. : L OF ORNL P 2358 itoni { : MICROCOPY RESOLUTION TEST CHART NATIONAL BUREAU OF STANDARDS -1963 !!77215? ORRL-P. 2358's Cont660720-2 Paper presented and to be published in the Proceedings (limited distribu- tion) of the Symposium on Separated Orbit Cyclotrons and Beam-Cavity Interactions, Weston-on-the-Green, Oxfordshire, England, July 6-8, 1966. H.C. $ 1.00:4.50 The 4-MeV Experimental soC--Design Details** E. D. Hudson, J. E. Mann, J. A. Martin, F. E. McDaniel, S. W. Mosko, E. G. Richardson, Jr., R. E. Worsham, and N. F. Ziegler Oak Ridge National Laboratory RELEASED FOR ANNOUNCEMENT Oak Ridge, Tennessee IN NUCLEAR SCIENCE ABSTRACTS The details of the beam dynamics in the 4-MeV experimental Soc have been discussed previously. This paper describes some of the novel de sign features of the accelerator, The 4-MeV SOC will be a multi-particle variable energy, accelerator, providing protons in the energy range 1.0 to 4.0 MeV, deu- terons from 1.7 to 4.0 MeV, and 3 He ions from 2. 7 to 8 MeV. Variable energy is accomplished by varying the magnetic field to provide reso- nance at the chosen harmonic number. The injector system for the SOC is a 250-ke V Cockcroft-Walton followed by a variable energy linear accelerator. The principal specifications of the machine are listed in Table 1. There are six sector magnets and the beam makes four turns. The overall diameter is 22 ft. The turn separation varies from 17. 8 in. at injection to 11. 8 in. at final energy. The six magnets contain a total of 44 tons of steel and 1.5 tons of copper; they will require 40 kW of power when accelerating protons to 4 MeV. T'he arrangement of the accelerator is shown in Fig. 1. *Research sponsored by the U. S. Atomic Energy Commission under contract with Union Carbide Corporation. The machine will be assembled and tested in the ORIC annex; Fig. 2 is a recent photo of the area in which the inachine will be located. Near the center, the full-scale prototype sector magnet for the 10-50 MeV SOC is now under test. The 4-MeV SOC will be located in the corner of the building opposite the rf amplifier, as shown in Fig. 3. Molecular hydrogen ions will probably be used for most tests, limiting the radiation problem to that of 2-MeV protons. Magnet System The magnet system for the 4-MeV SOC de parts radically from previous concepts. Magnetic focusing is "constant gradient" as in a weak focusing synchrotron but, as a result of the large circumference factor, the focusing is quite strong. To permit use of the simplified fabrication method described below, all pole tips are of constant radius. The magnetic field strength varies linearly with momentum, from 3.5 kG at injection to 7.0 kG at extraction for 4.0 MeV protons. The field index, n, is nearly constant, ranging from 0.58 to 0.52. The n value varies in steps with turns through the machine; all magnets on the first turn are n=0.58, on the second n=0.56, etc. The details of . -- -rro one sector magnet are shown in Fig. 4. Each pole tip has an individual excitation coil, with the number of turns in each pole-tip coil pair chosen to approximate the correct field. An adjustment winding, with a separate current supply, will be used to set the field exactly for each pole-tip pair. The magiet design readily lends itself to mass production tech- niques. A 360° ring of tips can be machined as a single operation with a boring mill. A pair of identical rings will be assembled as a urit by ai-siswa- tee:- . n*** (Rak.. * ***** A welding stainless steel rings at the inner and outer radii. To rninimize warpage, a very shallow weld will be used. The pole-tip assembly also serves as the vacuum chamber; suitable fittings will be provided at the erds to couple to the beam pipe. The small grooves in the side walls will be used to guide a field measuring plate. A Hall probe will be mounted on the plate at the radius to be measured and the plate will be moved azimuthally in one-degree steps by a precision indexing device. The machining of a prototype magnet ring is shown in Fig. 5. A one-quarter scale model of a single sector, Fig. 6, has been used for some preliminary measurements of ampere-turn requirements and pole tip interactions. It is necessary to evaluate the interaction among the four pole tip pairs of a sector to establish the ampere-turn requirements for the trimming coil system, and to permit exact calcu- lation of the correction currents. Typical interaction data for both 50% and 100% yoke geometries are tabulated in Table 2. These measurements were made with fields in the magnet gaps at the values required in accelerating protons to 4 Mev. With a 100% yoke, a 100-gauss increase in the magnetic field of gap 4 (the highest field gap) is accompanied by field decreases of 7. 3, 4.0, and 2. O gauss in gaps 3, 2, and 1, respec- tively. These results suggest that interaction is not a serious problem, but must be taken into account. Measurements of end effects on a short full-scale pole-tip model indicate that the effective edge of a magnet extends approximately 0.67 gap lengths beyond the end of the pole tins. RF System The accelerating system employs six coaxial resonators, such as shown in Fig. 7. A resonator consists of a quarter-wave resonant strip transmission line with four drift tubes mounted at the appropriate positions for the four turns. The outer shell of the resonator is of 1/2 in. thick copper-clad steel, with appropriate stiffeners. The ground- plane drift tubes can be moved to change ihe accelerating gaps and hence to control the energy gain of the particles by changing the transit time factor. These "tuning'' adjustments may be made without disturbing the accelerator vacuurn. The gap spacings and center conductor drift space length are 0.20 B1 and 0. 18 B, respectively for full energy proton opera- tion (32r.d harmonic). The gap widths vary from 3 in. at injection to 6 in. at final energy. The six resonators are nearly identical, differing only in location of drift tubes and width of gaps. The design of the reso- nators eliminates the requirements for precise dimensions in nearly all the areas that influence the frequency or gap voltage. Each cavity is provided with a trimming capacitor to adjust the resonant frequency. The six resonators will be excited individually, each power ampli- fier ?mploying an Eimac 4CW10,000A tetrode which is capable of deliver- ing about 14 kW of rf power at 50 MHz. As each resonator will require only 3 kW for excitation, these units will be capable of delivering enough power for a 20-mA beam. The initial installation, using an existing plate power supply, will be limited to 2-3 mA of beam at full energy. Later on, with a larger power supply, we shall be able to exploit the full power amplifier capability. Phase and voltage stabilization will be provided for each of the six resonator-power-amplifier systems. The amplitude and phase cf the resonator voltages will be adjustable, both individually and as a group. Injection The injector must possess unusual flexibility to match the variable- energy multi-particle capability of the SOC. This is provided by a system · - . consisting of several independent resonators much like the 400-keV to 1-MeV unit shuwn in Fig. 8. As in the soc resonators, the gaps and the center-stem drift-space lengths are 0.2 and 0. 18 B, respectively. Each resonator is driven by a separate power amplifier so that the voltage and phase of each unit may be adjusted independently. The power ampli- fiers will be identical to the six units used in the SOC. It is estimated that the rf excitation power for each resonator will be about 4 kW. The energy gain per cavity, in the unit illustrated, is 200 keV at a synchro- nous phase angle of -30° with 128-kV peak on the center electrode. Transverse focusing is provided by conventional quadrupoles external to the vacuum system. Injectiosi into the linear accelerator will be at 250 kV for maximum energy proton acceleration. A low current ~ 3-mA 250-kV Cockcroft-Walton has recently been made available at no cost. This will be used initially and be replaced later with one of higher capa- city. Both the dc accelerator and the linac will be mounted on a platform above the soc. Conclusion We believe that many of the features of the design of the 4-MeV experimental SOC will prove useful in larger machines, especially the magnet fabrication methods which can be readily adapted to doublet or triplet lens systems. We are also confident that the 4-MeV machine will be a very useful device for studying control and adjustment systems and beam dynamics problems. It will provide a vehicle for the study of a wide range of new ideas at relatively low cost. The design of many of the components is already well underway. If no unforeseen procurement difficulties arise, we expect to have the machine in operation in 12 to 15 months. Table ! - Specifications for the 1-4 MeV Soc A a 11.8 Energy range, MeV protons 1.0-4,0 deuterons 1.9.4.0 alpha particles 3. 4-8.0 3 He ions 2.7-8.0 Sectors Turns Turn separation, min, in. Turn separation, max, in. 17.8 Beam radius, min, in. 62.0 Beam radius, max, in. 115.2 Aperture, in. 1.5 by 3.0 Magnetic field, G 3300-6500 Gradient, G/in. 100-200 : agnet coppe:, tons 1.5 dscagnet steel, tons Magnet power, kW Harmonic number Frequency, MHZ Peak cavity voltage, kV (for 40-MeV protons) 83, 4 Beam current, ma Power to beam, kW Cavity power loss, kW Total rf power, kW 32 LEGAL NOTICE This report mo prepared us uo account of Government sponsored work, Neltbar to United sain, por the Commusloo, dor any person acting on behalf of the Comminlar: A. Makes any warranty or representation, expressed or implied, with rent lo the socy. ray, completeach, or wefulness of the information contained to this report, or that the more of any information, apparatus, morbod, or process declared to we mport may not betrage printsly owned righus; or B. Assines may Uadillues with respect to the use of, or for dennego rurality from the un of any information, apparatus, method, or process declared in this report. As und in the sbore, "person acttag on behalf of the Comminator" lacladus my IN- plogue or contractor of Abe Commission, or employee of such contractor, to the extent that scd er loyvo or contructor of the Commission, or employee of much contractor preparne, dissowntos, or provides access to, may information permuant to do employment or contract will be commissiou, or Me empioyment with mica contractor. པ་ ORNL-DWG 66-6671 -- 2g t -- ་ - [ འ་ཤ--4---བཟས་པ - - - - -- - བམ •， -- -- - འབཟཁམསཟཟབ ཁ• • -- • - - - 3 - Mev : •བཟ•བཟཟཀཟཟབཟཟ•E * * * * * ••ཟབབ.: 4f * * * ཁབ༌ • --བཟཟe=པཟསཟs ་བ བ པཟཟཟཐབ ་ . • 4 Mev p+ - - Fig. 1. Plan view of 1-4 Mev soc. TE. , | . ' ་ ་་ FEY. یم و به 1 * * * * او . به ". .: "" " : جهان ieم، با ما * با ایاز اه اه . .. مالية - . مد . .. و .... ... .. : ها حال * ه و . و از .. ..... 1 . | با اما و و کم و جم اعم - | جار و با ! ما " . ، " ' ا ور . ۱۰ ون * بل اوسط * * * م . * لا 2 مم . م وم : - - ا ا ان / ا T و - . می 8 مه 4 . : م * و کر مه نم د ماه ,هدیه وامه گ میں .. LIF و - . مه اور . " * - | " را || . .. ہے مج : و F1 11 - ای در بد و " است . . با . ۴ و مو ..په ووه 1 هوا نطا امها ج ا ام ابيه" " او |. ا 1 * . گر **و ان اکاب اله با مام و . : . بو ،، مام ه کی و نیز الم الورد 8•8-02-013-10R - .......... SI xx, TEST MAGNET .............. h. .. SO MOV soc PROTOTYPE MAGNET ...... ...... .. : - ----- - - - - - - - - - - -- - - - - - - - - - 50 MOV SOC PROTOTYPE CAVITY POLARIZED PROTON ION SOURCE DEVELOPMENT AREA SO MOV SOC PROTOTYPE POWER AMPLIFIER Fig. 3. Floor plan of ORIC annex, showing proposed location of 1-4 MeV SOC. ORNL-DWG 66-6518 21 inl. :DDD YOKE == = = -- .--- - - - -- - -- - - - - - - -- 88/4 in. ---- 10/2 in. 3211/16 in. X .-. * . · is . VIEW A-A 0 1 2 :- : 3 4 5 S INCHES 0 10 20 30 INCHES Fig. 4. A sector magnet for the 1-4 MeV SOC. . USL. : $ . . $ .- - - - r s WA 2 . 9 N 'T . NO . V HT 1 LA ..7 202 جدی نی ! . . .. در امور . . م ..." " . . = " ۹ نمر : -لم . + . دار و - ا ا د و "" . . . - |- | 44 : . : . ا اما . " ۴ . ون و یا -- | لماه يم . م اور ه . . ا .؟ و : و . . : " : ا ل -: . . ها جا علم | | :: . . ندا مابینت امام * . " 1 ابی .. * | | ولا || * S - ا } : له * " " . : * أ هم و با ما را ما ريم به لها : لا لا ، اور : : .ا | " بسم الله | . k! ء ء م م » * خ : مو " تین 1 T . " , ان " 1 ح ا داره * م ا .و IT م . . . . .. 13 Table 2 - Magnet Gap Interactions ORNL-DWG 66-6532 Change in Gap (gauss) Coil Number Coil Pair Turns Coju pats - Change in Gap jausele 50% Yoke 100 -12. 2 -7.2 -5.3 -9.7 100 17.5 11.5 -2 -17.8 100 -18.2 -3.9 -9.3 -17. 100 100% Yoke 100 -4.5 -3.6 - 2.0 -5.5 -5.1 100 -6.8 -7.7 100 -4.0 -7.3 -5.4 -7.2 100 .... 26.170 Q0 ГЕННЕН HHH 20 | 53.745 DIMENSIONS ARE IN INCHES 72 - ==------ -----::-:- -::- - C . Ei 12 ---------- ----- ------ - - - Fig. 7. RF cavity for 1-4 MeV SOC. ORNL-DWG 66-4652 QUADRUPOLE „-TUNER 400-keV TO 4-MeV BEAM- نننننننننننننننن CENTER CONDUCTOR- I . oo 5 100 20 400-MeV BEAM S . ...--- t eder hele er .. ...... demand manier . .. . ! . . id 27 in. ..- Variable Energy Linear Accelerator. Fig. 8. Variable ne energy linear accelera- tor with coaxial cavities . SA o * . AL 3 . END DATE FILMED 11 / 25 / 66 : - AN WWW L LLLL WINN Li...