New G4beamline pillbox improvements K.B.Beard 4/26/2011

cmd: pillbox Defines a pillbox RF cavity A Pillbox RF cavity is the basic RF element used to construct a linac. The G4beamline convention is that 0degRF is the positive going zero crossing of the electric field, so generally phaseAcc=90 (degRF) is on-crest. The timeOffset parameter sets the overall global absolute timing of the cavity relative to time=0 of the simulation. If unspecified, it is set according to the timingMethod setting. The default timingMethod=atZlocal sets timeOffset so that the test particle arrives at the timingAtZ=# location at the appropriate phase.

For longitudinal cavities, timingMethod=maxEnergyGain emulates how most cavities in linacs have their overall timing determined; while maxX would be appropriate for a horizontal transverse deflecting cavity. Independent of how timeOffset is set, exactly two of the set of maxGradient, phaseAcc, and one fixed output quantity (fixMomentum, fixEnergyGain, fixTransitTime, fixXdeflection, or fixYdeflection) must be specified to set the final pillbox timing. For example, with maxGradient and phaseAcc set, the energy gain would be determined, while if maxGradient and fixEnergyGain were set, the phaseAcc would be determined. The pipe, walls, and collars are made of copper by default. Pipe, wall, collar, win1, and win2 may be omitted by setting their thickness to 0. Common usage is to set the collar values such that, by placing multiple pillboxes sequentially, the collars form a beam pipe between them. Note that section 4.4 of the User's Guide has a dimensioned drawing of a pillbox. Due to the presence of an invisible timing volume, care must be taken when placing objects within a pillbox.

Named Arguments (#=cannot be changed in place cmd) maxGradient The peak gradient of the cavity color The color of the cavity frequency The frequency of the cavity (GHz) # innerLength The inside length of the cavity (mm) # innerRadius The inside radius of the cavity (mm) # pipeThick The thickness of the pipe wall (mm) # wallThick The thickness of the cavity walls (mm) # wallMat The material of all the walls [Cu] irisRadius The radius of the iris (mm) # collarRadialThick The radial thickness of the collar (mm) # collarThick The thickness of the collar along z(mm) # win1Thick The thickness of the central portion of the windows; zero for no window (mm) # win1OuterRadius The radius of the central portion of the windows (mm) # win2Thick The thickness of the outer portion of the windows; zero for no window (mm) # winMat The material of the windows [Be]. phaseAcc The reference phase of the cavity (degrees). skinDepth The skin depth (mm). # timingTolerance Tolerance for timing tuning (ns)

maxStep The maximum stepsize in the element (mm). cavityMaterial Material of cavity volume [Vacuum]. timeOffset Time offset for cavity [set via timingMethod] (ns). timingMethod Method for determining the nominal timeOffset {atZ, maxE, noE, minE, maxT, nomT, minT, maxX, noX, minX, maxY, noY, minY}. timingAtZ Local Z location for timing (mm). fixMomentum Specify total output momentum (MeV/c). fixEnergyGain Specify energy gain (MeV). fixTransitTime Specify transit time (ns). fixXdeflection Specify local output XZ angle (deg). fixYdeflection Specify local output YZ angle (deg). fixTolerance Specify allowable error on fixed settings [1.e-3]. timingDisplay Set nonzero to how timing volume and print info messages [1]. fieldMapFile Filename for BLFieldMap (pillbox if null). # kill Set nonzero to kill tracks that hit the pipe, walls, or collars [0].

timingMethod=atZ timingAtZ=0.0

timingMethod=maxE

timingMethod=minE

timingMethod=noE

timingMethod=minT

timingMethod=maxX

0-60m of the prelinac

maxGradient=MV/m phaseAcc=degRF  Pz out,  E, x’, y’,  t maxGradient=MV/m fixEnergyGain=MeV maxGradient=MV/m fixMomentum=MeV/c  phaseAcc=degRF maxGradient=MV/m fixXdeflection=deg maxGradient=MV/m fixYdeflection=deg … phaseAcc=degRF fixEnergyGain=MeV  maxGradient=MV/m … Independent of method Specify 2 of 3 ….