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MICROCOPY RESOLUTION TEST CHART
NATIONAL BUREAU OF STANDARDS -1963
ORNL-P-13575 1
C.ON+-660 120-1
Paper presented and to be published in the Proceedings (limited distri-
bution) of the Symposium on Separated Orbit Cyclotrons and Beam-Cavity
Interactions, Weston-on-the-Green, Oxfordshire, England, July 6-8, 1966.
9-22-66
MASTER
ri
Magnet Development for the 50-MeV SOC* H.C. 3 7.00: 4.50
E. D. Hudson, R. S. Lord, J. E. Mann, and F. E. McDaniel
Oak Ridge National Laboratory
Oak Ridge, Tennessee
We have recently placed a full-scale prototype sector magnet
in test operation. The 50-ton unit constitutes one sector of a proposed
12-sector 10-50 MeV machine. The magnet will be tested first with
eleven sets of AG lenses; this corresponds to a machine in which the
cavity voltage is constant with radius. Later tests will include a system
with fourteen lenses or turns, where the corresponding accelerating
voltage would increase by about a factor of two from minimum to maxi-
mum radius.
The characteristics of the 50-MeV SOC are listed in Table 1.
1
Note that the minimum turn separation is now about 11 inches. The
aperture is 1.5 in. axially by 3 in. radially. The steel weight is 560
tons. The copper weight is 30 tons, and the associated power loss is
120 kW. A beam current of 75 mA requires 3000 kW of rf power along
with 600 kW for the cavity iosses, or a total rf power of 3600 kW.
Details of a pair of pole tips are shown in Fig. 1. This draw-
ing shows a pair of pole tips and how they are attached to the yoke,
the adjustable coupling shims, and the pole tip coils.
*Research sponsored by the U. S. Atomic Energy Commission
under contract with Union Carbide Corporation.

RELEASED FOR ANNOUNCEMENT
IN NUCLEAR SCIENCE ABSTRACTS
To develop information on the variation of cost with tolerances,
price quotations for three levels of machining errors were requested
in the yoke bid package. In going from = 0.005 to + 0.002 in. on the
gap and parallelism of pole mounting surfaces, the cost quotation in-
creased only $2,100 out of $31, 250 or about 7%. Consequently, the
tightest tolerances were selected because it was felt that the relatively
small additional cost would be more than offset by economies in align-
ment procedures. The pole tip costs, in man-hours for 11 sets of tips
with a combined length of 20 ft, are summarized as follows:
Couplers
500
Tape preparation
500
1,000
Contouring gap surfaces
Preparing blank tips
Total
2,000
4,000 man-hours
The 4000 hours should be reduced about 25% to account for develop-
ment, leaving 3000 man-hours to machine 20 ft of pole tip pairs, or
150 man-hours per ft.
The maximum carbon content for the yoke was specified at
0.15% because that was our previous practice. The carbon content in
the yoke as received is 0.06%. This is of some concern to us because
we must consider the probability that the carbon content could be
higher in the steel for a run of production magnets.
The bottom yoke as installed at ORNL, see Fig. 2, was level
to within + 0.001 in. at every point checked, except one point which was
low by 0.002 in. It is interesting, if not surprising, that the 23 in.
thick yoke is flexible enough to be adjusted several thousandths of an
inch (by use of jacks) without affecting other support points. The top
yoke was flat to $ 0.001 in. at all measured points when the center was
supported by a suitable stanchion. The gap varies from 16.003 to
16.004 in. as measured at some 12 places. The deviation of the gap
from the specified 16.000 + 0.002 in. is not considered important.
The completed prototype sector magnet with pole-tip pairs in
place, is shown in Fig. 3. A close-up view, Fig. 4, shows such de-
tails as the yoke, the coupling shim adjustment bolts, the pole tip coils,
and a good view of the alternating-gradient pole-tip gaps. The pole tip
coils shown here are not required for protons, but are used to convert
the field for deuteron operation by making a few hundred gauss change
in the gap fields between minimum and maximum radius. Detailed
measurements of the physical dimensions of the tips and of their mag-
netic properties have not been made; a preliminary check indicates,
however, that the gaps are very close to the design value.
Before the 50-ton yoke was ready preliminary measurements
were made with the full-scale tips mounted in an old magnet yoke. A
constant gradient of 785 G/in. over three inches radial extent was ob-
tained on the 4.5 in. wide poles when the central field was 7000 gauss,
see Fig. 5. This pair of poles has since been checked in its permanent
location on the sector magnet and the gradient is 788 G/in.
The several stages in shaping the pole-tip section are shown in
Fig. 6. From the top curve it is apparent that we did not want to
remove too much metal on the first cut. The remaining curves, cor-
responding to subsequent cuts, illustrate our procedure for arriving
at the final contour. The main portion of the pole contour has remained
unchanged; it has the required hyperbolic surface for a gradient of 800
G/in.
From the magnetization curve for the full-scale sector magnet,
Fig. 7, we obtain an efficiency of 85% at 7000 gauss. When the number
of poles is increased from 11 to 14, the flux density in the yoke will in-
crease by about 14/11 and the efficiency will drop to about 67%.
The variation of field with gap position is shown in Fig. 8. The
250-gauss variation obtained here is somewhat less than was indicated
in our earlier model tests because the flux density in yoke is lower,
correction. Present thinking is that the 250-gauss variation shown on
this slide can be reduced to less than 50 gauss by some redesign of the
coupling shims to provide fixed air gaps. They can then be adjusted to
give a 50 gauss change for each inch of motion, or 2-1/2 gauss per turn
of the positioning bolts.
The distribution of the magnetic field of the pro totype sector
with 11 pairs of pole tips in place is shown in Fig. 9. Note that the
field between adjacent poles increases from less than one kilogauss at
the inside radius to two kilogauss at the outside.
Fig. 10 shows the variation of B, with z at three radial positions
in the gap. These curves illustrate the difficulty of locating the mag-
netic median plane. They also imply that the Hall probe does not have
to be precisely located vertically to obtain 0.01% data.
Summary
The prototype sector magnet is complete and preliminary tests
have established the magnet efficiency and magnet power for the system.
More detailed measurements will establish the effective magnetic length
of the elements, including the effects of the transition region at the
center and the fringing at the ends. The interaction between the fields
in the gaps caused by adjustments of the coupling shims and the pole tip
coils will also be studied. It is expected that the procedures developed
for these magnet tests will be applicable for similar SOC's operating at
higher energies.
LEGAL NOTICE
This report was prepared as an account of Government sponsored work. Neither the United
Suates, nor the Commission, nor any person acting on behalf of the Commiesion:
A. Makes any warranty or representition, expressed or implied, with respect to the accu-
racy, completeness, or uscfulness of the information contained in this report, or that the use
of any information, apparatus, method, or process disclosed in this repori may not Infringe
privately owned rights; or
B. Algumes any liabilities with respect to the use of, or for damages resulting from the
use of any information, apparatus, method, or process disclosed in this report.
As used in the above, “person acting on behalf of the Commission" includes any em-
ployee or contractor of the Commission, or employee of such contractor, to the extent that
such employee or contractor of the Commission, or employee of such contractor prepares,
disseminates, or provides access to any information pursuant to his employment or contract
with the Commission, or his employment with such contractor.
Table 1 - Specifications for the 10-50 MeV SOC
Energy range, MeV
protons
deuterons
alpha particles
Turns
Sectors
10-50
5-35
10-50
14
12
10.6
13,5
131.1
289.0
1.5 in. by 3.0 in.
7000
800
30
.
.
.
.
..
Turn separation, max, in.
Beam radius, min, in.
Beam radius, max, in.
Aperture
Magnetic field, G
Gradient, G/in.
Magnet copper, tons
Magnet steel, tons
Magnet power, kW
Harmonic number
Frequency, MHz
Beam current, mA
Power to beam, kW
Cavity power loss, kW
Total rf power, kW
560
..
.
..
.
120
.....
......
24
.
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.
50
75
3000
600
3600
.
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vs Radius
ORNL-DWG 66-6500
-
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800 gauss/in. REFERENCE
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Produced by Changes in
Fig. 6. Field Changes
-2.0
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DISTANCE FROM Ro (in.)
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FIELD (KG)
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ORNL-DWG 66-6388

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Fig. 7. Magnetization
Curve for 10-50 MeV
SOC
ORNL-DWG 66-6393
GAP FIELD (KG)
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GAP NUMBER
Fig. 8. Magnetic
Field Measured at R
for Each Gap (smooth
curve for reference
only)
ORNL-DWG 66-6394


FIELD (KG)
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RADIUS (in.)
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Fig. 9. Magnetic Field
of the Prototype Sector
With 11 Pairs of Pole
Tips

ORNL-DWG 66-6390
Ro-1.5 in.
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END
DATE FILMED
11 / 29 / 66


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