Transcript Channeling collimation discussion issues

Channeling collimation discussion issues
Dick Carrigan
Fermilab
9th LARP Collaboration Meeting
October 17 - 19, 2007
Stanford Linear Accelerator Center
Tevatron channeling projects
E853 – parasitic extraction done in mid nineties –
originally in connection with SSC
most successful, maybe only successful SSC activity
Politics and operational challenges:
funding, schedule, demise of SSC
tunnel access
Technical challenges:
alignment/goniometer
how to drive parasitic extraction – Peggs, …
stability of loss monitors
Channeling collimation 2005 – presentations by Mokhov, Still
directed toward LHC
important successes – confirms RHIC, shows collimation
Operational challenge:
running time
Technical challenges;
alignment/goniometer
stability of loss monitors
D. Carrigan
LARP CM9 Oct. 17-19,2007 SLAC
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E853 Crystal Extraction at the
Tevatron
see Carrigan, Mokhov, et al., Phys. Rev. ST Accel. Beams
AB 1, 022801 (1998)
http://prstab.aps.org/abstract/PRSTAB/v1/i2/e022801
Carrigan, Mokhov, et al., Phys. Rev. ST. Accel. Beams,
AB 5, 043501 (2002)
http://prst-ab.aps.org/abstract/PRSTAB/v5/i4/e043501
(see these for collaborators)
D. Carrigan
LARP CM9 Oct. 17-19,2007 SLAC
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E853 history and goals
History – In early 1990s, proposal for an SSC fixed
target B flavor experiment. Crystal proposed for
extraction. E853 given $100K to test at Tevatron. Used
existing C0 dump – not needed at 900 GeV. A location
with more dispersion would have helped longitudinal
noise excitation
Goals
•Extract 106 protons/s with 1012 circulating
•Study extraction efficiency
•Show luminosity lifetime not affected
•Investigate background at CDF and D0
D. Carrigan
LARP CM9 Oct. 17-19,2007 SLAC
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E853 Successes
•Extracted significant beams from the Tevatron
parasitic, kicked and RF stimulated
•First ever luminosity-driven extraction
•Highest energy channeling ever (until recent
Tevatron collimation studies)
•Useful collimation studies
•Extensive information on
time-dependent behavior
•Very robust
D. Carrigan
LARP CM9 Oct. 17-19,2007 SLAC
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First crystal extraction at the Tevatron C0
straight section June 6, 1995 (kick mode)
D. Carrigan
LARP CM9 Oct. 17-19,2007 SLAC
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E853 Experience
Bad:
•
•
•
•
Interaction counters very sensitive to beam motion <background?>
“Extracted” beams in the 108 - 109 regime need special instrumentation
Beam halo behavior is often non-linear
Lattice location important (RHIC – difficult, Tevatron extraction, collimation
better but imperfect)
Good:
• Crystal extraction works well, robust
• Extraction in diffusion modes means crystal collimation can work
• Multiple pass works, can take bigger goniometer steps
Neutral:
• Large variety of time dependent behavior
D. Carrigan
LARP CM9 Oct. 17-19,2007 SLAC
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Channeling collimation studies at the
Fermilab Tevatron
Dean Still, Jerry Anala, Todd Johnson,
Robert Reilly, Dwayne Plant, Dick
Carrigan, Sasha Drozhdin, Ray Fliller,
Nikolai Mokhov, and Vladimir Shiltzev
Fermilab
D. Carrigan
LARP CM9 Oct. 17-19,2007 SLAC
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Collimator scans for different crystal angles-Mokhov
Channel
•Channeled beam produces a shoulder 7 + 0.8 mm from the core
•The channeled beam should have been ~10.5 mm from the core.
•First data set suggested the channeled beam was hitting an aperture.
•But on 1/10/2006, after moving the crystal 10mm, new data proved there
was no aperture limit. Measured deflection ~ 325 μrad, not 440 μrad.
Scatter
Reflections
Crystal Angle vs displacement at E03H
2
1.8
Loss on LE033 (volts)
1.6
118 urad
1.4
343 urad
1.2
520 urad
1
806 urad
0.8
238 urad
0.6
out
0.4
0.2
0
-10
-8
-6
-4
E03H collimator position (mm)
-2
0
Beam probe w/out crystal
9
E03 data fitted and differentiated
3.5
angle (μrad)
500
400
300
200
Channeling peak
is > 50% of
deflected beam.
Remainder
dechanneling?
Sigma is twice
critical angle,
some due to beam
divergence.
100
3
LE033 yield
2.5
2
1.5
1
0.5
0
-10
-8
-6
-4
-2
0
2
EO3H (mm)
D. Carrigan
LARP CM9 Oct. 17-19,2007 SLAC
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Comments for the discussion paper
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•
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Instrumentation
Studies/Experiment
Simulation/theory needs
Radiation damage for some other time
D. Carrigan
LARP CM9 Oct. 17-19,2007 SLAC
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Instrumentation
• What does single particle instrumentation
mean?
• Need for Roman pots
• Reducing “background” in the BLMs. What
is “background?”
• Reducing fluctuations
• Goniometer – need for redundancy,
linearity, angular range, …,
D. Carrigan
LARP CM9 Oct. 17-19,2007 SLAC
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Studies/Experiment
• What is experiment plan (see draft of
“Discussion Document”)
O shaped vs strip crystal
• Strengthening the collimation results
• Speeding up measurements, particularly
alignment
• Should experiment also mirror LHC needs?
• Fundamental aligned crystal questions
for example - demonstrate that whole arc
processes (volume reflection) kicks in
opposite direction from channeled
D. Carrigan
LARP CM9 Oct. 17-19,2007 SLAC
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Simulation/theory needs
• What simulation is needed of alignment
curves with crystal bend, length
• Simulation of collimator withdrawal curves
• Simple parameterization of bend, crystal
length
D. Carrigan
LARP CM9 Oct. 17-19,2007 SLAC
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Comments?
D. Carrigan
LARP CM9 Oct. 17-19,2007 SLAC
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For more accelerator channeling information see:
Fermilab - Dean Still’s site:
http://www-bdnew.fnal.gov/tevatron/projects/crystal_collimator/index.htm
Fermilab channeling home:
http://home.fnal.gov/~carrigan/Channeling/Channeling_master.htm
Fermilab - Channeling Formulary:
http://home.fnal.gov/~carrigan/Channeling/Channeling_formulary.htm
Other sites
CERN:
http://www.fe.infn.it/%7Efiorini/
Serpukhov:
http://crystalbeam.narod.ru/
D. Carrigan
LARP CM9 Oct. 17-19,2007 SLAC
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