CW beam and bunch Freq. (MHz)

[FrancescoS]

Hi Nicolas,

I have been thinking about the issue with the .dst and I do not understand how to make it CW.
The dst is made like this:
Number_of_particle Mass(MeV) Beam_energy(MeV) Beam_Frequency(MHz) Beam_courant(A)
X0(m) Xp0(rad) Y0(m) Yp0(rad) Z0(m) Dp/p0
X1(m) Xp1(rad) Y1(m) Yp1(rad) Z1(m) Dp/p1

the Beam_Frequency in the header has the same value as the Bunch Freq in the main TW tab (I believe, because when importing it, this number change accordingly. I have done some test, maybe not very accurate, but even if I put a very big or very small Beam_Frequency the longitudinal phase space does not change).

then there is Dp/p0 and the others. to my understanding this is related to the energy spread.
Now, if my beam is CW and monochromatic, Dp/p0 =0 am I correct?

Anyway, even if I have a spread in the momentum it does not mean my beam is CW, and, on the other hand, no spread in the momentum does not make my beam bunched... or I am completely wrong...

Assuming my consideration are correct, what else can make my dst a CW?
Sorry, this is maybe a stupid question...

Thanks
F.

[npichoff]

Dear Francesco,

Sorry, I didn't see the post 11 (only first 10 were accessible on the page).

In TraceWin documentation, it is written dst format is :
2xCHAR+INT(Np)+DOUBLE(Ib(mA))+DOUBLE(freq(MHz))+CHAR+
Np×[6×DOUBLE(x(cm),x'(rad),y(cm),y'(rad),phi(rad),Energie(MeV))]+
DOUBLE(mc2(MeV))
see §Input & Output particle distribution

Please check with this format.

Best regards.

Nicolas.

[FrancescoS]

Thanks Nicola,
no worries, I understand, my post was kind of hidden.

I understand the dst format you mentioned, but I am referring to the plot win manual.
I am importing the particles from another program and I have a text file organized as written "Import particles from ASCII file:" section.
I now realize my previous message was not precise.
The correct question is then, where in the text file shall I give the phase info?

thanks a lot

[npichoff]

Dear Francesco,
I transmit your question to Didier who is more competent than me for this type of question (use of TraceWIN).
Best regards.
Nicolas

[FrancescoS]

Thank you Nicolas,

in the mean time I did some tets, adding Dz' in the Twiss Parameter popup window, maybe this is the way?

[Didier]

Dear Francesco,

Dz in the Twiss parameter you specified is the centroid of the beam, so I don't think that solves your problem.
Honestly, I'm not sure I understand your request but using PlotWin's input file format, if you want to make a CW beam, you should distribute your longitudinal particle distribution between +/-0.5*beta*lambda.
Attached is an example of a @10MHz, 30 MeV CW beam distribution that can be imported into PlotWin.

test2.txt

(73.76 KiB) Downloaded 83 times

Once the dst is created by PlotWin and used as input distribution in TraceWin, a frequency change in TraceWin will be directly applied to the input beam which will remain distributed between -180 & +180° (for that, think to select in the "Multiparticle" tab -> "input distriubution, "Use distribution form input particle file")

Regards,

Didier

[FrancescoS]

Dear Didier,

Thanks, also for the example file.
I'll have a look at it and I will try to make mine out of it and I'll be back to you

Cheers
F.

[FrancescoS]

Hi Didier,

I have created my new dst file starting form the previous txt.
Basically I have add the longitudinal distribution calculating the limits as you suggested.
I have calculated beta*lambda using 39MHz, as it is more or less the average frequency I should to have a correct space charge evaluation.
To sum up:
- from previous discussions with Nicolas, considering this test proton bunch which had 0 in the z column previously I calculated a set of random numbers between +/-0.5*beta*lambda
- I calculated lambda here as I did previously in the tests discussed by Nicolas but I specified 39MHz (RMS beam radius/frequency)

Can you please have a look and tell me if it is correct?

If I did it correctly, I can now basically change the bunch frequency in the Main tab and redo the tests.

[Didier]

Dear Francesco,

It seems correct to me, the longitudinal distribution goes well from -180 to 180°.

Regards,

Didier

[FrancescoS]

thanks, good.

I would have one more question (only because I am lazy to do test on this direction, I have to be honest)
The question is this one: I calculated beta*lambda according the previous discussion made with Nicolas, you used 10MHz for your example, can I know the reason?
and how much is important the frequency here? any frequency that distribute the beam from -180 to 180, as far as I am understanding

Thanks
Francesco