| Paper | Title | Page |
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| MOPME020 | Development of the New Measurement Method for the Incoherent Tune Spread and the Tune Shift Caused by the Space Charge Effect | 512 |
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| For the high intensity accelerator, the incoherent tune which is the frequency of the individual particles is shifted and decreases due to the space charge effect. In addition, the incoherent tune is formed into spread shape commonly. When the incoherent tune satisfies a resonance condition, it might be occurred the beam emittance growth and the beam loss. So it is necessary to reduce the incoherent tune spread and the tune shift as much as possible. To achieve this condition, it is desired to measure the incoherent tune spread and the tune shift directly. Therefore we are developing the new measurement method of the incoherent tune spread and the shift due to the space charge effect. From the simulation results, it was cleared that the beam distribution can be modified in the case of using the mono frequency dipole exciter because a particle which has the tune corresponding to the exciter can be resonated temporary. In addition, it was cleared that it is possible to evaluate the incoherent tune spread and the tune shift by the measurement of the distribution transition. We present the outline of this method and the developing plane at the J-PARC RCS. | ||
| MOPME022 | Beam Commissioning of Two Horizontal Pulse Steering Magnets for Changing Injection Painting Area from MLF to MR in the 3-GeV RCS of J-PARC | 518 |
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| We have been successfully commissioned two pulse steering magnets installed in the Linac to 3-GeV RCS (Rapid Cycling Synchrotron) injection beam transport (BT) line of J-PARC. RCS has to deliver a simultaneous as well as specific beam as demand by the downstream facilities of MLF (Material and Life Science Facility) and the MR (Main Ring). In order to obtain relatively a smaller transverse emittance at extraction, those magnets were designed to perform a smaller injection painting for the MR beam as compared to the MLF one. As stripper foil position is fixed for the charge exchange H− injection, inclination of the injected beam centroid on foil for the MR beam is only moved to a smaller value by the pulse steering magnets, while DC septum magnets are fixed as determined first for the MLF beam. Their parameters were found to be very consistent with expectation and thus already in operation for switching to a painting area of 100 pi mm mrad for the MR beam as compared to that of 150 pi mm mrad for the MLF beam. | ||
| MOPME025 | Production of Extraction Kicker Magnet of the J-PARC 3-GeV RCS | 526 |
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| The J-PARC 3-GeV rapid cycling synchrotron (RCS) has been provided proton beam to the Material and Life Science Facility (MLF)as well as to the 50 GeV Main Ring (MR). Proton beam is accelerated from 181 MeV to 3GeV in the RCS and immediately extracted it to the beam transport line to the MLF and the MR. Extraction kicker magnets are used for this fast extraction. To improve reliability of the RCS for user operation, production of a reserve kicker magnet has been performed. The kicker magnet mainly consists of Ni-Zn ferrite cores and Aluminum alloy plates, and these parts are installed in vacuum chamber to prevent discharge because a high voltage is applied to the magnet for a short period. Since it is important to reduce the outgassing of water vapor form these parts to prevent discharge, we has been produced the reserve magnet with low outgassing at high voltage discharge. Since assemble of the kicker magnet already finished and vacuum test has been performed, the result of vacuum test is reported. | ||
| MOPME028 | A Preliminary Study of the Vibration Wire Monitor for Beam Halo Diagnostic in J-PARC L3BT | 535 |
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| In the J-PARC 3-GeV Rapid Cycle Synchrotron (RCS), transverse beam halo diagnostic and scraping are required to increase the output beam power. Wire scanners and halo scrapers were used for measurement of projected beam distributions to determine the extent of beam halo formation at Linac-3GeV Beam Transport line (L3BT). In order to determine more detail of halo formation, Vibration Wire Monitor (VWM) was installed in L3BT for the beam halo measurement and the offline study at the test stand with low energy electron gun are started. The high sensitivity of the VWM makes it a prospective one for investigation of beam halo and weak beam scanning. In this paper, we will report a preliminary results of offline studies and beam halo measurement by VWM at L3BT. | ||
| MOPWA007 | Operating Experience of Kicker Magnet System in the J-PARC 3GeV RCS | 678 |
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| The J-PARC 3-GeV rapid cycling synchrotron (RCS) has been provided proton beam to the Material and Life Science Facility (MLF)as well as to the 50 GeV Main Ring (MR). Proton beam is accelerated from 181 MeV to 3GeV in the RCS and immediately extracted it to the beam transport line to the MLF and the MR. Extraction kicker system is used for this fast extraction. The RCS has been operated for the neutron and MLF users program from December 23rd, 2008. At the beginning of user operation there were many troubles for the extraction kicker system, especially, thyratron which are used for switch of power supply often caused failure. The beam stop rate due to RCS extraction kicker system was more than 13% in the total beam stop of the J-PARC, establishment and operation experience of the tuning for power supply of the extraction kicker make the beam stop rate less than 0.5% in November 2012. In this paper, we are going to report about daily operation whose main is about operation of thyratron and the maintenance held in summer 2012. And We also going to report about the aptitude test of thyratron as a plan of the future. | ||
| MOPWA008 | Power Supply of the Pulse Steering Magnet for Changing the Painting Area between the MLF and the MR at J-PARC 3 GeV RCS | 681 |
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| The power supply of the pulse steering magnet (PSTR) has been produced. The PSTR of the 3-GeV RCS (Rapid Cycling Synchrotron) in the J-PARC (Japan Proton Accelerator Research Complex) aims at changing the painting area in a pulse-to-pulse mode at 25Hz between the MLF (Material and Life science Experimental Facility) and the MR (50-GeV Main Ring synchrotron) at J-PARC. The power supply has the equipment used to excite the pulse current and the direct current (DC) to correspond to two modes that the paint injection for beam users and the central injection for beam commissioning. In case of the paint injection, the power supply excites the current from 40 A to 450 A in pulse mode, which has the capability to switch from positive to negative polarity. The pulse current has been performed with good accuracy whose deviation to a setting current becomes to be less than ± 0.2 %. In case of the central injection, the power supply excites the current from 1000 A to 3000A in DC mode, which has been realized output current deviation below ± 0.01 %. This paper summarizes the design parameters and the experimental results of the power supply. | ||
| WEPME020 | Alignment Plan and Survey Results of the Equipment for J-PARC 3 GeV RCS | 2971 |
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| Misalignment of several millimeters of the magnets of J-PARC 3GeV RCS in both horizontal and vertical directions was caused by the Tohoku Region Pacific Coast Earthquake on March 11, 2011. As the result of orbit calculation showed that the beam loss was acceptable for beam operation at 300kW, beam operation with the current placement has been implemented. Realignment of the equipment will be carried out from August to December in 2013. Survey carried out in the summer of 2013 found out misalignment of ceramic vacuum ducts therefore their positioning is necessary. In this paper, these measurement result and latest alignment plan for J-PARC 3GeV RCS are reported. | ||
| THPFI014 | Bellows with a New RF Shield Made of Metal Braid for High Intensity Proton Accelerators | 3321 |
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| In the 3 GeV-RCS (Rapid cycling Synchrotron) in J-PARC (Japan Accelerator Research Complex) project, large-scale hydro-formed bellows were developed to adjust the gap between the ceramic ducts and/or between the ceramic ducts and the transport ducts. They have been equipped with a newly developed RF shield, because the usual beryllium-copper spring finger contacts were found to be very hard (roughly 1000 N/mm) owing to the large size. This contact is made of Ti braid, which consists of wires with a diameter of 0.3 mm. This RF contact is a kind of basket (with two ports) made with the braids. Because of the spring effect, the contact can change shape easily. In addition, the contact can easily connect the different cross sections in a smooth fashion. Furthermore, this structure is almost free from the dust generation, which is one of the most troublesome problems for the usual spring finger contacts. This time, we have constructed reserve bellows with the RF shield made of SUS 316L wires to improve the reliability of user operation. The outline of the bellows will be presented, especially laying emphasis on the mechanical function of the RF shield. | ||
| THPFI015 | In-situ Degassing of the Ferrite Cores in the Extraction Kicker Magnets of the J-PARC 3-GeV RCS | 3324 |
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| Kicker magnets extract the accelerated beam to the beam transport lines in the RCS of the J-PARC. The kicker magnets mainly consist of Ni-Zn ferrite cores and Al alloy plates, and are installed in a vacuum to prevent discharge because a high voltage is applied for a short period. It is important to reduce the outgassing of water vapor from the ferrite cores. Although the kicker magnets have been working well, recently the vacuum quality became a little poor. Thus, we developed the in-situ degassing method for the ferrite cores. This is achieved by directing the heat from the heat source to the kicker magnet and not to the chamber wall. With the test stand we succeeded to flow almost all the heat toward the kicker magnet and to bake out the ferrite cores about 150°C, maintaining the temperature of the chamber wall less than 50°C. As the previous work with TDS measurements revealed that the absorbed water molecules can be easily removed by the bake-out at 100-150°C in a vacuum, the outgassing from the ferrite cores was successfully reduced. The details of the in-situ degassing method will be reported, including the practical method to reduce the outgassing of the working kickers. | ||
| THPFI016 | DESIGN CONSIDERATION OF BEAM DUCTS FOR QUADRUPOLE CORRECTORS IN J-PARC RCS | 3327 |
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which rapidly correct the tunes, are planned to be installed during the summer shutdown in 2013. The characteristic of the excitation pattern of such quadrupoles (quadrupole corrector) is their fast change of magnetic field, which are more than 200T/s at the fastest point. In this report, we describe a deliberation flow about the design of a vacuum chamber, which is installed in the quadrupole corrector. The effect of eddy current was calculated in the case of the current titanium vacuum chamber. The results showed that the temperature rise was too much (up to ~350oC) and the magnetic field in the vacuum chamber is largely distorted by the eddy current. Therefore we decided to employ an alumina ceramics vacuum chamber, for which we have a past achievement in RCS*. We estimated the displacement and stress, which is caused by the atmospheric pressure, for the alumina ceramics vacuum chamber and vacuum component around it by making the calculation model for the finite element method. It was found that there was no large displacement and stress by installing the alumina ceramics vacuum chamber.
*M. Kinsho, et al. Vacuum 81 (2007) 808. |
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| THPWO031 | Status of J-PARC Accelerators | 3830 |
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| After nine-months of beam shutdown by the Great Earthquake in March 2011, the J-PARC facility resumed beam operation. In December 2011, operations were carried out at low duty such as single-shots or 1 to 2.5 Hz for beam tuning. At the beginning of January 2012, we started beam tuning at the full repetition rate of 25 Hz at the linac and the 3 GeV Rapid Cycling Synchrotron (RCS). After the tuning, user programs of the Materials and Life Science Experiment Facility (MLF), the Neutrino facility and the Hadron facility started. The beam power was increased from 100 to 300 kW to the MLF users, from 3.3 kW to 6 kW to the Hadron users, and from 140 to 200 kW to the Neutrino users. The beam availability went lower to 73 % in JFY 2011 due to the trouble of the linac klystron power supply in March, but it has got back to 90-94 % as of November in JFY2012. We have also much upgrade work during the shutdown period or in parallel to the operation. We’ve demonstrated new record power beyond 500kW from the RCS. The status and progress of the J-PARC accelerators are presented. | ||
| THPWO032 | Progress of Injection Energy Upgrade Project for J-PARC RCS | 3833 |
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| The injection energy of the J-PARC RCS will be upgraded in 2013. New power supplies for the shift bump magnet system will be installed. Some of other systems, upgrade of the painting bump power supplies and pulse steering systems, are already installed and tested or used for the nominal operation. The paper reports the progress of injection energy upgrade project. | ||
| THPWO033 | High Intensity Beam Trial of up to 540 kW in J-PARC RCS | 3836 |
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| Recently we have performed a high intensity beam trial of up to 540 kW. In this paper, beam intensity dependece and injection painting parameter dependence of beam loss, observed in this beam experiment, will be discussed with the corresponding numerical simulation results. | ||
| THPWO037 | Status and Progress of the J-PARC 3 GeV RCS | 3848 |
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| The J-PARC rapid cycling synchrotron (RCS) has been delivered 300kW beam to both the MLF and the MR with high reliability and small beam loss for user operation. To realize simultaneously two kinds of beam shape which are required from the MLF and the MR, two pulse dipole magnets for injection painting were installed in the beam transport line from the Linac to the RCS. It was successful to make two kinds of beam shape with injection painting bump magnets and these added pulse dipole magnets. This injection painting system is used for user operation and works well for reduction of beam losses. Not only user operation but also high power beam test was performed, and beam power of 524kW for 35 second was achieved with low beam loss in the RCS. Almost all beam loss was localized at the ring collimator and the loss rate was about 2% and this was acceptable because design value of the beam loss was 3%. This power corresponds to 1.8MW for 400MeV injection in terms of the Lasslett tune shift. In this high-intensity trial, significant progress toward design output beam power of 1 MW was demonstrated. The status and progress of the RCS in J-PARC are presented. | ||