Quadrupole magnets

A QUADrupole is a magnetic lense. Its purpose is to focus the beam in one of the principal planes. Contrary to an optical lense (which focusses normally in both planes), a quadrupole focusses in one plane but defocusses in the other.

A QWL quadrupole

Length = 2.948 m
BL = 58 Tm/m
Field at pole tip = 0.98 T
Aperture diameter = 100 mm

In the SL/EA group several different types of QUADs are in use. Please find below some data on some of these types:

TypeMax.BL [T]B at tip [kG] Length [m]Aperture Ø[mm]Imax [A] R (mOhm)DC/pulsed
QNL80.810.82.9980500 240.0-
QTL80.810.82.9980500 276.0-
QTS39.910.71.4980500 120.0-
QNR10510.52.9960350? -
QTR12611.22.9952310? -
QWL589.82.948100500 200.0-
QSL569.33.01001000 130.0DC only
QPL22.411.22.0200750 205.0DC only
QPS12.212.21.0200750 205.0DC only
QFS15.79.80.8100500 63.5-
QDS16.39.040.8291500 62.0-

Quadrupoles can play different roles according to the optics chosen. As an example, in the X5 beam we see the following quadrupole functions:

  • Acceptance quadrupoles: Q1 and Q2 refocus particles produced in the production target to collect as many secondaries/tertiaries as possible and to refocus them on the momentum slit, where the beam momentum is defined.
  • Final focus quadrupoles: Q4 and Q5 focus the beam on the experimental apparatus, with a view to minimise the beam spot.
  • Field lense: Q3 serves to eliminate any remnant dispersion (correlation between position and momentum of the beam particles) after the final bend.