For accelerati on of high charge slate heavy ion beam. a major modification has been done in th e cyc lo tron ccntr< rl reg ion. For centerin g an d proper acceleration of beam. it is req uired to know th e pot ential distribution i n and around the rncdi:J n pl ane. It ha s been ca lculated us ing RELAX 3D Code. Potential obtained has been used for understandi ng th e hc;rrn behaviour in th e cycl otron. I Introduction The V a riabl e E ne rgy Cyc lo tron (V EC) of Calcutta wa s de li verin g

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... i g ht ions (a,p,d) with a sin g le 180° Dee system. A pull e r o f same potential o f Dee was ke pt in front o r PIG ion source located at cen tral reg ion. For high charge state heavy io n bea m acce le rati o n, th e cyc lotro n centra l reg ion has bee n modified. Prese nt I y, th e central reg io n co ns ists of a Dee, Dee-Inse rt (Fig. I). Dee Dummy-Dee, Dummy-Dee-In se rt and a ce ntrall y located mirror inflector (Fi g. 2). Th e hi g h c harge state hea vy ion s are produced in EC R ion so urce and transported thro ug h the axial inj ec tion lin e to the centre of the cyc lotro n where the infl ecto r be nds th e beam through 90° into the ho ri zonta l pla ne. The e lectric fi e ld a nd the pote ntial distributi o n have bee n ca lc ul ated for th e modifi ed central regio n usi ng RELAX3D code'. 2 Calculation of Electric Potential and Field There are three me thods ava il ab le to evaluate the e lectric fie ld in a reg io n. (I) Magne tic A na logue Meth od. (2) Electrolytic Tank Method. 0) Re laxati o n Me thod. First met hod is not used now-a-days. Second met hod is time-co ns umin g. With the Re laxati o n meth od the pote ntial is co mputed by solving Laplace's equation and th e e lectri c fi e ld is derived from th e pote ntial. We have used Relaxation method. Fig. I-Dee-In sert Fi g. 2-N ew axial inJ ec tion central reg ion