The OPAL Discussion Forum

["Dou Guoliang" <douglas610322 AT 163.com>]

Hi , all

I am using opal-cycl to simulate our compact-cyclotron these days. I started with single particle mode. But I always didn't get right initial phase （PHI0 in the element of 'RF cavity') of our double-gap RF cavities. So, I have some questions about the parameter "PHI0".

At first, I found "InjectII" in opal user-guide , which is an example with double-gap RF cavity.But there is no B-filed  and cavity E-field file for running it (maybe you should add them and I will get answer).So I reference its computing method of PHI0(I think I get right method) and set it for our RF cavities . But I got wrong energy gain(dE)   in the 'inputfile.out' . Maybe I got wrong calculation results,so I will explain my calculation process below.

Our cavites are two double-gap cavities with 33 deg opening angle in the  azimuth position of 16.5，-16.5，163.5，-163.5 deg (I added structure diagram in attachment). I know that the opal-cycl use 2 single-gap replacing the double-gap cavity . We set the initial azimuth(PHIINIT in element of 'cyclotron') of particle equal to 90 deg . When we pay no attention with PHIINIT,   I calculated the  accelerate phase , which are -156 and -124 deg with the function of cos(wf*t+phi)  RF volt(peak volt=0.065MV) for the first gap and second gap.  The dE of two gaps are  -0.065*26*cos(-156) and 0.065*26*cos(-24) . But 'inputfile.out' shows  different results in dE and phase . My detailed calculation process had added in the attachment .

I don't know whether I get right understanding. When we use 2 single-gaps to replace  the double-gap , their phases has no relation with opening angle of double-gap cavity. Their  acceleration phase should  set to 0.  And for dE ,do we need to modify the peak volt to V*cos(phi)?  

By the way,because of phase shift, the proper initial phase is difficult to find . Can you give me some advice to choose proper initial phase in OPAL ?

Sincerely,

Dou

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