1. 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

2. 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

3. 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

4. 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

5. Improvements in 2005
Poor electron injection efficiency resolved, reasons understood (saturation in beam line), further improved by better matching  % 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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 so far, operational efficiency acceptable (55-60)%
Polarization is ~30-40%
HERA, 61th PRC, 05/06

12. 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

13. 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

14. 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

15. 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

16. HERA, 61th PRC, 05/06

17. 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

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

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

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

21. 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

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

23. 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

24. HERA, 61th PRC, 05/06

25. 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

26. 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

27. 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

28. HERA, 61th PRC, 05/06

29. HERA, 61th PRC, 05/06

30. 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 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

31. 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

32. 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