Particle production for a muon storage ring: I. Targetry and pi/mu yield Page: 3 of 6
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Results of a detailed optimization of the particle yield Y are presented be-
low, in most cases for a sum of the numbers of r and of a given sign and
energy interval at a fixed distance z=9 m from the target. It turns out, that
for proton energies Ep from a few GeV to about 30 GeV, the shape of the
low energy spectrum of such a sum is energy-independent and peaks around
E=130 MeV, where E is r/p kinetic energy (Fig. 2). Moreover, the sum is
practically independent of z at z >9 m -confirming a good matching and
capturing with a growing number of muons and proportionally decreasing
number of pions along the decay channel. For the given parameters the inter-
val of 30 MeV<E<230 MeV around the spectrum maximum is considered as
the one to be captured by a phase rotation system.
" Hg, n +p*
0-0Hg, z +p 16 GeV on Hg +
0.30 R = 2.5G = 5 mm
6 0.2 0.28
0.0 8 12 16 20 24 0 50 100 150 200
Proton energy (GeV) Tilt angle (mrad)
Fig. 3. Yield from Hg and C targets vs Ep (left) and yield from a Hg target at
Ep=16 GeV vs tilt angle (right).
The yield Y grows with the proton energy Ep, is almost material-independent
at low energies and grows with target A at high energies, being almost a factor
of two higher for Hg than for C at Ep=16-30 GeV (Fig. 3). To avoid absorption
of spiraling pions by target material, the target and beam are tilted by an angle
a with respect to the solenoid axis. The yield is higher by 10-30% for the tilted
target. For a short Hg target, a=150 mrad seems to be the optimum (Fig. 3),
while a=50 mrad is chosen in Ref.  for a long C target to locate a primary
beam dump at -6 m from the target. Fig. 4 shows the dependence of the yield
on Hg and C target radii under the baseline RT = 2.5u,,y condition. Figs. 4
and 5 show that maximum yield occurs at target radius RT=7.5 mm for C and
RT=5 mm for Hg targets with RT = 3.5u,,y and RT = 4u,,y conditions for
the beam spot size, respectively. The baseline criterion RT = 2.5u,,y reduces
the yield by about 10% for the graphite target, but is more optimal from the
energy deposition point of view (Fig. 5).
The ratio of Hg to C yields varies with the beam energy, as well as with other
beam/target parameters. At 16 GeV it is in the range of 1.5-1.7 for positives
and 1.7-2.2 for negatives. Optimizing beam/target parameters, it is found that
the best results for the particle yield in the decay channel at 16 GeV with the
given cut are: Y,++N+ = 0.182 and Y,-+,- = 0.153 for the 80-cm C target and
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Mokhov, Nikolai V. Particle production for a muon storage ring: I. Targetry and pi/mu yield, article, September 14, 2000; Batavia, Illinois. (digital.library.unt.edu/ark:/67531/metadc720301/m1/3/: accessed September 23, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.