Increasing the number of bunches from 120 to 180 last week did not
cause any problems. The proton beam is more stable during collisions.
The positron intensity can be increased more quickly. The luminosity
is steadily increasing. There are no indications a non-linear increase
as the positron current is going up. The new luminosity record
is 2.5 10**31 cm-2 s-1.
The bunch pattern was changed at the same time. Putting a positron
pilot bunch at position 220 did not work (problem with configuration
file).
There were no major technical problems. A valve at the proton source
was defective, reducing the proton current to about 60mA on the weekend.
Coasting proton beam was observed on Friday. It got worse yesterday.
A proton RF amplitude modulation was found this morning. Experts are
trying to solve this.
ZEUS
In general, good data taking. Background conditions were however
poor with coasting proton beam. HV could not be turned on.
The radiation monitors tripped when HERA tried to scrape the coasting
beam. The positron dump signal was fired when the radiation monitors
were turned on again as the background was still very high.
H1
Data taking at high proton current did not cause any problem.
The maximum currents with HV on were Ip=90ma, Ie=34mA. The chamber
currents are acceptable, although slightly higher than expected.
NEG pumps should be regenerated during the maintenance day, including
warm-up of GO/GG magnets. There was a very good fill on Sunday. Other
fills had spiky background conditions, resulting in low data taking
efficiency.
There was an access on Sunday for the VFPS to repair a broken fiber
and for improving the water cooling. The FPS is operated routinely.
There was some discussion about the activities during the maintenance
days. The H1 plan was to regenerated NEG pumps Thursday morning. From the
machine point of view it would be very useful to do this on Wednesday.
HERMES
There were no problems during data taking. HV could always be switched
on. The only problem was a glass tube of the atomic beam source which
broke on Friday. It was scheduled to be exchanged during the access.
The positron lifetime was reduced from 12 to 10 hours.
The positron beam dump was triggered twice.
Polarimeter
The LPOL cavity laser is defective. It will be removed tomorrow and
and sent for repair. The damage may be caused by synchrotron radiation.
Tomorrow water cooling will be connected to the beam scrapers in the east
straight section. The hope is to reduced the synchrotron radiation
background by moving in the scrapers. It is however important to assure
that the cooling is sufficient for the synchrotron radiation power.
Schedule
Continue luminosity operation until tomorrow 05:30hrs.
Maintenance days:
Tunnel access tomorrow 06:00hrs, all interlocks broken.
Interlock WL will be reset at 10:00hrs.
Set tunnel interlocks until Thursday 10:00hrs.
Tunnel closed Thursday 12:00hrs. Afternoon test magnet power supplies.
Interlock of experiments set 22:00hrs.
Thursday - Friday night start beam operation.
Friday machine studies, followed by two days of dedicated polarization
studies.