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.
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A QWL quadrupole
Length = 2.948 m
BL = 58 Tm/m
Field at pole tip = 0.98 T
Aperture diameter = 100 mm
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In the SL/EA group several different types of QUADs are in
use. Please find below some data on some of these types:
| Type | Max.BL [T] | B at tip [kG] |
Length [m] | Aperture Ø[mm] | Imax [A] |
R (mOhm) | DC/pulsed |
| QNL | 80.8 | 10.8 | 2.99 | 80 | 500 |
240.0 | - |
| QTL | 80.8 | 10.8 | 2.99 | 80 | 500 |
276.0 | - |
| QTS | 39.9 | 10.7 | 1.49 | 80 | 500 |
120.0 | - |
| QNR | 105 | 10.5 | 2.99 | 60 | 350 | ? |
- |
| QTR | 126 | 11.2 | 2.99 | 52 | 310 | ? |
- |
| QWL | 58 | 9.8 | 2.948 | 100 | 500 |
200.0 | - |
| QSL | 56 | 9.3 | 3.0 | 100 | 1000 |
130.0 | DC only |
| QPL | 22.4 | 11.2 | 2.0 | 200 | 750 |
205.0 | DC only |
| QPS | 12.2 | 12.2 | 1.0 | 200 | 750 |
205.0 | DC only |
| QFS | 15.7 | 9.8 | 0.8 | 100 | 500 |
63.5 | - |
| QDS | 16.3 | 9.04 | 0.82 | 91 | 500 |
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.
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