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

Channeling at Fermilab, 1977

Drift chambers for K -- e experiment at 250 GeV

Solving cross-talk problem

Continuum potential energy for protons channeled in the (110) planes of Si. D. S. Gemmel, Reviews of Modern Physics, 46 (1974) 129.

What will happen with channeled particles if we bend the crystal?

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:”

The paper was rejected by Phys. Rev. Lett. 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.

Channeling at Dubna synchrophasotron 8.4 GeV protons

CERN COURIER, September 1977:

Goniometer

Si crystal, semiconductor detector and bending device

Ionization losses in Si crystal random direction (110) plane aligned

Beam deflection in bent silicon crystal low ionization all particles

Beam deflection in bent silicon crystal

Effect was lost after 12 mrad bending!

Beam deflection in bent silicon crystal

BEAM EXTRACTION: FIRST EXPERIMENT

Schematics of beam extraction from synchrophasotron

4.2 GeV Rcr = R0 - 300 mm

Beam extracted! 4.2 GeV Rcr = R0 - 250 mm

More beam extracted! 4.2 GeV Rcr = R0 - 200 mm

bent crystal extraction is proved! (1984) 7.5 GeV bent crystal extraction is proved! (1984) Rcr = R0 - 175 mm

Double Crystal Halo Extraction Efficient Crystal Scraper

Crystal mirror concept

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.

Impact parameter for different crystal mirrors SC2: a - silicon, b - tungsten.

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.”

thank you for your attention!