Madi, TJ, Camilla

This work is a continuation and analysis of the measurements taken 90848, where the HWS lens chain was redesigned so that the 532nm OzOptic laser beam matched the ALS beam at M11 ie the PBS (ALS beam measurements 90370). The goal is to verify lens design methods, as well as get another measurement of the 'badness' affecting the beam in-vacuum. 

Measurements were taken of the beam coming out of the OzOptic 532nm source before installation, to verify beam quality and identify location of the waist for further q-parameter calculations (see attachment). Measurements of the beam once it had traversed the new HWS path was then made after the PBS (and through a test-lens in order to make the beam small enough to be viewed by the Nanoscan head). These two sets of measurements were then extrapolated through a model of the (new) HWS on-table path, using ray transfer matrix methods. 

An initial discrepancy between these two traces prompted measuring of the focal lengths of the lenses, which confirmed their nominal values, and re-measuring of the location of all components on-table, compiled 91241.

With the updated on-table locations, the two measurements and the model are in agreement (see attachment). 

With confidence the beam before entering the vacuum has been characterised, the current knowledge of the in-vacuum optics is used as a model. The return beam was measured and compared to the output of the model. These results (Plot 1)(Plot 2) demonstrate that the knowledge of the EX in-vacuum optics is correct, evidenced by the trace extrapolated through the model coinciding with the measurements made of the return beam. 

The return beam of the OzOptic laser also demonstrates similar double-lobed features to that observed on the ALS return beam (see attachment)