22. A technique would most likely increase the signal-to-noise ratio of a photomultiplier tube is to
(A)operate the tube at a lower temperature
(B)operate the tube at higher voltage per dynode than usually specified
(C)use a radioactive source to saturate the noise level
(D)use a retarding potential on the first dynode
(E) use a photocathode of lower work function
23. Which of the following is NOT an attribute of a typical photomultiplier tube?
(A)It operates by producing an avalanche of ions in a gas.
(B)It can produce electrical output pulses less than 106 second long.
(C)It can produce 103 or more electrons per incident photon.
(D)It is affected by a ambient magnetic fields greater than a few gauss.
(E)It detects photoelectrons ejected by light from a photocathode.