{"id":"93e2b2b1-6200-4f11-9b84-14e226a095d1","arxiv_id":"2505.13083","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":5.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":4,"one_line_summary":"An active piezo-actuated optical table achieves 21 to 36 dB seismic suppression in the 0.5 to 1.3 Hz band, with about 1 nm/sqrt(Hz) of residual horizontal motion at 1 Hz.","lead":"This paper describes an optical table that uses piezo actuators and seismometers to actively cancel ground vibrations, cutting table motion by 21 to 36 dB between 0.5 and 1.3 Hz. It matters because a simple, low-cost isolator like this could reduce microseismic noise for auxiliary optics in gravitational wave detectors and precision laboratories.","discovery_kind":"new_application","skeptic_critique":{"model":"deepseek-v4-flash","headline":"Headline suppression rests on a single uncalibrated witness seismometer; the only independent mechanical witness (suspended-mass OSEM) shows ~6 dB, not 21-36 dB, so sensor self-noise or tilt coupling could dominate the residual and the quoted 1 nm/sqrt(Hz).","rationale":"The reader's conditional verdict is appropriate. The most load-bearing uncertainty is whether the witness seismometer output equals true table translation in the microseism band. The reader identified self-noise and tilt coupling; I add the independent OSEM result as a sharper check, since it is the only non-seismometer mechanical measurement in the paper and it shows far less improvement than the headline claim. This does not refute the claim, because the OSEM measures relative motion that can be dominated by non-seismic forces, but it does mean the central experimental result currently lacks independent corroboration. The proposed concrete test, using a different sensor type on the same table, would settle whether the seismometer-based suppression is real or an artifact of the sensor. If confirmed, the paper's engineering conclusion stands; if not, the suppression and residual numbers would need downward revision and a more cautious conclusion.","tokens_in":8592,"tokens_out":9547,"duration_ms":104849,"concrete_test":"Repeat the control-on/control-off measurement with an independent absolute-motion sensor on the table, e.g., a calibrated GS13 geophone or a laser interferometer referenced to a quiet inertial mass, placed beside the witness seismometer. Compute the ground-to-table transmissibility from 0.1 to 5 Hz for both sensors and compare the suppression and residual ASD in 0.5-1.3 Hz. If the independent sensor reproduces the 21-36 dB suppression and 1 nm/√Hz residual within ±3 dB, the witness assumption is validated; if not, the headline estimates must be revised for sensor self-noise or tilt contamination.","verdict_should_be":"UNCHANGED","load_bearing_attack":"The central claim, 21-36 dB suppression with 1 nm/√Hz residual at 1 Hz, is read from the ratio of a ground T120 seismometer to a witness T120 on the table (Section III, Figure 8). For this ratio to be the table's absolute horizontal translation, the witness must be free of self-noise and tilt-to-translation coupling in the 0.5-1.3 Hz band. The paper's internal checks are suggestive but not independent: the in-loop and witness sensors differ by ~12 dB, and the fitted self-noise curve is used to predict the witness spectrum. The only independent mechanical witness reported, the OSEM measuring mirror motion relative to the table (Figure 9), shows only a factor-of-2 (~6 dB) reduction in the control band, far short of 21-36 dB. The authors plausibly attribute this to non-seismic noise (acoustic or suspension interaction), but that attribution means no measurement confirms that the table's absolute horizontal translation actually drops by 21-36 dB. Without a second sensor type, error bars, or repeated trials, the headline numbers remain contingent on the witness seismometer faithfully representing table motion.","agreement_with_reader":"partial"},"referee_report":{"model":"deepseek-v4-flash","summary":"The manuscript describes an active seismic isolation table for auxiliary optics, using piezo actuators in five degrees of freedom (three translations and two tip-tilts) with a seismometer in the feedback loop. The authors report 21-36 dB suppression of ground motion between 0.5 and 1.3 Hz, with a residual horizontal motion of about 1 nm/sqrt(Hz) at 1 Hz, as measured by a witness seismometer on the table. They also discuss sensor self-noise, tilt-to-translation coupling, and table resonances as limitations that prevent control below 0.3 Hz, and they present a suspended-mass OSEM measurement that shows a smaller factor-of-two reduction in relative motion.","tokens_in":8808,"tokens_out":4416,"duration_ms":43296,"significance":"If the suppression claim is correct, this simple piezo-based pre-isolator would be a low-cost, easily manufactured option for reducing microseismic noise on auxiliary optical tables in gravitational wave detectors, with performance in the microseism band comparable to much more complex systems such as AEI-SAS. The paper is generally well organized and includes useful engineering details: measured open-loop transfer functions, a huddle-test self-noise fit, a noise budget (Figure 8), and an explicit discussion of tilt coupling and resonance limitations. However, the central quantitative claim rests on a single sensor type (the witness seismometer) and lacks independent mechanical verification, statistical uncertainty, and a clear statement of whether the residual is sensor-noise-limited.","major_comments":[{"comment":"The OSEM measurement of the suspended mirror relative to the table shows only a factor of two (~6 dB) reduction in the control band, whereas Figure 8 claims 21-36 dB suppression of the table itself. The attribution of this discrepancy to acoustic or suspension-related noise is plausible but is not supported by any quantitative analysis. Because the OSEM is the only independent mechanical witness of table motion in the paper, the headline suppression figure is not yet corroborated. Please provide a second independent measurement of table translation or a quantitative noise budget for the OSEM that demonstrates the consistency of a 6 dB relative-motion reduction with a 21-36 dB table-motion suppression.","section":"Section III, Figures 8 and 9"},{"comment":"The witness seismometer spectrum lies close to the fitted self-noise curve, and the 'Predicted Witness Seismometer' curve is the quadrature sum of self-noise and the seismometer response to predicted table motion. Consequently, the claimed 1 nm/sqrt(Hz) residual at 1 Hz is an interpretation that depends on the self-noise fit, not a direct measurement. The text should state explicitly whether this residual is an upper limit or a best estimate, and should give an uncertainty that includes sensor self-noise and tilt-to-translation coupling. If the witness were self-noise-limited, the suppression ratio might underestimate the true table suppression, so the direction of the bias should be quantified.","section":"Section III, Figure 8 and surrounding text"},{"comment":"The quantitative claims (21-36 dB and 1 nm/sqrt(Hz)) are presented without error bars or repeated trials. The suppression ratio is the ratio of ground to witness seismometer spectra and therefore depends on the relative calibration of the two instruments, but the calibration procedure is not described. Please add error bars from multiple measurements or from the spectral estimation method, and describe the relative calibration and its uncertainty.","section":"Section III, experimental methodology"},{"comment":"The text states 'This informed our target of 40 dB suppression in the control band' and the introduction gives a target band of 0.03-3 Hz, but the demonstrated performance is 21-36 dB over 0.5-1.3 Hz. The paper should clearly acknowledge that the target was not met and separate the achieved band from the target band in the abstract and conclusions to avoid overstatement.","section":"Section III, control band statement"}],"minor_comments":[{"comment":"There is a LaTeX typo in the abstract: '1 $\\mathrm{\\mathrm{nm/\\sqrt{Hz}}}$' has a double math-mode command; it should read '1 $\\mathrm{nm/\\sqrt{Hz}}$'.","section":"Abstract"},{"comment":"The word 'butter-worth' should be capitalized as 'Butterworth' when referring to the filter.","section":"Section III"},{"comment":"The table lists table mass as 20 kg and frame mass as 10 kg, but the vertical actuator text says 'Each piezo supports a load of 180 kg (for 720 kg total)'. Clarify what the 720 kg includes and how the load path through the feet relates to the table and frame masses.","section":"Section II, Table I and text"},{"comment":"The self-noise curve is labeled as a fit; the fit parameters or the measurement method should be described in the text or caption so the reader can judge the reliability of the noise floor.","section":"Figure 8"}],"recommendation":"major_revision","confidential_remarks":"The paper is a useful engineering report within the scope of astro-ph.IM. The main concern is the discrepancy between the witness-seismometer suppression claim (21-36 dB) and the OSEM relative-motion result (~6 dB). If the authors can provide an independent confirmation or a rigorous error analysis that resolves this discrepancy, the paper would be suitable for publication. As written, the headline quantitative claim is not fully supported by the presented evidence."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Short version: this is a solid, honest experimental paper about a new five-DOF piezo pre-isolator for optical tables, and the 21–36 dB suppression around 0.5–1.3 Hz is real as an observed ratio between a witness seismometer on the table and a ground seismometer. But the interpretation of that ratio as absolute residual table motion rests on one sensor type, and the OSEM-based relative measurement in Figure 9 shows only ~6 dB, so the headline should be presented with more caution.\n\nWhat's new: the driver/idler flexure actuator is a neat mechanical trick, the five-DOF table configuration with vertical actuation in the feet and horizontal flexure stages is different from existing AEI-SAS/HEPI/ISI designs, and installing it at Gingin HOPF is a new application. The paper also does a good job of discussing tilt-to-translation coupling and internal resonances; that is unusually frank.\n\nThe soft spots are in the measurement chain. The central suppression figure is read from a single witness T120 on the table. The authors show a huddle-test self-noise curve and a predicted witness ASD, but the prediction uses a fitted self-noise and fitted plant resonances. More importantly, the only non-seismometer witness—the OSEM measuring relative motion between the table and the suspended mirror—shows a factor-of-2 reduction, far from 21–36 dB. The authors attribute this to acoustic noise or suspension interaction, which is plausible but means no independent measurement confirms the absolute table translation drops by that much. There are no error bars or repeated trials, and no data/code to allow reanalysis. On the positive side, the suppression claim is not circular in the sense of being generated by the model; it is a measured ratio, and the model is only used to explain shape. The tilt coupling mechanism is explicitly admitted to be not understood, which is honest but is a real limitation.\n\nWho this is for: people building auxiliary optical tables for GW detectors or precision experiments who need a simple pre-isolation stage. It is a legitimate engineering contribution, and it deserves a serious referee. My recommendation would be major revision: add uncertainty quantification, show repeated measurements, and either get an independent witness of table motion (e.g., accelerometer or optical sensor) or explicitly narrow the claim to 'as measured by a witness seismometer'.","headline":"Useful, honest engineering paper on a new piezo pre-isolator for optical tables, but the headline 21–36 dB suppression rests on a single witness seismometer and lacks independent confirmation.","tokens_in":9404,"tokens_out":1739,"would_cite":true,"duration_ms":17445,"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":"A piezo-actuated optical table suppresses ground motion by 21–36 dB between 0.5 and 1.3 Hz, leaving about 1 nm/√Hz residual horizontal motion at 1 Hz.","keywords":["seismic isolation","piezo actuator","optical table","active vibration isolation","microseism band","feedback control","gravitational wave detector","tilt-to-translation coupling"],"falsifier":"Put an independent displacement sensor on the table, such as an optical interferometer measuring table position against a reference mass, and compare its 0.5–1.3 Hz spectrum with the table's control-on spectrum; if the independent readout does not show the same 21–36 dB suppression relative to ground, the claim is contaminated by sensor effects. A simpler check is a huddle test: place two sensors side by side on the table, difference them with control off, and see whether the fitted self-noise actually bounds the in-loop-versus-witness residual inside the control band.","tokens_in":8364,"feed_emoji":"🔬","tokens_out":11067,"duration_ms":102179,"temperature":0.7,"pith_summary":"An active vibration-isolation table for precision optics is built from piezo stack actuators embedded in its feet, giving it controlled motion in five degrees of freedom. With feedback from a ground-motion sensor on the table, the system reduces ground vibration by 21 to 36 dB between 0.5 and 1.3 Hz, the ocean-driven microseism band that excites suspended mirrors in gravitational-wave detectors. The residual horizontal table motion falls to about $1~\\mathrm{nm/\\sqrt{Hz}}$ at 1 Hz. The paper is trying to establish that a compact, simply manufactured piezo pre-isolator can deliver this suppression on auxiliary optical tables, as a complement to much larger multi-stage isolation systems. A sympathetic reader cares because this is the band that often sets the low-frequency noise floor for suspended optics.","feed_headline":"Piezo table cuts ground motion by 21 to 36 dB","feed_subtitle":"Five-axis active suppression leaves about 1 nm/√Hz of residual motion at 1 Hz.","key_machinery":"The load-bearing mechanism is the five-degree-of-freedom piezo pre-isolator: four vertical piezo stacks inside height-adjustment feet supply vertical, pitch, and roll, while four horizontal piezo stacks mounted on paired flexure stages supply X and Y translation, with the actuator geometry making the table stiff against rotation about the vertical axis. A broadband ground-motion sensor in the feedback loop senses table motion, a second sensor acts as an out-of-loop witness, and a third on the ground records the reference; the controller is a band-pass boost filter shaped as a ratio of two third-order band-pass filters with cutoff pairs (0.2, 3) Hz and (0.4, 1.4) Hz. This mechanism carries the argument by converting ground motion into a measurable open-loop gain and a control-on reduction in the displacement spectral density, with the tilt-coupling model used to explain the low-frequency transfer function shape.","core_discovery":"On its own terms, the paper claims that a five-degree-of-freedom table, actuated by piezo stacks and controlled by broadband ground-motion sensors, suppresses ground motion by 21 to 36 dB over 0.5 to 1.3 Hz along the optic axis, as measured by a witness sensor on the table, with the in-loop sensor suggesting even deeper suppression that is limited by sensor self-noise. The claim includes a specific performance point: residual horizontal motion of about $1~\\mathrm{nm/\\sqrt{Hz}}$ at 1 Hz, down from $20~\\mathrm{nm/\\sqrt{Hz}}$ with control off. The authors also report that this suppression reduces the broadband relative motion between the table and a suspended mirror by a factor of two, while noting that tilt-to-translation coupling and internal table resonances currently prevent extending control down to the 0.03 Hz target.","pith_inferences":["If the $1~\\mathrm{nm/\\sqrt{Hz}}$ residual is genuine table motion, the same flexure-plus-piezo architecture could transfer to non-gravitational precision metrology, where the microseism band is often the dominant environmental noise.","A clean test of the suppression claim would separate sensor from mechanical contributions: an independent optical readout of table position, or a second witness sensor at a different table location, would show whether the 21–36 dB numbers are true isolation or partly sensor correlation.","Because the tilt-to-translation coupling is estimated from the measured transfer function rather than measured directly, a dedicated tilt channel could make that mechanism quantitative and possibly extend the control band without new actuators."],"forward_implications":["Compact piezo pre-isolation can cut microseism-band table motion by one to two orders of magnitude, bringing auxiliary optical tables in gravitational-wave facilities toward the suppression of much larger active stages.","Suspended mirrors seated on such tables see less seismic excitation at their suspension resonances; the paper measures a factor-of-two reduction in broadband relative motion between table and mirror in the control band.","Because the fitted sensor self-noise at 1 Hz is roughly ten times the instrument specification, the demonstrated suppression is sensor-limited rather than actuator-limited, so quieter sensors should push the residual motion lower.","Correcting tilt-to-translation coupling and damping the roughly 15 Hz table resonance should let the same hardware reach toward the 0.03 Hz target band, as the authors plan."],"supporting_citations":[{"why":"Direct predecessor: a one-degree-of-freedom piezo pre-isolator achieved up to 20 dB suppression around 0.75–1.3 Hz, which this table extends to five degrees of freedom.","marker":"[17]"},{"why":"Comparison benchmark: a larger active isolation system achieved 40 dB horizontal suppression near 1 Hz, setting the target context for the claimed performance.","marker":"[11]"},{"why":"Characterizes low-frequency sensor self-noise that limits the sub-0.13 Hz band in comparable active systems.","marker":"[12]"},{"why":"Surveys large pre-isolation systems and reports suppression levels up to 60 dB, the performance context for the simpler table.","marker":"[9]"},{"why":"Supplies the site seismic array and average ground-motion conditions used to set the sensor-noise margin in the measurement.","marker":"[24]"},{"why":"Control and data acquisition system used for the swept-sine transfer-function measurements and spectral-density readouts.","marker":"[25]"},{"why":"Suspension used for the test mass whose relative table-to-mirror motion is measured with control on and off.","marker":"[26]"}],"fun_headline_variants":["Five-axis piezo table silences seismic noise by up to 36 dB","Piezo table tames ground motion: 21-36 dB off","Piezo table leaves 1 nm/√Hz residue, kills 21-36 dB","Piezo table cuts ground noise 21-36 dB, residual 1 nm/√Hz"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The claimed suppression numbers come from sensors on the table, and the argument treats the measured sensor self-noise as the floor; if tilting of the table that the sensors register as horizontal motion, or any other unmodeled sensor noise, is present inside 0.5–1.3 Hz, then the 21–36 dB figures would overstate the true isolation.","fun_headline_variants_meta":{"raw":{"variants":["Five-axis piezo table silences seismic noise by up to 36 dB","Piezo table tames ground motion: 21-36 dB off","Piezo table leaves 1 nm/√Hz residue, kills 21-36 dB","Piezo table cuts ground noise 21-36 dB, residual 1 nm/√Hz"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000885,"raw_usage":{"total_tokens":3807,"prompt_tokens":918,"completion_tokens":2889,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":534,"completion_tokens_details":{"reasoning_tokens":2797}},"tokens_in":534,"tokens_out":2889,"duration_ms":21226,"temperature":1.0,"reasoning_tokens":2797,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-15T20:20:04.617767+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"Put an independent displacement sensor on the table, such as an optical interferometer measuring table position against a reference mass, and compare its 0.5–1.3 Hz spectrum with the table's control-on spectrum; if the independent readout does not show the same 21–36 dB suppression relative to ground, the claim is contaminated by sensor effects. A simpler check is a huddle test: place two sensors side by side on the table, difference them with control off, and see whether the fitted self-noise actually bounds the in-loop-versus-witness residual inside the control band.","supporting_citations":[{"cited_title":"Abbott , author R","cited_arxiv_id":null,"evidence_quote":"Direct predecessor: a one-degree-of-freedom piezo pre-isolator achieved up to 20 dB suppression around 0.75–1.3 Hz, which this table extends to five degrees of freedom."},{"cited_title":"Wanner , author G","cited_arxiv_id":null,"evidence_quote":"Comparison benchmark: a larger active isolation system achieved 40 dB horizontal suppression near 1 Hz, setting the target context for the claimed performance."},{"cited_title":"Kirchhoff ,\\ title Implementation of an active seismic isolation system for the AEI 10 m prototype ,\\ 10.15488/11634 Ph.D","cited_arxiv_id":null,"evidence_quote":"Characterizes low-frequency sensor self-noise that limits the sub-0.13 Hz band in comparable active systems."},{"cited_title":"Matichard , author B","cited_arxiv_id":null,"evidence_quote":"Surveys large pre-isolation systems and reports suppression levels up to 60 dB, the performance context for the simpler table."},{"cited_title":"Satari , author C","cited_arxiv_id":null,"evidence_quote":"Supplies the site seismic array and average ground-motion conditions used to set the sensor-noise margin in the measurement."},{"cited_title":"An Overview of the LIGO Control and Data Acquisition System","cited_arxiv_id":"physics/0111077","evidence_quote":"Control and data acquisition system used for the swept-sine transfer-function measurements and spectral-density readouts."}],"review_version":1}