Alexandr Drozhdin

1
MI-10 Injection
Alexandr Drozhdin
March 16 , 2005
2
Outline

• Painting Injection Parameters
• Injection Scheme
• Results of Simulation
• Stripping Efficiency and Beam Loss
• Conclusions

3
Painting injection parameters
Painting injection is required to realize uniform
density distributions of the beam in the
transverse plane for space charge effect
reduction.
Location MI10
straight section Duration
90 turns (1 msec)
or 270 turns (3 msec) Repetition
rate 0.67 Hz Accumulated
intensity 1.5e14 ppp Injected beam
emittance 1.5 mm-mrad Emittance after painting
40 mm-mrad Beam power 143
KW Injection loss (600 µg/cm) 0.005(nuclear
interaction)
0.004(foil stripping)
0.005(field stripping)20 W
4
Painting injection
Painting injection is perfor- med by using fast
horizontal and vertical magnets. The closed orbit
is moved at the beginning of injection by 21 mm
to the graphite stripping foil. Gradual reduction
of kicker strength permits painting'' the
injected beam across the accelerator
aperture with the required emittance. Vertical
kicker magnets located in the injection line
provide injected beam angle sweeping during
injection time.
5
Painting injection scheme
A stripping foil is located upstream of focusing
quadrupole Q102. That is necessary for
unstrepped component of the beam separation from
the proton beam behind the stripping foil. A
septum-magnet is used to separate the circulating
beam and injected H- at the defocusing quadrupole
Q101 by 135 mm. Horizontal septum-magnet located
behind the stripping foil is used for removal of
unstripped beam to the external beam dump.
6
Circulating beam distribution
Horizontal kicker strength and vertical angle of
injected beam at the foil (top), horizontal
(middle) and vertical (bottom) density
distribution of the circulating beam after
90-turn injection.
7
Particle hits at the foil
Average number of hits upon the stripping foil
for each particle is equal to 4.4. This effects
pretty high level of nuclear interactions and
because of this causes 0.0046 (7 W) of particle
loss at injection. Multiple Coulomb scattering in
the foil and ionisation loss are negligible
small. The increase of painting injection
duration to 270 turns increases an average number
of hits upon the stripping foil to 16, that
increases foil heating and beam loss at
injection.

8
Stripping efficiency
The kicker strength drops fast to 60 of its
maximum during 20 turns, and then slowly
decreases to 50 during another 70 turns.
Stripping foil is located at the exit of kicker
number 2, very close to its edge in the fringe
field of the magnet. The kicker magnet field is
chosen such a way that during injection the
magnetic field provide stripping of Stark states
hydrogen atoms with principal quantum number n5
to protons.
9
Stripping efficiency
This corresponds to kicker maximum field of 0.1T
and length of 0.34 m. At these parameters the
magnetic field during 80 of injection cycle is
in the range of (0.05-0.06)T. The probability of
H- stripping by magnetic field of kicker magnet
during the first turn of injection (B0.1T) is
0.002. It drops to 0.00005 during five turns (B
0.08T). This gives
stripping of 5.e-05 of injected beam (7W) of
power lost in the injection region. An unstripped
part of the beam after interaction with the foil
- the H0 states hydrogen atoms - may be stripped
to protons by magnetic field of other accelerator
elements.
10
Stripping probability of Ho atoms
We assumed here that H- atoms pass a distance of
(1-2)cm in a fringe field of the kicker magnet
number 2. This distance is enough for H0 atoms
with n5 to be stripped. This part goes to
circulating beam without changing emittance of
the beam. Some part of atoms with n4 is left
unstripped and goes to the beam dump, and,
unfortunately, some fraction of them is stripped
along the kicker number 3. These protons
contribute to the circulating beam halo and cause
losses in the collimation system.

11
Experimental Data on H0 yields
Assuming that fraction of yields of different
states n almost does not depend on the foil
thickness and energy, one may expect 97 (n1, 2
and 3) of the total amount of H(o) to end at the
external beam dump, 1 (n4) contribute beam
halo, and 2 go to the circulating beam without
emittance increase. Foil number 3 is used for a
final stripping of atoms (n1-4) behind the
kicker number 3 to reduce field stripping and
losses along the extraction magnet and beam line.
n1, 2 93.3 n3 3.6
n4 1.5 n5
0.7 n6 0.3 ngt6
0.6 total 100
Measurement of H(-), H(o), and H()
yields produced by foil stripping of 800-MeV H(-)
ions, M.S.Gulley, P.B.Keating, H.C.Bryant,
E.P.MacKerrow, W.A.Miller, D.C.Rislove, S.Cohen,
J.B.Donahue, D.H.Fitzgerald, S.C.Frankle,
D.J.Funk, R.L.Hutson, R.J.Macek, M.A.Plum,
N.G.Stanciu, O.B.van Dyck, C.A.Wilkinson,
C.W.Planner, Physical Review A, Volume 53, Number
5, May 1996.
12
CONCLUSIONS
No show stoppers have been found at the painting
injection system simulations. Calculated
stripping efficiency is 99.5. It is shown that
all H0 atoms with ngt4 are stripped to protons and
go to circulating beam without changing
emittance of the beam. Atoms with nlt5 are left
unstripped and end at the beam dump. About 70 of
atoms with n4 are stripped to protons along
the injection kicker number 3. These protons
contribute the circu-lating beam halo and cause
losses (6 W) in the collimation system.
Magnetic field stripping in the kicker causes 7
W loss. Nuclear interactions in the foil cause 7
W loss at injection.