The BC-720 detects gammas just fine, but the level is over a full order of below the neutron based proton recoil flashes.
In testing my counter I placed a 5 roentgen gamma source of about .6mev gammas touching the detector head face. The preamp output was connected to a scope and counter. The scope was flooded with pulses at about the .08 volt level and the counter roared in the hundreds of thousands of counts per minute. The neutron pulses were found to peak out at about 1.8volts. Thus, over a full order of magnitude difference was seen. After setting the discriminator level to .5 volts and the count went from hundreds of thousands of counts per minute to one count every two miniutes. This was still with the gamma source touching the detector head.
So gammas are detected but are not even near the level of the intense flashes produced by the neutron induced proton recoils. It is absolute childs play to discriminate any gamma and X-rays totally out of the picture.
I found the BC-720 a superb fast neutron detector.
Richard Hull
Created on Thursday, January 18, 2001 11:03 AM EDT by Richard Hull