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Isochronous cyclotron U-120M Status
report Jan Štursa, Milan Cihák, Pavel Bém
Nuclear Physics Institute Academy of Sciences of
the Czech Republic p. r. i. Rež near Prague
Czech Republic
SSF workshop, Aghios Nikolaos, Crete, Greece, 7th
- 8th of September, 2007
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Layout of the cyclotron U-120M
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Beam parameters
ion E MeV Imax mA
p (internal beam) p (external beam) H- (external beam) 1038 1025 1038 100 5 4015
d (internal beam) d (external beam) D- (external beam) 1020 1020 1020 80 5 2510
3He (internal beam) 3He (external beam) 1753 1753 20 2
a (internal beam) a (external beam) 2040 2040 40 5
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Cyclotron U-120M
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Cyclotron conversion into H-, D- accelerator

• Status
• high intensive internal beam currents of p, D
• Limitations
• low extraction efficiency of the 4-section
  deflection electrostatic system (max. 35, max.
  external currents 5mA)
• Goal
• high intensive external p, D beams (tens of mA)
• possibility of external targets installation
  (fast neutron generation, liquid and gaseous
  targets for radioisotopes production)
• Solution
• conversion of the U-120M into negative machine
  p-, D-
• employment of high effective beam extraction by
  means of the stripping method
• project and realization of a new beam line

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New internal PIG ion source with a cold cathode
Effective production both positive and negative
ions, material Mo Optimisation arc volume
geometry, extraction slit dimensions, plasma gap
width, gas flow, cathode heat transfer,
cathode life time ( 800hours), H- DC current
2.0mA
Operation 200hours gas 3He2
Operation 800hours gas H2, D2
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Central region optimisation shape of the puller
electrode, mutual positions of the puller and ion
source extraction slit, minimisation of vertical
and radial oscillations, parasitic p, D
beams New water cooled puller made of Mo
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Upgrade of the cyclotron vacuum system
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Parameters of the cyclotron vacuum system
H- beam transmission for the different
combination of diffusion pumps in operation
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Stripping method of H-/D- extraction
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• Floods in August 2002
• technological cyclotron subsystems were located
  in the basement
• water level up to 1.5m, in some rooms up to 2.3m
• serious damage of the following cyclotron
  subsystems
• high current power supplies for the cyclotron
  magnetic system
• (main coil, 20 correction and harmonic coils)
• high voltage power supplies for the RF generator
  output cascade
• (anode voltage, screen grid voltage, AC
  stabilizer etc.)
• power supplies for cyclotron ion source
• more than twenty high current power supplies for
  the quadrupoles,
• bending and correction magnets of the beam line
  system
• primary pump of the cyclotron and beam line
  vacuum system incl. valves
• cooling system of the cyclotron
• all electric distribution frames and panel
  switchboards
• etc.

All flooded power supplies and equipments were
replaced by the new ones. (The main suppliers
F.u.G. Rosenheim, Germany Walker LDJ, USA) This
upgrade resulted in considerable increase of the
beam stability.
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View on the bridge crossing the Vltava river
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Cyclotron operation time in 1999 - 2006
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Experiments Research Development

• Mathematical simulations of accelerated beam
  properties
• Fast neutron generation
• Development of target systems for medical
  radionuclides
• Research and developement of cyclotron based
• radiopharmaceuticals
• Nuclear astrophysics experiments (talk of V.
  Kroha)

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Mathematical simulations
Magnetic field
The magnetic field topography in the cyclotron
median plane is computed for any required
accelerating regime. The results of the
formerly accomplished magnetic measurements are
processed to obtain satisfactory accuracy.
The fields of harmonic coils are included in
calculations as well.
Electrostatic field
The electrostatic field of given cyclotron
central part and duant structure is computed
using the RELAX 3-dimensional method. Fine mesh
with the step 0.25mm was used for the injection
region and more coarse one with step 1.0 mm was
used for the rest parts.
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Ion trajectory simulations
The trajectories of particular ions or beams
with initial parameters and selected accelerating
regime are computed using relativistic equations
of motion in 3-dimensional space. The ordinary
beam properties are computed and graphically
presented. Off-line model is used for tuning of
any accelerating regime including the beam
centering before the set up of real cyclotron
parameters.
Ion beam extraction by the stripping method
The trajectories of negative ions are computed
after stripping on the carbon foil. The
transport of the beam to various target
positions is thus possible. The properties of
extracted beam are computed as well.
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Accelerated beam properties
Regime HM_32_9.MeV (H- ions, final energy 32.9MeV)
Initial ion conditions at the ion source slit (4
x 1.5mm2)

• phase range related to RF phase
• (-40o,40o), step 10o
• starting energy 50eV

• vert. ion pos. z (-2.0, 2.0), step 1mm
• horizont. ion pos. dr (-1.0, 0.0), step 0.5mm
• vertical angle (-15o, 15o), step 5o

Phase of accelerated ions at various radii
Vertical ion positions at various radii
Transmission from the 1st to the final orbit
(491.8mm) 73.6 (accelerated 313 from 567 ions)
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Calculated properties ofthe H- beam (32MeV) at
the stripping foil radius (490mm)
Cross section 26mm2 Radial emitance 214
mm.mrad Azimuthal emitance 25 mm.mrad (at 80
of the beam)
beam cross section r-z ion distribution
radial emitance r-r ion distribution
vertical emitance z-z ion distribution
Corresponding beam density plots
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Calculated properties ofthe H- beam (32MeV) at
the entry to the quadrupole triplet
ion energy radial spread percentage ion
distribution
beam cross section y-z ion distribution
horizontalemitance y-y ion distribution
vertical emitance z-z ion distribution
Corresponding beam density plots
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Heavy water target up to 20 µA of proton
beam (18-37 MeV) from H(-) mode, high
beam-current stability to simulate the the
spectrum D2O(p,xn) source reaction
incident energy 37 MeV, thick D2O target,
investigated for the first time the
zero-degree spectral yield demonstrates ? mean
energy 13.9 MeV ? energy range up
to 33.0 MeV? angular FWHM lt 40
degree ? integral yield 9
x1011n/sr/s/µA ? flux
5 x1010 n/cm2/s (5 mm distance from the
target)Suitable for tests of detectors and
devices with fast neutrons
NPI cyclotron U-120M as fast neutron source
D2O neutron target station
Simulated neutron spectrum

• Be target is also available. Beam
• parameters are similar to D2O.
• Quasimonochromatic neutrons
• are also produced in 7Li(p,n) reaction.

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Internal target system
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Monitoring of the beam distribution on the target
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Internal target holder for production of 211At
Radius 48.6cm
Radius 49.6cm
Radial beam energy distribution for 30.3 MeV a
particles
Thick target yield is equal to theoretical
maximum available, i.e. ca 400 MBq/mA, while
keeping 210At/211At ratio below 10-3
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Universal gas targets for production of 81Rb and
123I
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Solid target for production of 86Y, 124I
The system includes integrated collimator water
cooling and automated control via pressurized
nitrogen
The target itself is located inside of the
evacuated chamber. Its design has to meet the
needs the given radionuclide production.
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Production of radionuclides current status
Position 3 68Zn(p,2n)67Ga 203Tl(p,3n)201Tl 112Cd(
p,2n)111In 209Bi(p,2n)208Po 209Bi(a,2n)211At
Position 2 liquid target H218O, 18O(p,n)18F, PET
studies gaseous target, production of 81Rb/81mKr
generator gaseous target, production 123I
targets for production noncommercial
radionuclides 124I, 86Y, 230U