# Increasing charge lifetime in DC polarized electron guns by offsetting the anode

## TL;DR

This paper proposes an offset anode scheme for DC polarized electron guns that significantly increases charge lifetime by reducing ion back bombardment, with simulation results supporting its effectiveness.

## Contribution

It introduces a novel offset anode design and demonstrates its potential to extend charge lifetime by an order of magnitude through simulation and experimental setup.

## Key findings

- Charge lifetime can be increased by an order of magnitude.
- The offset anode scheme reduces ion back bombardment.
- An in-vacuum movable anode assembly was designed and fabricated.

## Abstract

Charge lifetime of strained superlattice GaAs photocathodes in DC guns is limited by ion back bombardment. It needs to be improved at least an order of magnitude to meet the requirements for future colliders such as Electron-Ion Collider (EIC). In this work, we propose and present simulation results for an offset anode scheme to increase charge lifetime in DC guns. This scheme eliminates the bombardment of high energy ions on the cathode and enables maximum usage of the available cathode area. Depending on the size of the available cathode area, this method can increase the charge lifetime by an order of magnitude compared to the current best alternative method. An anode assembly capable of in-vacuum movement is required for this method, which has been designed and fabricated at Brookhaven National Laboratory.