The ante nna co nsider ed co nsists of a s mall toroidal core of magnetic materi al, upon whic h a uni· formly di stribute d driving wi ndin g is pl aced. Thin laye rs of in s ulation se parate th e windin g fro m th e core and from the hi ghly conduc tin g me dium in whic h th e ante nna is situ a te d. The exte rnal fi elds for th e drive n a nte nna are es timated using a sta ti c fi eld so luti on e mploying toroid al coordinates. The dri vin g-poi nt admitt a nce is th e n d ete rmined from th ese fi eld s. Th e effec tiv e electri c c urre nt mome nt of th e ante nn a is es timated by dualit y with the electric curren t loo p. Th e drivin g-point ad mitt a nce a nd the effecti ve mo me nt are the n combi ned to es ti mate the effective length a nd the re la tiv e effecti ve a rea of a tor o id a nt en na orie nt e d suc h t hat the e lectric mome nt prod uced is para ll el to t he su rface of the cond uct in g ha lf space. Wh ile the effective lengt h of a tu ned toroid antenn a ca n be made muc h greater th a n the e ffective length of an elect ric-di po le-in .radome ante nn a, t he effective areas of the t wo a nten na types are of t he same orde r of magnitud e if th e max imum exte ri or dimens ions are equal.
In the course of construction of the 805-MH;; linac, it was necessary to set 10 000 resonant cavities to precise frequencies and to check, and in some cases, to adjust the field distribution along the beam axis of the 104 rf tanks composing the linac. Since this was the first proton linac of the side-coupled type ever built, it was necessary to develop new techniques and instrumentation for structure tuning. An outline of the fabrication and installation process is given, showing how the tuning operations were interwoven with the fabrication steps and indicating the relation of tuning to other installation and check-out activities. The steps of the tuning procedure are then examined in detail. Tools for tuning by dinging, nose-stretching, and septum bending are described. Techniques for frequency measurements and for beadpull measurements of field distribution are discussed. The section on field distribution measurement includes results of research on measurement procedure and theory and observations confirming the low-power stability of field distributions for a three-year period. Selected results from the theory of chains of coupled resonators are given. Coupled resonator model parameters and various measured parameters for the 305-MHz linac are tabulated. *i n/^ rn'xJ* f r ,-Ci«ity frrrj 800 BO? MM/. 8 l«'jm»nll t.-om«..ti lilrf! nnj) .liejd< bta/«d on K E. O R. l«vi I-•-~-fj>j 4. Machine ni>»« on Î _i!l^ J U>«i latht 1 I incttMS* half gjp I j 1 MM/ or 1-H l~-1 All d.irr>'.hflti Y "'!l"" : ni tin-. ty|i** X ' " AJI wijrncnu lor on* tdnk / M^rjunf fnt giv»;n half g'J I«JI M^yf (Jmu'/iijuns rf? 800 807 MM/ 8 N'umlx'r and itarnp arrow, witli Ui»CPf Uthe
An instability in the Proton Storage Ring (PSR) is observed as fast loss of beam during accumulation and storage when the injected beam current exceeds a threshold value. Experimental study results of that instability are presented in this paper. The instability threshold depends significantly on rf voltage, injected momentum spread, and PSR sextupole and octupole strengths. The results are consistent with the hypothesis that the instability is a transverse instability excited by a transverse impedance ZJ.. with IZJ..I == 1 MQ/m. The driving impedance has significant magnitude in the 30-to 300-MHz frequency range.
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