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JAEA Reports

Noise countermeasures for inverter-controlled multi-stage roots vacuum pumps in J-PARC LINAC L3BT

Takano, Kazuhiro; Kotoku, Hirofumi*; Kobayashi, Fuminori*; Miyao, Tomoaki*; Moriya, Katsuhiro; Kamiya, Junichiro

JAEA-Technology 2021-017, 35 Pages, 2021/11

JAEA-Technology-2021-017.pdf:5.32MB

In J-PARC LINAC, the vacuum system of L3BT, which is a beam transport line connecting LINAC and 3GeV synchrotron, uses a turbo molecular pump and roots pump for rough exhaust and an ion pump for main exhaust. In addition, beam dumps are connected to the end of the L3BT at 0 degree, 30 degree, 90 degree, and 100 degree positions via vacuum partition windows. The roots pumps are used as the exhaust system for each beam dump. The roots pump controllers have been installed away from the pump in the accelerator tunnel to avoid radiation damages. Besides, the special controllers, which have no inverter circuit inside, have been used to reduce the electrical noise on the beam loss monitors nearby. However, using the special controller without inverters, several problems have occurred such as the instability or wide variability of the pumping speed. To solve such problems, the roots pump controller with the inverter circuit must be used after reducing the electrical noise. In this report, some countermeasures to reduce the electrical noise from the inverters were investigated. The noise reduction circuit was successfully optimized to the level where the beam loss monitors works unaffected.

Journal Articles

Dependence of charge-exchange efficiency on cooling water temperature of a beam transport line

Yamamoto, Kazami; Hatakeyama, Shuichiro; Saha, P. K.; Moriya, Katsuhiro; Okabe, Kota; Yoshimoto, Masahiro; Nakanoya, Takamitsu; Fujirai, Kosuke; Yamazaki, Yoshio; Suganuma, Kazuaki

EPJ Techniques and Instrumentation (Internet), 8(1), p.9_1 - 9_9, 2021/07

The 3 GeV Rapid Cycling Synchrotron at the Japan Proton Accelerator Research Complex supplies a high-intensity proton beam for neutron experiments. Various parameters are monitored to achieve a stable operation, and it was found that the oscillations of the charge-exchange efficiency and cooling water temperature were synchronized. We evaluated the orbit fluctuations at the injection point using a beam current of the injection dump, which is proportional to the number of particles that miss the foil and fail in the charge exchange, and profile of the injection beam. The total width of the fluctuations was approximately 0.072 mm. This value is negligible from the user operation viewpoint as our existing beam position monitors cannot detect such a small signal deviation. This displacement corresponds to a 1.63$$times$$10$$^{-5}$$ variation in the dipole magnetic field. Conversely, the magnetic field variation in the L3BT dipole magnet, which was estimated by the temperature change directly, is 4.08$$times$$10$$^{-5}$$. This result suggested that the change in the cooling water temperature is one of the major causes of the efficiency fluctuation.

Journal Articles

High-intensity beam profile measurement using a gas sheet monitor by beam induced fluorescence detection

Yamada, Ippei; Wada, Motoi*; Moriya, Katsuhiro; Kamiya, Junichiro; Saha, P. K.; Kinsho, Michikazu

Physical Review Accelerators and Beams (Internet), 24(4), p.042801_1 - 042801_13, 2021/04

A transverse beam profile monitor that visualizes a two-dimensional beam-induced fluorescent image was developed. The monitor employs a sheet-shaped gas flow formed by a technique of rarefied gas dynamics. A simplified analysis method was developed to reconstruct the beam intensity profile from the obtained image. The developed profile monitor and the analysis method were applied to measure the J-PARC 3 MeV H$$^-$$ beam profile. The root mean square values of the profiles were consistent with the ones obtained by a wire-scanning-type beam profile monitor. The beam loss due to the gas sheet injection was measured as a beam-current reduction. The amount of the beam current decreased in proportion to the gas sheet flux and the reduction ranged from 0.004 to 2.5%. The assembled system was capable of reconstructing a beam profile from a single shot beam pulse (1.7$$times$$10$$^{13}$$ protons in 50 $$mu$$s).

Journal Articles

Evaluation of 2-D transverse beam profile monitor using gas sheet at J-PARC LINAC

Kamiya, Junichiro; Okabe, Kota; Kinsho, Michikazu; Moriya, Katsuhiro; Yamada, Ippei; Ogiwara, Norio*; Hikichi, Yusuke*; Wada, K.*

Journal of Physics; Conference Series, 1350, p.012149_1 - 012149_6, 2019/12

 Times Cited Count:2 Percentile:84.98

To obtain a getter effect to titanium vacuum duct surface, the method to remove the oxide on the surface by sputtering with ionized molecules has been developed. In the method, a sheet-shaped gas distribution with a uniform and high density is generated through a narrow slit by a small amount of gas. In this report, the gas density distribution was calculated by the Monte Carlo simulation code. As a result, it was found that a gas injection from both directions was effective to generate uniform density distribution. Furthermore, the gas injection method was applied to a non-destructive beam profile monitor, that detects ions generated by the interaction between gas molecules and beam. In this monitor, dependence of the beam profile on the injected gas amount was measured. A small amount of injected gas was found to be ideal for the beam profile measurements in the unsaturated and a high S/N ratio region.

Journal Articles

Coupling impedance of the collimator without RF-Shields at the RCS in J-PARC

Shobuda, Yoshihiro; Okabe, Kota; Kamiya, Junichiro; Moriya, Katsuhiro

Journal of Physics; Conference Series, 1350, p.012113_1 - 012113_7, 2019/12

 Times Cited Count:0 Percentile:0.07

All holes on the chamber walls of synchrotrons should be filled with the radiofrequency (RF)-shields to suppress coupling impedances that excite beam instabilities. In a synchrotron, titanium nitride (TiN)-coated RF-shields are installed with collimators. If the holes, through which the collimator jaw enters and exits the chamber, are filled with such RF-shields, the shields may break down as the dynamic coefficient of TiN increases in vacuum. At the Rapid Cycling Synchrotron (RCS), the RF-shields are eliminated from the collimator after demonstrating that the effect due to the RF-shields is negligible on the impedance at low frequencies.

Journal Articles

Energy measurement and correction for stable operation in J-PARC

Moriya, Katsuhiro; Harada, Hiroyuki; Liu, Y.*; Otani, Masashi*

Journal of Physics; Conference Series, 1350, p.012140_1 - 012140_5, 2019/11

 Times Cited Count:0 Percentile:0.07

Journal Articles

Beam monitor data analysis of interlocked events at J-PARC RCS

Hayashi, Naoki; Yoshimoto, Masahiro; Moriya, Katsuhiro; Hatakeyama, Shuichiro*

Proceedings of 16th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1096 - 1100, 2019/07

It is necessary to understand the reason why the accelerator has been interrupted due to beam loss or other machine mal function in order to keep high availability in long term period. At J-PARC RCS, 25 Hz rapid-cycling synchrotron, there is a system to record beam intensity and beam loss monitor signal for all pulses with 10 ms period. At this time, in addition, new system to archive data with better time resolution if interlocked events occurred has been introduced. Using these archived data, the events only RCS BLM gives MPS have been analyzed and it turns out that these events are related to the ion source discharge which makes very low intensity within less than a second. In this paper other typical events are presented and discuss how to improve the accelerator performance in future.

Journal Articles

Bunch shape monitor for the high-intensity H$$^{-}$$ beam with 3 MeV using the carbon material

Kitamura, Ryo; Futatsukawa, Kenta*; Hayashi, Naoki; Hirano, Koichiro; Kosaka, Satoshi*; Miyao, Tomoaki*; Moriya, Katsuhiro; Nemoto, Yasuo*; Oguri, Hidetomo

Proceedings of 16th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.51 - 54, 2019/07

The longitudinal measurement and tuning at the beam transport after the RFQ are important to reduce the beam loss and the emittance growth in the J-PARC linac, when the high-intensity H$$^{-}$$ beam of more than 60 mA is supplied. The new bunch shape monitor (BSM) using the carbon-nanotube (CNT) wire is necessary to measure the bunch shape of the high-intensity H$$^{-}$$ beam with 3 MeV, because the CNT wire has a high-temperature tolerance and a small energy deposit. However, when the high voltage was applied to the CNT wire to extract the secondary electron derived, the discharge prevents the power supply from applying the voltage. Therefore, the discharge should be suppressed to measure the bunch shape with stability. Considering the characteristics of the CNT as the emitter, when the length of the CNT wire was short, the high voltage of -10 kV was applied to the CNT wire. The current status and future prospects of the BSM using the CNT wire are reported in this presentation.

Journal Articles

Evaluation of beam-loss suppression method by nonlinear space charge force in a high intensity linac

Chimura, Motoki*; Harada, Hiroyuki; Moriya, Katsuhiro; Okabe, Kota; Kinsho, Michikazu

Proceedings of 16th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.728 - 732, 2019/07

The increase of space charge effect in high intensity beam causes the increase of the beam-loss. Beam loss limits beam intensity for accelerator equipment activation. Therefore, it is important to suppress the emittance growth due to the space charge effect. I focused on the low energy region in the linac where the space charge effect becomes remarkable. In order to identify the origin of the emittance growth due to the effect, a simulation was performed with a 3-D particle-in-cell simulation code, and evaluated the influence of the effects in the J-PARC medium energy beam transport line (MEBT1) entrance to DTL exit. As a result, it was confirmed that distortion of phase space distribution occurred due to nonlinear space charge force and that leading to emittance growth. I proposed to suppress the emittance growth by using an octupole magnet that gives nonlinear force to the beam. We report the new method and simulation results.

Journal Articles

Development of the bunch shape monitor using the carbon-nano tube wire

Kitamura, Ryo; Hayashi, Naoki; Hirano, Koichiro; Kondo, Yasuhiro; Moriya, Katsuhiro; Oguri, Hidetomo; Futatsukawa, Kenta*; Miyao, Tomoaki*; Otani, Masashi*; Kosaka, Satoshi*; et al.

Proceedings of 10th International Particle Accelerator Conference (IPAC '19) (Internet), p.2543 - 2546, 2019/06

A bunch shape monitor (BSM) is one of the important instruments to measure the longitudinal phase space distribution. For example in the J-PARC linac, three BSMs using the tungsten wire are installed at the ACS section to measure the bunch shapes between the accelerating cavities. However, this conventional BSM is hard to measure the bunch shape of H$$^{-}$$ beam with 3 MeV at the beam transport between the RFQ and DTL sections, because the wire is broken around the center region of the beam. The new BSM using the carbon-nano-tube (CNT) wire is being developed to be able to measure the bunch shape of the H$$^{-}$$ beam with 3 MeV. The careful attention should be paid to apply the high voltage of $$-$$10 kV to the CNT wire. The several measures are taken to suppress the discharge from the wire and operate the CNT-BSM. This presentation reports the current status of the development and future prospective for the CNT-BSM.

Journal Articles

Coupling impedance of the collimator without RF-Shields at the RCS in J-PARC

Shobuda, Yoshihiro; Okabe, Kota; Kamiya, Junichiro; Moriya, Katsuhiro

Proceedings of 10th International Particle Accelerator Conference (IPAC '19) (Internet), p.163 - 166, 2019/06

All holes on the chamber walls of synchrotrons should be filled with the radiofrequency (RF)-shields to suppress coupling impedances that excite beam instabilities. In a synchrotron, titanium nitride (TiN)-coated RF-shields are installed with collimators. If the holes, through which the collimator jaw enters and exits the chamber, are filled with such RF-shields, the shields may break down as the dynamic coefficient of TiN increases in vacuum. At the Rapid Cycling Synchrotron (RCS), the RF-shields are eliminated from the collimator after demonstrating that the effect due to the RF-shields is negligible on the impedance at low frequencies.

Journal Articles

Study of a tuner for a high-accuracy bunch shape monitor

Moriya, Katsuhiro; Kawane, Yusuke*; Miura, Akihiko; Futatsukawa, Kenta*; Miyao, Tomoaki*

Journal of Physics; Conference Series, 1067, p.072009_1 - 072009_3, 2018/09

BB2017-2165.pdf:0.7MB

 Times Cited Count:0 Percentile:0.11

no abstracts in English

Journal Articles

Application of carbon nanotube wire for beam profile measurement of negative hydrogen ion beam

Miura, Akihiko; Moriya, Katsuhiro; Miyao, Tomoaki*

Proceedings of 9th International Particle Accelerator Conference (IPAC '18) (Internet), p.5022 - 5025, 2018/06

A wire-scanner monitor using metallic wire is reliably employed for the beam-profile measurement in the J-PARC linac. Because the loading of negative hydrogen (H$$^{-}$$) ion beam on a wire increases under high-current beam operation, we focus on using a high-durability beam profile monitors by attaching another wire material. Carbon nanotubes (CNT) are made of graphite in a cylindrical shape and have a tensile strength not less than 100 times that of steel. The electric conductivity has higher than that of metals, and hardness is endured thermally around 3000$$^{circ}$$C in a vacuum circumstance. We applied the wires made from CNT to WSM and measured transverse profiles with a 3-MeV H$$^{-}$$ beam. As a result, we obtained the equivalent signal levels taken by carbon wire made of polyacrylonitrile without any damage. In this paper, the signal response when the CNT is irradiated with an H$$^{-}$$ beam and the result of beam profile measurement. In addition, the surface of CNT after 3-MeV beam operation was observed.

Journal Articles

Development of the bunch shape monitor in the J-PARC L3BT

Moriya, Katsuhiro; Okabe, Kota; Liu, Y.*; Miura, Akihiko; Futatsukawa, Kenta*

Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1081 - 1083, 2017/12

no abstracts in English

Oral presentation

Oral presentation

Study of non-destructive beam profile monitor for longitudinal measurement

Moriya, Katsuhiro; Harada, Hiroyuki; Miura, Akihiko; Futatsukawa, Kenta*

no journal, , 

no abstracts in English

Oral presentation

Measurement and correction of energy fluctuation in J-PARC Linac

Moriya, Katsuhiro

no journal, , 

no abstracts in English

Oral presentation

Development of the bunch shape monitor for the H$$^{-}$$ beam with 3 MeV using the carbon-nano tube wire

Kitamura, Ryo; Futatsukawa, Kenta*; Hayashi, Naoki; Hirano, Koichiro; Miyao, Tomoaki*; Moriya, Katsuhiro; Nemoto, Yasuo*; Oguri, Hidetomo

no journal, , 

no abstracts in English

Oral presentation

Measurement and correction of energy fluctuation in the J-PARC Linac

Moriya, Katsuhiro; Harada, Hiroyuki

no journal, , 

no abstracts in English

Oral presentation

Development of the bunch shape monitor for the H$$^{-}$$ beam with 3 MeV using the carbon-nano tube wire

Kitamura, Ryo; Futatsukawa, Kenta*; Hayashi, Naoki; Hirano, Koichiro; Miyao, Tomoaki*; Moriya, Katsuhiro; Nemoto, Yasuo*; Oguri, Hidetomo

no journal, , 

In the linac of the Japan Proton Accelerator Research Complex, the bunch shape monitor (BSM) is being developed to tune the longitudinal beam matching between the accelerating cavities. When the beam irradiates the tungsten (W) wire in the BSM, the secondary electrons are emitted and extracted to the BSM in order to measure the bunch size of the H$$^{-}$$ beam. However, the W wire is less resistant to the high-intensity H$$^{-}$$ beam from the RFQ. Therefore, the BSM using the Carbon-Nano Tube wire (CNT-BSM) has been developed. The discharge from the CNT wire is the problem for the operation. To suppress the discharge, the baking process was introduced. Then, we succeeded in applying the high voltage to the CNT wire without the discharge. The signal responses from the W and CNT wires are being tested using the thermal electrons. We will reports the current status of the development and future prospects.

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