Conventional Thermometry Research Articles

CMOS on-chip thermometry at deep cryogenic temperatures

Accurate on-chip temperature sensing is critical for the optimal performance of modern complementary metal-oxide-semiconductor (CMOS) integrated circuits (ICs), to understand and monitor localized heating around the chip during operation. The development of quantum computers has stimulated much interest in ICs operating at deep cryogenic temperatures (typically 0.01–4 K), in which the reduced thermal conductivity of silicon and silicon oxide and the limited cooling power budgets make local on-chip temperature sensing even more important. Here, we report four different methods for on-chip temperature measurements native to CMOS industrial fabrication processes. These include secondary and primary thermometry methods and cover conventional thermometry structures used at room temperature as well as methods exploiting phenomena that emerge at cryogenic temperatures, such as superconductivity and Coulomb blockade. We benchmark the sensitivity of the methods as a function of temperature and use them to measure local excess temperature produced by on-chip heating elements. Our results demonstrate thermometry methods that may be readily integrated in CMOS chips with operation from the millikelvin range to room temperature.

Evidence of Paleoproterozoic metamorphism in Vestfold Hills, East Antarctica: Insights from phase equilibria modelling and monazite CHIME dating

The Vestfold Hills sector on the coastal fringe of the Princess Elizabeth Land forms part of an Archean to Paleoproterozoic aged cratonic nucleus of the East Antarctic Shield. A charnockite-granite association from the Mossel Gneiss Group in the northern region of the Vestfold Hills is investigated in this work to characterise the metamorphic-magmatic evolution of the area. Conventional thermometry and phase equilibria modelling indicate that the charnockite formed as a result of ultra-high temperature metamorphism at low-intermediate pressure (∼4 kbar). Phase equilibria modelling, reveals that the melt-integrated charnockite composition is a restitic product of a protolith of quartz diorite composition which underwent isobaric heating (peak temperature up to 960 °C) at 4 kbar pressure followed by anatexis. The anatexis of the quartz diorite protolith also resulted in the formation of the associated granitic melt. U–Th-PbTotal ages obtained from monazites of the granite integrated with CHIME ages extracted using the isochron method indicate an emplacement age of ∼2200 Ma and two younger events are recorded at ∼2000 Ma and ∼1700 Ma. The younger ages are ascribed to the resetting during the emplacement of younger basalt dykes that cross cut the charnockite-granite sequence. Vestfold Hills’ geological correlations with Indian and Australian cratons are discussed considering this new data.

Infrared Imaging of the Brain-Eyelid Thermal Tunnel: A Promising Method for Measuring Body Temperature in Afebrile Children.

(1) Infrared thermography of the inner canthus of the eye has emerged as a promising tool for temperature screening and fever diagnosis. Its non-invasive nature lends itself well to mass screening in diverse settings such as schools, public transport, and healthcare facilities. Swift and accurate temperature assessment plays a pivotal role in the early identification of potential fever cases, facilitating timely isolation, testing, and treatment, thereby mitigating the risk of disease transmission. Nonetheless, the reliability of this approach in the pediatric population, especially when compared to conventional thermometry methods, remains unexplored. This preliminary study aimed to evaluate the concordance between the temperature of the inner canthus of the eye (Tic,eye), referred to as the brain-eyelid thermal tunnel (BTT°), with axillary and tympanic methods in afebrile children. (2) Methods: A cohort of 36 children, matched in a 1:1 ratio for gender and age, underwent comprehensive assessments encompassing anthropometric data, blood pressure evaluations, axillary (Tax) and tympanic (Tty) temperature measurements, as well as BTT° infrared thermography. (3) Results: The findings revealed a high level of concordance among the tympanic, axillary, and BTT° measurement methods. Bland-Altman plots showed that the bias was minimal, and no statistically significant differences were observed when comparing BTT° with axillary (p = 0.136) and tympanic (p = 0.268) measurements. Passing-Bablok regression scatter plots further confirmed the agreement, aligning the fitted regression line closely with the identity line for both axillary versus BTT° and tympanic (Tty) versus BTT° comparisons. (4) Conclusions: This study holds significant implications for public health, especially in the context of infectious disease outbreaks such as COVID-19. BTT° infrared thermography of the inner canthus of the eye (Tic,eye) reliably measures body temperature in afebrile children in controlled settings; nevertheless, its practical application necessitates the adaptation of biothermodynamic parameters to accommodate diverse environmental conditions.

Enhancing process efficiency through improved temperature measurement: the EMPRESS projects

EMPRESS 2 is a European project to enhance the efficiency of high value manufacturing processes by improving temperature measurement and control capability. This project seeks to address four contemporary thermometry challenges in this sector, and new developments from this and its predecessor project, EMPRESS, will be described:• Below 1000°C many industrial processes require reliable surface thermometry e.g. welding, coating, forging and forming. Conventional non-contact surface thermometry techniques e.g. thermal imaging are prone to large errors (tens of degrees) due to reflected thermal radiation and unknown emissivity. Contact thermometry approaches are prone to similarly large errors. Traceable imaging phosphor thermometry is being developed to overcome these difficulties, and is being combined with quantitative thermography to determine emissivity for thermometry over wide fields of view.• Above 1300°C sensor drift is a significant unaddressed issue for casting, forging and heat treatment, causing large errors. There is a need for more stable sensors and standardisation of at least one new thermocouple type to fill the gap from 1300°C to 1800°C. This is being addressed through improved Pt-Rh thermocouples and optimisation of double-walled mineral insulated, metal sheathed thermocouples by mitigating insulation breakdown and drift effects.• Combustion temperature measurement is very challenging and traceability is almost non-existent; for example, thermocouple measurements of flame temperatures can be in error by hundreds of degrees. A ‘standard flame’ that can be transported to users’ sites has been developed, and is being deployed in several high value manufacturing and industrial applications to a) demonstrate the possibility of reducing flame temperature uncertainties by at least an order of magnitude and b) for the first time to demonstrate in-situ traceability to the International Temperature Scale of 1990 (ITS-90).• Many processes are not amenable to any conventional thermometry techniques due to inaccessibility, ionising radiation, electromagnetic interference, and contamination; here methods based on optical fibres are ideal but there are no traceable calibration techniques for such sensors currently available. A suite of different fibre-optic thermometers and calibration techniques is being developed to address this. In some cases (ionising radiation) darkening of the fibre is a problem, and this is being overcome by the development of novel thermometry approaches based on practical ‘hollow core’ fibres.

Expansion of Thermometry in Magnetic Hyperthermia Cancer Therapy: Antecedence and Aftermath

Magnetic hyperthermia cancer therapy (MHCT) is a promising antitumor therapy based on the generation of heat by magnetic nanoparticles under the influence of an alternating-current magnetic field. However, an often-overlooked factor hindering the translation of MHCT to clinics is the inability to accurately monitor temperature, thereby leading to erroneous thermal control. It is significant to address 'thermometry' during magnetic hyperthermia because numerous factors are affected by the magnetic fields employed, rendering traditional thermometry methods unsuitable for temperature estimation. Currently, there is a dearth of literature describing appropriate techniques for thermometry during MHCT. This review offers a general outline of the various modes of conventional thermometry as well as cutting-edge techniques operating at cellular/nanoscale levels (nanothermometry) as prospective thermometers for MHCT in the future.

Refertilization of depleted mantle peridotite in the Nagaland–Manipur ophiolite, north‐east India: Constraints from PGE, mineral, and whole‐rock geochemistry

This paper discusses whole‐rock geochemistry, mineral chemistry, and platinum group element (PGE) systematics of depleted mantle rocks (harzburgite and dunite) from the northern part of Nagaland–Manipur Ophiolite (NMO), north‐east India, to comprehend their source features, fractionation behaviour of PGE during magmatic evolution, and its tectonic origin. The studied ultramafic rocks are characterized by a low concentration of CaO (0.57–0.71 wt%), Al2O3 (0.18–0.92 wt%) with ∑REE of 1.135–2.702 ppm and high concentrations of MgO (38.70–44.21 wt%), Cr (1,843–4,572 ppm), and Ni (894–4,138 ppm). They show U‐shaped REE patterns [LREE and HREE enrichment (La/Sm)N = 1.85–4.11, (Dy/Yb)N = 0.51–0.85]. Olivine ranges Fo 88.18 to Fo92.23, whereas Cpx and Opx range En44.84 to En47.89 and En86.37 to En93.37 respectively. The chrome spinel Cr# [Cr/(Cr + Al)] and Mg# [Mg/(Mg + Fe2+)] are 0.47–0.83 and 0.31–0.60, respectively, which indicates recrystallization from a boninitic magma in a Supra‐Subduction Zone setting. Conventional thermometry indicates the equilibration temperatures of the dunite sample yielded high temperatures of ~850°C, suggesting their formation due to later interaction with high‐temperature percolating melts. The PGE contents in harzburgite are low (125.6–142.8 ppb) as compared to the dunite (248–360 ppb). They have high PPGE/IPGE and negative Pt* (Pt/Pt* = 0.73) anomaly, which is characteristic of re‐entry of PPGE into the system via reaction with percolating basaltic melt in the mantle wedge. Significantly higher concentration of PPGEs than IPGEs in the samples, indicating recrystallization of PPGEs with early sulphide fractionation. The presence of significant Rh and Pd enhancements relative to Pt in all samples suggests that Pt was removed during PGE fractionation. This could be one of the reasons for both harzburgite and dunite's sulphide undersaturation. PGE distribution in NMO ultramafic rocks was therefore validated as being governed by sulphide saturation in parental magma and altered not only by partial melting but also by fractionation during their production in the Supra‐Subduction Zone environment.

Persistent luminescence ratiometric thermometry

Over the past twenty years, luminescence intensity ratio (LIR)-based temperature sensing technology has become a research hotspot. Despite the great progress in this field, the main limitation of conventional LIR thermometry is the requirement of continuous exposure to excitation source during measurement that may result in thermal effect and thus disturb the accuracy of temperature readout. In order to solve this problem, a new type of thermometry is proposed here, exploiting NaYF4:Er3+ that exhibits long persistent luminescence (PersL) over almost one day. The LIR between the two green PersL bands associated with the 2H11/2→4I15/2 and 4S3/2→4I15/2 electronic transition of Er3+ ions in NaYF4:Er3+ is demonstrated to be a reliable indicator of temperature, which could effectively avoid the long-term exposure to irradiation source. To clearly emphasize the difference between a regular LIR and this research, the newly proposed strategy here is named as persistent luminescence intensity ratio (PLIR) thermometry. The density functional theory and thermoluminescence measurement indicate the PersL mechanism of NaYF4:Er3+ probably stems from the fluorine vacancy related defects. The proposed PLIR thermometry, different from the traditional LIR counterpart, is believed to open a new road to determine temperature via an interesting and reliable way, which will greatly inspire other researchers in the related fields.

Petrological implications of element redistribution during metamorphism: insights from meta-granite of the South Delhi Fold Belt, Rajasthan, India

AbstractMeta-granites of the South Delhi Fold Belt, northwestern India, contain spectacular reaction textures formed during the metamorphic replacement of primary minerals. Textural relationships imply that amphibole was replaced sequentially in two stages. Epidote + titanite + quartz symplectite formed syn-tectonically on amphibole grain boundaries/fractures, followed by post-deformational growth of euhedral garnet overprinting amphibole grains. Besides occurring as symplectite grown during deformation, titanite in this rock also developed as a post-tectonic corona around magnetite. Parent magnetite contains exsolutions of ilmenite and/or ultrafine lamellae of Ti-rich oxide (Ti-oxd). Textures involving coronal titanite suggest their formation through a magnetite + ilmenite(/Ti-oxd) + plagioclase → titanite reaction. Compositional attributes and the calculation of the gain versus loss of components during the reaction suggest that the Mn2+for garnet (XSpss= 0.23–0.29) that grew replacing amphibole was supplied by ilmenite (Mn2+is 0.118–0.128 apfu) as it disintegrated to form coronal titanite. The redistribution of components between the metamorphic reaction sites connects the texturally unrelated domains and suggests that these zones were in chemical equilibrium during metamorphism. We estimated theP–Tconditions of metamorphism for these post-tectonic assemblages as ∼650–700 °C from pseudosection modelling and conventional thermometry. Zircon data from this study suggest that the granitic rock crystallized at 988.8 ± 8.8 Ma. We propose that the metamorphic phases replaced the primary minerals during the mid Neoproterozoic tectonic activity reported from this terrane. The syn-tectonic symplectitic assemblage formed as the temperature increased during prograde metamorphism, and the post-tectonic minerals developed at peak conditions following the cessation of deformation.

La2O2S:Er3+/Yb3+ nanoparticles synthesized by the optimized furnace combustion technique and their high-resolution temperature sensing

Nanoparticles of less than 100 nm of La2O2S co-doped with Er3+ and Yb3+ in 2% and 12% concentrations, respectively, were synthesized by the improved furnace combustion technique that limits the precursor usage and without the hazardous chemicals. The lanthanum oxysulfide was identified in hexagonal crystal phase. Under 980 nm excitation the sample exhibits a typical upconversion photoluminescence for Yb3+/Er3+. Due to the high concentration of Yb3+, the red emission of Er3+ is of high intensity due to the energy back-transfer. The red emission is less pronounced in downshifting spectrum. Chromaticity analysis shows high color purities of emissions. La2O2S:Er3+/Yb3+ nanoparticle performances as a luminescent temperature sensor were first predicted by the Judd-Ofelt theory and then compared with the conventional experimental thermometry by Luminescence intensity ratio method, with an excellent match in all parameters. The relative sensitivity at 300 K is 1.14 K−1 and it remains relatively high at the physiologically relevant range. The obtained temperature resolution was 0.17 K at 300 K.

Tectonics of the Isua Supracrustal Belt 1: P‐T‐X‐d Constraints of a Poly‐Metamorphic Terrane

AbstractThe Eoarchean Isua supracrustal belt (ISB) has been interpreted as one of the earliest records of subduction processes, leading to the conclusion that a plate tectonic geodynamic system was likely operating since the early Archean. However, proposed tectonic models remain difficult to evaluate as our understanding of the metamorphic and structural evolution remains fragmentary. Here, we present a metamorphic study of the supracrustal rocks of the ISB. We used petrographic and microstructural observations, phase equilibria, isopleth geothermobarometry, and conventional thermometry to explore the prograde, peak, and retrograde metamorphic evolution of the northeastern ISB. Our results show that the ISB records a syn‐tectonic, amphibolite facies metamorphic event (M1) with peak conditions of 550°C–600°C and 0.5–0.7 GPa. M1 was followed by a static, lower amphibolite facies metamorphic event (M2; <540°C and <0.5 GPa). Published constraints suggest that M1 and M2 occurred in the late Eoarchean (>3.5 Ga) and the Neoarchean (<2.9 Ga), respectively. These events are partially overprinted by late low temperature (<500°C) retrogression (M3) that is most intensely developed in the northeastern part of the belt; it typically overprints some peak mineral phases while preserving the peak fabric. Our findings are consistent with spatially homogeneous syn‐tectonic amphibolite facies metamorphism and macroscale folding. Such features are predicted by a heat‐pipe tectonic model. Therefore, our findings permit the interpretation of the ISB as a record of early nonuniformitarian tectonic processes.

Titanium in calcium amphibole: Behavior and thermometry

Abstract Thermometry of high-grade metamorphic rocks is difficult due to fast cationic diffusion during slow cooling, but the titanium content of calcium amphibole (Ti-Amp) can retrieve amphibole-forming temperature as high as ~1000 °C. Based on pseudosection modeling and past research survey, we find that Ti-Amp is controlled by temperature under the conditions of oxygen fugacity <2 log units above the Ni-NiO oxygen buffer (ΔNNO+2), in subalkaline systems, and with the presence of Ti-phases (rutile, ilmenite, or titanite). We apply available experimental data to calibrate a new Ti-Amp thermometer for such conditions: T ( C ° ) = 2400 1.52 − log ⁡ Ti Amp − 273 where T is temperature and log TiAmp is the Ti content of amphibole in atom per formula unit (apfu) expressed in the logarithm to base 10. The standard error of the calibration experiments is ±35 °C. This thermometer can be applied only if the aforementioned conditions are fulfilled. Besides, caution should be taken when applying the thermometer to rocks under subsolidus water-unsaturated conditions, which can be observed as non-equilibrium textures or low bulk-rock water content (<1–1.5 wt%). The results of this thermometer may be underestimated if applied to rocks that are equilibrated above 850 °C and contain rutile and a significant amount of water (>3.5–4 wt%). The new thermometer can be successfully applied to amphibole-bearing natural igneous and meta-morphic rocks. In addition, we propose the Si vs. Ti in amphibole diagram that roughly demarcates the boundaries among the high amphibolite, high-temperature granulite, and ultrahigh-temperature granulite facies. Although pseudosection modeling provides details of the P-T evolution of studied rocks, the Ti-Amp thermometer is quick and easy to apply. However, further research is needed to improve our knowledge of the behavior and stability of amphibole and to improve the accuracy of both pseudosection modeling and conventional thermometry.

Optical thermometry based on thermolabile intrinsic polarons in Tm3+ and Yb3+ co-doped congruent lithium niobate single crystal

By contrast with the conventional optical thermometry based on fluorescence intensity ratio (FIR) of thermally coupled levels (TCLs), we propose a novel thermometry strategy based on the diversity in thermal responses of non-TCLs of Tm3+ (3H4→3H6/1G4→3F4). Notably, the exacerbated response-contrast stems from the intrinsic structure variation induced by thermolabile polarons of NbLi3+ and NbNb4+ in congruent Tm3+,Yb3+:LiNbO3(LN) single crystal. The luminescence mechanism incorporated with energy transfer processes associated with polarons levels is revealed by investigating the abnormal temperature dependence of emission spectra under 980 nm excitation. The maximum absolute (SA) and relative (SR) sensitivities reach as high as 3.7% K−1 and 1.25% K−1 at 80 K, much higher than those of the TCLs strategy based on thermally coupled Stark sublevels of Tm3+ (3H4|1→3H6/3H4|3→3H6) in Tm3+,Yb3+:LN. This study demonstrates an effective pathway for developing new FIR strategies with improved sensitivities via taking advantage of host structure variation.

Evidence for early fragmentation-reassembly of ordinary chondrite (H, L, and LL) parent bodies from REE-in-two-pyroxene thermometry

Ordinary chondrites (OCs) are variably thermally metamorphosed meteorites thought to originate from at least three different parent bodies (H, L, and LL) in the Main Belt of asteroids. The thermal evolutions of OC parent bodies are frequently explained by the onion shell model; however, a competing hypothesis is the fragmentation-reassembly model. The onion shell model proposes undisrupted, internally heated parent bodies with concentrically stratified thermal structure, and posits that OC petrologic types (i.e., 3–6) develop with increasing temperature and burial depth. In this model, petrologic types are inversely correlated with cooling rate in the parent body. The alternative fragmentation-reassembly model invokes catastrophic collisional disruption of parent bodies that initially possessed onion shell structures, followed by rapid reaccretion of hot fragments, forming rubble pile bodies. Fragmentation would result in fast cooling (quenching) of collisional fragments from the temperature experienced by the parent body at the time of collision. Discrimination between these two models may be possible via investigation of the thermal histories of OCs by application of geothermometry and geospeedometry, which are used to constrain the temperatures and rates through which igneous and metamorphic rock samples cool. Most published cooling rate data for OC parent bodies are based on methods that record rates through low closure temperatures (∼500–200 °C) rather than from peak metamorphic temperatures. Recently, a rare earth element (REE)-in-two-pyroxene thermometer has been shown to establish peak or magmatic temperatures (TREE; Liang et al. [2013]) for rocks that cooled at moderate to fast geologic rates. We applied the REE-in-two-pyroxene method to determine peak temperatures for 18 OC samples (mostly type 6), in conjunction with conventional two-pyroxene thermometry (TBKN; Brey and Köhler [1990]) and Ca-in-olivine thermometry (TCa-Ol; Köhler and Brey [1990]), to determine closure temperatures and estimate cooling rates for OC parent bodies. Inconsistent with slow cooling rates expected within an onion shell structure, we obtain fast cooling at rates ≳0.3 °C/y from peak temperatures of ∼900 °C. Corroborating the TREE and TBKN measurements, TCa-Ol suggests that the OCs cooled through TCa-Ol closure temperatures (∼700 to 800 °C) at ∼10−2 to 10−1 °C/y. These cooling rates are three to six orders of magnitude faster than rates determined using methods sensitive to low temperature (≤500 °C) cooling (e.g., metallography, 40Ar–39Ar ages, 244Pu fission track). We developed a novel numerical thermal model that incorporates fragmentation of an initial onion shell body and reassembly into a rubble pile body that reproduces both the fast cooling from high temperatures and the slow cooling through low temperatures observed in chondritic meteorites. We hypothesize that OC parent bodies initially possessed onion shell thermal structures, but later experienced collisional breakup, then reaccreted rapidly to form thermally stable rubble-pile asteroids.

PRELIMINARY STUDY OF A IMAGE ANALYSIS SETUP APPROACH OF THERMAL TRACING JET ENGINE PARTS USING THERMAL PAINTS

Reduced engine performance comes with a higher operating temperature, and that limit is imposed by component material life. It is critical to have an accurate, full-field evaluation of the metal temperature of the hot section components for engine designers to develop dependable and lasting engines. Using conventional thermometry isn't recommended since it fails to generate heat gradients and results in problems when transferring data from measurement sites to the readout unit. It has recently been discovered that the thermal transfer condition has changed, and as a result, the actual temperature of the components cannot be measured. A paint will permanently change color if it is exposed to heat, this kind of paint is known as a temperature signaling paint. The traditional method is to test the thermal coatings personally. A manual process of interpretation results in mistakes because there is no accurate detection of isothermal limits that impact human eyesight. A systematic methodology for automated interpretation of thermal paints is detailed in this paper. A technique for orderly picture capture, image segmentation, and image processing, which employs a correct algorithm for surface temperature interpretation, has been addressed.

Nd3+ doped TZPN glasses for NIR operating single band ratiometric approach of contactless temperature readout

The most commonly applied luminescent thermometry (LTs) approach, which are based on the luminescence intensity ratio (LIR), requires integration of the analyzed emission bands. This analysis is often cumbersome and technically challenging due to spectral overlap and vicinity of the two emission bands. These limitations can be overcome by a new, single emission band ratiometric (SBR) approach which involves excitation through thermally induced excited state absorption (ESA) and ground state absorption (GSA). What is more, the frequent problem of low intensity of one of the radiative transitions, which are analyzed in conventional luminescent thermometry, is overcome owing to the involving of the SBR approach. Due to the opposable behavior of the emission intensity with temperature changes upon these two excitation schemes, improved thermal sensitivity can be achieved. In this work, the suitability of Nd3+-doped oxyfluorotellurite (65-x)TeO2–20ZnF2–12PbO–3Nb2O5–xNd2O3 (x = 0.1, 1, 2, 5 and 10) glasses (TZPN) was analyzed for SBR-based luminescent thermometry. To excite Nd3+ ions, the 808 nm and 1060 nm wavelengths, which are related to GSA and ESA, respectively, were involved. In the biological temperature range the relative sensitivity reached SR = 2.95%/°C. The highest value of SR = 6.15%/°C was obtained at low temperature range for the 10%Nd3+:TZPN glass LT and decreased below 1%/°C only at temperatures above 200 °C.

Geothermometry using minor and trace elements in igneous and hydrothermal magnetite

The temperature (T) and oxygen fugacity (fO2) dependence of minor and trace elements (Mg, Al, Mn, Cr, Ni) in magnetite (Mag) in equilibrium with water-bearing silicate liquids varying in composition from basalt to rhyolite (49–77 wt% SiO2) is examined in a compilation of experimental data (n = 299) from 700 to 1050 °C, 50–900 MPa and five order of magnitude range in fO2. The XMg (=Mg/(Mg + Fetot)) of Mag is strongly dependent on T, and can be formulated into an empirical geothermometer: TMg−mag (°C) = − 8344(±320)/[lnXMg − 4.1(±0.28)] – 273 r2 = 0.83 that reproduces 72% of the experimentas to ±50 °C, and conventional FeTi oxide thermometry in tuffs and vitrophyres to better than ±60 °C for >85% of the samples. The TMg Mag thermometer may have potential application in igneous or hydrothermally altered rocks where conventional thermometry or oxybarometry is not possible. Application to natural Mag (n = 476) compiled from several settings shows igneous rocks mostly record >700 °C but with some lower temperatures in plutonic rocks due to slow cooling. Hydrothermal samples (skarns, porphyry deposits) show consistently subsolidus conditions (TMg-mag of 700–350 °C) consistent with other mineral and O isotopic equilibria. The element correlations in natural Mag from various settings are explored using multivariate statistical analysis, to identify which minor or trace elements most critically depend on T, fO2 or fluid composition.

Enhanced precision bound of low-temperature quantum thermometry via dynamical control

High-precision low-temperature thermometry is a challenge for experimental quantum physics and quantum sensing. Here we consider a thermometer modeled by a dynamically-controlled multilevel quantum probe in contact with a bath. Dynamical control in the form of periodic modulation of the energy-level spacings of the quantum probe can dramatically increase the maximum accuracy bound of low-temperatures estimation, by maximizing the relevant quantum Fisher information. As opposed to the diverging relative error bound at low temperatures in conventional quantum thermometry, periodic modulation of the probe allows for low-temperature thermometry with temperature-independent relative error bound. The proposed approach may find diverse applications related to precise probing of the temperature of many-body quantum systems in condensed matter and ultracold gases, as well as in different branches of quantum metrology beyond thermometry, for example in precise probing of different Hamiltonian parameters in many-body quantum critical systems.

Thermal Memory Based Photoacoustic Imaging of Temperature.

Temperature mapping is essential in many biomedical studies and interventions to precisely control the tissue's thermal conditions for optimal treatment efficiency and minimal side effects. Based on the Grüneisen parameter's temperature dependence, photoacoustic (PA) imaging can provide relative temperature measurement, but it has been traditionally challenging to measure absolute temperatures without knowing the baseline temperature, especially in deep tissues with unknown optical and acoustic properties. Here, we report a new thermal-energy-memory-based photoacoustic thermometry (TEMPT). By illuminating the tissue with a burst of nanosecond laser pulses, TEMPT exploits the temperature dependence of the thermal energy lingering, which is probed by the corresponding PA signals acquired within the thermal confinement. A self-normalized ratiometric measurement cancels out temperature-irrelevant quantities and estimates the Grüneisen parameter. The temperature can then be evaluated, given the tissue's temperature-dependent Grüneisen parameter, mass density, and specific heat capacity. Unlike the conventional PA thermometry, TEMPT does not require the knowledge of tissue's baseline temperature, nor the optical properties. We have developed a mathematical model to describe the temperature dependence in TEMPT. We have demonstrated the feasibility of the temperature evaluation on tissue phantoms at 1.5 cm depth within a clinically relevant temperature range. Finally, as proof-of-concept, we applied TEMPT for temperature mapping during focused ultrasound treatment in mice in vivo at 2 mm depth. As a generic temperature mapping method, TEMPT is expected to find applications in thermotherapy of cancers on small animal models.

Demonstration of a two-line Kr PLIF thermometry technique for gaseous combustion applications

Experiments were performed to demonstrate a dual-wavelength excitation krypton planar laser-induced fluorescence (Kr PLIF)-based 2D temperature imaging technique in a laminar non-sooting CH4/N2 diffusion flame. The technique exploits the thermochemical dependence of the overlap integral arising from Kr absorption and excitation laser spectra to yield the temperature without the need to know the local mixture composition. The choice of the two excitation wavelengths is made using the knowledge of the fuel mixture and pressure. The two excitation wavelengths lie within the same 4p6S01→→5p[32]2 transition, and their selection is informed such that the resulting Kr PLIF signal ratio depends primarily on the temperature and negligibly on local composition. Mean temperature fields show excellent agreement when compared to Fluent simulations across different regions of the combustion domain, while the single-shot temperature field exhibits slightly degraded accuracy. Overall, the technique provides very similar figures of merit compared to conventional composition-dependent thermometry approaches and showcases a promising scope for application in complex reacting flows.

Low‐Pand high‐Tmetamorphism of basalts: Insights from the Sudbury impact melt sheet aureole and thermodynamic modelling

AbstractLow‐pressure and high‐temperature (LP–HT) metamorphism of basaltic rocks, which occurs globally and throughout geological time, is rarely constrained by forward phase equilibrium modelling, yet such calculations provide valuable supplementary thermometric information and constraints on anatexis that are not possible to obtain from conventional thermometry. Metabasalts along the southern margin of the Sudbury Igneous Complex (SIC) record evidence of high‐grade contact metamorphism involving partial melting and melt segregation. Peak metamorphic temperatures reached at least ~925°C at ~1–3 kbar near theSICcontact. Preservation of the peak mineral assemblage indicates that most of the generated melt escaped from these rocks leaving a residuum characterized by a plagioclase–orthopyroxene–clinopyroxene–ilmenite‐magnetite±melt assemblage. Peak temperatures reached ~875°C up to 500 m from theSIClower contact, which marks the transition to metabasalts that only experienced incipient partial melting without melt loss. Metabasalts ~500 to 750 m from theSICcontact are characterized by a similar two‐pyroxene mineral assemblage, but typically contain abundant hornblende that overgrew clino‐ and orthopyroxene along an isobaric cooling path. Metabasalts ~750 to 1,000 m from theSICcontact are characterized by a hornblende–plagioclase–quartz–ilmenite assemblage indicating temperatures up to ~680°C. Mass balance and phase equilibria calculations indicate that anatexis resulted in 10–20% melt generation in the inner ~500 m of the aureole, with even higher degrees of melting towards the contact. Comparison of multiple models, experiments, and natural samples indicates that modelling in the Na2O–CaO–FeO–MgO–Al2O3–SiO2–H2O–TiO2–O2(NCFMASHTO) system results in the most reliable predictions for the temperature of the solidus. Incorporation of K2O in the most recent amphibole solution model now successfully predicts dehydration melting by the coexistence of high‐Ca amphibole and silicate melt at relatively low pressures (~1.5 kbar). However, inclusion of K2O as a system component results in prediction of the solidus at too low a temperature. Although there are discrepancies between modelling predictions and experimental results, this study demonstrates that the pseudosection approach to mafic rocks is an invaluable tool to constrain metamorphic processes atLP–HTconditions.