| Paper | Title | Page |
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| THPC155 | Modification of the BESSY II Optic for the Implementation of a Small Gap Undulator | 3251 |
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| At BESSY there is an increasing demand for photons in the range from 60 eV to 8 keV available at the same experimental station. The photons will be produced by a combination of two adjacent undulators, one of them will be a small period cryogenic undulator. Several optics schemes for the 1.7 GeV BESSY II storage ring are discussed to install the undulators. Two types of straight sections exist. A high beta straight with betaxmin=15 m and betaymin=4.5 m and a low beta straight with betaxmin=betaymin=1 m. We discuss the present plan, which clearly favours a small detuning of an existing low beta straight to shift the low beta waist to the centre of the low gap undulator, with only minor impact to the machine. | ||
| THPO024 | Development of a Non-Linear Kicker System to Facilitate a New Injection Scheme for the BESSY II Storage Ring | 3394 |
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Top-Up injections without noticeable motion of the stored beam is a challenge. The common method of beam accumulation with a local bump formed by four independent pulsed dipole kicker magnets usually causes beam oscillations. The matching of the four independent kicker systems regarding pulse jitters and shapes is technologically limited. Afterward the beam excitation was reduced more when two kicker magnets on each side of the septum were powered in series by one pulser unit. An even more promising approach is to adopt an alternative injection method deploying a single non-linear kicker magnet with zero Bx,y-field in the center and an off-axis maximum, By, which is horizontally displaced by 10-12 mm. There the injected beam gets kicked and looses half of its transverse momentum. Such a magnet was designed and built as a short in-vacuum magnet with a small vertical gap height. For first beam tests the kicker was placed in the second straight section after the injection point, and the 1.5 μs pulse was designed to deflect the 1.72 GeV beam by 1 mrad. In this paper, the calculations of the magnetic fields, the mechanical design as well as the electrical pulser circuit are described.
*New injection scheme using a pulsed quadrupole magnet in electron storage rings, Kentaro Harada, PHYSICAL REVIEW SPECIAL TOPICS - AB 10, 123501 (2007) |
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| THPO025 | Longitudinal Beam Dynamics of a Laser Sliced Bunch | 3397 |
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| Nowadays fs-laser slicing of a bunch of electrons in storage rings is quite common for creating short VUV- and soft X-ray light pulses or pulses of coherently emitted THz-radiation over a couple of revolutions. In this paper the longitudinal dynamics of the sliced bunch is studied numerically. The calculations are based on the one dimensional solution of the Vlasov-Fokker-Planck-equation assuming that the shielded CSR-wake is dominating the dynamics of the 100 fs-long slice. It is found that the density modulation survives longer and that the CSR-spectra extend to higher frequencies at later turns even below the corresponding instability threshold. This very simple model seems to support experimental observations at the Swiss Light Source. | ||