High-intensity heavy-ion accelerators have unique challenges in their beam intercepting devices that originate from the extremely high energy loss per distance traveled by heavy ions traversing their materials. These challenges often prohibit such accelerators from achieving higher beam power and thus determine the accelerator performance. In this paper, the challenges of operation of FRIB beam intercepting devices, as well as their statuses, and their future enhancements are discussed.

The Facility for Rare Isotope Beams (FRIB) SRF linear heavy-ion accelerator is designed to accelerate all ions up to uranium to a maximum beam power of 400 kW. Several beam intercepting devices (BIDs) are essential to the successful operation of the accelerator, including a low power charge selector (LPCS) made of copper containing 0.15% precipitated aluminum oxide by weight called Glidcop Al-15. As FRIB ramps up the primary beam power beyond the current 20 kW level, the charge selector must withstand higher radiation damage rates, typically measured in displacements per atom (dpa). Significant beam induced radiation damage including significant deformation, like swelling, blistering, and cracking has been observed on a recently removed LPCS. We also observed physical features up to about 5.5 mm wide and appear to be deeper than the projected range of any ions. This paper presents the results of Monte Carlo simulations carried out using the Particle and Heavy Ion Transport code System (PHITS), quantifying the total damage dose and ion concentration, etc. Simulating an accurate irradiation history is essential to determining the scope of post irradiation examination (PIE) work.

The Facility for Rare Isotope Beams (FRIB) is a high-power heavy-ion accelerator, completed in April 2022, designed to accelerate heavy ions to energies exceeding 200 MeV per nucleon (MeV/u). These ions collide with a rotating graphite target, while the residual beam is absorbed by a water-cooled static beam dump positioned at a 6-degree angle to the beam path. The current beam dump consists of a machined C18150 copper alloy block, explosion-bonded to AL2219 alloy with precision-machined cooling grooves. Cooling water is supplied through 3D-printed Aluminum 6061 inlet and outlet components, facilitating heat dissipation from the beam stopper. This paper examines the thermal-hydraulic performance of the Mini-Channel Beam Dump (MCBD) under both nominal and off-nominal conditions. The MCBD is designed to handle operational beam power up to 20 kW, with planned optimizations to support a power ramp-up to 30 kW.

The FRIB accelerator, constructed and commissioned in 2022, serves as a leading facility for producing rare isotope beams and exploring elements beyond the limits of stability. These beams are produced by reactions between stable primary beams and a graphite production target. Meanwhile, approximately 20–40% of the primary beam power is deposited in the target, necessitating efficient heat dissipation. Currently, FRIB operates at a primary beam power of 15 kW. To enhance thermal dissipation efficiency, a single-slice rotating graphite target with a diameter of approximately 30 cm is employed. This paper presents an overview of the current status of the production target system and ongoing R&D efforts to enhance its performance and durability under high-power beam conditions.

The Facility for Rare Isotope Beams (FRIB) is a high-power heavy ion accelerator facility at Michigan State University that completed in 2022. Its driver linac is designed to accelerate all stable ions to energies above 200 MeV/u with beam power of up to 400 kW. Currently, FRIB is operating between 10 to 20 kW, delivering multiple primary beam species. The beam dump absorbs approximately 75% of the primary beam power. The existing beam dump head can accommodate up to 20 kW operation, with a planned transition to an optimized mini-channel beam dump design with capability up to 30 kW and beyond. Presented here is an overview of the mini-channel beam dump head design optimization and supporting analysis.

The FRIB, a leading experimental nuclear physics facility, produces high-intensity beams of proton- and neutron-rich nuclei. FRIB provides high-yield, high-purity rare isotope beams via primary beams interactions with a graphite target. After the target, the unreacted primary beam should be absorbed by a beam dump. To support operations at 20 kW, an intermediate beam dump system, called the minichannel beam dump (MCBD), has been developed and implemented. This system features a static structure oriented at a 6° angle, reducing power density by 10 times. The MCBD is fabricated as a bimetal using an Al-Cu alloy, with a high-thermal-conductivity copper absorber for enhanced heat dissipation and 2 mm × 7 mm aluminum cooling channels that prevent copper oxidation and significantly improve cooling efficiency. The thermal performance of the MCBD was validated through experimental testing using a 17 keV e-beam at the Applied Research Laboratory, showing measured temperatures matching ANSYS simulation within 10% uncertainty. These results indicate that the MCBD can reliably support FRIB operations at 20 kW or higher, ensuring effective heat dissipation under high-power conditions.

The Facility for Rare Isotope Beams (FRIB) at Michigan State University is a high-power heavy-ion accelerator, completed in 2022. Its driver linac is designed to accelerate all stable ions to energies exceeding 200 MeV/u, with a maximum beam power of 400 kW. Currently, FRIB operates at beam powers between 10 and 20 kW, delivering multiple primary beam species. Approximately 75% of the primary beam power is absorbed by the beam dump. The existing mini-channel beam dump (MCBD) absorber is designed to handle up to 20 kW, with plans for an optimized beam dump capable of supporting 30 kW and beyond. This paper presents the design-by-analysis procedures outlined in ASME Boiler and Pressure Vessel Code that have been applied to the MCBD design.

To intercept unwanted charge states from stripped beams with higher power densities, an advanced charge selector is currently under development at the Facility for Rare Isotope Beams (FRIB). This upgraded charge selector is designed to intercept beam spots that have a power of up to 5 kW and an rms size as small as 0.7 mm × 1.25 mm. To enhance heat dissipation and mitigate thermal stress, rotating graphite wheels are employed as the beam-intercepting medium. An essential aspect of this design is the development of a robust vacuum system to ensure reliable and efficient operation while minimize beam losses in downstream sections. The high graphite temperature, maintained over 1000 °C for radiation damage annealing, raised concerns about gas load. To aid the vacuum system design, vacuum simulations were carried out using a Monte Carlo-based simulation code, MolFlow. The sublimation of graphite, outgassing from the vacuum chamber’s inner wall and the effect of pumping speed on vacuum performance are considered. The results demonstrate that the proposed vacuum system can maintain a pressure under $1×10^{-7}$ mbar, ensuring adequate vacuum conditions for beam operations.

The Facility for Rare Isotope Beams (FRIB) LINAC utilizes two stripper media: liquid lithium and carbon, the beam energy is 17-20 MeV/u. Thermal stress management in carbon strippers is crucial for improving the performance and durability of components. This study focuses on simulating the beam heating with a 460 nm laser beam as a heating source to evaluate its effect on a carbon foil and to guide design updates for use with high power heavy ion beams. The first objective is to measure the carbon foil's emissivity under controlled conditions, which is crucial for understanding thermal behavior and energy transfer. The laser beam has a predetermined intensity to accurately determine the foil's emissivity. Proposed design updates include replacing existing components with more durable metal gears, bearings, coating the inner walls with high-emissivity paint to improve thermal efficiency, and integrating a proximity sensor to monitor the rotational speed of the drive gear. These modifications are expected to optimize the measurements, which will consequently help improving the performance of the Carbon Stripper and ensure the longevity of the system under high-temperature conditions*

Abstract: The MeV-range energetic ions beyond Coulomb’s barrier of a target-beam combination lead to nuclear reactions, subsequently evaporation’s leave or submerge the target materials. This is through extreme high temperature referring as high burn up structure(HBS). The Erbium (Er) is used as burnable, neutron absorber with nuclear fuel matrix. Its quite interesting to observe pure Er under reaction environment. In this study, I present the evidence of HBS of 1. Elongated and vermicularinter-granular bubbles in Te. 2. Clustered spherical inter-granular bubbles and fuel cracks in Er and Tm. 3. Carbonaceous deposits on Sn. via SEM observation. The RBS, EDS and XRD characterization results of these nuclear targets will also be presented.The details of the experiments are in Table 1 with reference list.

At the FRIB (Facility for Rare Isotope Beams), a minichannel beam dump with 2 mm x 7mm water passages can dissipate about 20 kW of heat through high-velocity flow. Its central region features a 6°-tilted CuCrZr absorber plate with an explosion-bonded 2219 Al cooling channel for efficient convection. The wing-section surface, angled from 6° to 90° next to the absorber plate, experiences higher heat fluxes and maximum temperatures, becoming more severe as the beam size increases. Optimizing the beam dump’s geometry is therefore essential to accommodate variable beam sizes and absorb higher beam power. Even small angle changes in the surface orientation significantly affect the heat distribution, which raises the temperature of the CuCrZr plate and complicates global optimization in a limited space. To address this, a Genetic Algorithm (GA) explores a wide range of designs to prevent premature convergence, while a Soft Actor-Critic (SAC) method fine-tunes the details. A 2D finite volume method is employed to reduce the computational load. By merging the GA’s broad search with SAC’s adaptive refinement, the design can withstand higher heat loads under diverse beam conditions.

The charge state spectrum of heavy ions like uranium stripped at 1.4 MeV/u using nitrogen can be narrowed significantly by applying pulsed injection of hydrogen into a dedicated interaction chamber. Pulsing reduces the load of the pumping system to an acceptable amount. Such a set-up is under construction at GSI/Germany. Time-resolved investigations of the build-up of the stripping target have been carried out. Recently, a prototype set-up has been operated during six months of user beam time, mainly with nitrogen but also with hydrogen. A number of ion species has been stripped in the course of the beam time, and a considerable amount of data on stripping efficiencies have been measured using both gases. The contribution summarizes the challenges related to establish such a set-up and the results being obtained so far.