BEAM EXPERIMENTS WITH THE MURA 50 Mev FFAG ACCELERATOR [report]

C D Curtis, A Galonsky, R H Hilden
1963 unpublished
cmld bat operated a two-way accelerator or by ohaa#ta taf axeitation s owway ~ecelasafor of hfgbr energy. Tbe principal purporea for the conrtruc-$Eon of thier accelsratar were the investigation of many pwtick effeeta in carbrator#, aa experimental vetriiicat$on of radio-frarquemp accebrator eSkrrods, and a test of the two-wry accelerator, Earlier reaultr from PWURA ;;?$ z :'.ac&ms%~a published in these Pronsdfngs tkl98~lij) .nd 1961. 2,.3,4 dealt 7 /jn? kg% atth t b nriitcation o i t b t-bs of
more » ... ion o i t b t-bs of high e~b i e n c y h a 4 fieking, multitutb injM;9an aud oparatfbn of o tw-way aecrebrater, 6inee thfa time, b.tteatbn baon fwuaad on ri. variety ="P o accabmrtaf pcrbbns which bear on t b feu~tbfUty of the conetruetion oi high intensity, high energy proton 9% 8 ' . -. -1 % accsbrature and storage riagra. Thew tuqe tram studies ef mtn& :,. =. -: : -I , & -% -b -o * 2 : -3 WtEk remnant effect8 to coherent beam pb6narnenmt. 3 n 2.p p T h . r d i a I . l~o~~c i U u i o n t r a q~s c y . ' l l , . u d t b v e t l w l kt.tron O S~.~W P B i l~t m n t~y , Y = a brv, b n n IBWWWW! it^ ~m r l 1 , 0 ry Supprted by thrr V. S. Atomic Elwrgy CommhtOn. %&w with the U. I . Atarnie DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document. 2 amplitude o~cillations. The measurements were made at many radii in the acaelerator for which computer calauhted values of the tune have been obtained. The computed tune values were obtained for small amplitude oscfilations using measured magnetic fieM data 8nd the ParrnesrA.computer program. The results of thie computer investigation of the tunes were reported by Paurzen at the 1961 Brookhaven International Conference on High Energy Accelerators. 5 The experimental tune data was obtained by the method of resonant driving of b e t~t r o n oscilLations with o localized radio-frequency voltage, 6 In order to permit comparison of the measured tunes with the calculated tunes, the beam was limited in intensity zlnd in radial and vertical amplitudes. The radial amplitudes w e r e kept mall by injecting at the minimum energy that the accelerator would accept. Vertical amplitude fa were kep% small by a vertical aperture limit fag probe. , In order to obtain precision measurements of the frequencies that cause resonant growth of the betatron oscillation amplitudes, the knockout rP voltagct is pulsed on during the time the beam is coagting at a constant revolution frequency. For rnee~urernents at small radii the injection t h e is adjusted so , . that just enough energy is recefved from the injection betatron pulse to bring the beam out to the radius vhere the t-me i s to be rnassured. The beam circulates there until the analyzing betatron'pulsc?, give8 it enough additional energy to bring it out onto a target. . At larger radii, the betatron pulse does not provide enough energy to bring the beam out to the desired radius, so rf acceleration is used to provide the necesraary additional energy. Again the analyzing betatron pulse is used to bring the beam out to the tiulget. The knockout rf is pulsed on, in either case, shortly before the analjrzfne betatron comes on. A.t this time the particles are not under the influence of any accelerating voltage and have a constant revolution frequency. Resonant driving of the betatron oscillixtfons is detected by observing the appearance of scintillation pulses during the time the knockout rf fs pulsed on. These acintillebtiom pulses are produced when the amp2!tudes of Borne of the beam particles grow large enough for the particles to strike a target located very near the circulating beam. When vertical tunes are measured, the target is located above or below th6 beam. Whran radial tunes are measured, tha, target is at a slightly larger radius than tha circulating beam. The analyzing betatron pulse brinks the remainder of the beam out to a * target to provide an indication of the amount of beam being accelerated, The betatron oscillation fre~uenciee are obtlhined from the relation: 6 Where * in the betatron oscillation ireq.aency in &stion, fm is the vmock--. out rf frequency, fo i s the particle revolution frequeracy and N le an integer. I Precision determlnations of fo and fKO along with a knowledge of 9 to within -9 0.5 so that N can be determined permit the measurement of 9 with an accuraey of + -0,1% o r better, / Both the rnoaeured and the calculated values of Y r versus radiw 9 are shown in Fig. 1. The agreement between the experiwntal data,& : the calculated frequedcies is exceptbnally good except P o the large r a w I region. Ths discrepancy in this regiod i s probably due to feet azimuthal variations of the magnetic field in the pegion of the wnrscaling pols. Mnce there were only 10 mesh points per sector for the computer calculation, harmonices higher than the fourth sector harmonfq could not. be iocluded. The fact that the tune variations c a s h 630 sudden fs very swgrising. Measured and calculated values of L' versus radiua are shown in ~i g . 2. Again the agreement i s generally good, The &crepanci@s at
doi:10.2172/4660777 fatcat:uchgop46yrepjky3vjscibsmhm