Investigation of using the crystalline target in channeling mode for beam collimation in the LHC
Channeling collimation discussion issues
description
Transcript of Channeling collimation discussion issues
Channeling collimation discussion issues
Dick Carrigan
Fermilab
9th LARP Collaboration Meeting
October 17 - 19, 2007Stanford Linear Accelerator Center
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Tevatron channeling projectsE853 – parasitic extraction done in mid nineties –
originally in connection with SSCmost successful, maybe only successful SSC activity
Politics and operational challenges:funding, schedule, demise of SSCtunnel access
Technical challenges:alignment/goniometerhow to drive parasitic extraction – Peggs, …stability of loss monitors
Channeling collimation 2005 – presentations by Mokhov, Stilldirected toward LHCimportant successes – confirms RHIC, shows collimation
Operational challenge: running time
Technical challenges;alignment/goniometerstability of loss monitors
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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)
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E853 history and goalsHistory – 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
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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
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First crystal extraction at the Tevatron C0 straight section June 6, 1995 (kick mode)
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E853 ExperienceBad:• 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
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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
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Crystal Angle vs displacement at E03H
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Crystal Angle vs displacement at E03H
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Collimator scans for different crystal angles-Mokhov
ChannelChannel
ReflectionsReflections
ScatterScatter•Channeled beam produces a shoulder 7 + 0.8 mm from the coreChanneled beam produces a shoulder 7 + 0.8 mm from the core•The channeled beam should have been ~10.5 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.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 But on 1/10/2006, after moving the crystal 10mm, new data proved there was no aperture limit. was no aperture limit. Measured deflection ~ 325 Measured deflection ~ 325 μμrad, not 440 rad, not 440 μμradrad..
Beam probe w/out crystal
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E03 data fitted and differentiated
Channeling peak is > 50% of deflected beam. Remainder dechanneling? Sigma is twice critical angle, some due to beam divergence.
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EO3H (mm)
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500 400 300 200angle (μrad)
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Comments for the discussion paper
• Instrumentation
• Studies/Experiment
• Simulation/theory needs
Radiation damage for some other time
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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, …,
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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
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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
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Comments?
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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/