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Title: Permanent-magnet quadrupoles in RFQ Linacs

Abstract

We investigated the possibility of increasing the current-carrying capability of radio-frequency quadrupole (RFQ) linear accelerators by adding permanentmagnet quadrupole (PMQ) focusing to the existing transverse focusing provided by the rf electric field. Increased transverse focusing would also allow shortening RFQ linacs by permitting a larger accelerating gradient, which is normally accompanied by an undesirable increased transverse rf defocusing effect. We found that PMQs were not helpful in increasing the transverse focusing strength in an RFQ. This conclusion was reached after some particle tracing simulations and some analytical calculations. In our parameter regime, the addition of the magnets increases the betatron frequency but does not result in improved focusing because the increased flutter more than offsets the gain from the increased betatron frequency.

Authors:
;
Publication Date:
Research Org.:
Los Alamos National Laboratory, Los Alamos, NM
OSTI Identifier:
6189509
Report Number(s):
CONF-850504-
Journal ID: CODEN: IETNA; TRN: 86-004320
Resource Type:
Conference
Resource Relation:
Journal Name: IEEE Trans. Nucl. Sci.; (United States); Journal Volume: NS-32:5; Conference: Particle accelerator conference, Vancouver, Canada, 13 May 1985
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; QUADRUPOLE LINACS; BEAM FOCUSING MAGNETS; PERMANENT MAGNETS; BEAM DYNAMICS; BEAM TRANSPORT; BETATRON OSCILLATIONS; FEASIBILITY STUDIES; RF SYSTEMS; ACCELERATORS; ELECTRICAL EQUIPMENT; ELECTROMAGNETS; EQUIPMENT; LINEAR ACCELERATORS; MAGNETS; OSCILLATIONS; 430303* - Particle Accelerators- Experimental Facilities & Equipment

Citation Formats

Lysenko, W.P., and Wang, T.F.. Permanent-magnet quadrupoles in RFQ Linacs. United States: N. p., 1985. Web.
Lysenko, W.P., & Wang, T.F.. Permanent-magnet quadrupoles in RFQ Linacs. United States.
Lysenko, W.P., and Wang, T.F.. 1985. "Permanent-magnet quadrupoles in RFQ Linacs". United States. doi:.
@article{osti_6189509,
title = {Permanent-magnet quadrupoles in RFQ Linacs},
author = {Lysenko, W.P. and Wang, T.F.},
abstractNote = {We investigated the possibility of increasing the current-carrying capability of radio-frequency quadrupole (RFQ) linear accelerators by adding permanentmagnet quadrupole (PMQ) focusing to the existing transverse focusing provided by the rf electric field. Increased transverse focusing would also allow shortening RFQ linacs by permitting a larger accelerating gradient, which is normally accompanied by an undesirable increased transverse rf defocusing effect. We found that PMQs were not helpful in increasing the transverse focusing strength in an RFQ. This conclusion was reached after some particle tracing simulations and some analytical calculations. In our parameter regime, the addition of the magnets increases the betatron frequency but does not result in improved focusing because the increased flutter more than offsets the gain from the increased betatron frequency.},
doi = {},
journal = {IEEE Trans. Nucl. Sci.; (United States)},
number = ,
volume = NS-32:5,
place = {United States},
year = 1985,
month =
}

Conference:
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  • We investigated the possibility of increasing the current-carrying capability of radio-frequency quadrupole (RFQ) linear accelerators by adding permanent-magnet quadrupole (PMQ) focusing to the existing transverse focusing provided by the rf electric field. Increased transverse focusing would also allow shortening RFQ linacs by permitting a larger accelerating gradient, which is normally accomplished by an undesirable increased transverse rf defocusing effect. We found that PMQs were not helpful in increasing the transverse focusing strength in an RFQ. This conclusion was reached after some particle tracing simulations and some analytical calculations. In our parameter regime, the addition of the magnets increases the betatronmore » frequency but does not result in improved focusing because the increased flutter more than offsets the gain from the increased betatron frequency.« less
  • We plan to increase the peak luminosity of the Cornell Electron Storage Ring by providing tighter vertical focussing at the interaction points. The final focussing devices will be large permanent magnet quadrupoles operating inside the 10-15 kG solenoidal field of the experimental detector. We present the results of tests demonstrating that quadrupoles with the required field quality and resistance to demagnetization can be built from commercially available Rare Earth Cobalt magnets.
  • The current trend toward higher frequencies to power drift-tube linacs (DTLs) and coupled-cavity linacs (CCLs) reduces the space available for quadrupole focusing magnets. Similarly, the space available for matching sections between linac sections is limited, and often the matching section bunchers are designed in odd shapes to make them fit. This shaping further restricts focusing magnet space. One approach to attaining sufficient quadrupole strength is such situations is to use rare-earth permanent-magnet quadrupoles (PMQs) with cross sections tailored to fill as much of the available space as possible. In this paper, we describe some techniques we have developed to calculatemore » the properties of such magnets both singly and when other magnets are nearby. 3 refs., 4 figs.« less
  • Hybrid Permanent Magnet Quadrupoles are used in several applications for the Fermilab Recycler Ring and associated beam transfer lines. Most of these magnets use a 0.6096 m long iron shell and provide integrated gradients up to 1.4 T-m/m with an iron pole tip radius of 41.6 mm. A 58.4 mm pole radius design is also required. Bricks of 25. 4 mm thick strontium ferrite supply the flux to the back of the pole to produce the desired gradients (0.6 to 2.75 T/m). For temperature compensation, Ni-Fe alloy strips are interspersed between ferrite bricks to subtract flux in a temperature dependentmore » fashion. Adjustments of the permeance of each pole using iron between the pole and the flux return shell permits the matching of pole potentials. Magnetic potentials of the poles are adjusted to the desired value to achieve the prescribed strength and field uniformity based on rotating coil harmonic measurements. Procurement, fabrication, pole potential adjustment, and measured fields will be reported.« less
  • The proposed Next Linear Collider (NLC) will require over 1400 adjustable quadrupoles between the main linacs' accelerator structures. These 12.7 mm bore quadrupoles will have a range of integrated strength from 0.6 to 132 Tesla, with a maximum gradient of 135 Tesla per meter, an adjustment range of +0-20% and effective lengths from 324 mm to 972 mm. The magnetic center must remain stable to within 1 micrometer during the 20% adjustment. In an effort to reduce estimated costs and increase reliability, several designs using hybrid permanent magnets have been developed. All magnets have iron poles and use either Samariummore » Cobalt or Neodymium Iron to provide the magnetic fields. Two prototypes use rotating rods containing permanent magnetic material to vary the gradient. Gradient changes of 20% and center shifts of less than 20 microns have been measured. These data are compared to an equivalent electromagnet prototype.« less