Because the length of the blue laser pointers is relatively easy to achieve ultra fast, so the beam produced by the laser beam is basically a bunch of short

In the blue laser pointers is considered a cathode really easy to use, is to look at the thermal emittance, lifetime, emission efficiency, response time. Each is a pit. Because it is not what each cathode performance are very good. So in the design stage, to think what is most important to choose laser pointers1

First, blue laser pointers, the vacuum tube is hot cathode. Such as old-fashioned CRT TV, antique oscilloscope like. Now to see the play. In the high-end audio could be seen in the vacuum tube, after all. The power electronic principle thermal emission is bound to change due to the high temperature distribution in the end, the formation of a high-energy tail.

blue laser pointers2

If the electron energy is greater than the material work function, coupled with the external electric field, electron is emitted out. There are a lot of hot cathode materials, the mainstream is the LaB6 class blue laser pointers. advantage of long service life, low transverse emittance, simple and mature. That is the low emittance electron temperature is low, only 1400~1800 we used the accelerator with a 0.12~0.15eV. unit also so good things you laser pointers3

But blue laser pointers, the biggest problem is the bunch is very long. A little can after the longitudinal emittance is substantial. There are a bunch of serious problems in the RF gun. So there are very high requirements of the equipment will not used for electron beam length. Of course is one of the hot cathode can not be reconciled, they also have to come up with a counter grid short bunch.