Chromium coated silicon nitride electron beam exit window

• Chromium coated Si3N4 thin membrane was proposed as an electron beam exit widow.
• The device was experimented for low electron energy and high beam current.
• Finite element method analysis was carried out for thermal profile of the device.
• Maximum differential pressure across the device was experimentally tested.
• Metal coating has increased the transmitted beam current by four fold.

A Si3N4 membrane with a thin Cr coating is proposed and demonstrated as an electron beam exit window. On average, 85% electron power transmission efficiency was achieved with a 1 μm thick Si3N4 membrane coated with 1 μm thick Cr and the membrane sustained a beam current of up to 3  mA at 60 keV electron energy for the continuous operation of 3 min. However, for an uncoated membrane of same thickness, the average electron power transmission efficiency was 71% and the maximum beam current sustained was 800 μA. It was also shown that a one micron thick Si3N4 square membrane window of 10 mm × 10 mm could withstand a differential pressure of 1.3 bars.