我这儿正好有份程序，希望有所帮助。

代码：

一份蒙特卡洛程序

count=input('input the count:');%输入模拟粒子数

sigmaedata=[28370,13845,6908,2555,1223,2602,1925,905.3,479.7,164.5,74.24,23.86,66.60,36.62,22.29,9.978,5.298,1.668,0.7378,0.2361,0.1099,0.06211,0.03939,0.02030];

sigmacdata=[0.0220,0.0393,0.0568,0.0904,0.1209,0.1479,0.1722,0.2136,0.2480,0.3092,0.3486,0.3932,0.4153,0.4268,0.4319,0.4291,0.4215,0.3969,0.3691,0.3269,0.2944,0.2709,0.2512,0.2209];

Edata=[1,1.5,2,3,4,5,6,8,10,15,20,30,40,50,60,80,100,150,200,300,400,500,600,800];%截面数据

channel=zeros(1,ceil(662/5)+10);%多道数组

nget=0;%探测到的总计数

ntotal=0;%进入探测器的总计数

for ii=1:count%count个粒子循环

collidetime=0;%当前粒子碰撞次数

%粒子状态初始化

E0=622;

E=E0;

z=-2;

r=0;

theta=2*pi*rand(1);% 源抽样，z,r,theta坐标

miu=2*rand(1)-1;

fai=2*pi*rand(1);%方向角抽样

if miu

continue;

else

z=0;

r=2*sqrt(1-miu^2)/miu;

theta=fai;

end

while E>1%一个粒子在闪烁体中的输运过程

sigmae=interp1(Edata,sigmaedata,E,'linear');

sigmac=interp1(Edata,sigmacdata,E,'linear');

sigmat=sigmae+sigmac;%线性插值得到截面数据

L=-log(rand(1))/sigmat;%下次碰撞的距离

%计算下次碰撞位置坐标

rnew=sqrt(r^2+L^2*(1-miu^2)+2*r*L*sqrt(1-miu^2)*cos(fai-theta));

z=z+L*miu;

cdth=(rnew^2+r^2-L^2*(1-miu^2))/2/r/rnew;

sdth=L*sqrt(1-miu^2)*sin(fai-theta)/rnew;

dtheta=asin(sdth);

if cdth<0

dtheta=pi-dtheta;

end

theta=theta+dtheta;

r=rnew;

if(r>2)|(z>=4)|(z<0)%判断是否在闪烁体内

break;

else

collidetime=collidetime+1;

end

if rand(1)

E=0;

else%康普顿散射

alpha=E/511;

flag=0;

while flag==0

if rand(1)<=27/(4*alpha+29)

x=(1+2*alpha)/(1+2*alpha*rand(1));

if rand(1)<=0.5*((alpha+1-x/alpha)^2+1)

flag=1;

end

else

x=1+2*alpha*rand(1);

if rand(1)<=27/4*((x-1)^2)/x^3

flag=1;

end

end

end

E=E/x;

alphat=alpha/x;

miuL=1-1/alphat+1/alpha;%散射后的方向

a=miuL;

b=sqrt(1-a^2);

randangle=2*pi*rand(1);

miunew=a*miu+b*sqrt(1-miu^2)*cos(randangle);

sdf=b*sin(randangle)/sqrt(1-miunew^2);

cdf=(a-miu*miunew)/sqrt(1-miu^2)/sqrt(1-miunew^2);

sfn=sdf*cos(fai)+cdf*sin(fai);

cfn=cdf*cos(fai)-sdf*sin(fai);

fainew=asin(sfn);

if(cfn<0)

fainew=pi-fainew;

end

fai=fainew;

miu=miunew;

end%conputon/electtron

%记录结果

end%while

ntotal=ntotal+1;%进入探测器的总计数

if collidetime>0

nget=nget+1;%探测到的计数

Edown=E0-E;%沉积能量

FWHM=0.01+0.05*sqrt(Edown+0.4*Edown^2);

delta=0.4247*FWHM;

Eget=Edown+delta*randn(1);%记录能量

num=ceil(Eget/5); %寻道址

if num~=0

channel(num)=channel(num)+1;

end

end

end%for count

plot(channel);

fprintf(1,'探测效率为%1.5f',nget/ntotal);