Minutes of HERA Meeting
20.08.2002
HERA
Summary of last week:transparency
- Monday: tested the new positron feedback system, orbit steering when
going from flat top to luminosity optics. The procedure works fine, but
introduces same orbit oscillations, which will be studied next week.
The improved positron beam optics, 10-15% reduction of beta beat,
was implemented and successfully tested.
There is still a 30% beta beat in the protons optics, one of the reasons
that the specific luminosity is slightly lower than the design value.
- Dedicated background studies were performed on Wednesday:
- positron beam: firing of Ti sublimation pumps, position and angle
scans at IP.
- proton beam: energy scan. Beam was lost due RF problems.
- There were several technical problems on Wednesday: beam loss monitors
at the proton collimator WL19, water leak and failure of the proton
208MHz RF system C. The transmitter had to be changed.
- HERA delivered several luminosity fills during the weekend. The colliding
bunches were lost once when beams were not colliding properly.
- Machine studies were performed yesterday and last night. The beam beam
effect was studied. All positron BPMs are now working properly. The
new calibration and some hard modifications were implemented.
ZEUS
- Most of the results of the background studies were already presented
in the background meeting on Friday, see web page. Fitting the different background
components in the FADC drift time distribution results in a 20% particle
background in SL1 of the CTD at about 4mA beam current. This is in
agreement with the results of 15 to 20% obtained from firing the TSPs.
- Since Sunday the readout electronics of the CTD is defective.
H1
- No effect was seen in the chamber currents when the TSP were activated
last Tuesday. Presently, there is not enough data to extrapolate the
contribution of beam gas background to full positron current.
- The positron background as a function of beam position and angle at the
IP has a broad minimum and steep rise at large values. The vertical angle
required for good acceptance of the luminosity monitor is close to the
rising edge.
- At low beam proton beam energies, the CJC current was close to the
pedestal. The scan energy has to be repeated because the beam was lost.
- On Saturday and Sunday parts of the electronics had to be turned off
due to the high ambient temperature.
- A fast connection is being setup to get all background information
to the HERA control room.
HERMES
- The atomic beam source broke on Monday, and was repaired during an access
on Wednesday.
- The positron beam only on Friday (the proton ring was not yet running)
was used for data taking.
- The low current fills on the weekend were used for alignment data,
polarized target. Physics data was taken using the 15mA fill until the
target magnet was switched off, when the cooling water got too hot.
The integrated luminosity of last week was less than a single fill in
2000.
HERA B
- Target operation and data taking has been more efficient since the
procedure was changed on Saturday: as soon as proton collimators are
in and stable beam is declared, the target is moved in.
- The weekend was quite efficient: 11hours of continuous data taking on
Saturday with low backgrounds. On Sunday the background was somewhat
higher, but still acceptable. During the weekend the target was operated
for 22hours, compared to 14hrs the previous weekend.
The trigger is presently being commissioned. 60 proton bunches are
still fine.
Schedule
- Today: proton energy scan, beam scan at IP and firing of TSPs.
- Night shift: optimize positron injection.
- Tomorrow: high current (30mA) positron fill and horizontal
beam steering.
- Wednesday to Thursday: setup luminosity again. (p 25 to 30mA, e 20mA)
- Luminosity operation until Monday.
- Monday: machine studies
- Tuesday: access (tunnel 06:00 to 15:00hrs, experiments 06:00 to 22:00hrs).
- ZEUS is the coordinating experiments.
Next week the HERA meeting will be at 09:30hrs.
Uwe Schneekloth