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Entry  Wed Jul 24 21:08:24 2013, Deep Chatterjee, Optics, General, TR results for different dimensions Jul24.pdfJul24_acalc.pdf
    Reply  Thu Jul 25 11:36:17 2013, rana, Optics, General, TR results for different dimensions 
    Reply  Thu Jul 25 13:21:46 2013, Deep Chatterjee, Optics, General, TR results for different dimensions Jul_25.pdf
       Reply  Thu Jul 25 15:54:58 2013, Deep Chatterjee, Optics, General, TR results for different dimensions Jul_25_1.pdfJul_25_2.pdfrelative_plot.pdf
Message ID: 72     Entry time: Thu Jul 25 15:54:58 2013     In reply to: 71
Author: Deep Chatterjee 
Type: Optics 
Category: General 
Subject: TR results for different dimensions 

Quote:

Quote:

In this post I simulate the procedure of calculating the TR noise for finite cavities as proposed by Heinert and check for a
match.

The technique of performing all necessary calculations in COMSOL and exporting the results was applied to the TR codes.
It was seen that the codes gives similar output as the technique of extraction of Fourier coefficients in place of time averaging
as has been done in the codes of Koji Arai. One can see the output as the present code runs to be similar to the previous ones
found in the SVN.

However, the results in the present case were off by a constant factor close to 100. This maybe due to some 'm' - 'cm' or similar difference between
analytic calculations and COMSOL values of parameters. Although, it has not been found yet, the correction is hopeful to be
found soon.

The codes give results similar to the analytic result for other values of the mirror radius and beam radii (apart from the constant
factor I have mentioned above). One may have a look at the trend of the graphs between analytic and simulated values in the plots
attached. These plots are for the case when the mirror radius = 25m while the beam radius = 9 cm i.e. the original radii were 0.25m
and 9cm respectively i.e. the ratio has been changed by a order of 2.

As mentioned before the reason for the constant factor difference will be looked into.

 

 

The discrepancy related to the difference between the analytic and COMSOL results has been partially addressed. Attached is another
plot showing the comparison. The ratio this time between the COMSOL results and the analytic results is between 0.7 - 0.8. This difference
will be looked into. It is, however, observed that the difference is not a constant factor - it has to do with the model file.

 

 

 

The issue related to the difference between the analytic and simulated values has been resolved. The codes seems to give reasonable match
between the analytic and simulated case. There is, however, a difference between the formulas being used from the previous cases. Note that
the 1/2 in front of Eq.(15) of Heinert is a because the time average has already been considered. However, in the present codes, the volume
integral of grad_T is evaluated in COMSOL and exported as a function of time. It is then averaged in MATLAB. Thus the factor of 1/2 is to be
omitted in this case(see Liu and Thorne Eq.(5). The presence of this extra factor of 1/2 was giving error in the last upoaded plots. From the
relative difference plot, one can see the maximum difference between COMSOL and analytic results go upto 7% but for most of the graph
it is close to 1% which is a fair result.

Attachment 1: Jul_25_1.pdf  8 kB  | Hide | Hide all
Jul_25_1.pdf
Attachment 2: Jul_25_2.pdf  8 kB  | Hide | Hide all
Jul_25_2.pdf
Attachment 3: relative_plot.pdf  4 kB  | Hide | Hide all
relative_plot.pdf
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