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HERA StatusHERA Status
Joachim Keil, DESY (MPY)
59th Meeting of the Physics Research Committee May 26th, 2005
26/5/2005 J. Keil : HERA Status 2
Contents
Operation of HERA 04/05 with Electrons Luminosity Performance Major technical Problems Polarization Improvements Schedule 2005 Conclusions
26/5/2005 J. Keil : HERA Status 3
Re-Commissioning with Electrons HERA electron operation:
•More synchrotron radiation (for design currents: 26 kW 36 kW)•Different orbits for e and p in IR
Successful re-commissioning strategy (Oct.-Dec. ‘04):1.Set up/check HERA-e with positrons2.Move magnets in IR3.Continue with electrons4.Beam-based alignment; check of optic and correction; …
Start with electrons was smooth: No big problems found! But: It was necessary to move H1 by x=7 mm due to
limited space in GO magnet on left side Delay in schedule:
–Quadrupole GN NL20 had a burnt coil–Vacuum leak at GI07 NR
26/5/2005 J. Keil : HERA Status 4
Trajectories for e-/p and e+/p in IR
-15 -10 -5 0 5 10 15 20zm
-0.04
-0.02
0
0.02
0.04
xm
HERA IR for pe and pe
BO
GJ
GI
GO,HO
GG,HG
GI
GJ
GIp-beam for e+
p beam for e-
7.5 mm
+-
+-
+
-
+
-
e--beam
e+-beam
GM GMGM GM
e
p
Radial orbit shift at IP of 7.5 mm between electron and positron operation
26/5/2005 J. Keil : HERA Status 5
Parameters of Run ‘04/05 with Electrons
Parameter Electrons Protons
Energy E / GeV 27.5 920
Max. current I / mA (design for nb=180) 58 / 40 140 / 102
Number of bunches nb 180 / 63 126 153 180 / 60 120 150
Number of colliding bunches nc 174 / 57 114 147
Hor. beam emittance x / nmrad 20 / < 26 ? 5.1 / 4.7
Ver. beam emittance y / nmrad 3.0 ? 5.1 / 4.7
Hor. beta function at IP x* / m 0.63 2.45
Ver. beta function at IP y* / m 0.26 0.18
Bunch length p / m 0.103 0.191 / 0.21
Hour glass factor R 0.924 / 0.913
Specific luminosity L / 1030 cm-2 s-1mA-2 1.79 / 1.92.2
Peak luminosity L / 1031 cm-2 s-1 7.44 / 2.5 4.5
For p: Long. instability
Beam-Beam effects
Design
2005 with e-
For e-: Vacuum, RFFor p: Pre-accelerators
Hour glass factor included in design!
26/5/2005 J. Keil : HERA Status 6
Beam Currents
Peak currents for run ‘04/05 with electrons (150 bunches):
Ipmax = 102 mA
Iemax = 40 mA
Proton single bunch current is high:Would be 123 mA with 180 bunches!
Electron current was limited first by H1 background (vacuum)
No progress increasing the electron beam current in the last monthsslow conditioning of RF cavities, transmitter problems and vacuum
Switch to 180 bunches if 40 mA electrons can be routinely filled; but dust trapping probability will be higher!
2 0 4 0 6 0 8 0 1 0 0 1 2 0 1 4 0 1 6 00
2 0
4 0
6 0
8 0
1 0 0
1 2 0
R u n n u m b e r (s in ce 1 7 .1 2 .0 4 )
B e am C u rre n ts
1 5 0 b u n c h es1 2 0 b u n c h es6 0
Bea
m C
urre
nt I
/ m
A
e le c tro n s
p ro to n s
26/5/2005 J. Keil : HERA Status 7
Specific Luminosity
High specific luminosity with electrons for 2004/05 run: Ls = 1.8 - 2.2 1030 cm-1·s-1·mA-2
Specific Luminosity is larger than the design value of Ls = 1.84 1030 cm-1·s-1·mA-2
One reason for higher specific luminosity compared to last year with positrons (1.2 -1.61030) is the smaller proton emittance and bunch length
Calculated specific luminosity based on measured beam parameters can describe the measurements of H1 and ZEUS sufficiently good
5 0 1 0 0 1 5 00
0 .5
1
1 .5
2
2 .5M easu red an d C a lcu la ted S p ec ific L u m in o sity
Spe
cifi
cL
umin
osity
/L
s10
30m
A2
cm2
s1
ru n n u m b er (s in ce 1 7 .1 2 .2 0 0 4 )
H 1 m easu red
Z E U S m easu red
ca lcu la ted
overestimated
26/5/2005 J. Keil : HERA Status 8
Integrated Luminosity 04/05
Integrated luminosity is 95.3 pb-1 in 156 days (start: Dec. 17th, 2004)
Best run delivered 1.1 pb-1 within14 hours
On average 0.61 pb-1/d (number for last year: 0.41 pb-1/d)
Mid of May was best so far:HERA delivered 1.17 pb-1/d
New record peak luminosity ofL= 5.071031 cm-2·s-1 was achieved
But: high proton background and many spikes until BU SR coil was identified as the culprit fixed in April!
0 16 32 48 64 80 96 112 128 144 1600
10
20
30
40
50
60
70
80
90
100Integrated e/p Luminosity 2005 Leak GM NR
BU SRcoil exchange
GN NL23coil exchange
cryo systemfailure
christmas,MD
maintenance,MD
maintenance,MD
Inte
grat
ed L
umin
osit
y L
i/ p
b1
t / days (since 17.12.04)
H1
ZEUS
26/5/2005 J. Keil : HERA Status 9
Integrated Luminosity
Luminosity production rate with electrons in 2005 is higher than 2004 for positrons!
(ZEUS)
26/5/2005 J. Keil : HERA Status 10
HERA e--Lifetime
Lifetime event 4.5.2005
Again: Sudden lifetime reduction and lifetime recovery during electron operation
At the same time increased beam loss measured
Observed for I > 30 mA since January ‘05; but number of events is fortunately rare at the moment
Theory: trapping of positive ionized dust particles by the negative charged electron beam
Source of dust: Ion getter pumps (dipole pumps were already replaced in shutdown 1997/98)
If the number of bunches is increased, the probability of dust trapping gets higher
07:30 08:00 08:30 09:000
10
20
Time at 04/05/2005
Lifetim
e /
h
Lifetime and beam current
07:30 08:00 08:30 09:0010
20
30
Curr
ent
/ m
A
07:00 07:30 08:00 08:30 09:00 09:300
1000
2000
3000
4000
5000
6000
7000
Time at 04/05/2005
BLM
rate
/ H
z
Beam loss
NR191
NR216NR239
NR263
26/5/2005 J. Keil : HERA Status 11
HERA Operational Statistics 2005
MHE0%
Exp6%
Strahlverlust0%
MVA1%
Unbekannt0%
Temp.Alarm2%
e-HF3%
MST2%MDI
2%
MSK0%
sl-cav1%
Water0%
Klima0%
Power3%
MIN0%
Cryo-Control0%
Cryogenics19%
MKS40%
Linac30%
MVP0%
Pia1%
Desy20%
Desy30%
e-Dump0%
Linac20%
Senderstrom2%
Bedienung4%
p-HF3%
Quenchprotection
7%
PETRA8%Magnets
25%
Power supplies
8%
Relative large amount of faults is reducing the efficiency of operation; fraction for e- and p-injection times have decreased, fraction of luminosity-run increased since ‘04.
Main problems for faults and delays in ‘05 were due to magnet problems, cryogenics, power supplies, PETRA and problems with the proton quench protection.
HERA Operational Statistics 2005
Fault42%
p-Injection6%
Luminosity Run40%
Tuning0%
Experiment0%
Start-up1%
e-Injection4%
Lumi Tuning2%
MD2% Shutdown
3%
26/5/2005 J. Keil : HERA Status 12
Major technical problems
Nov. 2004: Burnt coil of proton quadrupole magnet GN NL 20
Coil exchanged Dec 2004:
GI NR 7 vacuum leak; broken feed through of NEG pump Jan. 2005:
Ground fault proton quadrupole magnet GN NL 23 Coil exchanged
Feb. 2005: Cryogenic compressor failure
quick repair but p-ring warmed up (1 week) Apr. 2005:
Periodic p-background spikes shorted coil of BU-magnet SR; coil exchanged (4 days)
May 2005: Vacuum leak in p-chamber between GM proton quadrupoles NR
welding of seam; bad vacuum (since 1 week)
26/5/2005 J. Keil : HERA Status 13
GN Magnet Problem During recommissioning in Nov. ‘04 the
magnet GN NL20 failed (cooling problem)
GN magnet: vertical focussing low beta quadrupole for protons; 12 magnets
Damaged lower inner coil had to be exchanged (six days lost)
In January ‘05 also the magnet GN NL23 failed with ground fault; all four coils were replaced (1 week)
Possible reason: Magnets have been operated with 1638 A during power supply tests in October last year exceeding the manufacturer limit of 1600 A
Measures:
Current of power supply limited to 1470 A (max. value for luminosity run)
New coils ordered!
26/5/2005 J. Keil : HERA Status 14
BU Magnet Problem
Since January ‘05: Periodic background spikes in combination with vertical orbit movements; not all the time
Reason was shorted coil of BU magnet SR; April: coil exchanged (4 days)
BU bend the protons upwards at end of straight sections; 18 magnets
Six BU-coils in NL (last shutdown) and one coil in SL were already exchanged
Candidate for another short: BU OL
Measures:
Measurement of voltage drop of coils
Exchange of all remaining BU coils in next shutdownShutdown delayed until all ordered coils are delivered (shutdown starting at 14th Nov. ‘05)
Collimator beam loss rate
26/5/2005 J. Keil : HERA Status 15
Polarization
Colliding bunches: 40%
Non-colliding bunches: ~50%
Even after long tuning polarization is dis-appointing low
Colliding bunches reaches 40% only at end of run (but non-colliding have 55%!)
Influence of beam-beam effect: Polarization is rising due to growth of proton emittance and declining proton intensity
Energy and harmonic bumps are optimized
Problem: Tunes are not optimal for electrons and polarization!
Measures:
Electron intensity related effects allows to decrease the tunes at lower electron currentBut: e-background spikes at H1!
Possible solution: Mirror tunes started test with mirror tunes last week!
Po
laris
atio
n
History of polarization and single bunch polarization
26/5/2005 J. Keil : HERA Status 16
Mirror Tunes
1/4
1/4
Q s
Q s
2Q s
2Q s
3Q s
3Q s
Standard tunes
M irror tunes
Non-collid ing bunches
Tune-shift for c.b. due to beam -beam effect
Collid ing bunches
H igh polarization:tunes near in tegerresonance
Q x
Q y
0
0
26/5/2005 J. Keil : HERA Status 17
Improved e--Transfer Efficiency Transfer efficiency of El-Weg between PETRA
and HERA-e:
• HERA I : never reached 100%
• HERA-II: sometimes only 30-40% and non-reproducible!
Better efficiency faster filling, less radiation during injection process
Measures:
• Calculation of a new matched optic for the EL-Weg adapted for HERA-II injection optic
• Installation of 6 beam position monitors in last summer shutdown
• Checked magnet rolls by survey ok!
• Measurement of response matrix of the EL-Weg large error in optics
• Measurement of quadrupole calibration curve calibration wrong!
Now: Transfer efficiency >70% Efficiency more stable than before Remaining losses: PETRA extraction
26/5/2005 J. Keil : HERA Status 18
Improvement: Proton Tune Controller
Energy ramp of protons is demanding:
Induced eddy currents in super- conductors Time varying dipole and sextupole fields
Tunes near coupling resonance
Control of beam parameters is done manually by operators watching beam signals and turning knobs; needs much experience!
Nevertheless p-beam often get lost
Measure:
Semi-automatic control of tunes was developed; ramping between 70 GeV and 920 GeV and electron refill are now far easier than before!
Coupling and chromaticity control under development
26/5/2005 J. Keil : HERA Status 19
Longitudinal Multi-Bunch Feedback
Proton-bunch lengthening due to longitudinal coherent multi-bunch instability
Longer bunches smaller specific luminosity („Hour glass effect“)
Happens during proton ramping
Measure:
Installation of an longitudinal multi-bunch feedback system for protrons
Status: Feedback cavity arrived; first measurements done
Installation in next shutdown
Goal: Reduction of bunch length at 920 GeV from 1.6 ns to 0.7 ns (FWHM); realistic?
Feedback Cavity
Schematic principle
26/5/2005 J. Keil : HERA Status 20
Schedule 2005 Schedule
– Start of luminosity operation: 17th Dec. ’04– Start of shutdown: 14th Nov. ’05– End of shutdown: End of Jan. ’06– Luminosity operation: 2nd week in Feb. ’06
Expectations for integrated luminosity– Until now: Li = 95 pb-1 in 156 days– Conservative assumption: Average increase of 0.61 pb-1/d – This includes hardware faults, maintenance days, …– 176 days remaining Additional 107 pb-1
– Lower bound for 2005: Li 200 pb-1 ?– Can be even more, if hardware problems happen not so frequently
and electron current can be increased!
Plans for hardware changes in the shutdown– Exchange of all remaining BU coils– Installation of the longitudinal proton feedback cavity
26/5/2005 J. Keil : HERA Status 21
Conclusions
High luminosity production with electrons; performanceof HERA has greatly improved
Integrated luminosity up to now with electrons has alreadyexceeded the value with positrons of year 2004
Background conditions are usually good after sourceof p-background spikes has been found; but there was againa vacuum leak in north!
Polarization with max. 40% disappointing investigation of mirror-tunes has started
Availability of HERA components and operational efficiencyis still too low
HERA will continue luminosity operation until wintershutdown (14th Nov. 2005 – Jan./Feb. 2006)