[Halla_parity] PREX shifts cancelled until Wed June 2

[Robert Michaels]

Dear Colleagues

Shifts on PREX are cancelled until Day shift Wed
June 2.

The experiment is down because of leaky O-rings in
the region after the target.  All the O-rings will
be replaced with Kalrez 7075 material (explained in
halog 323580) which should greatly reduce the chance
of thermal failure.  Replacing O-rings requires a
lot work and a re-survey.  We appreciate the hard
work of Ed Folts, his crew, ACC support and RadCon.

Shift volunteers will get credit for cancelled shifts,
and we may ask you later to take more shifts.

The two remaining major concerns for PREX are the
O-ring failures and radiation damage to controls
electronics.  The techs are continuously refining
our safeguards against radiation and "hardening"
the apparatus.  Other than those two issues, the
experiment seems to be in pretty good shape and
we've solved many other problems.  We'll try to
bring PREX back online next week.

- Bob