Short Review HERA Run 2002 / 2003 Luminosity Polarization Backgrounds Shutdown Activities Plans for Restart Report on HERA 64th Meeting of the DESY PRC May 7, 2003 F. Willeke, DESY

Short Review of HERA Run 2002/2003 January-March 2002Repairs, Collimator modifications, machine studies March 2002 Start up, machine studies, bakeout April 2002: Set-up of luminiosity, synchrotron radiation studies June-Sept. 2002Luminosity Run with low intensity (5d/w), machine studies, background studies (2d/w) Sept./Oct High Luminosity Studies, polarization Studies Nov Febr Luminosity Runs wih moderate intensity February 2003Machine Studies, high luminosity studies, polarization Tune-up

Operations Luminosity Efficiency in February 2003: 43% Luminosity operations in February 2003

D. Pitzl’s Plott of CJC2 Chamber currents contributions from ep gas events relative to values obtained in September 2002 Global trend follows the vacuum pressure, there is stagnation since December 2002

Accelerator Handling, Understanding, Modeling, Improvements Beam based alignment Orbit feedback Improved magnet cycling Online optics correction Improved background tuning algorithm On-line IR beam envelopes inside magnet aperture Working on proto emittance control Improved beam stability Improved beam handling More save operations Higher beam quality Larger luminosity

Beam Based Alignment

Improvement of accelerator lattice: on-line correction of beam envelope and phase beating

Online display of beam envelopes inside relative to limiting magnet apertures

Proton Logitudinal Stability Coupled Bunches 2p- Mode pattern Average Phase and Bunchlength Phase Ocsillation Monitor Coupled Bunches 4p- Mode pattern Finding: HERA p bunches lenghened by longitudinal bunch instability Cure: Bunch-to-bunch synchrotron frequency spread by RF amplitude modulation with f rev

High Luminosity 120 Bunches I p < 70 mA I e < 35 mA L peak <2.7 x cm -2 s Bunches I p < 70 mA I e < 35 mA L peak <2.7 x cm -2 s -1

Polarization 4 challenges HERA is operated now with three pairs of spin rotators. The solenoid fields are not locally compensated and the beam design trajectories are not perfectly parallel to the solenoid axis. The luminosity upgrade enhances the electromagnetic fields in collisions with the proton beam. The natural vertical positron emittance for a well compensated and spin tuned orbit does not match the proton vertical beam size. In order to avoid poor lifetime and transverse tails of the protons, the vertical positron emittance must be enlarged without affecting the polarization. 4 Steps Test Polarisation in 72o optics in old >IR in 2000 Repeat this test successfully in Oct 2002 with flat rotaotrs in South and North Turn all all three Rotators simultaneously and tune up polarization Collide polarized beam in North and South IR with protons 4 Measures Enhanced spin matching Enhanced harmonic bump scheme Improved closed orbit control Close to perfect optics

Shut Down Activities Survey straight sections in North and South rotators East, North, South, arc NE Vacuum e-beam pipe in GA-Magnet SL/NL 30m gets a NEG pump SR absorbers for RF-Finger in straigths coating of Absorber 4 SR, NR 11m with Cu-Mo movable collimator collimator ati 66m SL/NL Modification of RF screens at Pumping ports Absorbers 1 &2 NR, SR 3.5m, 6m New RF screens at rotator beam pipes beam pipes which replace HERA-B beam pipes new shutters at Insulation vacuum s GG/G install VPS with cold bypas p-Vacuumleck SR 28m Cold Magnets p Reconnect busses at VPS Stecker erneuen Diagnostics new e BPM system (electronics) partial replacement of p bpm electronic replace all fans for tunnel electronics Installation of OTR Monitors WL18m Wire measurment system repair work on electrical safety in tunnel electronics PS Installation of bipolare choppers for VO VG South & Nor repair some ground faults maintenance of dump switches Cooling Reduction of cooling water temperature GI/GJ NR, SR Improvement of QR cooling Improve water cooling of cavities Injection Improvement of fast e-injection kickers Superconducting Cavities Exchange RF Windows Repair of HV Isolation coupler shaft, p-HF New power tubes 208MHz Tuning of Feedbacksystems Troubleshooting Stoerlinien 52MHz e-HF Plunger exchange at several RF Stations Klystrons tuning Interlock New door contacts, new cabling Water rinterlock WR

NEG in –GA e-Chamber 7mm NEG Pump

Increase conductance of he pumping port Remove every second cross piece of the rf shield

Molybdenum coating of Absorber  m Mo, 10  m Cu 4 Absorber inserts available now But this is the critical path

Schedule Summer/Fall 2003 Start up with beams(3 days delay) July 14 Turn-on both Rings July Vacuum Conditioning operation August 1 -August GeV, frequent warm up GG/GO Polarization Studies September 1-14 High energy conditioning Set-up Luminosity Operation Sept Luminosity Operation for all experimentsOctober 1-Dec 15 Accelerator Studies Dec Maintenance days August 5, Sept 2, Oct. 7, Nov 4, Dec 2

Maximum Peak Luminosity I eb = 0.300mA (design) 0.600mA (2 x design) I pb = mA (Y2000 max) 1500 mA mA 2 A likely scenario Peak Luminosity Prospects 2003 Can’t get to maximum Luminosity with 180 bunches

Conclusions Backgrounds in Experiment widely, though not completely understood Operations poor due to ever changing conditions, accumulated luminosity far behind expectations Time was well used o polish up the accelerator, many improvements High luminosity demonstrated High polarazation with collisions demonstrated Improvement programme under way Plans for restart being finalized