Capillary tube for sample injection got fire when I turned the power source On!!!

[AbidHussain70]

The capillary tube caught fire. Below is the picture of the setup.

Here is gif file of the fire.

I used same brand power supply. And voltage was just 4KV on both sources. I did not connect the pulser circuit for this initial test.

Can you please point out the problem, I spent a so much resources on this project. Thanks