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Hi Sasha,<br>
just for clarification. You have the same type of F1TDC<br>
as I do. There is no new version yet available. The new<br>
versions will be only available by October 2012.<br>
<br>
cheers,<br>
Beni<br>
<blockquote
cite="mid:201102231606.02787.ostrov@hadron.physics.fsu.edu"
type="cite">
<pre wrap="">Beni,
As a follow up, I tried to repeat your F1 TDC resolution study in our
setup. I also plugged 2 outputs of the TI board into F1TDC. The
resolution I measured is 0.866*56.6ps=49.0ps (see the attached plot).
While it is not that far off from your value of 41.7ps (based
on your plot with 56ps bin width), it is still 15% worse. At this point,
I don't know if the newer F1TDC works 15% better than the older
one which we have, or if I should blame our VME crate with its
problematic -12V for that.
The good news is that directly measured 49ps is pretty close to
55ps resolution which I got with a pulser-simulated 3-bar method.
This means that, apart from F1TDC, there is very little contribution
to the resolution (i.e., about sqrt[55ps^2-49ps^2]=25ps only) either
from a discriminator jitter (for a fixed-amplitude signal), or from the
assumptions of the method itself (in which the 6-signal and 4-signal
distributions are used to extract the resolution of the remaining
2-signal distribution).
Sasha
On Monday, February 21, 2011, Beni Zihlmann wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Hi Sasha,
attached are two fits to the same data with different bin sizes.
one very fine with 25ps/channel and one with 56ps/channel
the actual bin size of the F1TDC. As you can see the fit results
do change a little but not drastically. The chi2/ndf is bad in
both cases because it is not really a Gaussian distribution
but closer to a square.
cheers,
Beni
</pre>
<blockquote type="cite">
<pre wrap="">Hi Beni,
Thanks for making these measurements! I have a quick question
about your timing resolution plot. Why did you choose a bin size of
50ps for this histogram? After all, TDC measurements (and their
differences) are integers, and it would be natural to histogram them
in these units, with a bin size of 1 TDC count or, at least, with the
proportional 56.6ps bin size. With your bin size choice, a bin with
about 3000 counts is followed by a bin with 0 counts, followed by
a bin with 5000 counts. This is "statistically unnatural" and is a
pure artifact of a non-aligned binning. Fitting a very narrow
(literally, a couple of bins) histogram to a gaus might be very
sensitive to how the binning is done. Seeing chi2 / ndf = 4892 / 9
makes me wonder how stable the obtained 36.7ps resolution value
is. Would it be possible to plot your data with the "natural" bin size
of one TDC count? Thanks.
Sasha
On Monday, February 21, 2011, Beni Zihlmann wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Hi All,
to follow up on the discussion about the timing resolution of our
F1TDC I looked at the data I took to test the Hamamatsu H10534 PMT.
Attached is a plot that shows the timing difference between the
trigger signal going to the TI board and the trigger signal output
from the TI board. The Gaussian fit gives a width of 36.7ps while
the position is 31.85 ns. This means that the TI response time to
the triggers was 31.85ns with a timing resolution of 36.7ps. This
resolution includes the timing jitter
of the TI board as well as the intrinsic timing resolution of the
F1TDC. In other words the intrinsic timing resolution of the F1TDC
is expected to be better than 36.7ps.
On a side note: looking at the open PMT and its base the active base
circuitry
is based on 3 transistors.
cheers,
Beni
</pre>
</blockquote>
<pre wrap="">
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