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Particularities of normal conducting L-band deflecting cavities Valentin Paramonov ,

Particularities of normal conducting L-band deflecting cavities Valentin Paramonov , Institute for Nuclear Reseach of the RAS, 117312 Moscow, Russia. General remarks.

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Particularities of normal conducting L-band deflecting cavities Valentin Paramonov ,

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  1. Particularities of normal conducting L-band deflecting cavities Valentin Paramonov, Institute for Nuclear Reseach of the RAS, 117312 Moscow, Russia

  2. General remarks 1. In S-band frequency range Normal Conducting (NC) structures operating both in Traveling Wave (TW) [SLAC, CERN] and in Standing Wave [SPARC] mode are known. Structure base is Disk Loaded Waveguide (DLW). 2. For NC structures the L-band frequency range is near the border between TW and SW mode of operation, (in the domain of SW influence). TW operation requires too much RF power. 2. SW operation – multi cell structure with operating p-mode for RF efficiency. ICFA BD Mini-Workshop on Deflecting/Crabbing Cavity

  3. SW operation, efficiency vs. stability (DLW) Efficiency Stability DLW practically has just one degree of freedom – aperture radius Ra. Both Rsh and kc are defined by Ra value, kc increases with Ra increasing , Rsh decreases. Deflection Coupling H E Even in S-band range only short deflecting cavities are known (N=5) [D. Alesini et al, PAC 07; P. Craievich et al., PAC 09] due to stability limitation. ICFA BD Mini-Workshop on Deflecting/Crabbing Cavity

  4. S-band SW operation. With lower frequency Rsh reduces, but Ra is already small .... Let us decouple functions. E-type Deflection Coupling H-type V. Paramonov et al., Linac 06 E field H field ICFA BD Mini-Workshop on Deflecting/Crabbing Cavity

  5. Field distributions along axis In the deflection participate transversal components both from electric and magnetic field. In E-type DLW transversal components work in phase, not so inH-type … Nevertheless… ICFA BD Mini-Workshop on Deflecting/Crabbing Cavity

  6. RF parameters E type H type Rsh ~ 1/Ra For L-band H type deflector has higher Rsh, higher coupling, but higher Esmax/E0. In last parameter it is not optimized finally. ICFA BD Mini-Workshop on Deflecting/Crabbing Cavity

  7. Aberrations Free from aberration is just DLW (b =1) in lower HEM passband. Any deterioration of rotational symmetry automatically leads to aberrations. Dependence of deflection in x-direction on the y position is dE0 ~ y2. Depending on Ra value, dE0/E0 <1% for y/Ra <0.4 is achievable by nose shape optimization. ICFA BD Mini-Workshop on Deflecting/Crabbing Cavity

  8. Dispersion properties Due to small transverse dimensions, Rc ~ 0.3 l, there is no HOM problem. TM01 Operating point ICFA BD Mini-Workshop on Deflecting/Crabbing Cavity

  9. Compensated RF structure (V. Paramonov,L.Krabchuk, Linac 2000) Operating point Branches due to waser+ stem Has no stability problem (compensated, bg=0.32, b=1). Efficiency ~ 0.9 from previous case. More complicated in design and dispersion properties. Field distribution for deflecting and coupling modes. ICFA BD Mini-Workshop on Deflecting/Crabbing Cavity

  10. Possible design Vacuum RF input, WR650 Beam pipe Tuning after brazing Cooling RF probes Possible parameters – Ra ~ 19 mm, Rsh ~ 38 MOhm/m, Ql ~ 7000, tt ~ 3 ms, L~ 1 m, P~30 kW, V~ 1 MV ICFA BD Mini-Workshop on Deflecting/Crabbing Cavity

  11. Summary • For application in L-band frequency range normal conducting standing wave deflectors are more effective. • As compared to Disk Loaded Waveguide structure, H-type structure has higher RF efficiency, essentially higher coupling and smaller transverse dimensions. • For H-type structure tolerable values both for aberrations and maximal surface fields can be obtained by appropriate shape optimization. • The high coupling value allows longer cavities without limitations for RF coupler position. ICFA BD Mini-Workshop on Deflecting/Crabbing Cavity

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