{"id":"4664fef1-1f63-456d-8ed9-35294acd6a0a","arxiv_id":"2412.16313","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":6.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":2,"one_line_summary":"A scalable tiled Micromegas readout plane and a face-to-face connector were developed and commissioned for the PandaX-III and TREX-DM rare-event searches.","lead":"This doctoral thesis develops large-area Micromegas readout planes for rare-event physics experiments by tiling 20 by 20 cm modules for PandaX-III and optimizing a 25 by 25 cm plane for TREX-DM. It also designs a new alpha-particle detector, AlphaCAMM, built on the same readout technology.","discovery_kind":"new_method","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Scalability claim rests on a 7-module prototype analyzed with selective regions and a 52-module plane built with a different, untested Micromegas technology; full-size performance is not demonstrated.","rationale":"The reader correctly identified a transfer-of-performance concern, but the more load-bearing instance is in Part I: the scalability claim for the full-size PandaX-III readout plane depends on a 7-module prototype whose published spectra were produced from selected regions and on a 52-module plane whose modules use a different fabrication technology and have no performance data in the thesis. This is distinct from, though related to, the reader's weakest_assumption about small-area characterization transferring to the large-area TREX-DM Micromegas. Both concerns point to the same general risk: measured performance on a small or partial system is being extrapolated to a larger or differently manufactured system without direct validation. The paper deserves credit for honestly reporting the 9.2% defective-channel fraction, the edge dead zones, the manufacturing error that blocked external-rim validation, and the fact that 52-module testing is outside scope; these disclosures make the limitation visible rather than hidden. The concern does not invalidate the engineering work, but it does mean the thesis's central scalability claim is supported only conditionally, consistent with the reader's verdict. A full-plane re-analysis of the existing 7-module data would be a concrete, low-cost check of whether the demonstrated tiled performance is representative; if it is not, the claim would need significant qualification.","tokens_in":49498,"tokens_out":4960,"duration_ms":47464,"concrete_test":"Re-analyze the raw 7-module commissioning data without the strategic dead-channel exclusion: compute the full-plane energy spectrum and charge-collection efficiency across all channels and module edges, and compare them with the selected-region spectra of Fig. 4.11; if full-plane resolution or efficiency is substantially worse than reported, the tiled-plane performance claim is not representative.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim of Part I is that tiling SR2M modules yields large readout planes usable for rare-event searches. The supporting evidence is incomplete in two linked places. First, Section 4.4 reports 9.2% defective channels in the 7-module plane and states that the spectra in Fig. 4.11 were obtained by \"strategically selecting areas with fewer defective channels\"; the full-plane response, including the missing-amplification-hole edge zones noted in the same section, is not quantified, and the manufacturing error prevented experimental validation of the external rim. Second, Section 5.2.4 states that the 52-module full-size plane is made with a different Micromegas technology (thermal bonding at USTC [55]) whose development and testing are outside the scope of the thesis. Assembly of the full-size detector is reported, but no gain, energy resolution, dead-channel fraction, or tiling-efficiency measurement for it is presented. The load-bearing unstated premise is therefore that selected-region results from a flawed 7-module prototype and an untested 52-module plane of different technology will both meet the performance requirements for neutrinoless double beta decay. This is a correctness risk for the scalability claim, not an internal inconsistency.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"This doctoral thesis reports the development of tiled microbulk Micromegas readout planes for two rare-event gaseous TPC experiments. Part I presents the Scalable Radiopure Readout Module (SR2M) for PandaX-III: the module design, the electron reintegration system, a custom feedthrough, a new Face-to-Face (FtF) connector, and two module versions. Commissioning results are shown for a single module and for a 7-module plane; the construction of a 52-module full-size plane is reported. Part II describes the commissioning and optimization of the TREX-DM detector, including a new 25x25 cm² Micromegas, background reduction, energy-threshold studies, and a GEM-Micromegas pre-amplification stage. Part III covers the design, background model, and commissioning of AlphaCAMM, a surface-alpha detector. The overarching claim is that tiling SR2M modules enables the construction of large readout planes for low-background rare-event experiments.","tokens_in":49686,"tokens_out":4034,"duration_ms":37160,"significance":"If the scalability claim is fully established, this work addresses a genuine bottleneck for ton-scale gaseous TPCs in neutrinoless double-beta decay and dark-matter searches. The engineering contributions are concrete and in several places well validated: the FtF connector is supported by an independent FEM-versus-Navier comparison and by 804 direct resistance measurements over eleven months, and the ERS behaviour is studied with Garfield++ simulations. The thesis is also commendably honest about many limitations, including defective channels, manufacturing errors, and the untested status of the full-size plane. However, the central scalability claim is only partially verified: the 7-module plane is characterized with selectively chosen regions and has 9.2% defective channels, while the 52-module full-size plane uses a different Micromegas technology whose performance is not presented. The significance of the work as a standalone demonstration of large-plane usability is therefore currently limited.","major_comments":[{"comment":"The 7-module plane is the main experimental evidence for the scalability claim, but its full-plane response is not quantified. The text states that the spectra in Fig. 4.11 were obtained by 'strategically selecting areas with fewer defective channels,' and Fig. 4.12 reports 9.2% defective channels. The manufacturing error that left no amplification holes at the module edges, also noted in this section, further reduces the active area and prevented experimental verification of the external rim. Please provide a full-plane efficiency map, the fraction of active area lost to dead zones and defective channels, and the energy resolution obtained with the complete plane, or explicitly restrict the scalability claim to the mechanical tiling rather than to the usable performance of a tiled readout plane.","section":"§4.4"},{"comment":"The construction of the 52-module full-size readout plane is reported, but this plane is fabricated with a different Micromegas technology (thermal bonding at USTC [55]) whose development and testing are 'outside the scope of this thesis.' No gain, energy resolution, dead-channel fraction, or tiling-efficiency measurement for this plane is presented. The central scalability claim for the final PandaX-III detector therefore extrapolates from the 7-module microbulk prototype to an untested technology. Please either provide the surface-test results for the 52-module plane or clearly state in the abstract and conclusions that the performance of the full-size plane remains unvalidated.","section":"§5.2.4"},{"comment":"The TREX-DM operating point is selected using systematic measurements from a 2 cm single-pixel microbulk Micromegas with 55 µm amplification holes [77], while the installed device is a 25x25 cm² pixelated Micromegas with 50 µm holes. The text explicitly assumes 'that the response and behavior of both are similar,' but the measured energy resolution in TREX-DM (23–29% FWHM) is substantially worse than the 11–13% FWHM reported for the small prototypes. This large discrepancy indicates that the transferability assumption is not yet established and is load-bearing for the chosen gain, threshold, and expected background discrimination. Please quantify the sources of the resolution degradation and validate the operating point directly on the large device, or reframe the assumption as an open item requiring dedicated measurement.","section":"§7.2"}],"minor_comments":[{"comment":"In Eqs. (5.1) and (5.2), the notation for the standard deviation is confusing: σ_i(R) is written as a sum over j, but the index i appears both as the label of the per-channel quantity and as the summation index in Eq. (5.1). Please use distinct indices for the channel label and the measurement index.","section":"§5.1.3"},{"comment":"The sentence comparing energy resolutions is incomplete: the text reads '11−13' and stops abruptly, presumably missing 'FWHM.' Please correct the typo.","section":"§7.2"},{"comment":"Several chapter and section titles appear in Spanish (e.g., 'Sistemas de apoyo...' in the table of contents and 'Necesidad de un detector de partículas alfa superficiales' in Chapter 10) while the rest of the text is in English. Please unify the language throughout.","section":"Chapter headings"},{"comment":"The thesis introduces many abbreviations (ERS, FtF, SR2M, FEC, TCM, MCA) without a central list of acronyms. Adding a glossary would improve readability for a journal-style audience.","section":"General"}],"recommendation":"major_revision","confidential_remarks":"The manuscript is a doctoral thesis with a much broader scope than a typical physics.ins-det article; if the journal is open to thesis-style contributions, the main concern is that the headline scalability claim is presented as demonstrated when the supporting evidence is partial. The authors should either strengthen the evidence or explicitly narrow the claim. I would not recommend reject, because the engineering work is solid and honestly reported, and the omissions are clearly identified in the text itself."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"The FtF connector reliability study and the internal-rim charge-collection measurements are the real new content here. 804 contacts over eleven months and six thermal cycles with zero contact loss is a solid, directly measured result; the relaxation data on expanded PTFE and the FEM/Navier cross-check are careful. The internal-rim edge data (Section 5.2.3) quantifies how charge loss at module edges depends on rim voltage and is genuinely useful for anyone designing tiled readout planes. The thesis is honest about the manufacturing defect that removed amplification holes at module edges and about the fact that the external rim was never tested. Citations are handled fairly—prior work is credited and the new measurements are clearly separated.\n\nThe soft spot is the scalability headline, and the stress-test concern is correct. The 7-module plane spectrum (Figure 4.11) was obtained by \"strategically selecting areas with fewer defective channels\" while 9.2% of channels were dead; full-plane response, including the missing-hole edge zones, is not quantified. The 52-module plane is explicitly made with a different technology—thermal bonding at USTC (Section 5.2.4)—whose development and testing are outside the thesis. No gain, resolution, or dead-channel data for that plane appear. So the claim that tiling SR2M modules enables large readout planes is only partially verified: it is supported for microbulk modules in a small tiled prototype with selected analysis, and not at all for the production plane. That does not make the thesis wrong, but the abstract and conclusions overstate what is demonstrated.\n\nA smaller related concern in TREX-DM: the operating point relies on transferring a 2 cm single-pixel laboratory Micromegas (55 µm holes) to the 25x25 cm² pixelated plane (50 µm holes), and the observed 23–29% FWHM resolution versus 11–13% in the small prototype suggests the transfer is less innocent than the thesis assumes. The thesis flags the difference but treats it as negligible; that deserves more scrutiny.\n\nWho this is for: detector instrumentation people working on MPGDs and rare-event TPCs. The FtF connector data is citable. The scalability claim needs to be qualified before it can be used. I would send this to a serious referee, but the referee should require that the production-plane status be stated plainly (it is not part of this work) and that the selective analysis be disclosed in the abstract-level claims.","headline":"A technically honest thesis with two solid new measurements, but the scalability headline is only partially supported: the 7-module prototype was analyzed in selected regions and the 52-module plane uses an untested, different Micromegas technology.","tokens_in":50260,"tokens_out":4013,"would_cite":true,"duration_ms":34820,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"This thesis shows that large, low-background readout planes for rare-event searches can be built by tiling modular microbulk Micromegas detectors, and demonstrates the approach with a seven-module prototype plane and a full-size 52-module…","keywords":["Micromegas","time projection chamber","rare-event searches","low-background detectors","neutrinoless double beta decay","WIMP dark matter","gaseous detectors","micro-pattern gas detectors"],"falsifier":"Take the installed 25 x 25 cm pixelated Micromegas and the 2 cm single-pixel Micromegas used for laboratory calibration, place both in the same gas mixture (Ar + 1% isobutane, 1.5 bar) with the same drift and amplification fields, and compare gain curves and energy resolution at the 22 keV line of a 109Cd source; if the large detector still shows 23-29% FWHM while the small one shows 11-13% FWHM under identical conditions, the transferability assumption is falsified.","tokens_in":49242,"feed_emoji":"🧩","tokens_out":8687,"duration_ms":70383,"temperature":0.7,"pith_summary":"This thesis develops a way to build large readout planes for gas time projection chambers used in rare-event searches, where detector materials must be extremely low in radioactivity. Because single microbulk Micromegas detectors cannot be manufactured larger than 20 by 20 centimeters, the author designs a tiled 'scalable radiopure readout module' (SR2M) and shows, with a seven-module prototype plane, that a mosaic can deliver useful electron transmission, gain, and energy resolution. The same modular concept was scaled to a full-size plane of 52 modules for a neutrinoless double beta decay search, with the detector assembled and awaiting underground installation after surface tests. The thesis also characterizes a single 25 by 25 centimeter Micromegas plane in a high-pressure gas TPC for WIMP dark matter searches, adds a GEM pre-amplification stage to lower the energy threshold, and repurposes the technology as AlphaCAMM, a detector for surface alpha contamination. The unifying claim is that microbulk Micromegas, in modular or large-format form, can meet the size, radiopurity, and threshold demands of next-generation rare-event experiments.","feed_headline":"Tiled Micromegas planes scale rare-event detectors past size limits","feed_subtitle":"A mosaic of 52 radiopure modules forms a two-meter readout plane to hunt for a rare nuclear decay.","key_machinery":"The load-bearing element is the modular readout tile: a microbulk Micromegas circuit — a copper-polyimide laminate with a thin mesh separated from a segmented anode by a roughly 50-micron amplification gap — fixed to a copper support. Around each active area sit rim electrodes that steer the drift electric field lines so that primary electrons are collected even at the gaps between tiles; simulations show collection efficiencies up to 99.94% with sufficient rim voltages. A second key piece is the face-to-face (FtF) connector, two flexible circuits pressed together through expanded PTFE so that pads make contact without a commercial high-radioactivity connector inside the detector; 804 contacts survived eleven months of temperature cycling with no loss of continuity. For the dark matter detector, the additional mechanism is a GEM (a gas electron multiplier foil) placed above the Micromegas to pre-amplify the charge and thereby reduce the energy threshold.","core_discovery":"The central claim is that microbulk Micromegas readout planes can be scaled to the sizes required by rare-event experiments without losing their advantage in radioactivity or energy resolution. The paper establishes this through the SR2M module: a 20 x 20 cm2 microbulk circuit mounted on a copper support with a tab that exits the chamber, an electron reintegration system of inner and outer rims that steer drift-field lines away from inter-module dead zones, and, in the second version, a radiopure face-to-face connector that replaces high-radioactivity commercial connectors inside the detector. A seven-module readout plane was commissioned with radioactive sources and achieved useful electron transmission, gain, and energy resolution, and a full-size plane of 52 modules was assembled for the finalized 140 kg double beta decay detector. For the WIMP-search detector, the thesis reports that a 25 x 25 cm2 microbulk Micromegas installed in a 10-bar TPC reproduced the expected gain curve, reached voltages close to the expected maximum before sparking, and achieved a 1–1.5 keV energy threshold, with a GEM-Micromegas system and a new low-radioactivity Micromegas designed to push that threshold lower. A separate demonstrator, AlphaCAMM, applies the same readout technology to detect surface alpha particles.","pith_inferences":["If the small-to-large transferability assumption holds for the current TREX-DM plane, the same characterization method could be extended to other gas mixtures and pressures, letting future large planes be tuned without building a new prototype for every operating point.","The tiling concept is not tied to microbulk Micromegas: the SR2M-v2 modules already use a thermally bonded mesh-and-circuit construction, suggesting the module design could accommodate whatever radiopure micropattern technology matures next.","The edge-loss behaviour measured with the internal rim implies that the optimal plane-level operating point is a trade-off between collecting charge at the boundaries and preserving track reconstruction in the last millimetres; a dedicated study of this trade-off would determine whether higher rim voltages are worth applying.","AlphaCAMM's emanation-based background model could be turned into a standard screening tool for radiopure materials, extending beyond the specific experiment that motivated it."],"forward_implications":["A readout plane for a ton-scale double beta decay TPC can be built by tiling 52 SR2M modules, reaching a diameter of nearly two meters with signals extracted through a small number of flanges.","The electron reintegration system recovers almost all primary electrons that would otherwise be lost in dead zones between modules: simulations reach 99.94% efficiency, and measurements with the internal rim show only a small loss in the last two millimeters at a modest rim voltage.","Eliminating the external rim and using the face-to-face connector reduced the fraction of dead channels in a seven-module plane from 9.2% to 1.1%, with connection losses removed entirely.","A GEM pre-amplification stage above a Micromegas can lower the energy threshold of a high-pressure gas TPC, which is the path to sensitivity for low-mass WIMPs.","The same readout technology, packaged as AlphaCAMM, provides a low-background detector for surface alpha contamination on detector materials."],"supporting_citations":[{"why":"Supplies the microbulk Micromegas manufacturing technique that the SR2M module is based on.","marker":"[11]"},{"why":"Provides radiopurity measurements of materials and commercial connectors that drive the module's material choices.","marker":"[36]"},{"why":"Gives the systematic characterization of microbulk Micromegas in Ar/Ne isobutane mixtures used to set operating points.","marker":"[77]"},{"why":"Describes the TREX-DM detector design and commissioning that the second part of the thesis optimizes.","marker":"[31]"},{"why":"Defines the PandaX-III TPC requirements and the decision to use a tessellated microbulk readout plane.","marker":"[34]"},{"why":"Reports the seven-module readout plane's commissioning results, including the 9.2% defective-channel activity map.","marker":"[48]"},{"why":"Documents the completed full-size detector with 52 SR2M-v2 modules and its planned underground installation.","marker":"[35]"},{"why":"Describes the thermal-bonding Micromegas fabrication used for the second-version SR2M modules.","marker":"[55]"},{"why":"Builds the radiopurity background model for TREX-DM and identifies dominant background contributions.","marker":"[28]"},{"why":"Provides earlier high-pressure microbulk Micromegas results in xenon that motivate the tiled readout approach.","marker":"[30]"}],"fun_headline_variants":["Mosaic Micromegas readout planes for giant rare-event TPCs","Tiled Micromegas modules enable low-background two-meter detectors","GEM-Micromegas system cuts energy threshold for WIMP search","AlphaCAMM: Micromegas-based alpha detector for ultra-low background","Scaling microbulk Micromegas to rare-event experiment dimensions"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The load-bearing premise, stated in Section 7.2, is that the small Micromegas used for laboratory calibration behaves like the large pixelated one installed in the detector despite a difference in amplification-hole size, and if that small-to-large transfer fails, the chosen operating voltages and expected resolutions are unsupported.","fun_headline_variants_meta":{"raw":{"variants":["Mosaic Micromegas readout planes for giant rare-event TPCs","Tiled Micromegas modules enable low-background two-meter detectors","GEM-Micromegas system cuts energy threshold for WIMP search","AlphaCAMM: Micromegas-based alpha detector for ultra-low background","Scaling microbulk Micromegas to rare-event experiment dimensions"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000446,"raw_usage":{"total_tokens":2377,"prompt_tokens":1195,"completion_tokens":1182,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":811,"completion_tokens_details":{"reasoning_tokens":1082}},"tokens_in":811,"tokens_out":1182,"duration_ms":9267,"temperature":1.0,"reasoning_tokens":1082,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-11T10:42:36.472989+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Take the installed 25 x 25 cm pixelated Micromegas and the 2 cm single-pixel Micromegas used for laboratory calibration, place both in the same gas mixture (Ar + 1% isobutane, 1.5 bar) with the same drift and amplification fields, and compare gain curves and energy resolution at the 22 keV line of a 109Cd source; if the large detector still shows 23-29% FWHM while the small one shows 11-13% FWHM under identical conditions, the transferability assumption is falsified.","supporting_citations":[{"cited_title":null,"cited_arxiv_id":null,"evidence_quote":"Gives the systematic characterization of microbulk Micromegas in Ar/Ne isobutane mixtures used to set operating points."},{"cited_title":"PandaX-III high pressure xenon TPC for Neutrinoless Double Beta Decay search","cited_arxiv_id":null,"evidence_quote":"Reports the seven-module readout plane's commissioning results, including the 9.2% defective-channel activity map."},{"cited_title":"A thermal bonding method for manufacturing Micromegas detectors","cited_arxiv_id":null,"evidence_quote":"Describes the thermal-bonding Micromegas fabrication used for the second-version SR2M modules."}],"review_version":1}