N-H Nuclear Instruments and Methods in Physics Research B 119 (1996) 23 I-238 ELSEVIER First results from bent crystal extraction at the Fermilab Tevatron CT. Murphy a’ * , R. Carrigan a, D. Chen a, G. Jackso? a, N. Mokhov a, H.-J. Shih b, B. Cox ‘, V. Golovatyuk ‘, A. McManus ‘, A. Bogacz a, D. Cline ‘, S. Ramachandran ‘, J. Rhoades d, J. Rosenzweig d, B. Newberger e, J.A. Ellison f, S. Baker g, C.R. Sun h, W. Gabella i, E. Tsyganov j, A. Taratin k, A. Asseev I, V. Biryukov ‘, A. Khanzadeev m, T. Prokofieva m, V. Samsonov m, G. Solodov m NOM B Beam Interactions with Ysterials 6 Atoms a Fermilab, Batavia, IL. USA b Superconducting Super Collider Laboratory, Dallas, TX. USA ’ The University of Virginia, Charlottesville. VA, USA ’ The University of California at Los Angeles, Los Angeles, CA. USA ’ The University of Texas, Austin. TX, USA ’ The University of New Mexico, Albuquerque, NM. USA g Argonne National Laboratory, Argonne, IL, USA ’ State University of New York, Albany. NY, USA i Vanderbilt University, Nashville. TN, USA ’ Southwestern Medical Center, University of Texas at Dallas, Dallas, TX, USA k Joint Institute for Nuclear Research. Dubna, Russia ’ Institute for High Energy Physics, Serpukhov. Russia m Petersburg Nuclear Physics Institute. Gatchina. Russia Received 3 January 1996; revised form received 21 June 1996 Abstract First results from Fermilab Experiment 853 are presented. E853 is an experiment to test the feasibility and efficiency of extracting a low-intensity beam from the halo of the Tevatron using channeling in a bent silicon crystal. The motivation of the experiment is to apply crystal extraction to trans-TeV accelerators iike the LHC. Extensive simulation work has been carried out. Two accelerator operating modes have been developed for crystal studies, “kick” mode and diffusion mode. Results from the first successful extraction in kick mode are presented. 1. Introduction Protons have already been extracted with bent crystals from the circulating beams at Dubna, Serpukhov, and the SPS at CERN. Experiment 853 extends these experiments by seeking to obtain significant parasitically extracted beam at 900 GeV in a superconducting accelerator. With 10” protons circulating, the goals of E853 are to extract IO6 protons/s and show that: 1) the luminosity lifetime is not seriously shortened; 2) the crystal can be aligned to the beam quickly; 3) no intolerable backgrounds are created at the collider experiments; 4) diffusion created by some kind of perturbation creates halo with an adequate step size, or ’ Corresponding author. Tel.: + 1 630 840 3150; fax: + 1 630 840 2950; e-mail: [email protected]. jump, to clear the edge region of the crystal (called the “septum”), where it would be bent by only part of the total bend angle of the crystal. E853 is also investigating the relative contributions of first-turn extraction and “multi-pass” extraction, the latter resulting from particles which encounter the crystal on the first turn but are not channeled, and then return to be channeled on some successive turn. The major goal of the experiment is to measure the extraction efficiency in the diffusion mode. The original motivation for this experiment was to test a proposal that a beam of 10’ protons/s be extracted from the SSC for a fixed target B-physics experiment. The new equipment for this experiment was funded by the SSC. Despite the demise of the SSC, the experiment remains of interest as a step towards possible applications at both LHC and Fermilab. 0168-583X/%/$15.00 Copyright 0 1996 Elsevier Science B.V. All rights reserved PII SO1 68-583X(96)00356-4232 C.T. Murphy et al./Nucl. Insrr. andbleth. in Phys. Res. B 119 (1996) 231-238 FERMILAB E853 CRYSTAL EXTRACTION CO LONG STRAIGHT SECTIOS MONITORS QUADRUPOLES -- EXTRACTED TEVATRON Fig. 1. Schematic of the beam line around the Tevatron CO region. The crystal bends up out of the page into the field-free region of the Lambenson magnet chain (see inset). 2. Beamline E853 is taking place in the CO straight section of the Tevatron, the normal location of the proton abort line. The abort line consists of a magnetic dogleg that provides a 4 mrad horizontal kick so the abort line can clear the mag- nets at the downstream end of the long straight section. The middle bend in the dogleg consists of a series of Lambertson magnets. A series of four vertical kicker mag- nets are used to abort the beam into the field-free region of the Lambertsons. During collider runs, the abort line is not used at 900 GeV, so one of the kicker magnets has been replaced by a bent crystal. A sketch of the beamline geometry of the Tevatron Collider crystal extraction system is shown in Fig. 1. Protons in the halo of the beam distribution which inter- cept the bent crystal with the correct angle are deflected by 640 prad upward into the field-free hole in the Lambert- sons (see inset, Fig. 1). Protons in the field free region travel straight into the Tevatron abort line toward the extracted beam detectors. The crystal is mounted at the upstream end of a 1 m beam pipe which ends with articulating bellows. Two precision motors (x,y) at each end of the pipe allow for the alignment of the crystal with four degrees of freedom. The most critical parameter is the alignment of the vertical angle of the crystal with the beam angle, which must be done to within 10 prad to match the critical angle of the crystal with the beam angle. Therefore, motors were se- lected such that the least step in angle changes was 2.5 prad. Fig. 2 shows the core of the beam with respect to the crystal. Schematically, beam is “pumped” from the outer edge of the