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RF parameters for the BNL and CEA cavities

RF parameters for the BNL and CEA cavities. *calculated with the “accelerator definition”. **http://rcalaga.web.cern.ch/rcalaga/704MHz/. Eacc =25 MV/m I 0 = 40 mA j s = 15°. Q ext (CEA) = 1.2*10 6 Q ext (BNL) = 1.3*10 6. Response time of the RF fields:. t cav (CEA) = 0.54 ms

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RF parameters for the BNL and CEA cavities

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  1. RF parameters for the BNL and CEA cavities *calculated with the “accelerator definition” **http://rcalaga.web.cern.ch/rcalaga/704MHz/ Eacc=25 MV/m I0 = 40 mA js = 15° Qext (CEA) = 1.2*106 Qext(BNL) = 1.3*106 Response time of the RF fields: tcav (CEA) = 0.54 ms tcav(BNL) = 0.59 ms tcav=2QL/w0 ≈ 2Qext/w0

  2. RF power provided to the cavities Variation in exp(1-t/tcav) Variation in 1-exp(-t/tcav) BEAM PULSE AND EACC IN THE CAVITY vsTIME Beam pulse length : LP-SPL : 0.9 ms* BEAM PULSE Dt=0.9 ms *https://twiki.cern.ch/twiki/bin/view/SPL/SPLparameterList RF PULSE AND EACC IN THE CAVITY vsTIME RF pulse length : CEA : 1.27 ms BNL : 1.31 ms RF PULSE Dt+tcav*ln2  Provided RF power : BNL = CEA + 2.7 %

  3. Energy dissipated in the cryogenics G(CEA)≈G(BNL) Q0 = G/Rs Q0(CEA) ≈ Q0(BNL) Rs(CEA)≈Rs(BNL) (only depends on material and surface treatment) • The total energy dissipated in the cavity corresponds to the integration of Pcav all along the pulse • depends on tcav(variation of Eacc) • depends on r/Q BEAM PULSE AND PCAV IN THE CAVITY vsTIME •  Calculations show that the dissipated energy is 10.7 % higher in the BNL case than in the CEA case

  4. Comparison between BNL and CEA cavities, from the point of view of the r/Q • This shows how a lower value of r/Q increases the RF energy supplied to the cavities and the cavity losses dissipated in the cryogenics • This concerns the fundamental mode at 704 MHz • What about the HOM ? • A more detailed report on this calculations has been written

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