Low momentum antiproton flux enhancement in the LESB Page: 3 of 7
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For both methods 1 and 2, multiple scattering is a large factor, thus
a low Z material, carbon, was used. Nuclear absorption was approximately
70% in degrading from 700 MeV/c to 450 MeV/c.
3. Degrading at the production target has five advantages:
a. The target and degrader are in focus so multiple Coulomb scattering
is minimized except in that it tends to smear out the angular distri-
bution of secondary particles - a dense, high Z material of short
length along the beam direction assures good optics,
b. since the LESB uses a 10.50 production angle and the angular distri-
bution of secondary particles is sharply peaked at smaller angles,
it is likely that multiple Coulomb scattering will lead to more
antiprotons scattered into the beam acceptance than scattered out,
c. tertiary production in the degrader may lead to a further enhancement
of the antiproton flux,
d. the antiprotons are fully momentum analyzed in the beam,
e. the degraded flux can be optimized by moving the degrader transverse
to the primary proton beam.
A hevimet target-degrader sketched in Fig. 2 was employed. Anti-
proton flux was optimized by moving the beam laterally across the target.
The "C" station 900 monitor was recalibrated with the new target by
putting the entire slowly extracted beam on the "C" target and normalizing
to the SEB secondary emission chamber.
Results of degrading in each of the three ways discussed above are
plotted in Fig. 3 with the curve of Carroll, et. al. The latter curve
was obtained with a 4-in. Cu target, whereas we used platinum and hevimet
which are expected to yield a larger flux. The curve also
was obtained with a momentum acceptance of *1%. In our case, the momentum
slits were fully open to ~ t2%.
It is clear that degrading at the target produces a large increase
in low momentum antiproton flux and gives a significant yield below 500 MeV/c,
thereby extending the momentum range available to experiment with anti-
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Lovett, B.; Mishina, M.; Nakano, I.; Snyder, J.; Zeller, M.E. & Lazarus, D. Low momentum antiproton flux enhancement in the LESB, report, December 28, 1974; Upton, New York. (https://digital.library.unt.edu/ark:/67531/metadc1020945/m1/3/: accessed April 23, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.