| 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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| THPC031 | Measurement of Longitudinal Dynamics of Injected Beam in a Storage Ring | 2978 |
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| Experimental observation of longitudinal dynamics of injected beam in a storage ring has been demonstrated. Since the injected beam undergoes synchrotron oscillation in a longitudinal phase space, two projected values, i.e., a bunch duration and an energy spread, oscillate at twice the synchrotron frequency. At SPring-8, the initial energy spread (~0.126%) at the injection goes up and down until it reaches the equilibrium energy spread (~0.11%). If the injection timing should not be optimized, an asymmetrically enhanced oscillation could distort the injection efficiency. The observation of such an oscillation helps make sure that no significant injection loss occurs. More importantly, the scheme is expected to enable us to observe non-linear longitudinal dynamics of ultra-short bunches injected from the XFEL linac; the bunches are in near future going to be transferred from the linac to the storage ring via 600-meter long transports, in which strong coherent synchrotron radiation and other high peak-current effects will not be ignorable. Experimental results obtained by a dual-scan streak camera and other devices as well as numerical simulations will be presented. | ||
| 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. | ||
| 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. | ||
| TUPC105 | Improvement of Beam Current Monitor with High Tc Current Sensor and SQUID at the RIBF | 1260 |
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| A highly sensitive beam current (position) monitor with a high Tc (Critical Temperature) current sensor and a SQUID (Superconducting QUantum Interference Device), that is the HTc-SQUID monitor, has been developed for the RIBF (RI Beam Factory) in RIKEN. The purpose of our work is to measure the DC of high-energy heavy-ion beams nondestructively in such a way that the beams are diagnosed in real time and the beam current extracted from the cyclotron can be recorded without interrupting the beam user's experiments. Both the HTc magnetic shield and the HTc current sensor were dip-coated by thin layer of Bi-Sr-Ca-Cu-O (2223-phase, Tc=106 K) on 99.9 % MgO ceramic substrates. Unlike other existing facilities, all these HTS fabrications are cooled by a low-vibration pulse-tube refrigerator. These technologies enable us to downsize the system. As a result, 1 uA Xe beam intensity (50 MeV/u) was successfully measured with a 100 nA resolution. From last year, aiming at the higher resolution, improvement of the new HTc current sensor with two turn coils has been started. We will report the present status and the measurement results of the HTc-SQUID monitor. | ||
| TUPS088 | Charge Stripping of Uranium-238 Ion Beam with Low-Z Gas Stripper | 1746 |
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| One of the primary goals of the RIKEN RI beam factory is to generate unprecedented high-power uranium beams (up to tens kW), which yield an enormous breakthrough for exploring new domains of the nuclear chart. The development of reliable and efficient charge stripping scheme for such high-power beams is a key unsolved issue, affecting the overall performance of the heavy ion accelerations. A charge stripper using low-Z (low atomic number Z) gas is an important candidate. Because of the suppression of the electron capture process, the high equilibrium mean charge states for the low-Z gas stripper are expected in conjunction with the intrinsic robustness of the gas. There was, however, no direct experimental data of the charge evolution, because of the difficulty in making massive windowless low-Z gas targets. In the present work, the charge evolution of the 238U beams injected at 10.75 MeV/u were investigated using thick hydrogen and helium gas strippers with huge differential pumping system newly developed. In the energy region of interest, near 10 MeV/u, achievable mean charge states around 65+ with the low-Z gas strippers are far superior to those of the medium-Z ones around 55+. | ||