| Paper | Title | Page |
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| TUPOW036 | Recent Developments and Operational Status of the Compact ERL at KEK | 1835 |
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| The Compact Energy Recovery Linac (cERL) at KEK is a test accelerator in order to develop key components to realize remarkable ERL performance as a future light source. After the beam commissioning in December 2013, the legal current limit has been increased step-by-step like 1 uA, 10 uA, and 100 uA. Survey for the source of beam losses has been conducted in each step, and the study on beam dynamics and tuning has also been carried out. As a next step, 1 mA operation is scheduled in February 2016. In parallel to the increase in beam current, a laser Compton scattering (LCS) system which can provide high-flux X-ray to a beamline has been successfully commissioned. We report recent progress in various kinds of beam tuning: improvement of electron gun performance, high bunch charge operation, mitigation of beam losses, LCS optics tuning and bunch compression for THz radiation. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW036 | |
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| TUPOW038 | Measurement and Control of Beam Losses Under High Average-current Operation of the Compact ERL at KEK | 1839 |
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The compact ERL (cERL)* is a superconducting accelerator aimed at demonstrating excellent ERL technologies for the future light source. The cERL comprises a 5 MeV injector, a main linac, and a recirculation loop. In the cERL, production and transportation of low-emittance and high average-current beams (tentative goals: 1 mm-mrad and 10 mA) is primarily important. At this moment (in December 2015), beam currents of up to 80 uA (CW) have successfully been transported through the recirculation loop at a beam energy of 20 MeV. Before such high-current operations, we carefully tuned up the machine so that beam losses became very small. The beam losses were watched using fast beam-loss detectors and radiation monitors while absolute losses were estimated from measured radiation levels on the roof of the shield. After careful beam-optics corrections and elimination of beam halos / tails at low-energy section, we achieved the beam losses of at most a few nA level at several locations along the loop, and those below 1 nA elsewhere in the loop. We will report these results together with the result of higher-current operation which is planned early in 2016.
* S. Sakanaka et al., IPAC'15, TUBC1; T. Obina et al., to be presented at IPAC'16. |
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| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW038 | |
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| TUPOW039 | Simulation Study of the Beam Halo Formation for Beam Loss Estimation and Mitigation at KEK Compact ERL | 1843 |
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Funding: Work supported by the "Grant-in-Aid for Creative Scientific Research" of JSPS (KAKENHI 15K04747) At KEK Compact ERL (cERL) we are aiming to produce high-current and low-emittance electron beams (up to 10 mA) without significant beam loss. We believe that beam halo makes a significant impact into the beam loss. Therefore, we are performing beam loss simulations to meet the results of the beam loss measurements*. In particular, a simulation of the bunch tail originated from the electron gun was performed to understand the mechanisms of the beam halo formation. Since some measured beam profiles demonstrated unexpected halo particles, several factors such as misalignment of beam line elements and kicks from the steering coils were added into the simulation. Simulation study results are compared with the related beam loss and halo measurements here. * Sakanaka et al., these proceedings |
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| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW039 | |
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| WEPOR020 | Beam Loss Estimation by Measurement of Secondarily Produced Photons under High Average-current Operations of Compact ERL in KEK | 2711 |
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| To increase the beam current in the Compact Energy Recovery Linac (cERL) at the High Energy Accelerator Research Organization (KEK), the beam loss must be reduced to less than 0.01% during the transportation of 20 MeV electrons in order to suppress the radiation dose outside the accelerator room. Beam loss locations were successfully identified using the gold activation method, and the beam loss rate was estimated by com-paring the measured dose rate with the simulated dose rate on the roof of the cERL room. Beam operation with beam current of 0.90 mA was achieved with a beam loss rate of less than 0.01%. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOR020 | |
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| WEPOW020 | Present Status of KEK Photon Factory and Future Project | 2871 |
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| Two synchrotron radiation sources of KEK, the PF-ring and the PF-AR, continue their user operation with various improvements. Scrap and build of the first generation undulators of 1980s at the PF-ring is pushed forward year by year. Five new elliptically polarized undulators have been installed in these five years, and we have also installed four very narrow-gap short-period undulators generating high brilliant X-ray. The new beam transport line that enables the 6.5-GeV full energy injection for PF-AR will be completed by the end of 2016 in order to make the top-up operation of the two SR sources compatible with the continuous injection for two main rings of the Super-KEKB. We have proposed a project of further upgrade of the 2.5-GeV PF-ring to improve its horizontal emittance as 8 nm rad using combined bending magnets at the arc sections. And we are also moving ahead on proposal of constructing a new KEK light source of an extremely low emittance as 0.3 nm rad. The progress and detail of our future project will be described in this paper. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOW020 | |
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| WEPOY010 | Bunch Compression at the Recirculation Loop of the Compact ERL | 3008 |
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| The compact Energy Recovery Linac (cERL) has been operated as a test facility for the future light-source since 2013. One of the targets of the beam commissioning of this winter is demonstration of bunch compression. The bunch has energy chirp in longitudinal direction by off crest acceleration and the bunch length is compressed in non-isochronous arc section. The short electron bunch is spread in the return arc to suppress the energy spread at the main beam dump. Four sextupole magnets were installed in two arcs in November 2015 to correct the squared term induced by RF curvature. The best position was determined by the beam tracking by elegant including Coherent Synchrotron Radiation (CSR) wake. The bunch length is measured by OTR in the south straight section just after the first arc. We present the demonstration of the bunch compression in this report. | ||
| DOI • | reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOY010 | |
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