test_rad_stab_cyl.m
a3531b44407cgeom_test

test_rad_stab_cyl.m
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			a=1e-3;
			b=0.03;
			phia=-5e3;
			phib=0;
			rm=2.8e-3;
			rp=0.02;%rm+3e-3;

			nB=200;
			nne=500;

			B=linspace(0.01,3,nB);
			ne=logspace(14,20,nne);

			vlight=299792458;
			qe=1.60217662E-19;
			me=9.109383E-31;
			eps_0=8.85418781762E-12;
			kb=1.38064852E-23;

			q=-qe;
			C=-qne/(4eps_0)*(rp^2-rm^2)/log(rp/rm)...
			+(phib-phia)/log(b/a)...
			+(qne/(2eps_0)rm^2log(brm/(arp))...
			+qne/(2eps_0)(rp^2-rm^2)(log(b/rp)+0.5*(1+log(a/b)/log(rp/rm))))/log(b/a);
			C=1/2qne*rm^2/eps_0;
			omegape2=qe^2*ne/eps_0/me;
			omegace2=qe^2*B.^2/me^2;

			r=linspace(rm,rp,100);
			for i=1:nB
			for j=1:nne
			[stab1(i,j),id]=min(1-2omegape2(j)/omegace2(i)+4q*C(j)/me/omegace2(i)./r.^2);
			rmin(i,j)=r(id);
			end
			end

			figure
			contourf(B,ne,stab1'>0,'edgecolor','none')
			set(gca,'YScale','log')
			title(sprintf('r_m=%2.1fmm r_p=%2.1fmm, \\phi_a=%2.1fkV, \\phi_b=%2.1fkV',rm1e3,rp1e3,phia/1e3,phib/1e3))