Specification of a new electron cooler for the low energy ion ...

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that of the injected ion beam. Moreover, the
strong longitudinal magnetic field in the gun
would give rise to a large deflection of the ion
beam in the toroid region, which would require
strong dipoles for the correction. The field after
expansion will be 750 G giving an expansion factor
of 3 and an orbit deflection in the toroids of about
15 mrad. A further extension of the expansion
could be to reduce the electron beam diameter
during the cooling process in order to be at the
maximum of the cooling force always.
In the toroidal bend a set of electrostatic plates
will be installed in order to improve the electron
beam collection efficiency. The superimposed
electric and magnetic fields completely compensate
the drift that the electrons usually acquire when
passing through the toroid. Therefore, reflected
and secondary electrons will not be lost as they
oscillate between the gun and collector, but instead
they will have the possibility to be reaccelerated
towards the collector. Initial tests made by INP
Novosibirsk [7] show that the loss rate DI/I can be
reduced to below 10 5 thus improving the vacuum
conditions in the drift section.
3.3. The drift section
The drift section, where the electrons and ions
are merged, will be 2.5 m in length. This is the
maximum space available for cooling after all the
correction elements (dipoles and anti-solenoids)
have been inserted into the straight section where
the cooler will be installed. Two electrostatic pickups,
capable of measuring both the electron beam
and ion beam trajectory in the drift section, will be
placed at the entrance and exit of this section.
Along with 10 electron beam steering coils it will
be possible to perfectly align the two beams for
optimum cooling.
Non-evaporable getter (NEG) strips will be
placed along the whole length of the drift section
between the vacuum chamber and a potential
continuity grid of 140 mm diameter. Activated
during the bake-out, these NEG pumps will ensure
that the vacuum level in the cooling section is as
low as possible during operations with ion beams.
ARTICLE IN PRESS
G. Tranquille / Nuclear Instruments and Methods in Physics Research A 532 (2004) 399–402
3.4. The electron beam collector
Efficient collection of the primary electron beam
is essential if an excessive load on the main highvoltage
power supply is to be avoided. The
collector for the LEIR cooler is designed to collect
electrons with relative current losses less than
10 4 . Combined with the electrostatic bend (see
Section 3.2) these losses can be further reduced by
one order of magnitude.
4. Conclusions
The main parameters of the LEIR electron
cooler have been determined and the construction
phase should soon commence. Building on the
experience of our Pb ion run in 1997 and recent
developments in electron cooling technology, the
new cooler should meet the requirements for ion
beam cooling and accumulation for the LHC. We
will keepa close eye on the cooling tests at IMP
Lanzhou [8], expected in 2004, in order to make
final adjustments such that the new device will be
fully commissioned for the second half of 2005
when the LEIR machine should come online.
References
[1] M. Chanel, Nucl. Instr. and Meth. A, (2004) these
Proceedings.
[2] J. Bosser, et al., Experimental investigation of electron
cooling and stacking of lead ions in a low energy
accumulation ring, Particle Accelerators, 63 171, 1999.
[3] G. Tranquille (on behalf of the AD team), Nucl. Instr. and
Meth. A, (2004) these Proceedings.
[4] J. Bosser, I. Meshkov, G. Tranquille, Magnetised electron
beam cooling time for heavy ions, Internal report CERN/
PS/AR Note 94–11, 1997.
[5] I. Meshkov, A. Sodorin, Nucl. Instr. and Meth. A, (2004)
these Proceedings.
[6] A.V. Ivanov, V.V. Parkhomchuk, B.N. Sukhina, M.A.
Tiunov, The hollow electron beam. The new opportunities
in electron cooling, Proceedings of the Workshopon Beam
Cooling and Related Topics, Bad-Honnef, May 13–18,
2001.
[7] V. Parkhomchuk, private communication.
[8] A. Bubley, Nucl. Instr. and Meth. A, (2004) these
Proceedings.