Abstract
J-PARC Main Ring (MR) delivers a slow extracted 30 GeV proton beam to the Hadron Experimental Facility using third-order resonance. One of the critical properties required for the proton ...beam is the flatness of the time structure of the extracted beam (spill structure). We performed a simple beam simulation of the MR slow beam extraction to investigate the effect of the current ripples of the main magnet power supplies on the beam spill structure. In addition, we investigated in the simulation the effects of the feedback control system on the betatron tune using fast Q magnets and the transverse RF system to improve the spill structure. The simulation qualitatively reproduced the measured spill structures. Now the attempts to optimize their parameters for better spill structure are ongoing.
Slow extraction from the J-PARC main ring using a dynamic bump Tomizawa, M.; Arakaki, Y.; Kimura, T. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2018, Letnik:
902
Journal Article
Recenzirano
A dynamic bump under the achromatic condition has been applied for third integer slow extraction from the Japan Proton Accelerator Research Complex main ring. This dynamic bump scheme has drastically ...reduced beam loss rate for slow extraction compared to that for a fixed bump mode. The low beam loss rate for slow extraction has been retained for high power operations. A beam power of 41−44.4 kW was achieved for physics runs using the slow extraction by applying the dynamic bump scheme. The beam profile measured just upstream of the target indicates that the beam spot at the target does not travel over the entire extraction time. This behavior is advantageous for experimental data acquisition.
A 30 GeV proton beam accelerated in the J-PARC Main Ring (MR) is slowly extracted by the third integer resonant extraction and delivered to the hadron experimental facility. A dynamic bump scheme ...under achromatic condition drastically reduces beam hit rate on the septa devices, and we have attained 51 kW SX operation at 5.2 s cycle with high slow extraction efficiency of 99.5%. A spill duty factor indicating a uniformity of the time structure of the extracted beam is typically 50%. The current SX performance and future plans for improvements will be presented.
After the radioactive material leak accident at the J-PARC hadron experimental facility on May 23, 2013, we designed a new production target, which is capable of a primary proton beam with the energy ...of 30 GeV and power of 50 kW. It is made of gold and cooled by water through a copper block. For the countermeasures of the recurrence of the accident, the target is enclosed by an airtight chamber and helium gas is circulated to monitor the target soundness. In this paper, technical details of the new target design are presented.
This paper reports developments of indirectly cooled radiation-resistant magnet coils, which can be loaded with 2000-A dc. This current capacity is required for the most upstream magnets of a new ...high-momentum beam line to be constructed in the future extension of the J-PARC hadron experimental facility. Indirectly cooled coils using solid-conductor-type mineral insulation cables (MICs) and stainless-steel water pipes were adopted to achieve high radiation hardness. MICs were sandwiched by independent cooling water pipes and stacked in a casing, and the entire coil assembly was filled with solder. However, the maximum load applied to the indirectly cooled MIC coils was limited to 1000-A dc, mainly owing to a heat problem at the end parts of the coils. In pursuit of the required current capability, we have carried out load tests using a test sample of the end parts, which consists of MIC current leads and a copper bus bar connecting the MIC conductors, instead of a whole MIC coil. By improving the structure of the end parts, we have succeeded to operate the test piece stably with 2000-A dc in a vacuum.
The new facility J-PARC has been constructed in Tokai, Japan. It aims at providing intense proton beams of 750 kW for next-generation particle and nuclear physics experiments. The Hadron Experimental ...Hall (HD-hall) is one of the two facilities at the J-PARC Main Ring and utilizes various secondary particles produced by the slowly extracted primary proton beam. We have constructed two charged and one neutral secondary beam lines. The K1.8 beam line transports separated charged secondaries with the maximum momentum of 2 GeV/c. Secondary particles are purified by two electrostatic separators (ESSs). The K1.8BR beam line is branched from the K1.8 at the bending magnet downstream of the first ESS. The K1.8BR delivers separated charged beams with the momentum up to 1.2 GeV/c. On January 27th, 2009, the first beam was successfully extracted to the HD-hall and transported to the beam dump. The first secondary beam extraction to the K1.8BR beam line succeeded in February 2009. The beam commissioning of the K1.8 and KL beam lines started in October 2009.
The target station in the hadron experimental facility at J-PARC consists of a production target and a huge vacuum chamber in which several secondary-beam-line magnets can work. This vacuum chamber ...system aims to remove the vacuum beam pipe from the magnet gap, because the cooling of the beam pipe is the most serious problem in the high intensity beam facility. We have developed indirectly cooled radiation-resistant magnets for the hadron target station. Their coils are made of solid-conductor type mineral-insulation cables and stainless-steel water pipes. They have the great advantages that electric circuits can be completely independent of water pass. The mechanical strength and the insulation performance of the coil are significantly improved also because the insulation water pipes can be avoided from the water pass. A C-type sector dipole and a figure-8-type quadrupole magnet have been fabricated by using indirectly cooled radiation-resistant magnet technology, and installed in the vacuum chamber. We have succeeded to operate them in vacuum stably with the current of DC 1000 A by improving the end structure of the MIC coils and increasing their emissivity. These magnets have been used for the real beam operation without any serious problems.
We have developed the most upstream dipole magnet K1.1D1 for a new secondary beam line at the hadron experimental hall in J-PARC. It is placed downstream of a production target and is close to the ...K1.8D1 magnet. Indirectly cooled coils using mineral insulation cables have been adopted for high radiation resistance. The coils have a slanting saddle shape in order to minimize the interference of the magnetic field between the two magnets. It has been operated during the beam time in the autumn of 2010 without any problems.
The present article described the synthesis of the coumarin-containing polypeptides using the water-soluble active ester method and the reinforcement of the polyion complex (PIC) fibers by the ...photochemical cross-linking between the polypeptide-pendant coumaryloxyacetyl groups. Two kinds of cationic polypeptides, poly(α,L-lysine) (PLL) and poly(α,L-ornithine) (PLO) were treated with (4-hydroxyphenyl)dimethyl sulfonium methyl sulfate ester in water to incorporate the photoreactive coumaryloxyacetyl groups into the side chain amino groups of the PLL and PLO. The contents of the photoreactive groups in the produced coumarin-containing polypepides were controlled by the molar ratios of the amino groups to the active ester. The resulting coumarin-containing cationic polypeptides were spun into the PIC fibers with the anionic polysaccharide gellan in water. The tensile strengths of the coumarin-containing PIC fibers were superior to those of the intact PLL- and PLO-gellan PIC fibers. The mechanical strength of the coumarin-containing PIC fibers further increased upon light-irradiation. From these results, we concluded that the hydrophobic interactions and the covalent cross-linking due to the photochemical dimerization between the coumaryloxyacetyl groups significantly contributed to reinforcement of the PIC fibers. The present results afford a new methodology to the PIC reinforcement that was achieved by the polymer modification reaction in watery process.
Beam extraction of FFAG-based neutrino factory Yokoi, T.; Shirakabe, Y.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2003, Letnik:
503, Številka:
1
Journal Article
Recenzirano
FFAG-based neutrino factory employs cascaded FFAG rings. The beam injection and extraction are one of the crucial issues in the configuration. In the study, based on the ring parameters of a typical ...muon FFAG accelerator, a simple tracking simulation is carried out.
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