The Japan Proton Accelerator Research Complex (J-PARC) has achieved stable 1 MW operation test on its neutron target and is advancing toward higher power levels of 1.5 MW to support high-power MR operations and a second target station. This progression presents challenges, including increased intra-beam stripping (IBSt) of H⁻ ions, chop leakage from higher beam currents and emittance, low-energy beam loss due to halo formation, frontend fluctuations affecting beam transmission, and RF phase and amplitude fluctuations. To address these issues, a redesigned lattice mitigates IBSt, a new MEBT1 improves chopping and collimation, and machine learning-based compensation schemes manage frontend and RF fluctuations. Additionally, longitudinal and transverse matching schemes enhance beam quality, validated through benchmarked longitudinal measurements. Results from studies at 50 mA and 60 mA beam currents demonstrate significant progress in overcoming these challenges.

Accelerator-based boron neutron capture therapy (BNCT) has been studied worldwide for a novel cancer therapy using neutrons generated by an accelerator system. The iBNCT (Ibaraki BNCT) project began in collaboration with KEK, the University of Tsukuba, Ibaraki Prefecture, and private companies in Japan. The iBNCT project aims to realize linac-based BNCT with a compact and low-activation accelerator system based on the design and experiences of the J-PARC linac. It consists of an H+ ECR ion source, a 3-MeV RFQ, an 8-MeV Alvarez-DTL, and a beryllium neutron-generation target. Since a high neutron flux is required for the BNCT treatment, an average beam current of more than 1 mA is necessary with the combination of the 8-MeV proton and the beryllium target. By improving the vacuum, cooling water and low-level RF system, stable operation was achieved with an average beam current of 2 mA. After completion of the non-clinical studies in parallel with neutron beam characteristic measurements, the iBNCT project has started a clinical study in January 2024. In this contribution, the present status together with the conducted upgrade and prospects of the iBNCT accelerator will be presented.

This paper presents the design of 750 MHz IH-DTL (Interdigital H-mode Drift Tube Linac) tank, specifically developed to be part of a carbon ion injector for medical treatment applications. These sections provide a highly efficient solution for ion acceleration in the 5 to 10 MeV per nucleon energy range, offering a high shunt impedance. The study includes simulations of electromagnetic fields using CST Software, and beam dynamics simulations through a KONUS-type configuration

CEA is committed to delivering a study for a warm linac in the frame of the ICONE project. It aims at accelerating an 80-mA beam of protons up to 25 MeV, with a 6% duty cycle. The LINAC consists of: a proton source with low-energy beam transport line, an RFQ, a medium-energy beam transport line, and a warm DTL. All these components must be tuned at 352.2 MHz, to reach the required output energy. This document presents the RF studies made by CEA and INFN on the main RF components, including the RFQ, the rebunchers, IH- and Alvarez DTL cavities and the RF amplifiers.

The University of Sarajevo Physics Department, in collaboration with CERN’s Accelerator Beam Physics group, proposes a compact linear accelerator design for applied physics research spanning from beam dynamics studies to material surface analysis. The Sarajevo Ion Accelerator (SARAI) consists of an electron cyclotron resonance ion source, a low energy beam transport line (LEBT) and a radiofrequency quadrupole (RFQ). The ion source can produce an array of ions extracted with 30 kV. This study presents an iterative parameter optimization method that suggests two LEBT optics: one for beam diagnostics and another for compact beam matching to the RFQ acceptance. The RFQ discussed here is a 750 MHz, 2.5 MeV/u RFQ, used for medical applications. SARAI RFQ aims at 0.5 - 2 MeV/u. A novel RFQ technology allows a significant reduction in footprint. This paper further discusses plans for source commissioning and potential research applications.

The Frankfurt Neutron Source FRANZ will be a compact accelerator driven neutron source utilizing the 7Li(p,n)7Be reaction with a 2 MeV proton beam. The 700 keV RFQ has been sucessfully commissioned with a 10 mA proton beam. Conditioning of the subsequent IH-type cavity has been performed up to 10 kW. We also report on RFQ emittance measurements performed with a slit grid emittance device. In addition, a fast faraday cup (FFC) was used for bunch shape measurements behind the RFQ.

As part of the MYRRHA project, which is being implemented in Mol, Belgium, two of the planned 17 normal-conducting CH cavities have been built and tested at several kilowatts of RF power. Since the cooling concept for the stems was revised after their construction, concerns arose that the two existing cavities might have suffered a degradation in performance during high-power testing due to the outdated cooling system. Consequently, it was decided to subject cavity CH02 to renewed LLRF measurements at IAP Frankfurt to ensure that its performance has not deteriorated. The cavity is then scheduled for high-power testing at the newly established high-power station at IAP. This will not only serve to commission the test stand but also recondition the cavity This paper summarizes the recent LLRF measurements performed on CH02 and reports on the current status of preparations for the upcoming conditioning.

PEEK is an advanced polymer known for its exceptional mechanical strength, thermal stability, and radiation resistance, making it a promising candidate for applications in extreme environments. This study explores the viability of PEEK as a vacuum window material in high-power radio frequency (RF) couplers. Traditionally, materials such as ceramics are employed for this purpose; however, they are costly to manufacture and impose limitations during the design process. PEEK offers additional advantages, including the possibility of additive manufacturing, which enables the integration of cooling channels for efficient thermal management. The research evaluates PEEK's electrical, thermal, and mechanical properties under conditions typical of high-power RF couplers, such as vacuum stability, RF-induced heating, and electromagnetic transparency. At the Institute for Applied Physics (IAP), PEEK is tested as a vacuum window material in high-power experiments up to 35 kW. Following these tests, the material is analyzed to assess its performance and suitability for RF applications.

The Japan Proton Accelerator Research Complex (J-PARC) has achieved stable 1 MW operation test on its neutron target and is advancing toward higher power levels of 1.5 MW to support high-power MR operations and a second target station. This progression presents challenges, including increased intra-beam stripping (IBSt) of H⁻ ions, chop leakage from higher beam currents and emittance, low-energy beam loss due to halo formation, frontend fluctuations affecting beam transmission, and RF phase and amplitude fluctuations. To address these issues, a redesigned lattice mitigates IBSt, a new MEBT1 improves chopping and collimation, and machine learning-based compensation schemes manage frontend and RF fluctuations. Additionally, longitudinal and transverse matching schemes enhance beam quality, validated through benchmarked longitudinal measurements. Results from studies at 50 mA and 60 mA beam currents demonstrate significant progress in overcoming these challenges.

Research on heavy ion linac was began more than ten years ago initially to improve the HIRFL operation at IMP. In China, the first continuous wave (CW) heavy ion linac, SSC Linac, working at 53.667 MHz was designed and constructed as the SSC injector. The ion particles can be accelerated to 1.48 MeV/u with the designed A/q≤5.17. At present stage, this CW linac has been put into operation and the Uranium has been accelerated to 1.48 MeV/u successfully in the end of 2023. To meet the rising requirements of the applications, a compact 162.5 MHz heavy ion linac operating in pulse mode was developed with A/q≤3. The “KONUS” beam dynamics was adopted in the IH-DTL design and the heavy ions can be accelerated to 4 MeV/u in 9m length. The 108.48 MHz SESRI linac was another pulse machine which was built at Harbin. Both of the heavy ions and proton beam can be accelerated by this linac to 2 MeV/u and 5.6 MeV, respectively. In this paper, the status of these three heavy ion linacs and their beam commissioning results were presented.

The radio frequency quadrupole (RFQ) is known for bunching, focusing and acceleration of ion beam and more importantly, it does not require transverse focusing element like quadrupole magnets between accelerating cells compared to drift tube linacs. By pushing the limits of handling surface electric field between RFQ vanes, it is possible to make a standalone 352 MHz RFQ reaching 1.8 MeV/u energy gain for swift heavy ions upto mass to charge ratio (A/q) ≤ 4. Special RFQ vane material of cryo Cu* is considered by which surface electric fields can be pushed around 50 MV/m** and the whole RFQ is designed within a length of 5m which is substantially less than any RFQ + DTL combination of equivalent energy gain accelerator for heavy ions. Such systems are highly promising for compact medical LINACS and as well as standalone facilities for nuclear physics experiments. The adiabatic bunching and focusing inherently stabilize the beam dynamics at proper RFQ power and cavity tuning. We present the beam optics design using PARMTEQ code and RFQ cavity design along with thermal analysis using CST MWS. The error analysis is provided to support the design in terms of practical feasibility.

Currently, in the J-PARC linac, beam commissioning between the ion source and RFQ mainly involves adjusting the extraction voltage of the ion source and the two solenoid magnets in the Low Energy Beam Transport line (LEBT) installed between the ion source and the RFQ. These parameters are determined to maximize the measured beam current at the current monitor (SCT) downstream of the RFQ. Previously, the SCT used as a reference had measured the beam current by cutting out a part of the macro bunch. However, to further improve the beam quality, we adjusted LEBT parameters using the newly measured method, which is an integrated whole macro bunch signal. The optimum value obtained by the new method differed from the previous. Therefore, to investigate the cause, we saved all the beam current waveforms of the SCT for reference and compared the ion sources and LEBT parameters of each. As a result, the current of the beam that passed through the RFQ changed over time within the macro bunch for certain ion source and LEBT parameter settings. In this presentation, we will introduce the above study results and discuss the cause of the temporal changes in beam current.

The quarter wave resonator (QWR, a.k.a. λ/4 resonator) for the new ISIS MEBT is a bunching cavity that longitudinally compresses the H- beam into smaller bunches. It has two gaps with a distance of βλ/2 between mid-gaps, and works in π mode at the resonant frequency of 202.5 MHz, with a phase angle of -90 degrees, and a maximum voltage per gap (E0L) of 55 kV. The detailed RF and thermal design was developed, followed by the manufacturing of a prototype, all being presented elsewhere. Several mechanical issues were noticed with the RF finger strips and tuners during the assembly of the prototype cavity. The manual tuner (to account for the manufacturing tolerances and the vacuum load) was machined to the final dimension to achieve the desired resonant frequency, according to the Vector Network Analyser (VNA) measurements. The measured quality factor was found to be much lower than expected, which required a redesign of some of the RF seals. The cavity was powered and conditioned in a relatively short time up to a nominal power, but severe multipacting was observed, initially only at low power, but later also at medium power levels, which required a creative approach to be fixed without a major cavity redesign.

FRIB is the first linac to deploy a large number of half-wave-resonators (220 HWRs) and the first heavy ion linac to operate at 2 K. Such key technology has enabled FRIB to operate as the world’s highest energy continuous-wave hadron linac and highest-energy heavy ion linac delivering world’s highest uranium beam power (>10 kW) on target. The key technological experience may be shared with our society. Key technologies that have sustained FRIB facility establishment and beam power ramp up include large-scale superconducting RF, SC magnets, liquid metal charge stripping, and high power targetry. This talk provides a summary of the technological development key to FRIB’s successful project completion and power ramp up to world’s frontier of high power heavy ion facilities.

This study presents the design and fabrication of a fully 3D-printed Crossbar H-mode (CH) cavity operating at 350 MHz, optimized for continuous-wave (CW) operation. The cavity is manufactured using a 1.4404-grade stainless steel additive manufacturing process, followed by electrochemical polishing and galvanic copper plating to enhance surface conductivity and reduce power losses. The structure will be tested at the FRANZ accelerator in Frankfurt with a 2 MeV proton beam. The accelerating gradient is designed to achieve approximately 1 MV/m, limited by the available RF-power-amplifier of 2 kW. This research demonstrates the feasibility of integrating additive manufacturing with high-frequency accelerator technology for cost-effective and robust cavity production.

This study deals with the design and performance analysis of H-mode drift-tube linac (DTL) accelerators in the ultra-high frequency (UHF; 0.3 - 3 GHz) range. Simulations of typical application scenarios were performed, including particle velocities from 0.05c to 0.25c and different drift-tube internal structures. The RF efficiency of different H modes was analyzed. In addition to the shunt impedance, the field distribution and the thermal load also play a role.

Tomographic reconstruction of beam distribution using four wirescanners has been carried out and a comparison is made with the Allison scanner data at the RAON. Tomography technique which is valid under strong space charge effect is applied in the LEBT, MEBT and SCL sections. Also comparison is made with method to get beam parameters using wirescanner rms beam sizes

Korea Multipurpose Accelerator Complex (KOMAC) proposes an energy upgrade of the 100 MeV proton linac. The design of the extended linac is based on a normal-conducting separated-DTL (SDTL) structure which has several advantages over other accelerating structures. The SDTL structure is the same as the DTL, however, unlike the general DTL, the quadrupole magnet is not placed inside the DT but is placed outside. This adds more flexibility to optimize the DT structure for better accelerating efficiency. In addition, since only 4 DTs are placed in the SDTL tank, a separated field gradient stabilization device is not needed, so it is known to be easier to manufacture and align than the general DTL. Our upgrade design consists of a beam matching section between the SDTL and the existing DTL, and 20 SDTL tanks each containing four drift tubes (DTs) with a doublet focusing lattice structure. Beam dynamics simulations were performed using an optimized DT structure to accelerate proton beams from 100 to 200 MeV. We report the preliminary beam dynamics study of the 200 MeV SDTL linac carried out at KOMAC.

Korea Multi-purpose Accelerator Complex (KOMAC) has been preparing 200 MeV energy upgrade. As a possible upgrade choice, separated drift tube linac (SDTL) type is considered in this study. From 2D analysis, optimum cell design deriving maximized effective shunt impedance and minimized Kilpatrick number is obtained. Then, final tank parameters considering stems, slug tuners, vacuum ports are determined under resonance frequency of 350 MHz. Based on that, 3D calculation is conducted to address electromagnetic and thermo-mechanical analysis. Electromagnetic mode and field flatness are analyzed by tuning slug tuners. In addition, appropriate cooling system is designed to minimize resonance frequency and electromagnetic structure variation.

In general, it is not easy to measure the drifting RF properties of a device during its operation. If the scatter matrix changes depending on the temperature, the vector network analyzer provides only a static or a starting point of the thermal development. In particular, it is impossible to fully characterize the component that has more than two ports only by the online measurement. So, in the model proposed, assuming that the heat source defined as the average dissipation is given by stored power in the device and the duty cycle, preliminary measurements for several average dissipations are performed. Analytical solutions are derived by using the preliminary and online measurement for the same average dissipation based on the input-output power pickups. As study case, the method is applied to the circulators and the RFQ of the Linear IFMIF Prototype Accelerator, for the three-port and eight-port device case respectively. The model, the results of experiments, and discussions will be summarized in this report.

Superconducting(SC) radio-frequency(RF) quadrupole (RFQ) integrates the high efficiency of SC technology with the strong focusing and stable acceleration capabilities of RFQ .It is a critical development in next-generation high-performance accelerators.In this study, we present the multi-physics analysis results of a SC RFQ test cavity operating at a frequency of 280 MHz. This test cavity is designed to be a constant voltage of 240 kV and can be used to accelerate a 10 mA proton beam. The RF design adopts a four-vane structure, which is both structurally stable and facilitates efficient liquid helium cooling. Multi-physics analysis indicates that the cavity deformation and thermal stress meet the operational requirements after the post-treatment of the electrodes.The SC RFQ holds significant potential in many areas, including medical isotopes,particle physics experiments,Boron Neutron Capture Therapy (BNCT) and Proton Therapy. Because of the low operational costs and compact structure, it provides an possibility to enable industrialization and applications of high-power accelerators.