy of the LHC to produce GeV-scale dark matter from the decays of dark photons in the cosmologically motivated mass range of $\sim 1-100$ GeV. We also provide a detailed calculation of the radiative dark matter-nucleon/electron elastic scattering cross section, which is relevant for estimating rates at direct detection experiments.

Commissioning and early experience with a new generation low-energy linear accelerator in zahedan

Introduction: Since commissioning beam data are treated as a reference and ultimately used by treatment planning systems, it is vitally important that the collected data are of the highest quality to avoid dosimetric and patient treatment errors that may subsequently lead to a poor radiation outcome. Beam data commissioning should be performed with appropriate knowledge and proper tools and should be independent of the person collecting the data. low-energy linear accelerator was introduced in the clinical area by ELEKTA Medical Systems. This machine was first installed in Sistan and Baluchestan state in 2016. The aim of the present contribution was to report experience about its commissioning and first year results from clinical operation. Materials and Methods: In this research, we used water phantom model DoseviewTM 3D version1.2 and A19 and A28 ion chambers. Commissioning data, beam characteristics and the modeling into the treatment planning system were summarized. . Finally, since the system is capable of delivering Threaetment dose with 6 Mev of energy , a summary of the tests performed for such modality to assess itsperformance in preclinicalsettings and during clinical usage was included. Results: The absorbed dose according to the TRS398 protocol in the absolute dosimetry was D = 0.010042Gy / Mu. In a relative dosimetry, PDD was calculated at different depths and fields, results at 10 cm depth for field 10 × 10 was equal to 0.661 and for the field 30 × 30 at the same depth of 10 cm was equal to 0.690. Also Measurements were made to determine the flatness and symmetry in different fields at a depth of 10cm. For example, the flatness in field 10×10 at depth of 10cm was 3.7 and its Asymmetry value was -0.7%. Conclusion: The results of the commissioning tests and of the first period of clinical operation, resulted meeting specifications and having good margins respect to tolerances. Linac was put into operation for all deliverytechniques; in particular, as shown by the pre-treatment quality assurance results, it enabledaccurate and safedelivery of 3D planning.

The design and fabrication of 81.25 MHz RFQ for Low Energy Accelerator Facility

Abstract To provide high shunt impendence with low power losses, an 81.25 MHz continuous wave (CW) radio frequency quadrupole (RFQ) accelerator has been designed and machined as parts of the Low Energy Accelerator Facility (LEAF). In this paper, the mechanical structure and the main processing technology of the RFQ cavities are described according to the physical and geometric parameters requirements of the RFQ. The fabrication of the RFQ has been completed and the test results agree well with the design requirements. The RFQ accelerator will work in Institute of Modern Physics, Chinese Academy of Sciences in 2018.

Charge-state distributions and charge-changing cross sections and their impact on the performance of AMS facilities

The charge state distributions of ions passing through gases or foils have a significant influence on the performance of AMS facilities. Most important is the stripping process in the terminal of the accelerator. Published data on charge state distributions have been collected as well as associated charge-changing cross sections for various projectiles and targets relevant to AMS. Based on these data, the stripping yields as function of the stripper thickness and ion energy are calculated. This allows to evaluate the stripping thickness required for reaching charge state equilibrium, as well as mass fractionation effects depending on energy and stripper thickness. The significantly different behavior of helium compared to other gases leads to very high stripping yields for specific charge states at low energies. The cross sections for electron detachment of negative ions give a tool for estimating beam losses in the low energy acceleration tube. Further, electron capture and loss cross sections allow the estimation of backgrounds caused by charge exchange processes in the acceleration tubes. The effects discussed here are illustrated with calculations and simulations for Carbon beams. The data are useful for the design of new AMS facilities or improving existing ones.

Measurement of the excitation function of 96Zr(α,n)99Mo for an alternative production source of medical radioisotopes

To assess the feasibility of an innovative medical 99Mo/99mTc production route using a low-energy accelerator, we measured the excitation function of the 96Zr(α,n)99Mo reaction in the energy range from 11 to 23 MeV using a 24 MeV α beam. The present results showed higher values than past data in the peak region, although both data were almost identical above 17 MeV. The production rate of 99Mo from a 96Zr target with incident energies of α particles below 23 MeV was also estimated using the measured excitation function.

Presence of 236U and 239,240Pu in soils from Southern Hemisphere

236U, 239Pu and 240Pu are present in soils mainly as a result of the local- and global-fallout from the atmospheric nuclear weapons tests carried out mainly in the 1950's and 1960's. In this work we provide new data on the presence of 236U and 239,240Pu in surface soils (i.e. up to 5 cm depth) from Chile and Africa. The results were obtained by low-energy Accelerator Mass Spectrometry (AMS). In the case of the Chilean samples, 236U/239Pu atom ratios show a high variability and are in general higher than the reported value for the global fallout in the Northern Hemisphere, ranging from 0.2 to 1.5. The 236U atomic concentrations range from 3.5 × 106 to 9.1 × 106 atoms/g, and are at least two orders of magnitude lower than the reported values in the Northern Hemisphere. The measured 240Pu/239Pu atom ratio in soils from South-Africa and Mozambique are of about 0.17, in agreement with the expected one for global-fallout at those coordinates. To best knowledge of the authors the present work is the first publication on 236U concentrations and 236U/239Pu atom ratios in soils from South-America and Africa.