Synchrotron Radiation Source R&D at BESSY II in Berlin
Synchrotron Radiation Source R&D at BESSY II in Berlin
Synchrotron Radiation Source R&D at BESSY II in Berlin
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1/<br />
I<br />
threshold<br />
� Z<br />
tot<br />
Cures for Coupled Bunch Oscill<strong>at</strong>ions<br />
�<br />
� Nc<br />
�<br />
�<br />
�<br />
R<br />
Q<br />
0<br />
�<br />
�<br />
�<br />
�<br />
HOM<br />
♦<br />
Detun<strong>in</strong>g of the dom<strong>in</strong>ant HOM<br />
- by chang<strong>in</strong>g cavity temper<strong>at</strong>ure e.g. ELETTRA<br />
- by a second tuner<br />
♦ Higher harmonic rf system for Landau damp<strong>in</strong>g e.g. SLS<br />
♦ Use broad band feedback systems e.g. ALS, <strong>BESSY</strong> <strong>II</strong><br />
However: All these methods have their specific limit<strong>at</strong>ions !<br />
►<br />
Q<br />
♦ M<strong>in</strong>imize number of cavities Nc<br />
♦ M<strong>in</strong>imize (R/Q0 ) HOM<br />
♦ M<strong>in</strong>imize Qext Damp all HOMs <strong>in</strong> the cavities <strong>in</strong> a broadband<br />
way by 2 - 3 orders of magnitude<br />
ext<br />
Two Concepts for Broadband HOM Damp<strong>in</strong>g:<br />
Waveguides Beam Tubes<br />
nc cavities sc cavities<br />
f rf < f cutoff < f HOM<br />
→ Trade off between<br />
• effective coupl<strong>in</strong>g to HOMs<br />
• M<strong>in</strong>imum coupl<strong>in</strong>g to<br />
fundamental mode<br />
4th N<strong>at</strong>. Congress on Particle Acceler<strong>at</strong>ors and Applic<strong>at</strong>ions / Bodrum / Turkey 30.8. – 1.9. 2010 Ernst Weihreter / HZB <strong>BESSY</strong> <strong>II</strong><br />
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