Log entry time 16:59:02 on October 26, 2005

Entry number 158088

keyword=Today's laser work was only on Hall B laser

Here's a copy of Matt Poelker's polog entry about the laser work done in
the tunnel today - Hall A laser was untouched, so our position
differences should not be changed.
--------------------------------------

We looked at the Hall B ti-sapphire laser with the service representative
from Time Bandwidth Products. We did not look at the Hall A laser
because we didn't want to accidentally mess up the alignment of the
pockels cell for the HAPPEx experiment.

Findings:
1) John and I are following good alignment procedures when we work on the
ti-sapphire lasers. We have adequate diagnostics in the tunnel. The
tunnel environment is good (clean, quiet).

2) Olaf of TimeBandwidth asserts that the weakest link associated with
the ti-sapp lasers is the green pump laser. The green pump laser inside
the Hall B laser is indeed finicky. Lots of spatial mode jumps and it
provides only 3.5 W instead of the nominal 4.5 W. We could not find
knobs to increase this value (temp of the cooling water, ti-sapp crystal,
frequency doubler crystal). This particular pump laser has given us
problems before - in fact, we returned this laser to the vendor in 2004
for pump laser repair. We increased the drive current to the pump laser,
from 21.5A to 21.65A and this seems to have improved pump laser
stability. At the moment, both ti-sapp lasers are locked and we
seem to be as well off as before the access.

On a related note;
3) Olaf has not been able to repair the spare ti-sapphire laser at
Building 58 Test Cave. Once again, the problem appears to be the pump
laser. It looks like we need to send this laser back or have Olaf visit
again with a new pump laser.

We entered the tunnel at 9 am and left ~ 1:30 pm. Beam restored to the
inline dump by ~ 3 pm.

User name lkaufman

Log entry time 16:59:02 on October 26, 2005

Entry number 158088