[Halld-cal] NIM article for FCAL beam test

[Elton Smith]

Hi Kei,

I have gone over the draft NIM paper and have several comments. I first 
start with some overall comments and then go to a list of specifics.

General:

o Abstract, emphasis
- I would suggest to discuss the significance of measurements near 
threshold, where few Pb glass measurements are in the literature. [At 
least I believe that to be the case, this should be confirmed and 
perhaps referenced. If so, it would be interesting to compare our 
measurements with what might be in the literature.] Also state that 
calorimeters typically do not have very good time resolution and the 
FADCs allow us to determine the impact times relatively accurately. 
Emphasis on improvements compared to RadPhi (probably unknown to the 
reader) is less important. Should also give some actual characteristic 
numbers for energy and time resolution.

o The paper is quite long and there is duplication of information, which 
could be consolidated.

o The lead glass itself should be discussed (and referenced) in a little 
more detail

Specifics:

p . 1 abstranct
shown -> show

p. 1 sec 2.1 Fcal components
Most of this section is background information and could be merged into 
the introduction.

p. 1. sec 2.1 first paragraph
Need to give somewhat more information about the lead glass (e.g. type). 
Should also reference the E852 papers
Brabson_NIMA332(1993)419
Crittenden_NIMA387(1997)377
Jones_NIMA566(2006)366
Jones_NIMA570(2007)384

It is worth perhaps referencing a review article on calorimetry for a 
context of lead glass detectors also.

p. 1 right column, figure
Magentic -> Magnetic

p. 1 right column middle, needs rework
magnetic shield, and acrylic light guides have been installed to encase ?
optical guides? Perhaps simply state that a small air gap was replaced 
with an acrylic cylinder to improve light collection and allow for 
better magnetic shielding. [Should perhaps mention the expected maximum 
field at the pmts, was it 150 G?]

further down
may wish to "beam bunch" instead of bucket
photon rate: 10^8/s is the photon rate in the coherent peak. [The photon 
rate is orders of magnitude higher]
The use of the timing to identify the beam bunch is desirable, but is 
not a requirement. In fact, it is difficult to argue that the bunches 
can be identified cleanly at low energies.

p. 2 left column, figure 2

It is probably worth being more specific regarding the prototype:
Al encasing for detectors -> Al encasing for Pb glass prototype
triggers -> trigger counters

p. 2 left column middle

perependicular sp?
use of "triggers" is slang for trigger counters (or scintillators) and 
should be reworded.

p 2 Figure 3

The blue-gray area of the trigger counter scintillators does not appear 
to be an array of counters. However, it does nicely show the outline of 
the prototype. I suggest trying to make both visible.

p 2 left column second paragraph, last sentence, suggestion
the digital output of the discriminators were recorded into the data 
stream using the same fADCs that were used for recording the pulse 
height for the lead glass.

p 2 right, top, suggestion
The purpose of the remote paddle was to tag electrons along the nominal 
electron trajectory and help eliminate particles scattering into the 
detector during offline analysis.

p 2 right third paragraph,
Figure 4 shows a diagram of our TRIGGER LOGIC, which...

end of paragraph, question: was the veto signal ever found to be on in 
the analysis?

p. 3 sec 2.3, title
Test setup in Hall B?

I would emphasize early on that the test was performed in parasitic 
mode, so we did not have control over beam parameters, such as beam 
energy or intensity. Early on, you should specify the running conditions 
or periods (e.g. beam energy and beam current). Also important is the 
radiator thickness (50 microns?)

p. 3 Fig 5

If the radiator is at (0,0), then the arrow with the photon beam 
direction is too low. You could eliminate the arrow and move the text up 
to the dotted line.

caption: Suggest use "The trajectories of DEGRADED electrons with 
varying....."

p. 3 left column, last paragraph

write out: "The detector was placed at the calculated location that 
intercepted electrons with 5% of the full beam enegy..."

p. 3 right column, first sentence under 3.1, reword
...our detector POSITION was fixed, and data were taken ...

p 3 right column second paragraph under 3.1
...every 4 ns and 50 samples were output for every channel. [Note: the 
fADC buffer is much deeper, up to 7 micros]

p. 3 Section 3.2
While the discussion is interesting, I would suggest to condense the 
discussion. The study of hardware vs software balancing is useful to 
provide a systematic uncertainty for the procedure, but does not require 
the description of all the details.

p 4
Figure 6, questions
What happened to the fADC top left (replaced by remote paddle)
Why are the baselines so high on fADCs 1,4 and 2,5?
Why do most of the channels show zero (should they not have a pedestal 
value?)

p 4 left, second paragraph

...8 samples around p?  the pedestal?

p 4 right

p 5 Figure 7, questions, comments
Left plot: Why is the rise sample distribution so broad: ~10 counts = 40 
ns. I would think the time variations in the system should be much 
smaller than that. The only think I can think of is the pmt rise time, 
but variations from tube to tube I would guess should be at most a few ns.
Comment: You may wish to pick colors with better contrast. My experience 
is to use red, blue and black and make lines thicker.

p. 5 left, middle
forumlated sp?

p. 5 right column, sec 3.3 first sentence
first sentence is confusing, it sounds like one run has three different 
energies. Sufficient to say all runs? or runs used in analysis?

sections on balancing range and different trigger combinations. I 
suggest to condense the entire discussion into a few sentences with a 
conclusion and estimate of the systematics.

p. 6 right column, middle, suggestion
...with a range of +/- 10% to cover the range of rays that would scatter 
into our acceptance.

Note some of the discussion here, e.g. the amount of material has been 
covered earlier in section 2.3

p 6, right, 3rd paragraph, question
statement: "...only one combination of the inside horizontal and 
vertical triggers had a hit."  How did you simulate pile-up? What rates 
did you assume for the electron beam?

p 6 fig 9
Why is the ratio of accepted to generated events so small (<~20%) ? Even 
in the data kept 1/3 of the data (p. 4, right, end first paragraph).

p 7 Table 1, suggestion
Results of simulation of spread of energies -> Predicted energy and 
spread of electrons incident on the prototype during three run periods.

Somewhere you should note that the spread in the energy of the primary 
electron beam is negligible (~10^-4).

p 7 fig 10, suggestion first sentence
The energy resolution plotted against incoming energy.

p. 7 right, sec 3.5 The first paragraph can be considerably shortened 
because this information has already been presented previously.

p. 7 right bottom.
When this data is compared to RadPhi, one should note the range over 
which RadPhi measured the resolution (0.6 to 3 GeV) to show that the fit 
is an extrapolation

p. 8 Table 2
It is odd to quote results with 0.0 uncertainty.
You may not need to include all the data in the table for all the 
configurations, especially since the average takes the standard 
deviation of the measurements. Could eliminate the table since the data 
are plotted in Fig 10. Summarize with a estimated systematic 
uncertainty, which is essentially the standard deviation.

p. 8 section 4 Timing first paragraph
for (2) might want to say that the comparison of the time of the hits in 
the FCAL with the vertex time (measured with charged particles) allows 
determination of the flight time and may help e/n discrimination.

p 8 Figure 12.
Why are there such large offsets between blocks, up to about 5 ns? Since 
they are looking at the same shower they should be at the same time. I 
guess there could be different delays in the pmt transit time.

p 9 Fig 13
You might want to label y-axis as "Two module sigma_ij(ns)" or something 
like that to distinguish from the single module timing.

p 9 right, below eq 2
"Figure 14 shows AN EXAMPLE OF the resolution of a single module." (If I 
understand what you mean)

p 9 fig 14
Do you want to show the data points and their averages? I suggest you 
only plot the average. The values are contained in Table 3, Although 
they are all consistent, so I might eliminate the table and simply quote 
the average with a short comment on systematics. As far as I can tell, 
the systematics are small, so it is not worth belaboring the differences.
Suggestion on curves: use "our fit" as solid, the other as dashed 
(easier to see)

p 9 second paragraph, middle, parameters a and b need units. Also in the 
comparison with the previous measurements (Ref 7?) you might consider 
removing the discussion in the text and adding some data points from the 
reference to Figure 14.

p 9 second paragraph, further down, omit comma
...heights of 300-1,500 -> heights of 300-1500 ADC counts.

p. 9 right discussion on units. I think you should make the conversion 
to energy, and quote a in units of ns/GeV. However, it is also nice to 
have the number in terms of ns/mVm, which gives the size of the signal.

p 9 Acknowledgements, see the wiki
https://halldweb1.jlab.org/wiki/index.php/GlueX_Publication_Policies
In particular you should include the JLab contact number:
"All instrumentation papers need to include an acknowledgement that 
Jefferson Science Associates, LLC operated Thomas Jefferson National 
Accelerator Facility for the United States Department of Energy under 
U.S. DOE Contract No. DE-AC05-06OR23177"
I'm sure you also need to include the IU grant number at the least.

p. 9 References.
Earlier I listed the E852 and Radphi papers.
You should also reference the JLab fADC. I don't have a handy reference, 
but make the citation and we can find a good one.

Cheers, Elton.


Elton Smith
Jefferson Lab MS 12H5
12000 Jefferson Ave STE 16
Newport News, VA 23606
(757) 269-7625
(757) 269-6331 fax

On 3/8/13 12:18 PM, Kei Moriya wrote:
> Dear all,
>
> The NIM article draft for the FCAL beam test is available at
> http://argus.phys.uregina.ca/cgi-bin/private/DocDB/ShowDocument?docid=2183
>
> Full details of the beam test are given in document 2118,
> which I intend to update once the NIM draft is approved.
>
> Please check the author list, and also send me comments/questions.
> I will wait until the end of next week, and then send it to the
> collaboration for approval.
>
> Thanks,
> 	Kei
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