  The recent achievements in the performance of superconducting RF (SRF)
photoinjectors have opened a new era in the development of the reliable
high-brightness CW electron sources. While the SRF guns become one of the most
promising technologies, the compatibility of SRF environment with the complex
photocathodes remains on the forefront of the modern accelerator science. The
SRF cavities operate at cryogenic temperatures providing the ultra-high vacuum
(UHV) environment highly beneficial for the photocathode performance. However,
the necessity to keep the photocathodes at room temperature while being
surrounded by the cavity walls that are kept at cryogenic temperatures creates
an additional complexity for the SRF gun design and operation. The complex and
volatile chemical compounds used for photocathodes have a high chance of
contaminating the surfaces of an SRF cavity. When deposited, such compounds
could create centers for cold electron emission which degrade performance of
the SRF guns. Such a circumstance would require development of the in-situ
processing techniques for restoring the SRF cavity performance. This paper
presents the results of the successful implementation and application of the He
conditioning method for cavity restoration using the existing SRF photoinjector
at Brookhaven National Laboratory (BNL). The method has proven to be extremely
effective and resulted in a dramatic improvement of the BNL gun performance.
