Performance-based Fisher optimization for CMB-S4, 44cm aperture

 (Victor Buza)

Update: This posting contains an error. Please see the corrected version of this posting -- here

This posting is in the style of the post-CDT optimization posting. Previously to that, there was also a similar optimization which lead to the definition of the noise spectra that in turn were used to define Data Challenge 2.0. In this posting I try to contrast the post-CDT optimization, which was performed under the assumption of 52cm apertures, to a version that considers a 44cm aperture, as requested by the technical council. This change of aperture results in larger beams (by 52/44=1.18), while all else is held the same.

1. Worked-out Example; Experiment Specification

Below, similar to Section 2 and 3 of the posting linked above, I present an application of this framework to an optimization grounded in achieved performance.

2. Parameter Constraints; \(\sigma_r\) performance

Figure 1:

(Top, Left) Optimal path indicating the total number of det-yrs, and the individual distribution of det-yrs at each point.
(Top, Right) Individual map depths for every channel, in \(\mu K\)-arcmin. Calculated from the accumulated weights in each channel, scaled from achieved performances.
(Bottom, Left) Ratio of the total effort that is spent on delensing, as a function of total effort, and the effective RMS lensing residual as a function of total effort.
(Bottom, Right) Resulting \(\sigma(r)\) constraints for each level of delensing.

2. Conclusions

For the CDT optimization, the end point was chosen to be 1.160M det-yrs, yielding a \(\sigma_r\) of \(6.5 \times 10^{-4}\) (for the optimal solution). To achieve the same constraint with a 44cm aperture instrument we need 1.395M det-yrs -- a 20% increase in effort. For the same level of effort as the CDT report, we achieve a \(\sigma_r\) that is \(7.4 \times 10^{-4}\) with the 44cm aperture instrument -- lower by ~13% than the 52cm one.

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