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### Generating convergence power spectrum

Posted: **March 14 2018**

by **Laura Turnbull**

I'm new to CAMB and I've been looking around the documentation for a few days now. I'm looking to generate a convergence power spectrum C_{\ell}^{\kappa} with a specific window function. I'm not sure if I should use get_lensed_scalar_cls (or what this generates) or if the easiest way is to use get_lensed_potential_cls (which generates C_{\ell}^{\phi} )and take second derivatives.

Any help would be amazing

### Re: Generating convergence power spectrum

Posted: **March 14 2018**

by **Antony Lewis**

There's no built-in specific support with a particular window function (only for CMB lensing). You can use python wrapper: see box 30 and below on

http://camb.readthedocs.io/en/latest/CAMBdemo.html
for the specific example of calculating the CMB lensing convergence. You'd just have to generalize it by integrating over your source window function.

Alternatively you can use CAMB sources (or devel camb branch). which does support setting your own window function.

### Generating convergence power spectrum

Posted: **March 17 2018**

by **Laura Turnbull**

Thank you for replying! Looking at the Python wrapper I can take the C_\ell ^\phi and transform it to the C_\ell ^\kappa I need but I'm wondering how the get_lens_potential_cls function actually works. I can't see in the documetation, but to compute the power spectrum does it not need more than information than just \ell? I'm looking to make the power spectrum for a specific redshift distribution of sources and can't see how to generate this.

Thanks

### Generating convergence power spectrum

Posted: **March 17 2018**

by **Laura Turnbull**

Never mind I've figured out how to do it!

I took the basic set up of [30] but instead of finding a redshift distribution from the \chi distribution, I found the \chi s from the desired z list.