STARTING UP OF A CYCLOTRON WITH A WIDE VARIATION IN THE MAGNETIC FIELD INTENSITY

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP80T00246A008500370002-6
• Release Decision: RIPPUB
• Original Classification: U
• Document Page Count: 7
• Document Creation Date: December 22, 2016
• Document Release Date: August 7, 2009
• Sequence Number: 2
• Publication Date: November 24, 1959
• Content Type: REPORT

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V ._
Joint Institute for Nuclear Research
Laboratory of Nuclear Problems
Starting Up of a Cyclotron with a Wide Variation
TAT
In the Magnetic Field Intensity
D. P. Vasilevskaya, A. A. Glazov, V. I. Danilov, U. N. Denisov
V. P. Dzhelepov, V. P. Dmitrievsky, B. I. Zamolodnikov
N. L. Zaplatin, V. V. Kolga, A. A. Kropin, Liu Nai-Chang
V. C. Ribalko, A. L. Savenkov, L. A. Sarkisian
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Starting Up of a Cyclotron with a Wide Variation
In the Magnetic Field Intensity
In January, 1959 in the Laboratory of Nuclear Problems of the Joint
Institute for Nuclear Research in Dubna, a cyclic accelerator of new design
was started which has a periodic pattern of the magnetic field both azimuthally
and radially. The diameter of the magnet is 1200 mm. The line of constant flux
of the magnetic field is bent according to Archimedes spiral1 r = 16. 2 99 (cm),
the periodicity of the magnetic field pattern being N = 6.
The mean value of the magnetic flux increases along the radius in
accordance with the relativistic increase in the mass of the accelerated ion. As
the acceleration starts at the center of the magnet, the frequency of the free
oscillations vary accordingly from Qz = 0, Qr = 1 at r = 0 to Qz = 0. 2, Qr = 1.01
at r = 52 cm. The operating point moves in the stable area, never crossing the
line of the corresponding resonance frequencies. An exception to this is the non-
linear resonance effect in the center of the magnet (Qr = 1). This effect was
studied in detail in 1958 on a model whose magnetic field had a periodic pattern
with N = 4. The radial step of this pattern was 2 = 8. 72 cm, and the line
of constant field was bent according to the spiral r = 5. 41P cm.
It was shown theoretically that the required increase of the mean value of
the magnetic flux along the radius necessary for the removal of the nonlinear
resonance effect in the center of the accelerator decreases with an increase in
N and with
2N 1)!
an increase of the radial step (with a fixed N) a 7~ 1 N-2
2
Since the development of the non-linear resonance effect at Qz = 1 is
N, hence in the order of the non-linear resonance; as
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dependent on the displacement of the center of the instantaneous orbits relative
to the center of the magnetic field, it was decided that studies of the conditions
for vertical stability in displaced orbits should be made. As a result of these
studies, it was established that in order to avoid producing changes in the
character of the vertical oscillations, the displacement of the centers of the
instantaneous orbits should not exceed*. Similar requirements are necessary
for small deviations of the period of particle revolution on the displaced orbit
from the resonance value.
The results of these studies were put to use when choosing the parameters
for the above indicated six-spiral pattern of magnetic field in which the non-
linear resonance in the center of the accelerator was not observed. The
necessary variation in the magnetic field was achieved with the help of iron
shims of perpendicular transverse section. The configuration for optimum
dimensions of the shims, which quarantee the necessary depth of variation in
intensity of the magnetic field, was based on the assumption of complete mag-
n etic saturation of the shims. The increase in the intensity of the center of
the magnetic field along the radius corresponding to the necessary constancy
in the revolution frequency of the ion, was accomplished xilh the help of thin
cylindrical shims, which were considered when the as.-irnptu.on of uni`orill
magnetizaticn was made For the removal of the influt.n,-e -! the simple and
parametric resonance (Q.1, - t) a shimming of the firs' .t:c: sc cond hai rnoni_ in
the pattern of the magnetic field was performed with tit!' of syytnn.etric?ally
placed cylinders of small dia.netert (8 min. ). All tI-,t? tti ,..rt,trer,ts ,)f the
-.nagrietic field intensity were p#'rfornied )r nta~ uto 3.cc,; racy
t t
1
. 5 oersted 2 . The c unst.tnc t ' the magneti el:? n t , r . , ; . I t > ? 11 ~ = t 1 v inc d
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by a nuclear stabilizer3.
For accelerating the ions, a resonant quarter wave system with one dee
was used. The feeding of the resonant system was accomplished by a generator
with a separate excitation, making available an accelerating voltage of up to 40 KV.
On this cyclotron, deutrons were accelerated up to 12 Mev in energy, and
alpha particles up to 24 Mev with a minimum amplitude of the accelerating
voltage on the dee of 8 KV. The measurement of the energies of the accelerated
particles on the maximum radius of 52 cm. was performed in two ways.
a. Measurement of the center of curvature of the orbit by means of
three probes.
b. Measurement of the passing of the deutrons through an aluminum
foil.
All measurements were performed at beam intensities of^-/-ka; as a result of
which there was no noticeable increase in activity on the interior of the chamber.
In Fig. 1 are shown autoradiographs of the beam at different radii of the
accelerator. A general view of the accelerator is shown in Fig. 2. The results
of the experiments performed indicate the feasability of a relativistic proton
cyclotron at energies which can only be achieved at present with a synchbphasatron.
Papers Submitted to the Publishing Department, April 11, 195*
Literature.
1. D. W. Kerst, K. M. Terwilliger, K. R. Symon, L. W. Jones, Bull. Amer.
Phys. Soc. 30, I (1955).
2. U. N. Denisov. Universal Nuclear Magnetometer. PTE No. 5, 1958.
3. U. N. Denisov. Magnetic field Stabilizer, Based on Nuclear Induction
PTC No. 1, 1959.
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Publishing Dept., Joint Institue of Nuclear Research, May, 1959.
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