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Yb3+:CaF2â€"YF3 transparent ceramics with excellent optical quality was successfully fabricated by hot-pressed method. Pulsed laser properties of this ceramics were investigated for the first time. Laser diode (LD) was applied as the pump source to generate a dual-wavelength mode-locked (ML) laser. The maximum average output power was 310 mW, which represents the highest output power of ultrafast calcium fluoride ceramic laser. The spectrum separated at 1048.9 nm and 1049.7 nm with a total pulse duration of 8.9 ps. The interval period between the beating signals was about 4.3 ps, corresponding to a 0.23 THz beat pulse repetition rate. These results demonstrate its potential in producing dual-wavelength ultrashort pulses. These Yb3+:CaF2â€"YF3 ceramics with low-cost and short-preparation period are ideal candidate materials for ultrafast lasers. [ABSTRACT FROM AUTHOR]

Magneto-optical trapping (MOT) is a key technique on the route towards ultracold molecular ensembles. However, the realization and optimization of magneto-optical traps with their wide parameter space is particularly difficult. Here, we present a very general method for the optimization of molecular magneto-optical trap operation by means of Bayesian optimization. As an example for a possible application, we consider the optimization of a calcium fluoride MOT for maximum capture velocity. We find that both the X2Σ+ to A2Π1/2 and the X2Σ+ to B2Σ+ transition to allow for capture velocities with 24 m s−1 and 23 m s−1 respectively at a total laser power of 200 mW. In our simulation, the optimized capture velocity depends logarithmically on the beam power within the simulated power range of 25 to 400 mW. Applied to heavy molecules such as BaH, BaF, YbF and YbOH with their low capture velocity MOTs it might offer a route to far more robust MOT. [ABSTRACT FROM AUTHOR]

Fundamental research and practical assembly of rechargeable calcium (Ca) batteries will benefit from an ability to use Ca foil anodes. Given that Ca electrochemistry is considered a surface-film-controlled process, understanding the interface's role is paramount. This study examines electrochemical signatures of several Ca interfaces in a benchmark electrolyte, Ca(BH4)2/tetrahydrofuran (THF). Preparation methodologies of Ca foils are presented, along with Ca plating/stripping through either pre-existing, native calcium hydride (CaH2), or pre-formed calcium fluoride (CaF2) interfaces. In contrast to earlier work examining Ca foil in other electrolytes, Ca foils are accessible for reversible electrochemistry in Ca(BH4)2/THF. However, the first cyclic voltammetry (CV) cycle reflects persistent, history-dependent behavior from prior handling, which manifests as characteristic interface-derived features. This behavior diminishes as Ca is cycled, though formation of a native interface can return the CV to interface-dominated behavior. CaF2 modification enhances such interface-dominance; however, continued cycling suppresses such features, collectively indicating the dynamic nature of certain Ca interfaces. Cell configuration is also found to significantly influence electrochemistry. With appropriate preparation of Ca foils, the signature of interface-dominated behavior is still present during the first cycle in coin cells, but higher current density compared to three-electrode cells along with moderate cycle life are readily achievable. [ABSTRACT FROM AUTHOR]

We report the elongation of embedded Au nanoparticles (NPs) in three different matrices, i.e. amorphous carbon (a-C), crystalline indium tin oxide (InxSn1-xOz; ITO) and crystalline calcium fluoride (CaF2), under irradiations of 4 MeV C60+ cluster ions and 200 MeV Xe14+ ions. Under 4 MeV C60 cluster irradiation, strong sputtering is induced in CaF2 layer so that the whole the layer was completely lost at a fluence of 5 × 1013 ions cm−2. Au NPs were partly observed in the SiO2, probably due to the recoil implantation. Amorphous carbon (a-C) layer exhibits low sputtering loss even under 4 MeV C60 irradiation. However, the elongation in a-C layer was low. While the ITO layer showed a certain decrease in thickness under 4 MeV C60 irradiation, large elongation of Au NPs was observed under both 4 MeV C60 and 200 MeV Xe irradiation. The ITO layer preserved the crystallinity even after large elongation was induced. This is the first report of the elongation of metal NPs in a crystalline matrix. [ABSTRACT FROM AUTHOR]

Wedemonstrate the one-dimensional, transverse magneto-optical compression of a cold beam of calcium monofluoride (CaF). By continually alternating the magnetic field direction and laser polarizations of themagneto-optical trap (RFMOT), a photon scattering rate of 2π × 0.4 MHz is achieved. A 3Dmodel for this RF MOT, validated by agreement with data, predicts a 3DRFMOT capture velocity for CaF of 5ms-1. [ABSTRACT FROM AUTHOR]

The electrochemistry of thorium in molten LiF-CaF2 was examined on inert (Mo) and reactive (Ni) electrodes at 1173 K using cyclic voltammetry and chronopotentiometry. A single-step reduction mechanism was observed on the Mo electrode. Voltammetric results show signs of irreversibility. The diffusion coefficient of Th(IV) ions was calculated from the chronopotentiometric data. Deposition of metallic thorium was verified from the electrolytic experiment and subsequent XRD and SEM analyses. The formation of Th-Ni alloys was confirmed on the Ni electrode using cyclic voltammetry, open-circuit chronopotentiometry and SEM + EDS analysis of the deposit after a short electrolysis. [ABSTRACT FROM AUTHOR]

Innovative bi-electrolyte solid-state cells incorporating single crystal CaF2 and composition-graded solid electrolyte (LaF3)y ⋅ (CaF2)1-y (y = 0 to 0.32) were used for measurement of the standard Gibbs energy of formation of hexagonal La0.885Al11.782O19 and cubic LaAlO3 from component binary oxides La2O3 and α-Al2O3 in the temperature range from 875 to 1175 K. The cells were designed based on experimentally verified relevant phase relations in the systems La2O3-Al2O3-LaF3 and CaF2-LaF3. The results can be summarized as: 5.891 α-Al2O3 + 0.4425 La2O3 (A-rare earth) → La0.885Al11.782O19 (hex), ΔGf(ox)o(±2005)/Jmol-1 = -80982 + 7.313(T/K); 1/2 La2O3 (A-rare earth) + 1/2 α-Al2O3 → LaAlO3 (cubic), ΔGf(ox)o(±2100)/Jmol-1 = -59810 + 4.51(T/K). Electron probe microanalysis was used to ascertain the non-stoichiometric range of the hexaaluminate phase. The results are critically analyzed in the light of earlier electrochemical measurements. Several imperfections in the electrochemical cells used by former investigators are identified. Data obtained in the study for LaAlO3 are consistent with calorimetric enthalpy of formation and entropy derived from heat capacity data. Estimated are the standard entropy and the standard enthalpy of formation from elements of hexagonal La0.885Al11.782O19 and rhombohedral LaAlO3 at 298.15 K. [ABSTRACT FROM AUTHOR]

To understand the chemical reaction at the interface of Fe(Te, Se) and CaF2 materials, we used transmission electron microscopy to analyze five types of Fe(Te, Se) superconducting thin films prepared on different types of substrate: two on a CaF2 substrate, one on a CaF2 substrate with a CaF2 buffer layer, one on a CaF2 substrate with an FeSe buffer layer, and one on a LaAlO3 substrate with a CaF2 buffer layer. Energy-dispersive x-ray spectroscopy analysis revealed a potential interdiffusion between fluorine and selenium that plays a significant role in the variation of the lattice parameters. We conclude that the lattice parameters of the Fe(Te, Se) thin films are primarily determined by the chemical substitution of anions, while the lattice mismatch plays a secondary role. [ABSTRACT FROM AUTHOR]

To understand the chemical reaction at the interface of Fe(Te, Se) and CaF2 materials, we used transmission electron microscopy to analyze five types of Fe(Te, Se) superconducting thin films prepared on different types of substrate: two on a CaF2 substrate, one on a CaF2 substrate with a CaF2 buffer layer, one on a CaF2 substrate with an FeSe buffer layer, and one on a LaAlO3 substrate with a CaF2 buffer layer. Energy-dispersive x-ray spectroscopy analysis revealed a potential interdiffusion between fluorine and selenium that plays a significant role in the variation of the lattice parameters. We conclude that the lattice parameters of the Fe(Te, Se) thin films are primarily determined by the chemical substitution of anions, while the lattice mismatch plays a secondary role. [ABSTRACT FROM AUTHOR]

The 7.8 eV nuclear isomer transition in 229thorium has been suggested as a clock transition in a new type of optical frequency standard. Here we discuss the construction of a 'solid-state nuclear clock' from thorium nuclei implanted into single crystals transparent in the vacuum ultraviolet range. We investigate crystal-induced line shifts and broadening effects for the specific system of calcium fluoride. At liquid nitrogen temperatures, the clock performance will be limited by decoherence due to magnetic coupling of the thorium nuclei to neighboring nuclear moments, ruling out the commonly used Rabi or Ramsey interrogation schemes. We propose clock stabilization based on a fluorescence spectroscopy method and present optimized operation parameters. Taking advantage of the large number of quantum oscillators under continuous interrogation, a fractional instability level of 10-19 might be reached within the solid-state approach. [ABSTRACT FROM AUTHOR]

H-and Cl-terminal groups of bicyclo[2.2.2]octane (BCO) derivatives in a mixedself-assembled monolayer (SAM) on Au(111) were imaged using a modified Si tip with aCaF2 nanocluster to differentiate the two terminals, which have different electronegativities.In order to achieve this we fabricated a new sample holder, on which aCaF2 single crystal and the mixed SAM on Au(111) could be mounted side byside. We transferred the holder with the two samples into a ultrahighvacuum (UHV) atomic force microscopy (AFM) chamber. Upon cleaving theCaF2 single crystal underUHV, a fresh and clean CaF2(111) surface parallel with the SAM surface appeared within 2mm of the separation. Themodified Si tip was prepared by repeatedly making contact between a Si tip and theCaF2(111) surface. The resulting modified tip could image the atomic periodicity of aCa2+ and anF− sublatticeon the CaF2(111) surface depending on the sign of the tip-terminating ion, i.e.anF− anda Ca2+ ion, respectively, as reported previously (Foster et al 2002 Phys.Rev.B 66235417). Using the modified Si tip with the known tip-terminating ion, weobserved the Cl-terminal in the surrounding H-terminals in the mixed SAM bynoncontact (NC) AFM. Here, the Cl-terminal is negatively charged due to itselectronegativity and thus the BCO moiety with the Cl-terminal is terminated by aCδ+–Clδ− permanent dipole, while the H-terminal is almost neutral. The Cl-terminal appearedbrighter (more attractive) and darker (more repulsive) than the surrounding H-terminalsin NC-AFM images depending on the sign of the tip-terminating ion, i.e.aCa2+ andan F− on the modified tip, respectively, although the relationship between the image contrast andthe sign of the tip-terminating ion was not always perfect because of the instability of thetip-terminating ion on the nanocluster. The present method can be used to distinguishterminal groups with different electronegativities. [ABSTRACT FROM AUTHOR]

Atomic scale manipulation on insulating surfaces is one of the great challenges ofnon-contact atomic force microscopy. Here we demonstrate lateral manipulation ofdefects occupying single ionic sites on a calcium fluoride (111)-surface. Defectsstem from the interaction of the residual gas with the surface. The process ofsurface degradation is briefly discussed. Manipulation is performed over a widerange of path lengths ranging from tens of nanometres down to a few latticeconstants. We introduce a simple manipulation protocol based on line-by-linescanning of a surface region containing defects to be manipulated, and recordtip–surface distance and cantilever resonance frequency detuning as a function ofthe manipulation pathway in real time. We suggest a hopping model to describemanipulation where the tip–defect interaction is governed by repulsive forces. [ABSTRACT FROM AUTHOR]

We demonstrate a crystalline CaF2 resonator with thermal sensitivity of the optical modes approaching zero. The resonator is made by laminating a calcium fluoride layer forming an optical monolithic cavity with ceramic compensation layers. The ceramics is characterized with negative thermal expansion coefficient achievable in a certain temperature range. The thermally compensated resonator has a potential application for laser frequency stabilization. [ABSTRACT FROM AUTHOR]

We report on the growth of epitaxial Fe1+δSe0.5Te0.5 thin films on 0°, 5°, 10°, 15° and 20° vicinal cut CaF2 single crystals by pulsed laser deposition. In situ electron and ex situ x-ray diffraction studies reveal a tilted growth of the Fe1+δSe0.5Te0.5 films, whereby under optimized deposition conditions the c-axis alignment coincides with the substrate [001] tilted axis up to a vicinal angle of 10°. Atomic force microscopy shows a flat island growth for all films. From resistivity measurements in longitudinal and transversal directions, the ab- and c-axis components of resistivity are derived and the mass anisotropy parameter is determined. Analysis of the critical current density indicates that no effective c-axis correlated defects are generated by vicinal growth, and pinning by normal point core defects dominates. However, for H∣∣ab the effective pinning centers change from surface defects to point core defects near the superconducting transition due to the vicinal cut. Furthermore, we show in angular-dependent critical current density data a shift of the ab-planes maxima position with the magnetic field strength. [ABSTRACT FROM AUTHOR]

A CaF2–CeF3 disordered crystal containing 1.06% of Er3+ ions was grown by the temperature gradient technique. Optical absorption and emission spectra recorded at room temperature and at 10 K, luminescence decay curve recorded at room temperature, and extended x-ray-absorption fine structure spectra were analyzed with an intention to assess the laser potential related to the transition of Er3+. In addition, the thermal diffusivity of the crystal was measured at room temperature. The analysis of room-temperature spectra revealed that the emission is long-lived with a radiative lifetime value of 5.5 ms, peak emission cross section of , and large spectral width pointing at the tunability of the emission wavelength in the region stretching from approximately 1480 nm to 1630 nm. The energies of the crystal field components for the ground and excited multiplets determined from low-temperature absorption and emission spectra made it possible to predict successfully the spectral position and shape of the room-temperature emission band. Based on the correlation of the optical spectra and dynamics of the luminescence decay, it was concluded that in contrast to Yb3+ ions in heavily doped CaF2 erbium ions in the CaF2–CeF3 crystal reside in numerous sites with dissimilar relaxation rates. [ABSTRACT FROM AUTHOR]

Recent advancement in liquid-environment atomic force microscopy (AFM) has enabled us to visualize three-dimensional (3D) hydration structures as well as two-dimensional (2D) surface structures with subnanometer-scale resolution at solid–water interfaces. However, the influence of ions present in solution on the 2D- and 3D-AFM measurements has not been well understood. In this study, we perform atomic-scale 2D- and 3D-AFM measurements at fluorite–water interfaces in pure water and a supersaturated solution of fluorite. The images obtained in these two environments are compared to understand the influence of the ions in solution on these measurements. In the 2D images, we found clear difference in the nanoscale structures but no significant difference in the atomic-scale contrasts. However, the 3D force images show clear difference in the subnanometer-scale contrasts. The force contrasts measured in pure water largely agree with those expected from the molecular dynamics simulation and the solvent tip approximation model. In the supersaturated solution, an additional force peak is observed over the negatively charged fluorine ion site. This location suggests that the observed force peak may originate from cations adsorbed on the fluorite surface. These results demonstrate that the ions can significantly alter the subnanometer-scale force contrasts in the 3D-AFM images. [ABSTRACT FROM AUTHOR]

The N and C doping effects on the crystal structures, electronic and optical properties of fluorite structure CeO2 have been investigated using the first-principles calculation. Co-doping these two elements results in the local lattice distortion and volume expansion of CeO2. Compared with the energy band structure of pure CeO2, some local energy levels appear in the forbidden band, which may facilitate the light absorption. Moreover, the enhanced photo-catalytic properties of CeO2 were explained through the absorption spectra and the selection rule of the band-to-band transitions. [ABSTRACT FROM AUTHOR]

Using frequency-chirped radiation pressure slowing, we precisely control the velocity of a pulsed CaF molecular beam down to a few m s–1, compressing its velocity spread by a factor of 10 while retaining high intensity: at a velocity of 15 m s–1 the flux, measured 1.3 m from the source, is 7 × 105 molecules per cm2 per shot in a single rovibrational state. The beam is suitable for loading a magneto-optical trap or, when combined with transverse laser cooling, improving the precision of spectroscopic measurements that test fundamental physics. We compare the frequency-chirped slowing method with the more commonly used frequency-broadened slowing method. [ABSTRACT FROM AUTHOR]

There is an ongoing debate regarding the mechanism of swift heavy ion (SHI) track formation in CaF2. The objective of this study is to shed light on this important topic using a range of complementary experimental techniques. Evidence of the threshold for ion track formation being below 3 keV nm−1 is provided by both transmission electron microscopy (TEM) and Rutherford backscattering spectroscopy in the channelling mode, which has direct consequences for the validity of models describing the response of CaF2 to SHI irradiation. Furthermore, information about the elemental composition within the ion tracks is obtained using scanning TEM, electron energy loss spectroscopy, and with respect to the stoichiometry of the materials surface by in situ time of flight elastic recoil detection analysis. Advances in the analyses of the experimental data presented here pave the way for a better understanding of the ion track formation. [ABSTRACT FROM AUTHOR]

Magneto-optical (MO) characterizations and the angular-dependent critical current density (Jc(Θ)) of epitaxial FeSe0.5Te0.5 (FST) thin films grown on CaF2 single-crystalline substrates were performed. The MO images show typical rooftop patterns in the remanent state from which a large, homogeneous, and almost isotropic self-field Jc over 2 × 106 A cm−2 at 8 K was obtained. The vortex pinning mechanism is investigated measuring the magnetic field and angular-dependent critical current density Jc. The FST films exhibit small anisotropy of Jc in the whole applied magnetic field range below 15 K. The Dew-Hughes model and angular scaling analyses prove that pointlike normal cores, which are distributed randomly in the FST film, dominate the pinning in the FST films on CaF2 substrates. [ABSTRACT FROM AUTHOR]

Wavelength 1064 nm is one of the most widely used laser wavelengths in industries and science. The high-precision measurement of the refractive index of optical materials at 1064 nm is significant for improving the optical design. We study the direct measurement of refractive index at 1064 nm of lasers, including calcium fluoride (CaF2), fused silica and zinc selenide (ZnSe), whose refractive indices cover a large range from 1.42847 to 2.48272. The measurement system is built based on the quasi-common-path Nd:YAG laser feedback interferometry. The thickness can be measured simultaneously with the refractive index. The results demonstrate that the system has absolute uncertainties of ∼10−5 and ∼10−4 mm in refractive index and thickness measurement, respectively. [ABSTRACT FROM AUTHOR]

The accuracy of the special quasirandom structure (SQS) approach for modeling the structure and energetics of fluorite-structured oxide solid solutions with aliovalent cation substitutions is assessed in an ionic-pair potential study of urania and ceria based systems mixed with trivalent rare-earth ions. Mixing enthalpies for SQS supercells containing 96 and 324 lattice sites were calculated using ionic pair potentials for U0.5La0.5O1.75, U0.5Y0.5O1.75, Ce0.5La0.5O1.75, Ce0.5Y0.5O1.75, and Ce0.5Gd0.5O1.75, which all have stoichiometries of pyrochlores. The SQS results were compared to benchmark values for random substitutional disorder obtained using large supercell models. The calculations show significant improvement of the mixing enthalpy for the larger 324 site SQS, which is attributed to a better description of the structural distortions, as characterized by the radial distribution functions in relaxed systems. [ABSTRACT FROM AUTHOR]

We study the high- to low- temperature signal ratio (HLTR) of the CaF2:Tm glow curve as a function of beam quality for low-energy photon beams with effective energy between 15.2 and 33.6 keV, generated with W, Mo and Rh anodes. CaF2:Tm dosemeters (TLD-300) were exposed to x-rays and 60Co gamma-rays. Glow curves were deconvoluted into 7 peaks, using computerized glow curve deconvolution and HLTR was evaluated. Air kerma and dose in water were between 2.1–15.0 mGy and 49.8–373.8 mGy, respectively. All peaks in the glow curve showed a linear response with respect to air kerma and dose in water. HLTR values decreased monotonically between 1.029  ±  0.010 (at 15.2 keV) and 0.821  ±  0.011 (33.6 keV), and no effects due to the use of different anode/filter combinations were observed. The results indicate a relatively high value of HLTR (about 1 for 17 keV effective energy, or 3 keV μm−1 track-average LET) and a measurable dependence on the photon beam quality. Comparison of these photon data with HLTR for ions shows good quantitative agreement. The reported evolution of the CaF2:Tm glow curve could facilitate the estimation of the effective energy of unknown photon fields by this technique. [ABSTRACT FROM AUTHOR]

CaF2:Ho3+/Yb3+ nano-particles with intense green up-conversion (UC) luminescence are successfully synthesized via a facile hydrothermal approach by using NH4F as the fluoride source and Na2EDTA as a chelating reagent. Powder X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), and UC emission spectra are used to characterize the structures, shapes, and luminescent properties of the samples. The effects from fluoride sources and chelating reagents on the formations of CaF2 nano-particles are investigated, and the formation process is also deduced. Under the excitation of a 980-nm laser diode, the samples each show a green up-conversion emission centered at 540 nm corresponding to the 5S2/5F4→5I8 transitions of Ho3+. Moreover, the UC mechanisms of Ho3+/Yb3+ co-doped CaF2 nano-particles are also discussed. [ABSTRACT FROM AUTHOR]

This work reports on the study of surface properties of CaF2 films (30 and 10 nm thick) grown on (1 1 1) Si by molecular beam epitaxy at substrate temperatures from 400 to 700 degC. Reflection high-energy electron diffraction (RHEED) analysis indicated that CaF2 films with smooth surfaces were obtained in temperature ranges 500-550 degC and 620-700 degC, while at temperatures from 400 to 500 degC and in the vicinity of 600 degC the films showed grains randomly oriented on top of the surface. Atomic force microscopy (AFM) investigation corroborated with the RHEED results and confirmed the presence of grains on the film surface, with an evident transition near 600 degC. The dependence of grain density on the growth temperature followed the expectation from the RHEED analysis. The arithmetical average roughness of the CaF2 surface obtained from the AFM images remained below 1 nm for the best quality films. The x-ray reflectivity curves of all samples exhibited well-defined interference fringes, whose oscillation damping behaviour agreed with the RHEED and AFM results. The CaF2 layer thickness and roughness were accurately determined by a best-fit procedure applied to the x-ray reflectivity data. By combining all results, the temperature range between 525 and 550 degC was found to be the most suitable to grow CaF2 layers on (1 1 1) Si. For growth temperatures above 650 degC, pinholes and cracks started to reduce the CaF2 surface quality. [ABSTRACT FROM AUTHOR]

A Monte Carlo simulation of the quality dependence of different TL materials, in the form of discs 3.61 mm in diameter and 0.9 mm thick, in radiotherapy photon beams relative to 60Co gamma-rays has been performed. The beam qualities ranged from 50 kV to 25 MV x-rays. The TL materials were: CaF2, CaSO4, LiF and Li2B4O7. The effects of the dopants on energy deposition in the TL material have also been determined for the highly sensitive LiF:Mg:Cu:P (TLD-100H) and for CaF2:Mn. It was found that there was a significant difference in the quality dependence factor derived from Monte Carlo simulations between LiF and LiF:Mg:Cu:P but not between CaF2 and CaF2:Mn. The quality dependence factors for Li2B4O7 varied from 0.990 +/- 0.008 (1 sd) for 25 MV x-rays to 0.940 +/- 0.009 (1 sd) for 50 kV x-rays relative to 60Co gamma-rays; Monte Carlo simulations were also performed for Li2B4O7 in megavoltage electron beams. For CaF2, the quality dependence factor varied from 0.927 +/- 0.008 (1 sd) for 25 MV x-rays to 10.561 +/- 0.008 (1 sd) for 50 kV x-rays. The figure for CaSO4 ranged from 0.943 +/- 0.008 (1 sd) for 25 MV x-rays to 9.010 +/- 0.008 (1 sd) for 50 kV x-rays. The quality dependence factor for CaF2 increases by up to 5% with depth and by up to 15% with field size for the kilovoltage x-ray beams. For LiF-TLD, however, there was no significant dependence on the field size or depth of irradiation in the kilovoltage energy range.

Various thermoluminescent materials (6LiF, 7LiF, Li2B4O7:Mn, CaSO4:Dy, CaF2:Mn, CaF2-Dy, CaF2:Tm) were irradiated with pi- mesons throughout the depth dose distribution of a beam with central momentum of 176 MeV/c. Doses from 0.05 to 2 Gy were used and linearity and reproducibility were investigated. For LiF, CaF2:Dy and CaF2:Tm, low- and high-temperature peaks were analysed separately. CaF2:Tm was found to be the most suitable for pi- dosimetry since the total dose and the high LET component could be determined using the integral TL signal and the peak height ratio of the 150 degrees C and 240 degrees C peaks. In the dose range used, both peak responses are linear with dose and the sensitivity of the materials is 10 times that of LiF. The reproducibility was +/- 3%. The high temperature peak of 7LiF is too small to be determined accurately and the high temperature peak of CaF2:Dy decreases with increasing LET in the same way was the low temperature peak does, so that no LET information can be extracted.

A silicon semiconductor photodiode was used to measure the TL-signal of TLD-300 (CaF2:Tm) detectors irradiated with 60Co gamma rays and 226Ra alpha particles. The applied dose values varied from 0.12 to 14.3 Gy for gamma rays and from about 50 to 300 Gy for alpha particles. Because of the infrared sensitivity of the photodiode the infrared emission of the planchet and the TLD-detector produced a high output signal above about 200 degrees C. In addition to this background signal an infrared emission from the TLD-300 detectors could be detected. This infrared TL-signal exhibited the same dose dependences as the visible signal, but the amplitude was higher than that of the visible TL-signal. For the applied photodiode the ratio of the infrared TL-signal to the visible TL-signal was about 24 for the 100 degrees C peak, about 15 for the 150 degrees C peak and 6 for the 240 degrees C peak.

Some thermal properties of A-150 tissue-equivalent plastic have been determined. The results are: thermal diffusivity, 2.72 x 10(-3) cm2s-1 +/- 0.4%; specific heat, 1.72 J g-1 K-1 +/- 1.3%; and thermal conductivity, 5.3 x 10(-3) WK-1 cm-1 +/- 1.4%. The significance of the measurements for the design of a calorimeter core calibration heater is briefly described.

The response of common TLD materials has been measured in a 14-7 MeV neutron field with a small and well known gamma component. Values for the thermal neutron response of some TLD materials with low thermal neutron sensitivity have been determined in the NPL standard thermal flux facility.