| Paper | Title | Page |
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| THPC028 | A Proposal of Short X-ray Pulse Generation from Compressed Bunches by mm-wave iFEL in the SPring-8 Upgrade Plan | 2969 |
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| In the SPring-8 upgrade plan, short pulse options are prepared for time-resolved experiments of pico-second order with high repetition rate. The best scenario is that selected bunches have equilibrium bunch length of 1 ps or less. A mm-wave storage-ring iFEL may be one possible solution for it. If resonant wavelength of the FEL is a few millimeters, which is about ten times longer than typical short bunch length of 0.3 mm corresponding to 1 ps, almost all electrons of a bunch can be confined in one valley of ponderomotive potentials formed by the FEL mechanism. The system consists of a helical wiggler with period length of several meters and a mm-wave resonator. Numerical simulations with coherent synchrotron radiation effect at bunch charge of 479 pC show that an ultra-short injection bunch is trapped in a mm-wave “bucket” and kept shorter than 1 ps (r.m.s.) even after twice the longitudinal damping time from the injection. The ultra-short bunches need to be injected from the XFEL linac. XFEL-to-Storage Ring beam transport line is designed to suppress dispersions which cause bunch lengthening. Tracking calculations show promising results for bunch qualities at the transport line. | ||
| THPC030 | Design of a BeamTransport Line from the SACLA Linac to the SPring-8 Storage Ring | 2975 |
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The SPring-8 Angstrom Compact Free Electron Laser (SACLA) linac has high beam qualities. The normalized emittance is less than 1 mm.mrad and the bunch length is less than 100 fs. If this high quality beam is injected to the SPring-8 storage ring, many interesting experiments can be done. On the other hand, the upgrade of the SPring-8 storage ring is under contemplation. The dynamic aperture of the new storage ring is expected to be so small that the small emittance beam is required to keep high beam injection efficiency. The SACLA linac beam also fulfills this requirement. For these reasons, it was decided to connect the SACLA linac and the SPring-8 storage ring. Since there is already an injection transport line from the SPring-8 synchrotron to the storage ring, the new transport line from the linac to this transport line has been constructed*. We designed the three types of magnet lattice for the new transport line; FODO, Double Bend Achromat and Triple Bend Achromat lattice. Emittance growth and bunch lengthening are calculated for each lattice and the beam qualities are compared. In this paper, lattice design and the comparison of the beam quality for each lattice are described.
* C. Mitsuda et al., this conference. |
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| THPC032 | Current Status of SPring-8 Upgrade Plan | 2981 |
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| The SPring-8 upgrade plan has been discussed. The main goal is to replace the storage ring in the existing tunnel so that the resulting emittance will get as close to the diffraction limit in hard x-ray region as possible. For 10 keV photons, for instance, the diffraction limit corresponds to the emittance of as small as 10 pm.rad. For the challenging goal, the new ring features a multi-bend lattice with damping wigglers, which presumably enables us to reduce an emittance by two orders of magnitudes or more compared with the current double-bend lattice without damping wigglers. Up to now, a six-bend lattice has been mainly studied, which is supposed to generate a natural emittance of 60–70 pm.rad for 6 GeV. In addition, damping wigglers and coupling control should assist to reduce the emittance even more for approaching the ultimate goal. The major modification requires not only an advanced lattice design via manipulation of non-linear beam dynamics but also extensive technological developments in almost every component such as magnets, monitors, and RF systems. The overall review of the upgrade plan, including some detailed discussions on the critical issues, will be presented. | ||
| THPC143 | Beam-based Alignment for Injection Bump Magnets of the Storage Ring using Remote Tilt-control System | 3221 |
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Stored beam is oscillated in vertical if the injection-bump magnets have alignment error in rotation around the beam-axis (tilt). In addition, even if the tilt is negligibly small, the beam out of the median plane is kicked in vertical direction. Also, there is a small long-term drift of the vertical beam positions in the bump magnets, which causes the gradual increase of the oscillation. We have already developed a remote tilt-control system to make a smooth realignment*. To observe the oscillation, the beam position was measured bunch-by-bunch and turn-by-turn by using a bunch-by-bunch feedback system** with high resolution strip-line type beam position monitor. To obtain responses to the tilts of each magnet, the oscillations were measured under the condition that the magnets were tilted intentionally. Tilt errors were calculated with least-squares method using the responses. In order to confirm the source of the residual oscillation, a frequency analysis was carried out with FFT method using the position data from 1st to 128th turns. We succeeded in suppressing the vertical oscillation to sub-microns order, the value of less than one tenth of the beam size.
* K. Fukami et al., Proc. of EPAC'08, p. 2172 (2008). ** T. Nakamura et al., Proc. of ICALEPCS'05, PO2.022-2 (2005). |
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| THPC144 | The Construction Status of Beam Transport Line from XFEL-linac to SPring-8 Storage Ring | 3224 |
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| The beam transport line from XFEL-linac to SPring-8 storage ring is now under construction to use the ultra short bunched electron beam at the storage ring. The newly constructed line is about 300 m, which is just a half of the whole path from the XFEL linac to the storage ring. The beam extracted from XFEL-linac is guided to the beam transport tunnel connected to the matching section of booster synchrotron bending by 55.2 degrees horizontally and by 10.0 degrees vertically. A double-bend based lattice was adopted to reasonably suppress emittance growth and bunch lengthening. Supposing a bunch length and horizontal emittance at the exit of the XFEL-linac are estimated about 100 fs and 0.04 nmrad respectively, it is expected that the current beam emittance in storage ring is improved to about 0.4 nmrad and almost same bunch length including coherent synchrotron radiation effect. In 2010, the construction of extracting part from XFEL-linac was completed and we finished the installation and alignment of main components. The conceptual design and construction status of transport line will be presented with the emphasis on the detail magnet design and the fabrication. | ||