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%                                                      
% Name: LP_Walker.m                                    
% Author: Anders I Eriksson                                   
% Description:                                         
%              LP_Walker(v,n,T,a) -- spherical probe sheath radius                                        
%                                                      
%                                                      
%                                                      
% Input:                                               
%        v: probe potential [V]                                               
%        n: electron density [cm-3]                                               
%        T: electron temperature [eV]                                               
%        a: probe radius [m]                                                
% Output:                                              
%        rs: sheath radius [m]                                              
%                                                      
%                                                      
% Notes:                                               
%        Relevant for electron collection. From Whipple (1965),
%        eqns (3.5) - (3.6), citing Walker (1964).                                              
%                                                      
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function rs = LP_Walker(v,n,T,a)

debye=LP_Debye(n,T);
rs = a + 0.83 * debye .* (a/debye).^(1/3) .* sqrt(v/T);
