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DESIGN AND SHIELDING OF A BEAM LINE FROM ELENA TO ATRAP
USING ELECTROSTATIC QUADRUPOLE LENSES AND BENDS*
Yosuke Yuri,
Takasaki Advanced Radiation Research Institute, Japan Atomic Energy Agency,
1233 Watanuki-machi, Takasaki, Gunma, 370-1292, Japan.
Edward Lee,
Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California, 94720, USA.
Abstract
The construction of the Extra Low ENergy Antiprotons
(ELENA) upgrade to the Antiproton Decelerator (AD)
ring has been proposed at CERN to produce a greatly
increased current of low-energy antiprotons for various
experiments including anti-hydrogen studies. This
upgrade involves the addition of a small storage ring and
electrostatic beam lines. The 5.3-MeV antiproton beams
from AD are decelerated down to 100 keV in the compact
ring and transported to each experimental apparatus. In
this paper, we describe an electrostatic beam line from the
ELENA ring to the ATRAP experimental apparatus and
magnetic shielding of the low-energy beam line against
the ATRAP superconducting solenoid magnet. A possible
rough conceptual design of this system is displayed.
INTRODUCTION
The Antiproton Decelerator (AD) has been providing
slow antiprotons of 5.3 MeV for various experiments,
ATRAP, ALPHA, ASACUSA, etc. at CERN since 2000.
However, the antiproton utilization efficiency is very low
since many are lost in the process of the deceleration for
the experiments. Recently, an upgrade of AD has been
proposed for more efficient experiments using low-energy
_ -_ --- __ - ------ - -- _
1 .
ELENA - 2 J. P
one 2
i bi
Antiproton Decelerator
~ .
Figure 1: Schematic view of the layout of AD,
ELENA, two ATRAP experimental zones, and their
beam lines.
* This work was performed under the auspices of the U.S. Department
of Enerev Contract No. DE-AC02-O5CH11231.
antiprotons [1, 2]. The project, called Extra Low ENergy
Antiprotons (ELENA), includes the construction of a
small storage ring equipped with an electron cooling
device for the further deceleration of antiprotons from 5.3
MeV to 100 keV and for lower emittance, and the
renovation of the transport line of the low-energy
antiproton beams to each experimental apparatus, as
shown in Fig. 1.
In this paper, we describe an electrostatic beam line
from the ELENA ring to the ATRAP experimental
apparatus and magnetic shielding of the low-energy beam
line against the ATRAP superconducting solenoid magnet.
A possible conceptual design of this system is displayed.
LOW-ENERGY BEAM TRANSPORT LINE
The present transport line of 5.3-MeV antiproton beams
(Bp = 0.33 Tm) from AD to ATRAP is composed of
quadrupole and dipole bending magnets. An electrostatic
beam line is desirable for a compact system since the
magnetic transport system is less efficient for 100-keV
beams (Bp = 0.046 Tm). In addition, the emittance of the
beam will be lowered (designed normalized emittance: Sr
mm mrad) by the electron cooling system installed in the
ELENA ring. To prevent a blow-up of the emittance
during the transport, the lattice should be periodic and
kept at as low phase advance as possible.
According to these requirements, a possible beam
optics was designed. The main specifications of the beam
line are listed in Table 1. The focusing lattice period is
composed of the electrostatic quadrupole FODO doublet.
Its phase advances per 1-m lattice period can be set at 60
degrees in the two transverse directions by applying the
voltage of 2.9 kV at the quadrupole rods. The beta
Table 1: Main specifications of
electrostatic beam line.
the designed
Magnetic rigidity of 100-keV antiprotons 0.046 Tm
Normalized emittance (95%) [1] 57r mm mrad
Length of the focusing period 1.0 m
Axial length of the quadrupole 0.12 m
Bore radius of the quadrupole 40 mm
Voltage amplitude the quadrupole 2.9 kV
Phase advance per period 60 deg.
Bending radius of the vertical deflection 0.19 m
