HERA Running 2005 F. Willeke, DESY 60 th Meeting of the DESY PRC November 10-11 2005 Luminosity Polarization Backgrounds Improvements Technical Issues

HERA Running 2005F. Willeke, DESY

60th Meeting of the DESY PRCNovember 10-11 2005

• Luminosity

• Polarization• Backgrounds• Improvements• Technical Issues• Further Planned Improvements• Switching from electrons to positrons• Low Energy Running

•Outlook

F. Willeke, HERA, 60th PRC 2

Proton (1982) design intensity

Electron (1982) Design Beam Current


Peak Luminosity

goal peak luminosity


Specific Luminosity

Design Level

Larger than design: * smaller p emittance

* strong dynamic beta reduction e Well understood

H1 ZEUS

Alternative working pointAlternative working point


Luminosity Production

High peak luminosity and efficient operating

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


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

+ - + -


Beam-Beam Effect on Polarization

Peak Polarization achieved after slow decay of specific luminosity

Experiment: Beam-Beam Tunes spread of electrons is the problem

Proposed cure:Mirror Tunes allow to run with the beam core at favorable (low) tunes

Test in June:Confirmed, but beam core is too close to resonances, loss of luminosity

Decided to stay with nominal tune


Background Conditions: Poor HV conditions

Reasons for background conditions:

• Large Global p Background in H1 after venting IR in shut down

• BU-Magnet short, problems in March/April coil replace in April

• Electronics problem in large PS, spikes in June, July found, fixed in July

• Reasonable conditions in August-Nov, but careful tuning required


Operational Efficiency

About 50% of the failure time lost due to a few incidents

measures taken

Global failure statistics is encouraging


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


Technical Issues Coils of n.c. vertical bend in

HERA p (BU)

Damage by corrosionRefurbishing Program:

6 coils already replaced in previous shut down

2 coils replace during the run

All the (remaining) 27 Coils will be replaced in Shutdown


Technical IssuesRotator Vacuum System Bellows produced 2 leaks in 2004

and 3 leaks in 2005 (insufficient fix in 2004 shut down)


Further planned Improvements(coming winter shut down):

• Implementation of a longitudinal broad band damper system for protons to preserve the longitudinal emittance

• 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 one RF straight

• Implementation of an operational permit system to prevent operator mistakes

• Fast electron orbit stabilization at Ip’s (0-100Hz) to improve on proton beam diffusion and corresponding backgrounds


Switching from Electrons to Positrons

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


Planned Date Actual Date

El-Weg Studies Friday, October 15, 2004 Friday, October 15, 2004

Hall North PS p Thursday, October 14, 2004 Thursday, October 14, 2004

p / e Monday, October 18, 2004 Monday, October 18, 2004

e Wednesday, October 27, 2004 Wednesday, October 27, 2004

Hall South PS p Thursday, October 14, 2004 Thursday, October 14, 2004

p / e Monday, October 18, 2004 Monday, October 18, 2004

Large PS Circuits Monday, October 18, 2004 Monday, October 18, 2004

Wire installation Monday, October 25, 2004 Monday, October 25, 2004

Start-up with protons I Friday, October 22, 2004 Friday, October 22, 2004

Start-up with positrons Friday, October 29, 2004 Friday, October 29, 2004

e-BPM Recommissioning Monday, November 01, 2004 Monday, November 01, 2004

switch to electrons Tuesday, November 02, 2004 Tuesday, November 02, 2004

Adjust IR magnet for e- Wednesday, November 03, 2004 Wednesday, November 03, 2004

shielding removal Wednesday, November 03, 2004 Wednesday, November 03, 2004

survey Wednesday, November 03, 2004 Wednesday, November 03, 2004

magnet adjustment Thursday, November 04, 2004 Thursday, November 04, 2004

survey Friday, November 05, 2004 Friday, November 05, 2004

Start-up Electrons Friday, November 05, 2004 Friday, November 05, 2004

first turn steering Friday, November 05, 2004 Friday, November 05, 2004

injection optimization Sunday, November 07, 2004 Sunday, November 07, 2004

adjust wire system Monday, November 08, 2004 Monday, November 08, 2004

completion of shielding Tuesday, November 09, 2004 Tuesday, November 09, 2004

GN Exchange Monday, November 08, 2004

electron acceleration Thursday, November 11, 2004 Tuesday, November 16, 2004

Electron-proton files Friday, November 12, 2004 Wednesday, November 17, 2004

IR-Orbit, BBA, SR-Studies Monday, November 15, 2004 Saturday, November 20, 2004

Luminosity Set-up + test Sunday, November 21, 2004 Sunday, November 28, 2004

Lumirun Sunday, November 28, 2004 Friday, December 03, 2004

November 2004: Switching from positrons to electrons


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• If turn-over is after shut down: Absorb 7 days of survey,

magnet movement, shielding installation, wire system installation in shut down

= 18 days A normal startup is about 1-2 weeks, subtract from turn-on

time = ~(4-11) days needed additionally for switching

Switching from e- to e+ after shutdown takes 7 days extra turn on time

switching from e+ to e- during the run takes 25 days




Sacrifice


HERA Running Until 2007

• Shut Down Nov 14 2005- Jan 26 2006• Start up 2006 Jan 26- Febr 21• Luminosity Running until switching leptons• 25 days switching leptons• Christmas break 2006/2007?• Run 2007 from Jan2-June 30• ~450 Days of running


Conclusiono HERA made a big step in improving performance compared to 2004, more than 210 pb-1

of luminosity have been delivered, polarization is in competition with luminosity

o A number of improvements increased the operational efficiency

o Running with electron turned out to be slightly more difficult: somewhat larger background, occasional lifetime break down

o However this was more than balanced by a large luminosity enhanced by dynamic

o There have been a number of technical problems reducing operation time by about 40%

o The technical problems and the background problems have either be solved during the run or are addressed in the HERA improvement program.

o There is a rich HERA improvement program to overcome technical problems and to improve on performance and backgrounds

o switching from e t e- or vice versa during the run is time consuming (25d) switching e t e- or vice versa after the shut down more commissioning time (~7days)

o Operating HERA with lower energy is most likely possible, parameters need to be worked out. The luminosity scales with 2. The loss in luminosity is estimated to be 90pb-1

Documents

HERA Running 2005 F. Willeke, DESY 60 th Meeting of the DESY PRC November 10-11 2005 Luminosity Polarization Backgrounds Improvements Technical Issues