Gaseous Detectors for Field Applications: Quality Control, Thermal and Mechanical Stability

Round 1

Reviewer 1 Report

The spectacular use of cosmic muons detection for different purposes is presented by the Authors and the cited references.

Using a gas-filled detector like MWPC or MRPC for cosmic muons detection is very convenient because of the cost of detectors, their maintenance, and detection efficiency. But these kinds of detectors could present issues when they need to work not in standard conditions like the one offered by a research laboratory.

The present paper shows an interesting and well-detailed investigation of the performance of detectors in different work conditions, and possible improvements in construction.

In my opinion, this work is very useful and deserves publication.

 

Author Response

Thank you very much for your review! We appreciate your comments!

Reviewer 2 Report

This paper describes wire chambers for field applications. Field conditions are much more demanding than laboratory stabilized conditions. Detailed and highly technical studies are presented concerning the mechanical robustness, tensile strength of glued parts, the electrical stability, the sensitivity to environmental conditions. 

One would appreciate to find some more details, as the high voltage range, the diameter and composition of the sense and field wires (this is probably in one of the references, but it would be practical to have it in the paper itself). 

The explanation of the 'tempering effect' (Section 3.2) is not given. It is presented as a 'conditioning' effect, but it is not clear that it is not an ageing effect (though line 210 seems to imply this). The results on lowering dark current after 3 heat cycles should be supplemented by gas gain measurements after each cycle. 

Despites this small detail, the paper is of very good quality and certainly deserve publication in Instruments. 

Author Response

First of all thank you very much for your comments and suggestions! I would like to show our answers:

"One would appreciate to find some more details, as the high voltage range, the diameter and composition of the sense and field wires (this is probably in one of the references, but it would be practical to have it in the paper itself). "

The sense wires are 20 micrometer diameter Au-plated tungsten wires, a very typical choice for such detectors. Both field wires and pick-up wires are 0.1mm diameter, made out of uncoated brass. The high voltage, 1700V, was chosen to have a conveniently low gas gain, below 10000, but to ensure a very high signal-to-noise ratio. The text was modified accordingly and the reference added, where these information appeared. (We studied different wire thicknesses, where thicker anode wire means higher operating voltage, thinner wire requires a more careful construction -- the conclusion was that anything between 15-25 micron diameter suits well the purpose).

"The explanation of the 'tempering effect' (Section 3.2) is not given. It is presented as a 'conditioning' effect, but it is not clear that it is not an ageing effect (though line 210 seems to imply this). The results on lowering dark current after 3 heat cycles should be supplemented by gas gain measurements after each cycle. "

The "tempering effect" is indeed unexplained, as this finding may be very complicated to explain based on glue chemistry. Most probably it has to do with the reduction of radicals, as higher temperature allows more diffusion, leading actually to a more complete curing. In fact heat treatment during curing may also be relevant, however, due to lack of time this was not yet experimented on.

It is very clearly not ageing: in fact the figure shows the gain evolution, which is rather stable (better than 10%, for the presented case even increasing due to environmental conditions).

We fully agree, and remark in the improved draft, that this follow-up of the gain is an important checkpoint of the process.

Reviewer 3 Report

See annotated manuscript

Comments for author File: Comments.pdf

Author Response

We really appreciate your comments and suggestions! Here we present our answers and thoughts.

"Why should the low material budget matter?

Indeed this is misleading, in muography this is not quite relevant (unlike HEP). The remark was referring to low overall weight which makes life easier during transport and installation.

"Cathodes are not made of fiberglass"

Sure, it was not detailed enough, the cathode planes have a thin copper layer on both sides.

"in view of further considerations, it is suggested to specify the quality or grade of the gas (for argon, 99.999 or better)"

One of the key merit of these detectors is that poor gas quality is sufficient. It was studied earlier (Varga AHEP 2016) that air contamination as much as 5000ppm (effective oxygen 1000ppm) does not degrade detection quality.

During measurements, we simply wait for the gain to reach a plateau, using an industrial standard welding gas ("Ferroline C18" in our case, marketed in Europe by the Messer company), which has a typical 100ppm purity.

"some data on the actual moisture content of the filling gas and its evolution with time would have been appropriate"

Some quick studies confirmed that "sensitivity to humidity" exclusively means external humidity. The filling gas humidity is usually low due to the dry gas input. When adding ambient air to the detector volume (using a bypass), gain would drop sharply (mainly due to oxygen); however, dark current remains low. This means that even considerable filling gas moisture would not lead to increase in dark current.

When reducing input flow, one would expect that filling gas humidity increases. This study has been done (Nyitrai JAP 2021), and there was no indication of correlated increased current. Dark current increased either due to temperature (as shown in this paper), or sustained high external humidity. When these conditions faded, dark current went back to normal.

For future studies, with even more reduced gas flow, or even operating in sealed mode, we will consider this possibility, and carefully exclude (if can be excluded) the effect of filling gas humidity.

 

All the other typos and the suggested changing in the language and style were added to the manuscript.