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**
**  SOURCE CONTROLS FOR KNOCK-ONS (electrons)
**  namelist sousetup
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**
**  knockon.ne."disabled", gives source of "knock-on" electrons
 
**    ="fpld_dsk" also writes disk file "fpld_dsk" with source*dtr 
**                for test of source (see sourceko.f and finit.f),
**                then exits.
**    ="fpld_ds1" also writes disk file "fpld_dsk1" with source*dtr
**                PLUS f(i,j,1,1) (no-renormalization), 
**                for test of source (see sourceko.f and finit.f),
**                and another file "fpld_dsk2" containing only f,
**                then exits.
**  komodel="mr", Marshall Rosenbluth mode, with primary electrons
**                approximated by pitch-angle averaged distribution,
**                and source directly from MR expression, averaged
**                over pitch angle and interpolated on to code u,theta grid,
**                as suggested by SCChiu.
**                Presently, this is the only choice, so komodel has
**                no effect (bh: 980501).
**  nonko=the on cycle for the source.
**  noffko=the off cycle for the source.
**  isoucof=0(mode for lower cutoff of source, per bh), 
**          .ne.0 (based on ucrit, per sc). (default=0)
**    Per bh:
**      soffvte=if positive, a factor (times v_thermal_e) for velocity below 
**          which the knockon source is set to zero (to avoid double
**          counting of FP and knockon collisions).
**         =if negative, factor is abs(soffvte)*sqrt(E_c/E)*v_thermal_e,
**            where E_c=2*E_Dreicer (see Fuchs et al, Phys. Fl. 29, 2931 
**            (1986).
**          (default: soffvte=3.0)
**  isoucof==1:
**    Per sc:
**      soffvte=(.gt.0.)a minimum value for source cutoff and defn. of runaways
**            given as a factor of vthe(lr_)/vnorm.
**            (.le.0) then faccof*ucrit is used for cutoff. See sourceko.f.
**      faccof= factor times ucrit for cutoff. (default=1.)  (sc)
**      (Should combine bh and sc methods for cutoff).
**  soffpr=a factor which is multiplied by the above source cutoff velocity 
**         (from soffvte or faccof) giving absolute value of the parallel  
**         momentum-per-mass below which the primary electron distribution 
**         for the knockon process is set equal to zero. 
**c  nkorfn=.ne.1, refined the theta grid calc of the knockon source.
**c         It is the number of theta mesh points between the theta
**c         grid points at which the knockon source is calculated.
**c         (default: nkorfn=1).  Evidently, no longer used [BH071012].
**  flemodel="pol" or "fsa" to invoke poloidally dependent, or flux
**           surface average calc of the parallel distribution, 
**           respectively, for plotting purposes (pltprppr).
**           (For knockon.ne."disabled", only a pitch angle averaged
**           reduced distn is used, and plotting of this is presently
**           "disabled" (bh: 980501).
**  jfl=number of grid points in parallel (reduced) distribution function
**      (Hard-wired to jx, for knockon.ne."disabled")
**      
**  xlfac=parallel velocity mesh spacing factor
**    (Not used if knockon="enabled", in which case the parallel
**     mesh is same as the x-mesh.)
**    xlfac=1. ==> uniform mesh;
**    xlfac<1. ==> geometric mesh with greater mesh resolution at x=0;
**    xlfac>1. ==> greater resolution at xmax.
**    xlfac<0. ==> xpctmdl,xpctlwr,xmdl,xlwr must be input.
**    xlfac<0. ==> the momentum (velocity) mesh contains three regions:
**    The region +/-[0,xllwr] will have jfl*xlpctlwr evenly spaced 
**    mesh points.
**    The region +/-[xllwr,xlmdl] will have xlpctmdl*jfl mesh points.
**    The region +/-[xlmdl,xmax] will have the balance of the jfl points.
**    default: xlfac=1.
**   For knock-on source:
**    Need to have nso.ne.0 to turn it on.  nsou is as for the
**    analytic sources. Need soucoord="disabled" to turn
**    off above analytic sources, when nso.ne.0. 
**    pltso controls plotting.  
**    Also need nonso(1,1) and noffso(1,1) set so source 
**      goes on.
**
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