RADiCAL—Precision Timing, Ultracompact, Radiation-Hard Electromagnetic Calorimetry

Round 1

Reviewer 1 Report

Here are a few specific suggestions for the text:

line 50 - missing space in "1MeV" -> "1 MeV"

line 59 - misspelled "schematics"

line 73 - inconsistency with rest of paper by capitalizing "module" in "RADiCAL Module". Should not capitalize "module".

line 110 - "Module" capitalized again.  For consistency with rest of text it should not be capitalized.

line 119 - missing space in "28GeV" -> "28 GeV"

line 134 - for consistency with rest of paper, don't capitalize "modular" or "array"

line 139 - for consistency with rest of paper, don't capitalize "array"

lines 62, 73, 104, 160  - "Radius" is sometimes capitalized and sometimes not in "Moliere radius". Suggest not capitalizing and being consistent.

line 172 - missing one "mm" in "...14 mm by 14 at the center..."

Author Response

The suggested changes are very valuable and I have made all of the suggested changes recommended by the reviewer.  Thank you.

Reviewer 2 Report

Dear colleagues,

A few cosmetic remarks first.  In many instances, an atypical style is chosen, for example in “50ps.”  I think the correct way is “50 ps,” i.e., with a space between the value and the unit.  The journal editor might want to weigh in on this point.

There is a double identification in many figure captions.  For example, “(a) Left:”. Why not adopt one way of doing this?  Either “(a)” or “Left”?  It would be better to pick one and stick with it.

L50: 1MeV n_eq is awkward.  I think everyone will understand n_eq/cm^2

L61:  You probably mean “25 Xo or 0.9 Lambda,” not “and”

L93:  “… near the shower max.”

L111:  “In the…” (spelling)

Figure 4 b.  I think there is something to learn if you plot the energy resolution against one over E squared.  The deviation from this scaling, if there is any, might be useful to see.  I will return to this point at the end because a lot of information is hiding in this plot.

L168: “… this timing resolution might be reached.”  Maybe, maybe not; this is speculative.  I would suggest rephrasing.

L171: “… 14mm \times 14.”  How about 14 \times 14 mm^2?

L180-183: I am puzzled by this assertion:  are you suggesting increasing the sampling fraction (thicker crystals) and increasing the module length by additional layers to achieve (s=10%, n=0.3, c=0.7%) from your measurements of (s=15.7%, n=0.1, c=1%)?  

To me, it looks like the main difference comes from the photo-statistics (1/sqrt(N)) in the stochastic term. Before increasing the (costly) crystal thickness, improving the light collection would be a better/cheaper bet.  It is hard to imagine that your measurement should suffer from photo-statistics when you are using the brightest crystal (LYSO) in existence.  What is the coupling efficiency between the crystal and fiber? 

Another thing to check is the contribution of the sampling frequency.  Evaluating pure photo-statistics and sampling frequency contributions into the stochastic term might also prove illuminating.  You probably already have some MC or beam data to check this.  

Lastly, I think increasing the depth beyond 25 X_o is not going to be helpful.  So, let me ask for a crisper conclusion section for the proceedings.

RA”n”DiCAL  is a nice project and I wish you all the best.  I would love to see the recent results from your Fermilab beam tests.

Nural

Author Response

I thank the reviewer for a very careful and constructive review of the paper.  I have effectively accepted all of the corrective comments into the text.  For the comments on energy resolution, for lack of space I did not include a plot showing a GEANT4 simulation study of the contributions to the energy resolution as a function of energy.  We are not photon limited, but rather at the lower energies, the predominant contribution to the energy resolution is the sampling fraction.  This information is presented elsewhere (Figure 2 in reference 2: arXiv.2203.12806).  The constant term can be reduced at higher energies by increasing the module length.  In reference 3: M. Alexa, et al, 29 radiation lengths was considered an appropriate choice.  For lack of resources, we have neither made modules of such length nor with thicker scintillation crystals.  Our principa effort now is directed toward the timing capabilities and the radiation hardness of the overall structure.  Sincerely, Randy