Understanding "CSRconstant" in CSBEND.c

[Zamank]

Hi All,

I am trying to better understand the CSR calculations involved in Elegant. I am unfortunatley getting a little mixed up with all the different unit conventions being quoted:

1. In the Saldin 95 (http://cds.cern.ch/record/291102?ln=en) treatment they use: (-2Ne^2) / ((3r^2)^1/3) which is in CGS units.

2. In Sagan's paper eq. 43 (http://arxiv.org/pdf/0806.2893.pdf) they use: (-2Nrmc^2) / ((3r^2)^1/3) which is in CGS units (lack of permittivity constant).

3. In Borland/ELEGANT CSBEND.c (line:1499) the constant is: (2Ne^2) / ((3r^2)^1/3)(4*pi*epsilon*m*c^2) which is in MKS as stated in the code (code attached).

I understand 1 and 2 but I do not know how to get to 3, the ELEGANT treatment. I think I am making a small mistake somewhere. Any help would be greatly appreciated! Also, please feel free to correct any of my statments I made above; its imperative I am understanding each step!

Thank you!

[michael_borland]

Zamank,

I don't know about the Sagan paper, but starting from Saldin et al. NIM A 398, 373 (1997) we have 2*N*e^2/(3*rho^2)^(1/3) having units of energy/meter in CGS convention. To be used in elegant, we first convert to MKS which gives the factor 1/(4*pi*epsilon_0). Then, we normalize to the electron rest mass by multiplying by 1/(m_e*c^2), since elegant uses dimensionless p=beta*gamma as the momentum.

--Michael

[Zamank]

Ahhhh, ok that makes sense now...the last line really cleared it up for me! Thank you again Michael...