Solar calibration

Fig. 2. (Left panel) evolutionary tracks using FST in the logTefj vs. log g plane (solid line non gray models with rph = 10 by Montalban et al.,2004) and 2D calibrated MLT (dashed line).(Right panel) Lithium evolution for the solar mass with different assumptions about convection and model atmospheres. The dotted line at bottom represents today s solar lithium abundance. MLT models with AH97 model atmospheres down to Tph = 10 and 100 are shown dotted for cum = 1 and dash-dotted for cpr, = 1.9. The Montalban et al. (2004) MLT models with Heiter et al. (2002) atmospheres down to Tph = 10 (lower) and 100 (upper) are dashed The continuous lines show the non gray FST models for rph = 10 and 100, and, in between, the long dashed model employing the 2D calibrated MLT.

Generally convection is calibrated by requiring that its free parameter(s) are chosen to reproduce the solar radius at the solar age. However, it is also possible to use models which do not fit the solar location, and in fact these seem to reproduce much better two observational constraints of the pre main sequence, namely the PMS Lithium depletion and the HR diagram location of some binary stars for which masses are known. 

Fig. 3. Location in the HR diagram of three binaries with well determined masses, labelled in the figure RXJ 0529.4+0041 (Covino et al. 2000), V1174 Ori (Stassun et al. 2004) and NTT 045251+3016 (Steffen et al. 2001). The PMS tracks superimposed are, on the left, the AH97 Oj = oatm = 1 tracks, and on the right the tracks in which the MLT is calibrated on the 2D models. Notice that the left tracks, which are more consistent with the observed data, fail to fit the solar location by 400 K.

We see that the models which best reproduce the location of all the six data points are the tracks which do not fit the solar location. The models whose convection is calibrated on the 2D simulation make a poor job, as the FST models and other models with efficient convection do therefore this result can not be inputed to the fact that we employ local convection models. A possibility is that we are in front of an opacity problem, more that in front of a convection problem. Actually we would be inclined to say that opacities are not a problem (we have shown this in Montalban et al. (2004), by comparing models computed with Heiter et al (2002) or with AH97 model atmospheres), but something can still be badly wrong, as implied by the recent redetermination of solar metallicity (Asplund et al., 2004). A further possibility is that the inefficient convection in PMS requires the introduction of a second parameter -linked to the stellar rotation and magnetic field, as we have suggested in the past (Ventura et al., 1998 D Antona et al., 2000), but this remains to be worked out. 

In a cryogenic experiment, one or several detectors are used for a definite goal for which they have been optimized. For example, in CUORE experiment described in Section 16.5, the sensors are the Ge thermistors, i.e. thermometers used in a small temperature range (around 10 mK). One detector is a bolometer made up of an absorber and a Ge sensor. The experiment is the array of 1000 bolometers arranged in anticoincidence circuits for the detection of the neutrinoless double-beta decay. Note that the sensors, if calibrated, could be used, as well, as very low-temperature thermometers. Also the array of bolometers can be considered a single large detector and used for different purposes as the detection of solar axions or dark matter. 

One of the most interesting of the geophysics results from radiocarbon dates is the history of the sun. Apparently, it is registered in fluctuations of the cosmic ray intensity. These are fluctuations of rather short duration in terms of the radiocarbon lifetime, perhaps a century or so, and apparently they are caused by variations in the solar wind due to long-term changes in the solar emissions. This idea has been developed in some detail recently by Dr. Lai and his collaborators. It promises to give us a way of watching the history of the sun over tens of thousands of years. This fine structure on the curve of calibration was discovered by Dr. Suess and others. 

It is necessary to calibrate the 14C time scale for greater dating accuracy. However, the second-order variations are at least as important as the first-order constancy of atmospheric 14C. For example, they provide a record of prehistoric solar variations, changes in the Earth s dipole moment and an insight into the fate of C02 from fossil fuel combustion. Improved techniques are needed that will enable the precise measurement of small cellulose samples from single tree rings. The tandem accelerator mass spectrometer (TAMS) may fill this need. 

Emery KA, Osterwald CR (1986) Solar-cell efficiency measurements. Sol Cells 17 253 Matson RJ, Emery KA, Bird RE (1984) Terrestrial solar spectra, solar simulation and solarcell short-circuit current calibration - a review. Sol Cells 11 105... 

Dosimetry was based either directly on the Fricke Dosimeter (I) (using GFes+ = 15.5) or on an n-on-p solar cell (18) that was frequently calibrated against the Fricke dosimeter. 

Depth scale calibration of an SIMS depth profile requires the determination of the sputter rate used for the analysis from the crater depth measurement. An analytical technique for depth scale calibration of SIMS depth profiles via an online crater depth measurement was developed by De Chambost and co-workers.103 The authors proposed an in situ crater depth measurement system based on a heterodyne laser interferometer mounted onto the CAMECA IMS Wf instrument. It was demonstrated that crater depths can be measured from the nm to p,m range with accuracy better than 5 % in different matrices whereas the reproducibility was determined as 1 %.103 SIMS depth profiling of CdTe based solar cells (with the CdTe/CdS/TCO structure) is utilized for growing studies of several matrix elements and impurities (Br, F, Na, Si, Sn, In, O, Cl, S and ) on sapphire substrates.104 The Sn02 layer was found to play an important role in preventing the diffusion of indium from the indium containing TCO layer. 

Figure 9 Photocurrent-voltage curve obtained for a nanocrystalline 2 solar cell sensitized by black dye. The results plotted were obtained at the NREL calibration laboratory. (From Ref. 20.)...

In principle, there are two ways to achieve the radiometric calibration of an instrument measuring solar radiation. The first is by comparison to a standard radiation source of known output and the second by comparison to a prototype standard instrument that is capable in measuring the same radiometric quantity. The fist can be applied to broadband detectors only if their spectral response over the whole range of the radiation source is known with sufficient accuracy. The second method requires that the standard instrument has exactly the same spectral response, which is rather unlikely to occur. 

This calibration factor can be determined at any instant from (1), if the spectrum of solar radiation (from the sun and sky) can be measured in absolute units and if the detector s relative spectral sensitivity w(X) is known. 

The variation of solar zenith angle during a spectral measurement may introduce errors in the determination of the calibration factor by altering the shape of the spectrum. This problem can be partly overcome by performing the measurements preferably near the local noon, when the change of solar zenith angle with time is much... 

Hilsenrath, E., R.P. Cebula, M.T. Deland, K. Laamann, S. Taylor, C. Wellemeyer and P.K. Bhartia (1995) Calibration of the NOAA-11 solar backscatter ultraviolet (SBUV/2) ozone data set from 1989 to 1993 using in-flight calibration data and SSBUV. Journal of Geophysical Research 100 1351-1366. 

The solar to electric power conversion efficiency of dye-sensitized solar cells of laboratory scale (0.158 cm2), validated by an accredited photovoltaic calibration laboratory, has reached 11.1% under standard reporting conditions, i.e., air mass 1.5 global sunlight at 1000 Wm-2 intensity and 298 K temperature, rendering it a credible alternative to conventional p-n junction photovoltaic devices [68]. Photovoltaic performance data obtained with a sandwich cell under illumination by simulated AM 1.5 solar light using complex 26 are shown in Fig. 16. At 1 sun the 26-sensitized solar cell exhibited 17.73 =b 0.5 mA current, 846 mV potential, and a fill factor of 0.75 yielding an overall conversion efficiency of 11.18%. 

The next step in the procedure is to adjust the solar simulator so that the reference cell reads an Isc of Lt/M. where I0 is its calibration value for SRC. This establishes SRC for the test cell. Then the I/V characteristic is measured and the efficiency 77 can be calculated using (5.16). 

However, for relatively new types of solar cells such as the polymer-based solar cells described here, suitable stable reference cells cannot yet be fabricated. This implies that, for measurements concerning these cells, calibrated reference cells are used (Si, GaAs) with a different spectral response to the device under test, resulting in mismatch factors that deviate significantly from 1. It is therefore of the utmost importance to carry out the procedure as precisely as possible in order to minimise measurement errors. 

I. Reda, J. Hickey, C. Long, D. Myers, T. Stoffel, S. Wilcox, J. J. Michalsky, E. G. Dutton, and D. Nelson, Using a blackbody to calculate net-longwave responsivity of shortwave solar pyranometers to correct for their thermal offset error during outdoor calibration using the component sum method, Journal of Atmospheric and Oceanic Technology 22 1531 (2005). 

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