A 0. 5 to 3. 0 MeV monoenergetic positron beam Page: 1 of 3
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BNL-41953
A 0.5 to 3.0 NeV MUNUENERGETIC POSITRON BE-AM
H. Iluomo1*, P. AsokaKumkr2, S.D. lienderson3, B.P. Phlips3, R. Mayer,
J. -llonoug h3, I. Hacker , S. McCorkle , P. Schnitzenbaumer,
J.S. Greenberg3, M.S. Lubell2, K.G. Lynn1 and A. Vehanen
1Illroukhaiven Nat Lonai. Laboratory1 Upton, NY 1 1973
2City College of New York, NY 10031
3WNSL, Yale University, New Haven, CT 06511
BNL--41953
DE89 004531AbstraLt
An adjusLab le, 0.5 to 3 MeV aonuener-
gftLe positrvn beam has been constructed at
Broukhaven. Currently a 22Na source with a
W(100) foUi transmission moderator produces
a 1.1 ktm FWIM beaa with an intensity of
3x105 eIsev at a target located downstream
from the accelerator. The divergence of
the beam is less than 0.10 at 2.2 MeV ener-
gy. A S0A gun with 2 I.ens transport system
brings the beam to a focus at the entrance
of an elect ros tat ic 3 MeV Dynamit ron accel-
erator. '11 post aiceleration beam trans-
porL systems comprises 3 focusing solenoids,
4 sets of steering magnets and a 90* double
focusing bend ing magnet. The bean energy
.premad at the target is (1 keV FlIL1 deduced
Croc tike baema sire. below we descrLbe the
positrow extraction opt ics and accelera-
tion, the unnstruct ion of the beamline and
the beam diagnostic devices. The salient
beam parameters are listed at the end of
this paper.
POSITRON EXTRACTION OPTICS
The positron beam is generated using a
70 mCi 22Na source capsule (fabricated by
NEN) in a Lransmssion geometry with a
6000 A thick l(100) single crystal modera-
tor foil1 as shown in figure 1. The posi-
trons. are extracted with a modified SUA gun
followed by a 65 cm long two lens element
transport system, which injects a 400 eV
beam through the 4 mm entrance aperture of
tie main accelerator. le have also
installed a set of steering plates into the
transport system to guide the beam. The
aperture and the transport lens system also
serve as a passive filter reducing the con-
tribution of the unmoderated positron by a
factor of 10. This is the essential step
to obtain a highly monoenergetic beam.2 Na source
Moderator
Source Grad
WchnelL
SOA Tube Anode
I Transpor-
i LensesApertur
/1
Figure 1. The positron extraction optics,
which consists of a modified SOA gun
followed b' a 65 cm long two lens
trans sASTE R
WST8IBUTION OF TilS DOCUMENT IS UNI
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Huomo, H.; AsokaKumar, P.; Henderson, S. D.; Phlips, B. F.; Mayer, R.; McDonough, J. et al. A 0. 5 to 3. 0 MeV monoenergetic positron beam, article, 1988~; Upton, New York. (https://digital.library.unt.edu/ark:/67531/metadc1185562/m1/1/: accessed May 29, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.