hera_minutes_020924.html

F.Willeke summarized the HERA operation of last week, see transparency

During the machine studies last Monday, the vertical emittance of the positron beam was increased by a factor of 2 in order to match the beam sizes at the IP and to reduce the beam-beam-effect. The specific luminosity was constant after the increase of the emittance.
On Tuesday the GO/GG magnets were warmed up for activation of the NEG and TSP pumps. During the access the positron wire scanner was improved, the defective sextupole coil was replaced.
Wednesday, the TSP pumps on the proton upstream side of the south and north IPs were fired to study the proton beam gas background.
The background rates were studied for non-colliding (offset bunch trains) and colliding ep beams.
HERA delivered luminosity from Thursday to Monday morning: proton currents 20 to 24mA, positron currents 15 to 21mA. The specific luminosity measured by H1 was around 1.5 10*30 cm-2 s-1 mA-2.
There was some delay due to proton RF problems in PETRA and HERA.
Part of the positron beam was lost occasionally.

The data taking efficiency was low. During collisions the CTD HV was usually set to 90% of the nominal value. For positron currents less than it was raised to 95%. Very small background spikes resulted in CTD HV trips.

The chamber HV could be turned on soon after stable conditions were declared. The slope (CJC current vs Ie) improved. Maximum currents for safe chamber operation are now Ie*Ip = 1000mA**2
HERA delivered 830nb-1.
Background spikes were observed.

Successful data taking: 33180 polarized events, 83000 unpolarized events were taken last week. The total data sample in 2002 is now 180800 pol., 210000 unpolarized events.
2ns jumps of the positron timing signal were observed.
Would like to go to higher positron currents.

Had 47 hours of target operation.
The background was very high, a factor of 10 to 20, for most of the fills on the weekend.

Uwe Schneekloth