HERA Status F. Willeke, DESY 61th DESY PRC Meeting May 11 2006 Short Summary 2005 Improvements in Shutdown Operation 2006 Schedule 2006 Further Planned Improvements Switching from electrons to positrons Low Energy Running Polarimeter Status Outlook

2005 Luminosity Production High peak luminosity and efficient operating (HERA II Luminosity Goal reached)  At the end of the run production rates of 1.5pb-1/d achieved Technical problems in the beginning and middle of the run lead to substantial luminosity loss 215 pb-1 HERA, 61th PRC, 05/06

Operational Efficiency About 50% of the failure time lost due to a few incidents  measures taken Global failure statistics is encouraging HERA, 61th PRC, 05/06

Electron Spin Polarization + - + - Routine Running with polarized electron beams in collisions Several times switching of helicity Polarization level (40-50) % (coll) (50-60)% non-colliding beam Issues: Strong Beam-Beam Effect Non-understood asymmetry of polarization w.r.t. helicity  CHECK IN SHUTDOWN: ROTATOR CABLING IS NOT THE PROBLEM HERA, 61th PRC, 05/06

Improvements in 2005 Poor electron injection efficiency resolved, reasons understood (saturation in beam line), further improved by better matching  70-80% efficiency Enhanced temperature monitoring prevented further damage to beam pipe despite harder radiation Improvements in diagnostics: e-BPM electronics, improved synchrotron radiation monitoring and imaging (e+p), further improvements in controls and data logging Improved machine protection by fast magnet current change detection (helps to prevent uncontrolled beam loss) Implementation of proton tune controller Improved beam lifetime evaluation Automation of timing and synchronization system  Positive impact on operational efficiency and operability of the accelerators HERA, 61th PRC, 05/06

Technical Issues solved in Shutdown Nov 14-Jan 31 Coils of n.c. vertical bend in HERA p (BU) Damage by corrosion Refurbishing Program completed during Shutdown (all 36 half-coils replaced) HERA, 61th PRC, 05/06

Technical Issues Rotator Vacuum System Bellows produced 2 leaks in 2004 and 3 leaks in 2005 (insufficient fix in 2004 shut down) All bellows have been improved during the shutdown HERA, 61th PRC, 05/06

Further Improvement during the shutdown Further reduction of beam cross sections at collisions due to using up margins and making use of dynamic beta  25% more Luminosity Improvements in proton BPM (replacement of 12 critical BPMs in IR) Improvements of klystron protection to prevent unnecessary transmitter trips Increased pumping (x2) in SR RF straight Next slide HERA, 61th PRC, 05/06

First step in further increasing HERA Luminosity: Damping of longitudinal instabilities Implementation of a longitudinal broad band damper system for protons to preserve the longitudinal emittance System commissioned, tuned up and tested during Start-up  SUCCESS! Feb 11-06 HERA p Acceleration without emittance blow-up Need further studies to reduce emittance growth by RF noise and IBS sp=12.7cm Emittance growth due to RF noise and IBS HERA, 61th PRC, 05/06

Delays of ~2-3 weeks because unexpectedly necessary of transformer, HERA Start-up 2006: Delays of ~2-3 weeks because unexpectedly necessary of transformer, a broken quadrupole coil, and a power-blackout of the HERA Mainstation C. Besides this relatively smooth start-up Recent Changes Two shutdown periods May 8-13 June 12-19 to exchange HERMES Target cell  Change to e+ in June ´to minimize lost time HERA, 61th PRC, 05/06

Ramp Up of HERA Luminosity Production 2006 HERA is running presently with 150 bunches ~85-95 mA of protons ~35-40 mA of e- 60 pb-1 delivered in 2006 so far, operational efficiency acceptable (55-60)% Polarization is ~30-40% HERA, 61th PRC, 05/06

Further improvements planned: Suppress longitudinal emittance growth at 920GeV by increased RF voltage and reduced RF noise  We still do not have a reliable procedure Implement beam optics with smaller beta at the IP to increase luminosity by 10-20% Build and install a fast orbit stabilizer up to 100Hz bandwidth (June) HERA, 61th PRC, 05/06

Fast Orbit Feedback aim for compensating orbit oscillations up 100Hz to the level of about 10mm BPM electronics existing (readout based on 10kHz Field bus (FAST SEDAC)) Exiting driver supplies (DORIS) for air coil correctors being upgraded for I x 3 Prototype of air coil built and tested, production will start in May on site Programming of the feedback algorithm in progress HERA, 61th PRC, 05/06

Switching from Electrons to Positrons Planned now for mid June Requirements of Experiments: The remainder of HERA Luminosity should be split equally in electron-proton and positron proton collisions Need to switch from e+/e- or vice versa at least once during the run HERA, 61th PRC, 05/06

Switching leptons from 2004 Experience: Needed 30 days in Nov 2004 from start switching to first luminosity subtract 5 days of hardware problem (GN repair Nov 2004) = 25 days switching from e+ to e- during the run takes 25 days HERA, 61th PRC, 05/06

HERA, 61th PRC, 05/06

Concept GM GM SepMag Reduce GM Halfquad in strength to provide local compensation of the increased dipole kicks from separator magnets leave all p-magnets in the nominal proton-positron/electron positions, quadrupole wiring unchanged positron Lattice unchanged, positron IR quads unchanged Positron optics in the arc: 60 degree, no frequency offset  40nm nominal positron/proton IP (-1mm?) (-7.5mm radially displace from detector axis )  Optical Parameters: bxp=4.9m bxe = 1.20m byp=0.36m bye = 0.52m eNp=16 mm exe = 40nm eye = 6 nm HERA, 61th PRC, 05/06

Factor of ~4 reduction HERA, 61th PRC, 05/06

IR Top View P-Magnets: Nominal positron/electron positions E-Magnets: Nominal positron positions HERA, 61th PRC, 05/06

IR Top View Close-up HERA, 61th PRC, 05/06

All p-magnets are now at nominal positions GM GM GN GN GN GA GB GB GB9 QR QR QR QR ~4mm P-magnets axis IP P-Trajectory HERA, 61th PRC, 05/06

P-Optics Positron Optics Coutesy M. Vogt HERA, 61th PRC, 05/06

Required Preparation and Running Time ∫one day Ldt = 200 nb-1 @ 460GeV Assuming a data taking efficiency of 70% luminosity of of 14.4 pb-1 needs to be delivered to get 10pb-1 on tape In order to deliver an integrated Luminosity of 14.4 pb-1, with 200nb-1d-1 Need 72 days plus a two week set up time  The accumulation of 10 pb-1 by the experiments will require a running time of 86 days. Some of the preparation can be performed at MD after maintenance days Some of the preparation could be absorbed in the switching from electrons to positrons HERA, 61th PRC, 05/06

HERA, 61th PRC, 05/06

Transverse Polarimeter Running: Stable routine operation with close to 100% efficiency. Successfully provides online/offline polarisation to BKR and Collaborations. Control and Monitoring: Essential calibrations done online in automatic mode: calorimeter channels matching, energy and beam spot corrections, luminosity and linear light optimizations. Absolute Scale and Error: Still relies on Monte-Carlo extrapolation of the HERA-I rise-time measurements. Ongoing activities to measure polarisation by the Silicon for the scale calibration and the systematic error estimation. Ongoing activities to understand LPOL/TPOL ratio Transverse polarisation and some important TPOL parameters HERA, 61th PRC, 05/06

Longitudinal Polarimeter Stable and reliable operation, similar efficiency as TPOL (close to 100%) No major hardware problems or failures: expect to be able to operate the LPOL till the end of HERA2 running. Example: study of dependence on laser beam parameters: Laser circular polarisation remains stable independent of the position and alignment of the laser beam HERA, 61th PRC, 05/06

Status LPOL and TPOL both operate stable and reliable Main problem: not-understood ratio of LPOL/TPOL <> 1: currently dominates the systematic error of the Polarisation measurement Measured LPOL/TPOL per fill in 2005 Clearly visible: problematic period in August 2005 HERA, 61th PRC, 05/06

HERA, 61th PRC, 05/06

HERA, 61th PRC, 05/06

Cavity LPOL Status and Plan An example for one single bunch Fabry-Pérot Cavity: locking very stable since the last winter shutdown A first polarization measurement: performed successfully on April 25, 2006 with sandwich calo Fiber-tungsten calo: Reinstalled beginning of Feb. after a beam test in Jan. Shielding with lead foil & tungsten plate (being) added since March Performance improved but under further investigation Plan: Perform systematic studies of the polarization measurement Be ready either as a regular running device (in a few weeks) or as a precise reference device for other polarimeters An example for one single bunch (taken in 4 + 4 seconds) Compton peak & asymmetry measured Fitted Pe: (29.7±2.5stat)% (one bunch in 8s) (33.3±0.4stat)% (all bunches in 8s) (TPOL Pe: (29.6±1.3stat)% (all bunches in 1min) Cavity LPOL group PRC May 11, 2006

HERA Running Until 2007 Luminosity Running until switching leptons in June 06 25 days switching leptons Short Christmas break 2006/2007 (TO BE DECIDED) Run 2007 from Dec.26-June 30 ~380 Days of running (– switching to lower energy running if requested) HERA, 61th PRC, 05/06

Conclusion Many improvements performed during the shut down Part of the remaining HERA improvement program to increase luminosity and to improve backgrounds is implemented, other improvements still in preparation Start-up of 2006 Running with some hardware problems but without major difficulties. HERA continues to run on in 2006 on the same high level than at the end of 2005 Operating HERA with lower energy is most likely possible, parameters have been worked out. The luminosity scales with g2. To obtain 10pb-1 at Ep=460GeV, the loss in high energy-luminosity is estimated to be 90pb-1 HERA, 61th PRC, 05/06