Transcript Document 7525730

HERA
54th Meeting of the PRC
October 30-31 2002 at DESY
F. Willeke, DESY MHE
Status of Operations and Present Performance
Limitations
Accelerator Physics Progress and Issues
Strategy and Plans
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Status of Operations and Present Performance
Limitations
•
•
•
•
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HERA Operations
Beam Current Limitations
Backgrounds
Luminosity
HERA, F.Willeke, PRC Oct30 02
HERA Operations
Week of September 18: Luminosity Operation wit 60 bunches
Ip
Ie
HERA Operation is now more difficult than before (as stated in spring)
•Aggressive Beam Optics with vulnerable Beam Stability
•Uncompensated Solenoids
•Poor support of the low-b quadrupoles in detectors
•Strong influence of the detector iron on low-b quadrupoles
•Sensitive detectors close to the beam
•Background tuning much more tedious
 Operational toolbox needed to be adapted and extended
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Operational Improvements
• Orbit stabilization feedback
•
controls beam positions and synchrotron radiation during critical operation
Ramping,
low-b squeeze,
closing ZEUS Calorimeter
implemented tested and used routinely with good success
 Routinely Accelerated respectable e+ Beams of 20mA of Current
beam losses and uncontrolled irradiation avoided, interferences and poor magnet
support compensated
• Semi-automized SR Background Optimization implemented
• Refinement of the Operational procedures: Many improvements since
spring:
>> Operational procedures re-established
>> Operations automated to a large extent
>> new features: checking voltage vs currents of all magnets automatically
>> automatic file checking avoids accumulative errors in the operation system
>> improving archive features
• Improved Communications
Electronic Logbook available (on-site or via VPN: http://ttfinfo.desy.de/HERA/logbook/)
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Remaining Operational Issues
• Changes in Operational conditions require painfully long tuning
• There is still not sufficient control to avoid occasional accidental
irradiation of close-to-the-beam detectors by uncontrolled beam loss
or uncontrolled synchrotron radiation in case of a faulty component,
While restrictive interlock systems would affect seriously operational
effectivity
 This needs further work, thought and experience in
routine running
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Beam Current Limitations
p-injection
Beam currents in luminosity operations are limited by
experimental backgrounds and radiation damage considerations
Ip x Ie < 1000 mA2 (extrapolation)
( y2000 value is 5000 mA2; design is 8000 mA2)
100ms/div
Proton –Beam Intensity
• PETRA made steady progress over the last years and has recently accelerated
Design Intensity I=126mA @ 40GeV/c
• Injection and Acceleration Efficiency < 80% due to injection line aperture and HERA
dynamic aperture restrictions
• High proton beam intensity needs some beam conditioning of the cold vacuum
e-Beam Intensity
Intensity is limited at design currents by RF power
vacuum system has not seen much beam current >30mA  needs slow, steady
conditioning
 Besides backgrounds and radiation damage considerations, it should be possible to
collide y2000 beam currents (need to work on it and test)
•
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Experimental Backgrounds
There are four sources of backgrounds, all of which have
been explored by experiments and by simulations
• direct synchrotron radiation: tolerable after tuning
• direct leptons
noticeable contribution for e+ only runs, collimators not
very effective for e+  need condition vacuum
• backscattered synchrotron radiation
shielding needs to be improved
• direct proton background
beam gas scattering close to IP, related to vacuum,
correlation with cold surface, gas composition unclear
Also unclear: what has changed since y2000?
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Workshop on Synchrotron Radiation- and Particle Background in
HERA
July 23-24 2002 at DESY in Hamburg
HERA, the electron proton collider at DESY in Hamburg turned on last year
after a major upgrade of the interaction regions which should give at least a
factor of 3 in luminosity in each of the experiments H1 and ZEUS. While
there where no unusual problems in recommissioning the accelerator, the
background problems have been found more difficult than expected. After
the situation has been analyzed and studied, a point is reached where it
appears to be desirable to review the HERA background problems and
compare them to backgrounds at other accelerators.
For this reason, a short workshop is being organized which will be held at
DESY on July 24-23
Review on HERA Background and Vacuum Issues
October 21-23, 2002
at DESY
Room 459, building 30b
 Report of the Chairman
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HERA Vacuum Tests: What is the influence of the
40K cold Beam pipes in the IR’s?
 Running with increased temperatures of 110K
110K GG Beam pipe
Since October 10
Running with protons
only:
Experimental
backgrounds seem to
be significantly lower
ep Running:
Warmup
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No improvements
seen yet
Vacuum Studies and Plans
•
•
•
Model and Understand Vacuum
around the cold beampipes in the
IR
Understand the production of
Hydrocarbons in IR Vacuum
Increase IR Pumping: Improve
Pumping port conductance and
Install additional Pumps (f.e. cryopumps, Integrated IonP)
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Luminosity
Luminosity Test Data with variable Bunch-Charge and -Number
normalized to nominal Bunch Number =180
Meas.Lumi. scaled to full # of bunches
31
7 10
Luminosity
Design
[1031cm-2sec6-110
]
31
L zeus
Calc. from beam param.
i
H1 Measurements
L H1  1.12  4
4 10
i
31
2002 Goal
ZEUS measurem.
Lc
i
2 102
31
0
0
0
0
7.1210
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0.05
3
0.1
I eb I pb
i
i

mA mA
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0.15
0.2
.23
Accelerator Physics Issues
• Full Understanding of Specific Luminosity beambeam tune shift
• Understanding of Nonlinear Resonances and
synchro-betatron resonances and e-Beam
stability in luminosity state
• Beam Vacuum Interactions in the IR’s
• Proton Dynamic Aperture at Injection
• Proton longitudinal Emittance Preservation
• …
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Beam-beam studies
low intensity luminosity scans
Hor.Lumiscan H1 30.9.02, Fit: S x=154mm
spez. Lumi H1 / 10 30cm -2s -1mA -2
2
using measured beam parameters
Specific Luminosity/1030cm-2sec-1mA-2
calculated from beam parameters
2.40
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
-0.80
-0.60
-0.40
-0.20
0.00
0.20
0.40
0.60
0.80
x / mm
2.24
1.99
1.7
2.44
ZEUS max 30.9.
ZEUS during hor scan
ZEUS during vertical scan
ZEUS scan result
2.11
1.50
1.87
2.22
Vert.LumiscanZeus 30.9.02, Fit: S =36mm
Hor.LumiScan ZEUS 30.9.02, Fit: S=165mm
1.6
2
1.4
1.8
sepz. Lumi bei ZEUS / 1E30
spez. Lumi bei ZEUS / 1E30
H1 max 30.9.
H1 during hor Scan
H1 during vertical scan
H1 scan result
1.2
1
0.8
0.6
0.4
0.2
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
-0.7
-0.5
-0.3
-0.1
x / mm
0.1
0.3
0.5
0
-0.2
-0.1
0
0.1
0.2
z / mm
luminosity measurements from luminosity
scans and calculations in reasonable agreement
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Beam-Beam Tuneshift & Specific Luminosity
e coh. bb tuneshift vs p Bunch current
.05
Measured vs
calculated beam
beam tuneshift
0.04
0.005
D yem
i
0
0.02
D f x,y/kHz
-0.005
-0.01
0
0
-0.015
0
0.011
-0.02
0.02
0.04
D ey
i
.05
-0.025
0
100
200
300
400
500
600
H1 Specific Luminosity vs p Bunch
current, Mess.3/4.Oct02
Ibp/mA
3
-2
1
mA
2
1
-2 30
Lsp/10 cm s
Measured lepton beambeam –tuneshift vs
proton bunch current
0
0
200
400
600
Ipb/mA
Specific luminosity is above design for low and
below design for large proton bunch charge
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e+ Beam-Beam Limit
tune footprint appears to be limited by 3rd & 4th order resonances
H1 and Zeus spec. lumi vs time
beams separated
in South IP
luminosity in the0.35
North increases
Explored Tune Region
Explored Tune Region
0.35
3Qy
qy
qy
0.3
i
0.3
i
R p  q x    m (   N) 
R p  q x    m (   N) 
R m q x    m (   N) 
R m q x    m (   N) 
R x q x   
R x q x   




i
i
i

 0.25



R yq x   

i

i
 0.25
i
i

R yq x   


i

0.2
0.2
.15
.15
0.15
0.15
0.15
0.2
0.25
qx
0.15
0.15
0.3
.35
i
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0.15
0.2
0.25
qx
i
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0.3
.35
Polarization without
ZEUS and H1
solenoids on October
17 2002 measured at
40%
20%
Tpol & Lpol
Polarization
Six tuning steps
1) North &South Rotators flat, Solenoids off
week41/42 ok
2) North & East Rotator on
3)North&South&East Rotator on
4) All Rotators+Solenoids on
postponed to
5) All Rotators+Solenoids, large vertical emittance (3.5nm)
Febr03
6) Polarization during Luminosity operation
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Strategy and Plans
Overall Plan:
Understand the Background Problems,
Prepare Improvements
Shutdown to implement improvements
High Luminosity Running
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Strategy and Plans
Priorities until Shutdown
• Fully understand the present background
problems and develop credible plans for
improvements, prepare the necessary changes
• Demonstrate that HERA can deliver High Luminosity
as planned
• Provide Proton Beam for HERA-B
• Demonstrate longitudinal Polarization for H1, HERMES, ZEUS
• Deliver Beams for HERMES, ZEUS and H1
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HERA Running until the End of the Year02
Deliver Colliding Beams with
20mA of protons in 180 bunches and 30mA of positrons in 190 bunches for
all 4 Experiments
thereby
• Consolidate Operations
• Condition the IR vacuum with beam to verify expected improvements
• Increase continuously the Beam Current to verify background extrapolations
Two days/week of Accelerator physics, Vacuum and Background Studies
per week reserved for dedicated studies
Collaborative, organized effort between Accelerator and experiments
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Schedule (conditional)
02 Oct 1-30
Accelerator Studies
Luminosity and Polarization
02 Oct.30-Dec21
Colliding Beam Operation with increasing
Beam Intensities
Background and Accelerator Studies
as needed up to 2days per week
03 Jan02-Febr28
03 March-June
Colliding Beam Operation
Polarization Studies
Shutdown
03 July
Start-up HERA Run II
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Summary
• HERA has solved its operational problems to a
large extent and is ready to deliver beams
routinely
• The background problems however are only
partially solved and there is yet no final
satisfactory solution
• A major component in the backgrounds is the IR
vacuum and a large effort is underway to provide
more understanding and improvement
• There is a strategy to solve the problems until
March 03, to implement the improvements and
start up HERA for physics running in July 03
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