| Paper | Title | Page |
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| MOPRO001 | Upgrade Status of Injector LINAC for SuperKEKB | 59 |
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| The SuperKEKB collider is under construction to achieve 40-times higher luminosity than that of previous KEKB collider. The injector LINAC should provide high-intensity and low-emittance beams of 7-GeV electron and 4-GeV positron for SuperKEKB based on a nano-beam scheme. A photocathode RF-gun for low emittance electron beam has been already installed and the commissioning has started. The construction of positron capture section using a flux-concentrator and the dumping ring for low emittance positron beam is in progress. The simultaneous top-up injections to four storage-rings including photon factories is also required. In the upstream of dumping ring, the compatible optics between positron and electron has been designed. In the downstream of dumping ring, RF phase, focusing, and steering magnets will be switched by pulse to pulse against each beam-mode for optimising beam-transportation. This paper describes recent upgrade status toward the SuperKEKB. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRO001 | |
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| MOPRO110 | Present Status of the Compact ERL at KEK | 353 |
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| The Compact Energy Recovery Linac (cERL) project is ongoing at KEK in order to demonstrate excellent ERL performance as a future light source. The cERL injector was already constructed with its diagnostic beamline and successfully commissioned from April to June in 2013. In the next step, the cERL recirculation loop with a main superconducting linac and merger and dump sections has been constructed and its commissioning is scheduled to start in December 2013. Significant progress is expected by the IPAC14 conference date. In this presentation, we will describe the present status of the cERL including future developments. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRO110 | |
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| MOPRI004 | SuperKEKB Positron Source Construction Status | 579 |
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| The KEKB positron source is under the upgrade for SuperKEKB. The previous positron production target and capture section have been removed and the new system is constructed at a location forty meters upstream to have sufficient energy margin for beam injection to the newly introduced damping ring. A flux concentrator is introduced in the new capture section to make an adiabatic matching system. Large aperture (30mm in diameter) S-band accelerating structures are introduced in the capture section and in the subsequent accelerator module to enlarge the transverse phase space acceptance. The beam focusing system of quadrupoles is also upgraded for a comparable beam acceptance to that of the capture section. This paper reports on the status of the SuperKEKB positron source construction and the preliminary positron beam commissioning. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI004 | |
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| MOPRI009 | Study on New Method for Generating Highly Charged Ions with Double Pulse Laser Ion Source | 595 |
| SUSPSNE029 | use link to see paper's listing under its alternate paper code | |
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| Laser ion source capable of generating high intensity ions is best for the ion source of RI beam facilities. A great deal of effort has been made on particle number as DPIS. Only few attempts have so far been made at generating highly charged ions. One of previous research has reported that Au+53 ions are produced by PALS laser. "Nonlinear process" mechanisms such as resonance absorption and self-focusing were used for this. However, these methods have limitation due to low repetition rate of the laser. Nd (λ=1064nm, E<1.2J, t~10ns) and Yb laser(λ=1030nm, E<10J, t~500fs) systems is possible to operate at 10 - 50Hz repetition rate. This double pulse laser system, with attainable laser intensity up to about 1017[W/cm2], was used to generate highly charged ions of solid target. First, the Nd laser creates a plasma plume. Next, the Yb laser reheats plasma plume by high intensity pulse at delay time of nanosecond. The properties of ions were investigated mainly on the base of time-of-flight method. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI009 | |
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| MOPRI030 | Basic Design of a 20K C-band 2.6-cell Photocathode RF Gun | 658 |
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Funding: This research was supported by the Photon and Quantum Basic Research Coordinated Development Program of the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT). A cryocooled C-band photocathode RF gun operating at 20K is under design at Nihon University. The RF gun is of BNL-type 2.6-cell pillbox cavity with a resonant frequency of 5712 MHz. With high-purity Oxygen-free copper used as the cavity material, the quality factor of the cavity is expected to be approximately 60000 from theoretical prediction of the anomalous skin effect at low temperatures. Considering the cooling capacity, initial operation of the RF gun is assumed at a duty factor of 0.01%. The cavity elements designed for low-power test is in preparation for machining. The low-power test at room temperature is scheduled early spring in 2014 before assembled at KEK by means of diffusion bonding technique. Since it is intended for the basic understanding and measurements of low temperature RF properties, the cavity is not equipped with structures for the photocathode assembling or the RF input coupler. The cavity design and the results of RF properties measured at room temperature before diffusion bonding will be reported. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI030 | |
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| MOPRI033 | Quasi-traveling Wave Side Couple RF Gun Commissioning for SuperKEKB | 667 |
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| We are developing a new RF gun for SuperKEKB. High-charge low-emittance electron and positron beams are required for SuperKEKB. We will generate 7.0 GeV electron beam at 5 nC 20 mm-mrad by J-linac. In this linac, a photo cathode S-band RF gun will be used as the electron beam source. For this reason, we are developing an advanced RF gun. New RF gun which has two side coupled standing wave field is developed. We call it quasi traveling wave side couple RF gun. This gun has a strong focusing field at the cathode and the acceleration field distribution also has a focusing effect. Beam commissioning has been started with the new RF gun. I will report the result of beam commissioning. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI033 | |
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| MOPRI037 | Development of Iridium Cerium Photocathode for the Generation of High-Charge Electron Beam | 679 |
| SUSPSNE033 | use link to see paper's listing under its alternate paper code | |
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| We developed an iridium cerium cathode material made by new production method for multi-purpose electron source. For multi-purpose electron source, we focused on the Ir5Ce compound which has a high melting point (> 2100 K) and a low work function (2.57 eV). This material has some excellent properties as both a thermionic cathode and a photocathode. For example, Ir5Ce thermionic cathode can generate one-order higher electrical current than a LaB6 cathode at the same temperature. Another advantage is that an Ir5Ce thermionic cathode has a lifetime two orders longer than that of a LaB6 thermionic cathode under the same conditions. Moreover, we discovered that this material has a reasonably high quantum efficiency (2.70 × 10−3 @213nm at 1000°C) and long-lifetime (> LaB6) as a photocathode. Our research shows that Ir5Ce compound is optimum material for a thermionic cathode and photocathode. We focused on this good emission properties under the high temperature and we tried to develop a backside electron beam heating system and demonstrate a laser pre-pulse heating for a high current thermionic gun system or high charge photocathode gun. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI037 | |
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| TUPME035 | Design Study of the Laser-driven Dielectric Accelerator | 1428 |
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Funding: This work was partly supported by KAKENHI, Grant-in-Aid for Scientific Research (C) 24510120. Laser driven dielectric accelerators (LDA) are vigorously studied in order to apply to various fields in recent years. Characteristics of the LDA output such as sub-micron diameter, atto-second bunch and high acceleration field are suitable for in-situ investigating the biological effects of low doses of radiation in a living cell. The output energy of 1 MeV is sufficient for sniping a cell nucleus or DNA. Although the electronic charge in the bunch is in the order of 10 fC, the tightly focused beam enable to cause a local damage in the cell. We have reported optimum structure parameters of dielectric in the nonrelativistic regime. The low acceleration efficiency of slow electrons by short laser pulses is the serious problem. The accelerator length, laser intensity, pulse width, and optical system must be adjusted to design the practical LDA. We present the design principle of the LDA for nonrelativistic electrons and present status of the pumping laser of us. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME035 | |
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| TUPME037 | Development on On-chip Radiation Source using Dielectric Laser Accelerator | 1434 |
| SUSPSNE019 | use link to see paper's listing under its alternate paper code | |
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Funding: This work was partly supported by KAKENHI, Grant-in-Aid for Scientific Research (C) 24510120. One of the state-of-the-art acceleration schemes, where high intensity laser pulses are modulated by dielectric grating structure such as quartz to accelerate charged particles, is dielectric laser acceleration (DLA)*. The difference of our DLA concept from other schemes is installation of a prism: the tilted wave-front in a prism shape refractive medium leads the suitable delay to match the phase advance of the electron beam. We plan to apply this method to build an on-chip radiation source which can hit and damage target elements of the cells. Such an application is useful in radiation biology, i.e., for investigation on bystander effects. The x-rays with small radius and adequate intensity required for this goal can be obtained using sub-micron beams from the small accelerating structure at high repetition rate (such as 50 kHz). In addition, the mass productivity of the DLA based on the consumer-grade laser and the photolithography has advantage compared to the conventional RF accelerator using high power klystrons. We will present field simulation and preliminary experimental results for demonstration on our concept of DLA. * Demonstration of electron acceleration in a laser-driven dielectric microstructure, Nature 2013 ** Laser-Based Acceleration of Nonrelativistic Electrons at a Dielectric Structure, Phys. Rev. 2013 |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPME037 | |
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| WEPME061 | Ytterbium Fiber and Disk Laser of RF Gun for SuperKEKB | 2415 |
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| For SuperKEKB project, the electron beams with a charge of 5 nC and a normalized emittance of 10 μm are expected to be generated in the photocathode RF gun at the injector linac. An ytterbium (Yb)-doped laser system with a center wavelength of 259 nm and a pulse width of 30 ps is employed to obtain high peak energy pulses. Although, the pulse repetition of 25 Hz with double-bunch is required, more than 5 nC electron with single-bunch has so far been generated in the 2 Hz. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPME061 | |
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