Design objectives are proposed for a continuous beam 2 GeV electron accelerator. Various accelerator concepts are examined in light of these requirements. A double-sided microtron shows promise for yielding major savings in capital cost and excellent beam characteristics

Cho, Y.

Holt, R.J.

Jackson, H.E.

Khoe, T.K.

Mavrogenes, G.

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ri *DESIGN OBJECTIVES FOR A GeV C.W. ELECTRON ACCELERATORbyY. Cho, R.J. Holt, H.E. Jackson, T.K. Khoe, and G. Mavrogeres-DISCLAIMER -This book W K prepared as an account of work sponsored by an agency ol the Un led Stales Government.Neither the United States Go*«nmer>l nor any agency thereof, nor any of their employees, makes anywarranty, express or im i i lM, o> ammes any legal lidbilitv or responsibility ' o r t f w *xur*cy,cuTnpleienen, or usefulness ot any information, apparatus, product, or process diKlOMd. orr«prt>*>nls that i l i 'i-& would not infringe privately Owned tights. Reference Herein la any specificcommercial product, procets, or service by tradd name. 1'«Jemjrt, manufaclurv. Of olherwiw, Ooe*not nccessrity consiiiuie or imply its endorsement, recommendation, or *-voring by itie UnitedSlates Gov«rvnent or any agency thereof. The views and opinions ot authors eKtvsaed herein do notnecessarily state or lef lect thoteof the Unit«d Stales Government or any jqency tttveol.Prepared forSymposium onPerspectives in Electro- and Photo-Nuclear PhysicsSaclaySeptember 29, 1980 - October 3, 1980HtfCMMKNEARGONNE NATIONAL LABORATORY, ARGONNE, ILLINOISOperated under Contract W-31-109-Eng-38 for theU. S. DEPARTMENT OF ENERGYSymposium on Perspectives in Electro- and Photo-Nuclear Physics,Saclay, September 29 - October 3, 1980 - H. E. JacksonDESIGN OBJECTIVES FOR A GeV C.W. ELECTRON ACCELERATOR*Y. Cho, R. J. Holt, H. E. Jackson, T. K. Khoe, G. MavrogenesArgonne National Laboratory, Argonne, Illinois 60439 U.S.A.Design objectives are proposed for a continuous beam 2 GeV electronaccelerator. Various accelerator concepts are examined in light of theserequirements. A double-sided microtron shows promise for yielding majorsavings in capital cost and excellent beam characteristics.A strong concensus has developed recently among the nuclear physicscommunity that research with electromagnetic probes in the 1-2 GeV rangegenerated by a high current 100% duty factor electron accelerator representsan exciting frontier. In order to assess possible accelerator concepts foran accelerator facility we have reviewed recent discussions of future needs.The design objectives listed in Table I result from the consideration ofperspective experiments which place the most stringent requirements on thepertinent beam properties. They are design goals which should serve asstandards against which to measure the various alternatives. After examin-ing the various possibilities we have developed detailed conceptual designsfor a 2 CeV linac-stretcher ring accelerator and n double-sided microtron.The linac-ring system consists of a 2 GeV SLAC type linac which injects intoa storage ring consisting of a lattice of computer-controlled-separatedfunctions. The storage ring includes an r.f. cavity system whose purposeis to compensate for synchrotron radiation losses, control the beam orbitand the rate of extraction from the ring. Single turn injection into thering is used, and extraction is accomplished by inducing a third-integer re-sonance in the horizontal phase space which permits extraction at suitablylocated septum magnets. The features of the ANL microtron design are shownin Table II and figure 1.Table I. Accelerator system design objectivesE ?2 GeVmaxVariability in steps of ̂ lOO MeV from -v-500 MeVI (per beam) -100 pANumber of beams >1Duty factor 70 - 100%AE - ±200 keVEmittance 0.2 v mmrorE reproducibility T/100 keVE stability ^300 keVI a v stability 1 - 5 %Work performed under the auspices of the United States Department of Energy.w *itimiilf<1 manuti-'itit ft** tht'n aoihoivda cooti* tot oi ihr U. S liiNnnmrnidet cunfatl No VM 31 1091 NO 3«lv. the U. U Gowirmicnt mt.imi »* . fOV«(tV llW <« «'««• 1,1 |Mf|>|IShre tttf |Ktl.iitfi»<i f,.im (if (hit. t# AtliHV OllMtl III <ln «i . | ,MTable II. ANL Microtron ParametersMaximum energyInjection energyLinac peak voltageSynchronous phaseEnergy gain per turnLength of linacNumber of linacAccelerating fieldFrequency rf fieldBending magnet fieldMaximum orbit radiusOrbit separationMaximum number of recirculationFirst turn harmonic numberIncrease of harmonic number per turnLength of long straight sectionsMaximum length of short straight sectionDesign intensityEnergy spreadBeam emittance2 Gev5 MeV25.3 MV9°50 MeV18.75 m2l.A MV/m2.4 GHz1.523 T4.38 ra0.1095 m40530221.72 m11.17 m300 uA±100 keV0.2 mm-mradeStraight\ imiSchematic DiagramFig. 1.Plan ViewANL Double-Sided MicrotronTable III. Comparison of Accelerator DesignsCharacteristicBeam Quality, AE/EEraittanceCapital CostPower Req.Scaling Law, Capital CostLinac-RingU0~3^0.2mm-mr$28.6M5.0 MWMicrotron^10~ 4iO.lmm-mr$17.4M3.6MW-VE3The characteristics of the two approaches are compared in Table III. Amajor attraction of the linac-stretcher ring system lies in its use ofstate-of-the-art technology developed in the design of storage ring systemsfor research in elementary particle physics. It is evident from the concep-tual design data that no research and development is needed to prepare aproposal for a system capable of furnishing 100 pA external beams. Such asystem can be built with designs taken from existing high-energy physicsfacilities. With a limited development effort directed at refining the extrac-tion technique this design can be exploited to give stretcher ring currentssuitable for multiple beam operation. The stretcher ring has the added appealof great flexibility for extension to operation at higher beam enei-gies. Nochange in ring design would be required and a simple linear increase inlinac-accelerator structure is all that is required.However, the linac-ring system does not meet our design objective forbeam quality. In this respect the microtron design is a much better option.This may be a very important factor in the design selection because of theimplications of beam quality for the design of the high-resolution spectrometersused in electron scattering measurements. At the present time we estimatethat the capital cost of experimental facilities will be approximately $20million. Spectrometer design could be considerably simplified if a highquality electron beam (AE/E ̂!1O~4) j s available, with attendant savings incapital costs.From the discussion presented we have reached the following conclusions:• A GeV continuous beam accelerator consisting of a SLAC type linacand a conventional stretcher-ring can be built using existing technology.The energy spread for the stretcher ring in the extracted beam isexpected to be an order of magnitude larger than the design objective.The double-sided microtron is a promising option which may meet allthe design objectives.• The savings in capital cost which could be realized by developmentof a jnicrotron accelerator could be as large as $11M.• Operating costs for the microtron systems would be substantiallyless than those expected for a linac-stretcher ring system.

Design objectives for a GeV C. W. electron accelerator

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Design objectives for a GeV C. W. electron accelerator

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