CaF example in SI units

[dong kyu Lim]

Hi,

First, thank you for this convenient packages! It is very helpful for simulating MOT with various atoms and molecules.

I have a question for CaF example. I checked the values in reproduced figure, changing the units to SI units. Acceleration vs velocity plot looks almost same but force vs displacement plot looks different with the Fig.3 in Physical Review A 92 053401 (2015), which you mentioned in CaF example. The peak value is slightly increased about 10~20% than paper.

I`ve tried to find the reason why these two are different, but I haven`t find yet. Is there any reason why the acceleration increased only for displacement? Here I attach the reproduced figure in SI unit.

Any help would be appreciated.

Best Regrads,

Dongkyu

[Eckel, Stephen P. (Fed)]

Hi Dongkyu,

 

I had thought I mentioned this in the comments of the example, but I am pretty sure that the difference comes down to my example using uniform (flat-top) beams and the Physical Review A 92 053401 (2015) model using Gaussian beams.  With Gaussian beams, the force falls off with distance more quickly (because there is less laser intensity).  However, I have not independently verified this.

 

Because you have put the example into SI units, it should be easy for you to verify.  Just change the beam type being passed to conventional3DMOTBeams to a Gaussian beam and pass the 12 mm beam radius used in the PRA.

 

Hope that helps!

 

-Steve

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[dong kyu Lim]

Hi Steve,

Thanks for quick responce. Although I changed the contenvional3DMOTBeams to a Gaussian beam and set wb = 12 mm, there is same difference at force vs displacement plot. Here is my code to change CaF example to SI unit. I add "mass" term because we calculate the acceleration, and change length unit to "1/k" unit.

I hope you can check it.

Thanks,

Dongkyu

2022년 11월 1일 화요일 오후 9시 57분 19초 UTC+9에 stephen.eckel님이 작성:

[Eckel, Stephen P. (Fed)]

Hi Dongkyu,

 

I have gone over your code, and everything that you have put in looks correct. I am now quite unsure where the discrepancy lies.

 

I think to really track it down, you would have to make a more thorough comparison of the pylcp results to the code from the Tarbutt group.  That sounds like a daunting task to track down what appears to be about a 20 % discrepancy.

 

Sorry I cannot be more help on this issue,

.
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