The muon experiment facility called the Muon Science Establishment (MUSE) is the world’s highest intensity pulsed muon source. The MUSE facility is integrated into the Materials and Life Science Facility building in J-PARC where an intense proton beam is shared with a neutron experimental facility. Graphite was adopted as the target material because of its predominance in chemical stability and radiation hardness. To prolong the lifetime of the target against the radiation damage, the rotating target was developed after the preceding use of the fixed target. In this article, the development process and the issues in the maintenance of the muon production targets are reviewed.
The high-power pulsed spallation neutron source is one of the most convenient tools to conduct cutting-edge research in several domains of materials and life science. In this system, proton beams of several hundred kW to MW order extracted from the high power accelerator is injected into a target and vast amount of neutrons are generated via the spallation reactions with the target material nuclei. The neutron beams are then supplied to the state-of-the-art suite of various experimental devices for fundamental research activities. In this paper outline of the spallation neutron source, target design and technical topics are reviewed by referring mainly to the mercury target system of J-PARC.
The J-PARC neutrino production target was developed for the long-baseline neutrino experiment using the high intensity proton beam by J-PARC MR accelerator. It has been operational since 2009 with maximal beam power of 522 kW. Upgrades of the J-PARC MR and neutrino beam-line are currently ongoing to increase the beam power up to 1.3 MW. In this article, we describe the design concept of the neutrino production target, operation status so far, and target cooling system upgrade to accept the higher beam power.
A production target of secondary particles for a slowly-extracted high-intensity proton facility needs to accept large heat production at a very limited volume, as the source of the secondary particles should be as small as possible for a good quality secondary beam. High radiation is also an issue. The Hadron Experimental Facility at the Japan Proton Accelerator Research Complex, J-PARC, has developed the production targets with indirect-water cooling, which can be used for the proton beams up to 95 kW, and a target system aiming at receiving more than 150-kW proton beams is under development. In this article, these targets are discussed.
Lead bismuth eutectic alloy (LBE) is a promising option as a spallation target for accelerator-driven transmutation systems (ADS) to reduce the radiological toxicity from long-lived radioactive waste. LBE is a heavy metal and has suitable characteristics both as a spallation target and as a coolant for transmutation systems. However, LBE is also known as a highly corrosive with structural materials. In this paper, technological developments to overcome the issue, the latest research activities such as high-temperature operation and oxygen concentration control to ensure corrosion resistance, are introduced together with the outline of the target for ADS.
Water-cooled rotating target system was designed and constructed for RI beam production at RI beam factory (RIBF) in 2006. The system was designed to withstand for an intense 238U beam at 345 MeV/nucleon and 1 particle μA, corresponding beam power of 82 kW. Maximum heat load in the target system is as high as 20 kW, 5.7 W/mm3. The system has been operated successfully without big troubles with beam powers of up to 10 kW. Using those beams, validation of the design is ongoing by comparing the measured temperatures of the beam spot with the results of thermal model calculations.
The ultra-durable strippers developed at the RIKEN RI beam factory for high intensity heavy ion beams, He gas stripper and rotating disk stripper, will be reviewed. Future prospects of them will also be discussed.
The Facility for Rare Isotope Beams (FRIB) at Michigan State University is the world’s first accelerator facility where a liquid lithium charge stripper (LLCS) is used. Charge strippers play a critical role in many high intensity heavy ion accelerators. Because of the anticipated beam intensity to produce 400 kW heavy ion beams, a conventional material such as a carbon foil cannot be used as the charge stripper at FRIB, and thus a liquid lithium film has been selected as its baseline charge stripper. The LLCS development at FRIB has been progressing in a step-by-step basis, starting with collaboration with Argonne National Laboratory for proof-of-principle experiments, and finally has reached its commissioning with heavy ion beams. Its performance as a charge stripper for high power heavy ion beams was found to be excellent. A high power test during the beam commissioning shows no issue in its thermal performance.
High intensity positron sources in the past, at present and in the future are reviewed especially focusing on the thermal aspect of the positron production target. As an example of the positron source for high energy physics, the source used in the SuperKEKB is described in detail.