EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH

CRAB Cavity

label: CRABCAVITY, L=real,VOLT=real,LAG=real,FREQ=real,
rv1=integer, rv2=integer, rv3=integer, rv4=integer, 
rph1=integer, rph2=integer,lagf=real;
                  

• L: The length of the cavity (default: 0 m)
• VOLT: The peak RF voltage (default: 0 MV). The effect of the cavity is

  delta(px) = VOLT * sin( PHI - OMEGA * t)
  delta(E) = - VOLT * OMEGA * x * cos( PHI - OMEGA * t )
  
  where PHI = 2 π * (LAG - HARMON * f₀ t),   and  OMEGA = 2 π * FREQ / c
  

• LAG: The initial phase lag [2pi] (default: 0).
• FREQ: The frequency [MHz] (no default). Note that if the RF frequency is not given, it is computed from the harmonic number and the revolution frequency f₀ as before. However, fo deflecting structures this makes no sense, and the frequency is mandatory.
  
• RV1: Number of initial turns with zero voltage(default: 0).
• RV2: Number of turns to ramp voltage from zero to nominal(default: 0).
• RV3: Number of turns with nominal voltage (default: 0).
• RV4: Number of turns to ramp voltage from nominal to zero(default: 0).
  
• LAGF: Value of the final crab RF phase lag [2pi] (default: 0).
  
• RPH1: Number of initial turns with nominal phase (default: 0).
• RPH2: Number of turns to ramp phase [2pi] from nominal to specified value(default: 0).
  
• HARMON: The harmonic number h (no default). Only if the frequency is not given.
• Please take note, that the following MAD8 attributes: BETRF, PG, SHUNT and TFILL are currently not implemented in MAD-X!<
• Note that crab cavities are only implemented for tracking purposes. TWISS will ignore any effect of the crab cavity.

Example:

BEAM, PARTICLE=PROTON, ENERGY=7000.0;
CAVITY:  CRABCAVITY, L=10.0, VOLT=5.0, LAG=0.0, FREQ=400,
rv1=0, rv2=50, rv3=1000, rv4=50, rph1=100, rph2=500,lagf=0.125;