atsigma

ATSIGMA constructs a beam sigma matrix 2x2 4x4 or 6x6

   SIGMA=ATSIGMA(BETA,ALPHA,EMIT)
       builds a 2x2 sigma matrix for a transverse plane

   SIGMA=ATSIGMA(ESPREAD,BLENGTH)
       builds a 2x2 sigma matrix for the longitudinal plane

   SIGMA=ATSIGMA(BETAX,ALPHAX,EMITX,BETAZ,ALPHAZ,EMITZ)
       builds a 4x4 sigma matrix

   SIGMA=ATSIGMA(BETAX,ALPHAX,EMITX,BETAZ,ALPHAZ,EMITZ,ESPREAD,BLENGTH)
       builds a 6x6 sigma matrix

   SIGMA=ATSIGMA(ATSTRUCT)
       builds a 6x6 sigma matrix

  See also atx

0001 function sigma = atsigma(varargin)
0002 %ATSIGMA constructs a beam sigma matrix 2x2 4x4 or 6x6
0003 %
0004 %   SIGMA=ATSIGMA(BETA,ALPHA,EMIT)
0005 %       builds a 2x2 sigma matrix for a transverse plane
0006 %
0007 %   SIGMA=ATSIGMA(ESPREAD,BLENGTH)
0008 %       builds a 2x2 sigma matrix for the longitudinal plane
0009 %
0010 %   SIGMA=ATSIGMA(BETAX,ALPHAX,EMITX,BETAZ,ALPHAZ,EMITZ)
0011 %       builds a 4x4 sigma matrix
0012 %
0013 %   SIGMA=ATSIGMA(BETAX,ALPHAX,EMITX,BETAZ,ALPHAZ,EMITZ,ESPREAD,BLENGTH)
0014 %       builds a 6x6 sigma matrix
0015 %
0016 %   SIGMA=ATSIGMA(ATSTRUCT)
0017 %       builds a 6x6 sigma matrix
0018 %
0019 %  See also atx
0020 
0021 if iscell(varargin{1})
0022     beamdata=atx(varargin{1},0,1);
0023     sigma=beamdata(1).beam66;
0024 elseif nargin == 2
0025     [espread,blength]=deal(varargin{:});
0026     sigma=[espread.*espread 0;0 blength.*blength];
0027 elseif nargin == 3
0028     [bx,ax,epsx]=deal(varargin{:});
0029     sigma=epsx*[bx -ax;-ax (1+ax*ax)/bx];
0030 elseif nargin == 6
0031     [bx,ax,epsx,bz,az,epsz]=deal(varargin{:});
0032     sigma=[atsigma(bx,ax,epsx) zeros(2,2);...
0033         zeros(2,2) atsigma(bz,az,epsz)];
0034 else
0035     [bx,ax,epsx,bz,az,epsz,espread,blength]=deal(varargin{:});
0036     sigma=[atsigma(bx,ax,epsx) zeros(2,4);...
0037         zeros(2,2) atsigma(bz,az,epsz) zeros(2,2);...
0038         zeros(2,4) atsigma(espread,blength)];
0039 end
0040 
0041 end