Historical%20Perspective

1
Historical Perspective and First Experiments
with Bent Crystals E. Tsyganov The University
of Texas Southwestern Medical Center at
Dallas and Joint Institute for Nuclear Research,
Dubna March 7, 2005
2
(No Transcript)
3
Channeling at Fermilab, 1977
4
Drift chambers for K -- e experiment at 250
GeV
5
Solving cross-talk problem
6
Continuum potential energy for protons channeled
in the (110) planes of Si. D. S. Gemmel, Reviews
of Modern Physics, 46 (1974) 129.
7
What will happen with channeled particles if we
bend the crystal?
8
(No Transcript)
9
Quotation What will happen with the trajectory
of the channeled particles if we bend the
crystal? Up to some critical value of the
bending radius a particle trajectory will repeat
the shape of a bent crystal. This unexpected
phenomenon caused by the fact that the particle
in this case gradually goes to high electric
field of the atoms. It then starts to be bent in
the direction of the crystal bending. A stabile
trajectory in this case goes away from the
potential minimum, in the region where electrical
fields are strong enough to create the necessary
transverse acceleration. The critical radius of
bending is given by the following expression
10
6 - MEMBER SCIENTIFIC PANEL HELD AT
FERMILAB (including Prof. D. S. Gemmel from
Argonne National Laboratory) REJECTED PROPOSAL
TO DEFLECT HIGH ENERGY BEAM USING
BENT CRYSTAL The paper was rejected by Phys.
Rev. Lett. Prof. Alexis A. Maraddudin from UC
Irving proved that the paper is scientific
absurd, silly, unintelligent, bizarre proposal.
11
Channeling at Dubna synchrophasotron 8.4 GeV
protons
12
CERN COURIER, September 1977
13
Goniometer
14
Si crystal, semiconductor detector and bending
device
15
Ionization losses in Si crystal
(110) plane aligned
random direction
16
Beam deflection in bent silicon crystal
low ionization
all particles
17
Beam deflection in bent silicon crystal
18
Effect was lost after 12 mrad bending!
19
Beam deflection in bent silicon crystal
20
(No Transcript)
21
BEAM EXTRACTION FIRST EXPERIMENT
22
Schematics of beam extraction from
synchrophasotron
23
4.2 GeV
Rcr R0 - 300 mm
24
Beam extracted!
4.2 GeV
Rcr R0 - 250 mm
25
More beam extracted!
4.2 GeV
Rcr R0 - 200 mm
26
7.5 GeV
bent crystal extraction is proved! (1984)
Rcr R0 - 175 mm
27
(No Transcript)
28
(No Transcript)
29
Double Crystal Halo Extraction Efficient Crystal
Scraper
30
(No Transcript)
31
(No Transcript)
32
Crystal mirror concept
33
Angular distributions of outgoing particles for
the cases when the tungsten crystal planes (110)
are tilted (a) by 0 mrad, (b) by 8.5 mrad, (c) by
12.75 mrad, and (d) by 68 mrad relative to the
direction of an incident 900 GeV-protons.
Thickness of the crystal is 24 mm.
34
Impact parameter for different crystal mirrors
SC2 a - silicon, b - tungsten.
35
Quotation The device is suitable for cleaning
up the proton beam halo (a clean crystal
scraper), or for useful extraction of the proton
beam halo particles with a 99 efficiency. When
it is used as a clean scraper, it could work as
an efficient clean radiation drain preventing
radiation due to a proton beam loss that now is
spreading around the Tevatron. The device is
suitable to be used at the LHC collider for both
circulating proton beams. It could reduce the
background radiation due to a beam halo loss by a
factor of about 100.
36

• thank you for your attention!