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A Dual Fabry-Perot Based Imaging Spectrometer for the National Large Solar Telescope
- Oliver Lester
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1 A Dual Fabry-Perot Based Imaging Spectrometer for the National Large Solar Telescope B. Ravindra and Ravinder Kumar Banyal Indian Institute of Astrophysics Koramangala, Bengaluru & 1 Abstract This report provides a detailed design of a dual Fabry-Perot based narrow band imaging system intended to make observations of solar atmosphere at visible and near infrared wavelengths. The narrow band imager will serve as one of the back end instrument planned for a proposed 2m class National Large Solar Telescope (NLST) by Indian Institute of Astrophysics. The narrow band imager comprises an air spaced, high reflectivity, large free spectral range Fabry-Perot interferometer. The instrument will have a spectral resolution of about 40 må to provide narrow band images of the solar atmosphere. The dopplergrams can also be made at a spatial resolution of 0.06 arcsec/pixel. By combining it with the polarimeter, the narrow band imager can also provide magnetograms. Several simulations and numerical studies are carried out to arrive at the instrument design. The study of the important design parameters including optimum spacing ratio, field-of-view, optical layout, spectral and spatial resolution, signal-to-noise ratio etc is presented in detail. Finally, a comparison between the proposed instrument and similar instruments used in other solar observatories around the world is also made. 2 Introduction National Large Solar Telescope (NLST) is being proposed, by the Indian Institute of Astrophysics (IIA), as a 2-m class next generation telescope to study the dynamics of the solar atmosphere (especially photosphere and chromosphere). The telescope will be placed in a suitable location in India where the sky and the atmospheric conditions will allow the maximum output from this instrument. More details of the NLST can be obtained from Singh (2008). The telescope will also be equipped with a high order adaptive optics system to correct the image degradation resulting from the atmospheric turbulence. The potential of this instrument can be maximized with state-of-the-art back-end instruments. NLST equipped with high class back-end instruments, that will 1
2 2 INTRODUCTION 2 not only help the solar community in solving many outstanding scientific problems in solar physics, but also attract many young researchers to undertake challenging areas of research in solar physics. One such potential back-end instrument is a narrow-band imager providing high contrast images of the solar atmosphere at various wavelengths in the visible spectrum. This report is to build an imaging spectrograph using Fabry- Perot (FP) etalon in tandem. The proposed instrument will be capable of fast narrow band imaging at multiple wavelengths in the visible and near Infra-red spectrum. Addition of a polarimetric capability, which will be carried out as a separate project, would further enhance the scientific output of this instrument. Over the past decade, the quality and quantity of solar observations from space- as well as ground-based observatories have improved dramatically. These observations have produced much detailed knowledge of structure and evolution of the solar atmosphere both in magnetically active as well as quiet period. At the same time a great progress has been made in theory to understand the physical processes that take place in the sun s interior and the solar atmosphere. Scientifically rich observations of the solar atmosphere have become possible due to the enormous progress in the imaging systems and high-end spectroscopic instruments. There is a huge demand for the solar data with high temporal, spatial and spectral resolution taken in various wavelengths. Moreover, researchers often require observations of different layers of the solar atmosphere near simultaneously. It is well understood that features in the solar atmosphere change very rapidly. The speed of evolution of these features increase with decreasing size. Hence, high spatial resolution observations always demand high temporal cadence. At high spatial resolution, these features usually evolve at the rate of sound speed. The chromospheric features, for example, are believed to change at much faster rate than the features at the photosphere. This can be attributed purely to the faster sound speed at the chromosphere compared to the photosphere. Also, within the limited exposure time enough photons need to be collected for good signal-to-noise estimates of the physical parameters. The collection of a large amount of photons can be achieved by using a large aperture solar telescope. But the spatial resolution is usually limited by the Earth s atmospheric seeing. By using the high-order adaptive optics and/or post-facto techniques, one can minimize the atmospheric seeing effects to achieve high spatial resolution imaging within a limited field-of-view (FOV). It is well known that during active phenomena on the sun, there is a rapid change in the magnetic field, velocity field and intensity (at a rate faster than 1 sec) at various heights in the solar atmosphere (photosphere to corona). To observe the solar atmosphere at various heights simultaneously, it is necessary to image the sun at different wavelengths since each spectral line forms at different temperature and pressure (e.g., Ca II H and K 3968 and 3933 Å in the lower chromosphere, H α 6563 Å in the chromosphere and He I Å in the upper chromosphere). It is not enough to do only the photometry of the solar atmosphere. In many occasions, it is more meaningful to have Doppler velocity and polarization measurements by scanning the spectral line profiles at different wavelength positions. This is only possible either using a high resolution spectrograph or very narrow-band imaging system (like a Lyot filter or FP based system). A basic requirement of such an instrument is the wavelength coverage (preferably from 4000 Å to 1.5µm), together with high wavelength stability (10 må /hr) and
3 3 ANTICIPATED SCIENCE GOALS 3 reproducibility of the selected spectral points over the observing period. The stated objectives can be achieved with a narrow band imaging system capable of high temporal cadence and fast imaging performance (3 or more image frames/sec), large spectral ( ) and spatial (0.1 arcsec) resolution without compromising the large FOV (1.5 arcmin) of the target object. 3 Anticipated Science Goals Several scientific problems require high spatial, spectral and temporal resolution data of the solar atmosphere observed at several spectral lines over a long time basis. In the following, we briefly describe various scientific problems that require high quality narrow band imaging data on a regular basis. 1. Shear in the active region magnetic fields at various heights in the solar atmosphere and its role in triggering the solar flares and coronal mass ejections. 2. Propagation of Alfven waves and acoustic waves in the solar chromosphere under high spatial and spectral resolution. 3. Evolution of magnetic fields in the photosphere and chromosphere during filament eruption. 4. Evolution of magnetic fields in the emerging active regions. 5. Flare induced changes in the spectral line properties. 6. On the relationship between the velocity and magnetic fields in the magnetic structures. In addition to the above suggested problems, the filter-based, high spectral, spatial and temporal resolution can also help us to address the broader issues like: (1) the region of magnetic flux cancellations in the solar atmosphere and (2) the question of when, where and why do we observe the small scale jet-like features in the penumbral chromosphere and so on. 4 Instrument Requirement In order to study and examine problems suggested above it is extremely important to build narrow band imaging systems. The narrow band imaging system should be capable of fast scanning at finer spectral resolution without significant loss in the spatial resolution. Some of the commonly used methods for narrow band imaging are:
4 5 FABRY PEROT INTERFEROMETER 4 Spectrograph and spectral scanning method. Lyot Filter (using a set of wave plates and polarizers). Michelson Interferometer. Fabry-Perot Interferometer. The relative merits and drawbacks of the narrow band imaging systems suggested above are as follows: The spectrograph based instruments offer very high spectral resolution but suffer from the low temporal cadence due to long scanning time requirement of the required FOV (typically takes 1 hr to scan a large active region). Moreover the FOV is limited by the length and scan range of the spectrograph slit. The Lyot filters are good for narrow band imaging but the light throughput is very low (a few %) and hence need long exposures. Michelson interferometer is good, but the achieved spectral resolution is very low. Also, it cannot be used for a large wavelength range and cannot shift to different wavelength using a single interferometer. So, one need to build different Michelson interferometer for a different wavelength range. Fabry Perot (FP), as a single instrument may not be very useful for narrow band imaging. But it gives a very good spectral resolution when used in tandem. The rasterization of the spectrograph to make the image can be avoided in the FP based narrow band imaging. But at the same time it needs a sequential tuning to scan the line profile. Since the light throughput is very high for the FP based system, the sequential scanning on the line profile can be done very rapidly (typically of the order of few seconds). This scanning speed may not be sufficient during flares as the line profile itself can change within few seconds. As a result, the dopplergrams and magnetograms obtained during the flares may not be very reliable. Despite this apparent drawback, the information about the line profile change itself is useful and hence it is still worth using. One of the major advantages of using scanning FP is that it can be switched between wavelengths very fast. So, by combining the FP with different set of filters it is possible to obtain the images in different wavelengths. This is one of our goals as described in Section 3. Given these relative merits and limitations of these different types of instruments, FP based spectrograph is chosen to achieve all the scientific goals presented in Section 3. 5 Fabry Perot Interferometer A Fabry-Perot (FP) interferometer is a device which consists of two highly reflecting parallel plates. It selectively transmits a particular wavelength of light (when it is combined with the order sorting filter) corresponding to the resonance of the etalon.
5 5 FABRY PEROT INTERFEROMETER 5 In solar astronomy the narrow band imaging instruments are constructed by combining the FP with the birefringent filters; And also by using 2 or 3 FP in series in combination with the interference filter as an order sorter to form a multi-etalon system, it can be used as bi-dimensional imaging spectrometer (Kentischer et al. 1998; Cavallini, 2006). The transmitted beam from the Fabry-Perot etalon is a fringe pattern. The intensity distribution of the transmitted beam is given by the Airy s formula (Jenkins and White, 1937), I = I max 1+Fsin 2 (δ/2), (1) where I max = A 2 T 2 /(1 R 2 ) is the maximum value of the intensity. F = 4R/(1 R) 2 is the reflective finesse. A, T and R are the amplitude of the incident light, transmitivity of the Fabry Perot etalon and reflectivity of the etalon surface respectively. δ is the phase difference between the transmitted rays and is given by, δ = (2µdcosθ)2π/λ, (2) where µ is the refractive index of the media between the plates and λ is wavelength of the incident ray, d is the distance between the plates and θ is the angle of the incident ray with the normal. So, one can vary the phase between the successive transmitted rays by changing the refractive index of the material between the plates or by changing the distance between the plates or by changing the inclination of the FP surface or the angle of incidence of the rays. In other words, the wavelength scanning on the spectral line profile can be done with one of the above methods. But in practice it is easy to vary the phase difference by moving one of the plates or by varying the refractive index of the media between the plates. The transmitted beam is a periodic fringes with a maximum intensity of I max and the minimum intensity is I min = A 2 T 2 /(1+R) 2. The performance of the FP is characterized by two parameters: (a) the finesse and (b) the free spectral range. The finesse relates to the sharpness of the fringes. Apart from the reflectance, there are other parameters that also reduce the finesse and some of these are flatness of the plates and parallelism of the plates etc. The wavelength spacing between two adjacent maxima in the channel that can be determined without ambiguity is called the free spectral range (FSR) and is given by FSR = λ 2 2µdcosθ. (3) So, the FSR decreases with increase in spacing between the plates. For solar observation in the desired wavelength band, the FSR should be larger than the closely spaced spectral lines so that there will not be any overlapping of the other line while scanning. The passband of the FP can be estimated from the FSR and finesse that are related as λ=fsr/f = λ 2 /µd F. By decreasing the spacing between the plates the FWHM of the transmitted ray will increase. In a single etalon system the spectral resolution depends on the finesse of the etalon and is given by,
6 5 FABRY PEROT INTERFEROMETER 6 λ λ F2d λ. (4) The detailed results of how the effective finesse changes with the wavelength, how the wavelength varies as the distance between the plates changes, the relationship between the spectral resolution and wavelength are given in Appendix A. 5.1 Types of FPI Table 1: Comparison between different types of Fabry-Perot Interferometers. Air-gap FPI Solid-gap FPI Liquid-gap FPI Refractive index FWHM (min.) 20 må 100 må - Total light 50% 50% - throughput FOV variation λ/λ θ 2 λ/λ θ 2 /µ 2 λ/λ θ 2 /µ 2 Tuning device Piezoelectric Lithium Niobate Liquid Electronic Capacitance Voltage regulator - requirement ±600 V ± 3000 V - Lifetime factors Dielectric coatings Material breakdown leakage Maintainance Parallelism Parallelism - requirement - Technology Large etalons Thin elements - Ghost reflections super-polishing - Disadvantage Large etalons Wavefront error - Local Finesse minimum etalon - variations thickness - - High voltages - Advantage Simplicity Larger FOV Large FOV than air-gap FP Technology is Technology not well known is not well known known Historically, two types of Fabry-Perot interferometers (FPIs) have been used in solar observatories around the world. These are (1) air gap FP and (2) solid gap FP. Recently, another type of FP i.e., liquid gap FP has been introduced into the market. The defining features of different types of FPIs are described in Table 1 (cf. Gary, Balasubramaniam and Sigwarth, 2002). Many details in the Table 1 are self explanatory. With the current technology, it is possible to fabricate a large FP of diameter about 20 cm. Maintaining the plate parallelism is still a technically challenging task. Also, a prefilter of that big size (about 20 cm) is not readily available in the market. Large air-gap based etalons need large optics and more space.
7 5 FABRY PEROT INTERFEROMETER 7 In the case of solid etalons the wafer should be thin and it should be well polished with surface accuracy of λ/200 or better. The solid gap based etalon offers a large FOV for the same size of air-gap based etalons. A very thin wafer is extremely fragile and may require several careful trials to make one. Only a very few companies have the expertise to make the solid-gap based etalons. Due to large refractive index of the material, any surface imperfection in the wafer will lead to larger error in the wavefront. In changing the refractive index in the solid state etalons it is necessary to use a high voltages. Even though it may not be a problem to build a high voltage power supply, the substrate could easily breakdown at very high voltages. Moreover, the solid etalon are very sensitive to ambient temperature changes. Therefore, an accurate temperature control is extremely necessary to ensure the desired performance. In comparison to solid etalon, the air-gap based etalons are less complex and easy to handle in day to day operation. 0.8 Air gap Solid gap Intensity Wavelength (A) Figure 1: The transmission profile of the air gap (solid line) and solid gap (dashed line) based interferometer. The intensity is normalized to unity. The transmission profile of the air gap and solid gap based FP is shown in Figure 1. From Table 1 and Figure 1, it is clear that the air-gap based etalon has many advantages compared to the solid gap: (i) FSR is larger hence order sorting filter can have broader FWHM, (ii) Smaller voltage requirement to drive the electronics and (iii) Large finesse. In the solid gap etalons, Because of complex process involved in polishing the wafer it is very difficult to produce etalons with an effective finesse larger than 25. The high refractive index ( 2.3) of the solid wafer (crystal) increase the surface irregularities
8 5 FABRY PEROT INTERFEROMETER 8 and the crystal should be polished at least 5 times better than the surface accuracy of the glass substrates used in the air-gap etalons. The disadvantages of smaller FOV compared to the solid-fp will be overcome by having a large aperture air-gapped FPI. With the advanced technology of piezoelectric feedback drivers it is possible now to maintain the parallelism with an accuracy of better than λ/10000 in air-gap FP. The wavefront errors, super-polishing of the Lithium-Niobate and the induced polarization by the crystal are unknown yet in solid-gap FP. Even we do not know how much is the variation in the refractive index of the material for different temperature. Also, once the solid etalons are made available it is impossible to change its plate separation and it is very important to reduce the parasitic light (see Section 5.5). In case of airbased etalons, one can change the nominal plate separation if needed. Because of the operational complexity and uncertainties of the solid etalons, we prefer to use the air gap etalons in our design. 5.2 Fabry-Perot Optical Mounting There are mainly two common ways to mount the Fabry-Perot interferometer (FPI) in the optical path. These are: (1) collimated mounting and (2) telecentric mounting. Collimated mounting: Figure 2: An optical layout for the FPI system in collimated beam (Kentischer et al. 1998). The lens L1 images the telescope aperture into the FPI. The re-imaging lens L2 forms the image on to the CCD camera through the FPI. Figure 2 shows the FPI in collimated configuration. In this configuration the FPI is kept in the collimated beam. In other words, the FPI is positioned close to the image of the telescope s entrance pupil. Hence, every point on the image will subtend certain angle with respect to the optical axis of the FPI and hence different plate separations for each image point. This leads to a wavelength shift across the FOV of interest. In other words wavelength of the transmitted light at the edges of the FOV is blue shifted.
9 5 FABRY PEROT INTERFEROMETER 9 Figure 3: Left: Wavelength gradient developed across the FOV in air-gap FPI. Right: same as left side image but for solid-gap FPI. Also in this configuration, any non-uniformity or parallelism errors will lead to spectral broadening since the beams are collimated going through the FPI. The shift in the wavelength due to the angle of incidence is given by, λ = λ 2 where θ is the maximum angle of incidence and is given by, ( ) θ 2 (5) µ θ = FOV 1/2 A telescope A f p (6) FOV 1/2 is half diagonal FOV, A telescope is the aperture of the telescope and A f p is the aperture of the FP. For FP with an aperture of 15 cm with an air gap (µ =1), telescope with a size of 2 m, a FOV of 1.5 arcmin and observation done at a wavelength of 6300 Å, a shift in the wavelength is about 27 må (Figure 3, left). The wavelength gradient developed in the solid gap (µ = 2.3) is very small compared to the air gap based FP for the same FOV (Figure 3, right). This is purely due to their refractive index which is larger in solid-gap than in the air-gap FPI. Telecentric Configuration: In telecentric configuration (Figure 4), the FPI is placed in an intermediate image plane and the pupil image is collimated. In this configuration, there is no systematic wavelength shift over the FOV due to the reason that each point on the final image passes through the full cone angle at the FPI. The maximum allowable beam angle within this cone is a function of the f -number of the telecentric beam. In order to obtain the desired spectral resolution, the angle of the cone should be minimized. In fact, the telecentric mode allows one to trade spectral resolution against FOV. Table 2 summarizes the merits and demerits of these two configurations. In spite of this, the cone angle can produce broadening of the effective passband and is given by, FWHM e f f = (FWHM 2 + λ 2 s )1/2, (7)
10 5 FABRY PEROT INTERFEROMETER 10 Figure 4: An optical layout for the FPI system in telecentric beam (Kentischer et al. 1998). The solar image (FS) with 90 arcsec FOV is projected into the FPI system using L1 & L2. L3 & L4 re-image the FOV onto the detector (FP2). PS1 and PS2 restricts the beam size. Table 2: Comparison between the collimated and telecentric optical configurations of FPIs. Collimated Telecentric Wavelength shift across the FOV yes no Wavefront distortion large small Influence of dust on the image low large Alignment sensitivity large low Blocking ghost reflections difficult easy Influence of plate shape broadening wavelength shift Spectral line broadening No Yes where, FW HM is the full width at half maximum of the FP and λ s is the wavelength shift across the FOV. For example, to achieve a spectral resolution of (an effective broadening of 32 må at 6302Å ) using 15 cm aperture FP, 1.5 arcmin FOV, the FWHM of the FP should be less than 18 må. With the same setup for a solid-gap FP with refractive index of 2.3, the required FWHM will be close to 30 må. So, there is very little broadening of the spectral line in the solid-gap compared to the air-gap based FPs. 5.3 Instrument Design Specifications The FP etalons in series has better performance than just a single FP. For our purpose we would like to have: (1) high spectral resolution, (2) large spectral range, (3) large field-of-view to cover the sunspot as a whole, (4) high light throughput to have sufficient light, (5) fast change between wavelengths, (6) good wavelength stability, and (7) minimum stray light. Table 3 shows the required parameters to achieve the different science goals as presented in Section 3.. Table 4 gives the design specifications of the FP based imaging spectrometer that can meet our scientific goals.
11 5 FABRY PEROT INTERFEROMETER 11 Table 3: The requirements to achieve the proposed science goals are listed here. In the Table SG, SL, IC, RQ, RES, FOV, AR and CAD corresponds to science goals, spectral line, image cadence, requirement, spatial resolution, field-of-view, additional requirement and the cadence required for the additional requirement respectively. And Dop, VMG, SPL, LM and Int corresponds to Dopplergram, Vector Magnetogram, Spectral line, line-of-sight magnetogram and intensity image respectively. The science goals are written in a sequence as described in Section 3. SG SL IC RQ RES FOV AR CAD 1. H α s Int VMG 2 min Frame/s Int VMG 20 min Dop 2/min min Int LM 60 VMG 20 min Dop min LM VMG min DOP sec SPL sec LM sec DOP min 0.1 VMG Int 10 sec min 0.1 VMG to to min 0.1 Velocity Table 4: The design specifications of the narrow band imaging system with 2 FP in series. Spectral Resolution at 6000Å Spectral Range 5000 Å Å. Field of View 1.5 arcmin Maximum Ghost Transmission 10 4 Signal to Noise Ratio 500 Peak Transmission 50% Wavelength Stability 10 må/hr Tuning Rate 10 pm/ms Blocking Prefilter 2-3 Å range Maximum Stray Light 10 3 Image Cadence 1 frame per sec 5.4 Optical Configurations of the FP Based Spectrometer Figure 5 shows a typical optical layout for the dual FP in a telecentric configuration. A set of collimator lens and imaging lens before the FPs form an intermediate image near the first FP and then another set of collimator and re-imaging lens forms the final image on the CCD camera. A prefilter with a 3 Å passband can be used in between the FPs
12 5 FABRY PEROT INTERFEROMETER 12 Figure 5: Schematic layout of the optical elements for a dual Fabry-Perot etalons in tandem. or in the collimated beam. If we keep the prefilter in between the FPs it will reduce the ghost reflections between the FPs (Cavallini, 2006). On the other hand by keeping the prefilter in the collimated beam will reduce the size of the prefilter. Small size filters ( 5-6 cm) are readily available in the market. A CCD camera with a required area for the chosen FOV will be kept at the final image plane. The prefilter assembly can be kept inside the temperature controlled oven with motorized control to change different filters. The field stop restricts the FOV and it also prevents the scattered light from entering into the FP optical system. A beam splitter placed after the field stop (not shown in Figure 5) is used to tap a small amount of beam (may be < 10% of the main beam) to form continuum images. These continuum images are useful for doing post-processing on the images (like destreching, co-alignment of various images taken in different wavelengths etc). Since the system is dual FP in series, there will be ghost images formed by the reflection between the two FPs. The intensity of the ghost images is about 12% of the transmitted beam for the first reflection and 5% of the transmitted beam for the second reflection. The ghost can be removed by tilting the FPs by a small angle of 0.1 or by placing the order sorting filter in-between the two FPs. Even though the tilt removes the ghost but it introduces intensity gradients in the transmitted beam due to the shift in the passband of two FPs. The whole system including the CCD camera needs to be automated. The automa-
13 5 FABRY PEROT INTERFEROMETER 13 tion software should do the following: (1) maintain the parallelism of the two plates in FPs, (2) lock both the FPs on the desired solar line, (3) scanning over the line profile, (4) centering of the prefilter passband, (5) synchronization between the CCD and FP scanning, and (6) take the flat field on various wavelength over the line profile. A graphical user interface (GUI) will be required to communicate between the computer and the observer. Most of the tasks for the etalon shall work automatically and they should be synchronized with the temperature controller, CCD camera and the prefilter assembly. And finally - at the later stage - the whole setup can be made controllable remotely. 5.5 Fabry-Perot Etalons in Combination With the Order Sorting Filter Figure 6: A plot of parasitic light vs spacing ratio for dual-etalon system. The two vertical lines define a range where the contribution from the parasitic light is the minimum. The two horizontal lines indicate the 10% and 1% level of the parasitic light. In the proposed narrow band imager (Section 5.4) there are two FPs kept in tandem with the narrow band order sorting interference filter. If N such FPs are kept in series with the order sorting filter then the resulting instrumental profile I(λ) is obtained by,
14 5 FABRY PEROT INTERFEROMETER 14 I(λ) = I IF (λ) N i=1 I i (λ). (8) where, I IF is the transmission of the order sorting filter, and i varies from 1 to N. The advantages of using more FPs are: (1) the unwanted side interference orders are suppressed, (2) the spectral resolving power increases, and (3) the interference filter (IF) with larger passband can be used. Some of the disadvantages are: (1) increase in system complexity, (2) the overall decrease in transparency, and (3) the loss in optical quality. The main goal of our project is to achieve a high spatial and spectral resolution without losing the optical quality. Hence, we preferred a dual etalon system rather than triple or more. Figure 7: Top: A plot of parasitic light (P) at 6300 Å vs the spacing of the thickest FPI is shown. Bottom: Spectral resolving power (R) at 8600 Å is plotted as a function of spacing of the thickest FPI. These plots are shown for reflectivity of 0.9 to 0.95 in steps of The middle dashed line refers to a reflectivity of Once the number of etalons and the mounting system have been defined, the next step is to search for the optimum ratio between the interferometer spacings at which it best reduces the parasitic light from the side bands. The parasitic light is defined as the ratio between the flux outside and inside the instrumental profile. By using the methodology given in Cavallini (2003) we estimated the parasitic light with the following parameters: the refractive index µ=1, the incidence angle θ=0, absorption coefficient A = 0.01, coating reflectivity R = 0.95, FWHM IF = 3Å centered at 6302 Å, and peak transparency τ IF =0.3. Figure 6 shows the plot of parasitic light vs the ratio of the FPs spacing. Here we have kept the first FPI (FPI-I) at 2 mm and varied the spacing
15 5 FABRY PEROT INTERFEROMETER 15 of the second FPI (FPI-II) insteps of 0.01, till the ratio equal to 1 (ratio = d 2 /d 1 where d 1 & d 2 are the separation between the plates in FPI-I and FPI-II). From the plot (Figure 6) it is clear that the smallest level of the parasitic light is obtained for the spacing ratio of The estimated parasitic light is for 6302 Å wavelength. This being the optimum ratio, now one can adjust the spacing between the plates of FP-I such that the spectral resolution is optimized. Again by following the method of Cavallini (2003) we optimize the spectral resolution R = (Figure 7, bottom) for a spacing of FPI-I = mm at which the parasitic light is less than 2% (Figure 7, top). So, the dual FPs with a spacing of FPI-I mm and FPI-II mm and a coating reflectivity R = 0.93 have been considered as the best values for getting the best parameters such as large transparency, low ghosts, low parasitic light, high image quality and high spectral resolution. 5.6 Minimum Size of the Required Fabry-Perot The spectral resolution in the telecentric mounting depends on the focal ratio of the beam. In the collimated beam the FWHM of the transmitted spectral line can be approximated as, λ FW HM λ 2 0 πd 1 F(1+ε 2 ). (9) where, λ 0 is the central wavelength, d 1 is the spacing of the FPI-I in the series and ε = d 2 /d 1. In this calculation, d 1 = 2.3 mm (obtained from Section 5.5) and ε = At the 6302 Å line, the FWHM ( λ FW HM ) is estimated as 19.2 må. In the telecentric configuration, the collimated FWHM ( λ FW HM ) adds with the telecentric spread λ s as follows: λ = λ 2 FW HM + λ2 s. (10) With the requirement that λ equal to 33mÅ we get a telecentric spread λ s = 27 må. The change in the FWHM as a function of half angle α of the telecentric ray cone is approximated as, λ s = λ 0 8Fno 2. (11) where, the F no is the focal ratio of the telecentric beam. For 6302 Å line, the estimated focal ratio is Following Darvann and Owner-Petersen (1994), the required size of the FP for a given FOV is given by, D FPI = F no α FOV D. (12) where, the α FOV is the FOV and D is the diameter of the telescope. For a telescope of 2 m class and a FOV of 1.5 arc-min, the clear aperture of the FP should be 14.9 cm. Hence, the adoption of 15 cm aperture air gap FP from IC Optical Systems Ltd. (UK) or any other company can be utilized for this project. At this focal ratio the spectral
16 5 FABRY PEROT INTERFEROMETER 16 resolution at 6302 Å is which is close to the desired parameter in the design specification that meets all our scientific goals. 5.7 The Transmission Profile of the Air Gap FPI system Figure 8: The transmission profile of the dual air-gap FPIs in combination with a 3 Å transmission filter. The reflectivity of 0.93 is taken in computing the transmission profile. Figure 8 shows the transmission profile of the air gap media of dual FPs in tandem. In estimating the transmission profile of the dual FPI system we have used the spacing of the FPI-I as mm and the FPI-II as mm, with a reflectivity of 0.93 and the FWHM of the transmission filter as 3 Å with two cavities. The profile shown here is for the FPs kept in the collimated beam. In the telecentric configuration, the transmission profiles will be similar except that the spectral line will be broadened due to the large FOV.
17 5 FABRY PEROT INTERFEROMETER Specifications of the Fabry-Perot Etalons The IC Optics T M makes piezoelectrically tunable etalons that are constructed using two highly polished glass plates. One of the glass plates is mounted on the movable piezoelectric stacks. The IC Optics FP operates on the three channel bridge system using capacitance micrometers and piezoelectric actuators. A combination of capacitance micrometer and piezoelectric actuators monitor and correct the errors in mirror parallelism and spacing. Out of three channels, two channels control parallelism and the third maintains the plate spacing by locking it to the cavity length. This is achieved by referencing the capacitor to a high stability standard reference capacitor. The whole unit functions in a closed loop servo system, thus eliminating any nonlinearity and hysteresis in the piezo drive. The detailed specifications of the required FP is given in Table 5. Table 5: Details of the required specifications of the FPs for narrow band imaging system. Specification Value Fabry Perot Substrate Material Fused Silica Reflectivity 0.95 at λ Å Type of FP ET 150 IC Optics Inc. Clear Aperture 15 cm Surface Accuracy λ/200 Number of FPs 2 Etalons Plate spacing mm for FP-I and mm for FP-II Coating Multilayer Coating Displacement ± 2µm with 4096 steps 5.9 Stability of the Spectrometer Over the Wavelength The FP based spectrometer are usually kept inside a temperature controlled enclosure with the ambient temperature specified by the manufacturer. The temperature should be maintained constant within 0.1 C or better depending on the manufacturers specification of the FP. Temperature controller is calibrated based on the careful laboratory measurements of the wavelength drift with temperature. Wavelength stability of the FP system is generally calculated from the accuracy of the temperature controller, tolerance to the parallelism of the plates, beam angle with respect to the plates and plate separation etc. Typically the required stability of the wavelength is about 10 må /hr, which is much smaller than the resolution of the spectrometer The Exposure Time and Signal to Noise Ratio It is very important to know the exposure time and the signal to noise ratio (SNR) at the detector. These quantities can be calculated by using the reflectance and transmittance
18 5 FABRY PEROT INTERFEROMETER 18 of all the optical components in the path of the beam. The solar flux at 6318 Å continuum wavelength (which is close to 6302 Å) is J m 2 m 1 s 1 (1.638 W m 2 nm 1 ) (obtained from which corresponds to a photon flux of photons m 2 m 1 s 1. We can relate the photon flux to the number of electrons at the detector per second assuming the specific characteristics of the telescope and the imaging instrument. We assume the atmospheric transmission is τ atm =0.95. This is almost close to the quoted value of atmospheric transmission if one neglects molecular scattering and aerosol absorption (Cox, 2000). The proposed NLST telescope will have a six mirrors (including the primary) each with a reflectivity of 95%. The intensity of the reflected beam from the primary of the telescope to the end of sixth reflecting surface is reduced to 70% which takes the atmospheric transmission into account. The lens-let array of the adaptive optics system will take-out a few percent of the beam and other instrument will require a few more percent of the main beam. Hence, while reaching the proposed narrow band imaging system the intensity of the beam will be reduced to 60%. The transmission of the etalon is 80% each and the order sorting filter transmits the light by about 40%. Hence, the final beam will have an intensity of 15% of the original solar flux. The FWHM of the imaging instrument is 33 må. The FOV is 1.5 arcmin circular. For a pixel CCD camera (pixel resolution of 0.06 arcsec) with 60% quantum efficiency we should be able to detect electrons s 1 which corresponds to an exposure time of about 54 ms for a full well of electrons. To avoid the image saturation, it is sufficient to consider about 80% of the full well capacity with 43 ms exposure time. If the CCD readout time is about 100 ms then we should be able to get at least 6 images per second. At this photon detection level the SNR is 532. So, for a 0.06 arcsec resolution there are enough photons to achieve the desired SNR. For a Nyquist sampling at the diffraction limit of the 2-m class telescope, (0.039 arcsec per pixel), a CCD larger than pixels is necessary to cover the required FOV. The SNR of > 500 can be attained with an exposure time of 100 ms or larger. Even at this resolution, the cadence will be around 5-frames per second. It is also possible to make the dopplergrams with this dual FPI system. By acquiring the intensity images in the red and blue wing(s) of the 6302 Å line (or any other line) one can make the dopplergrams. The intensity can be measured in the red and blue wing at a position of 60% level below the continuum. Then by using the simple relation, one can construct the Doppler maps as, V dop = K I red I blue I red + I blue. (13) The error in measuring the Doppler velocity for zero shift in the wavelength position is given by, 1 σ v = K. (14) I red + I blue The photon counts at the 60% intensity of the continuum will be photons s 1. Using this value, the error in measuring the velocity can be estimated to be K. Here, the K is the calibration constant, measured in terms of km s 1.
19 6 ITEMS NEEDED AND COST OF THE PROJECT 19 This constant will vary with different spectral lines. After using the 6302 Å line with a 40 må FWHM (of the narrow band FPI system) the value of K is km s 1. Using this value of K we estimated the error in the Doppler velocity to be about 24 m s 1. The estimation of the error in measuring the magnetic field using polarimetry will be discussed in a separate technical report. 6 Items Needed and Cost of the Project Table 6: The required components for the project. Items Fabry Perot Interferometer Order sorting filters CCD camera Lenses, prism, optical table & opto-mechanical mounts etc Temperature controlled enclosure and platform Electronic and electrical items Enclosure, Filter Wheel & Miscellaneous Total Price = Rs. 260 lakh = Rs. 25 lakhs 40 lakhs 30 lakhs 5 lakh 10 lakhs 20 lakhs 390 lakhs Based on the above suggested optical layout for the FP based spectrometer (Figure 5) it is necessary to have a set of combination of lenses. The lenses will be achromatic doublet and will be able to cover a wavelength range of Å. A 5-10% beam splitter is required to tap a portion of the main beam to be utilized for the continuum imaging purpose. It is also necessary to have a set of interference filters with a pass band of 2-3 Å for different wavelengths of interest. Few wavelengths of interest are: H α 6563 Å, Fe I 6302 Å filter, and Ca II 8542 Å line. It is also important to have a good performance CCD camera with the specifications mentioned in Section Other accessories include mechanical components, holders, clamps, posts etc. Finally an optical table, a tunable laser or a spectrometer are necessary to calibrate the FPs in the laboratory and study its performance. The cost of each item depends on the quality, quantity and the vendor who provides them. The most expensive item in this project is the FPs. The cost would include the interface card, control software, piezo-electric controller, power supply etc. The next expensive item is the prefilter assembly. The optical and mechanical items (CCD camera, vibration free table, temperature controller, optics etc) would also cost a significant amount. Based on the current estimates, the tentative budget of the entire project is around Rs. 400 lakhs. The material cost may change with time. A revised cost estimate would be made at the time of detailed project report.
20 7 OTHER CONTEMPORARY INSTRUMENTS 20 7 Other Contemporary Instruments Table 7: Comparison of FP based narrow band imaging system around the world. TESOS, IBIS, VTT and NLST corresponds to Telecentric Etalon SOlar Spectrometer, Interferometric Bidimensional Spectrometer, Vacuum Tower Telescope and National Large Solar Telescope respectively. In the Table, λ corresponds to spectral resolution, Pixel Res corresponds to spatial resolution in terms of arcsec/pixel and FOV is the field-of-view. System λ Pixel Res arcsec FOV arcsec TESOS / IBIS VTT NLST & The Telecentric Etalon SOlar Spectrometer (TESOS) is a triple etalon system, developed and installed at the Observatorio del Teide, Tenerife. The observation is done at 0.15 arcsec resolution and FOV is 100 arcsec. The system works in the optical wavelength region. The Interferometric Bidimentional Spectrometer (IBIS) was developed by the Italian group and installed at the Dunn Solar Telescope (DST) of the National Solar Observatory, USA. This is a dual etalon system with a spatial resolution of 0.2 arcsec and a FOV of 80 arcsec. The spectral resolution is and operating at near infra-red wavelength range. The Institut Für Astrophysik developed a 2D spectrometer for the VTT in 1986 and they have upgraded it in The FOV is 78 arcsec 58 arcsec, with a pixel resolution of 0.11 arcsec. This instrument works in the wavelength range of Å with a spectral resolution of Table 7 shows the comparison of all the instruments including the proposed narrow band imaging system for the NLST. In all these instruments, the spectral resolution and FOV is comparable to our proposed imaging system, except the spatial resolution which is large by a factor of 2 or more in our case. With this resolution we will be able to achieve the projected science goals. We will follow some of the concepts in the designs and characteristics of these instruments in our proposed instrument. 8 Summary The Indian Institute of Astrophysics is planning to build a 2-m class telescope to be commissioned in one of the high altitude sites in Himalayas. This telescope will be dedicated to the solar astronomy to do the observations at high angular resolution. The current report describes an instrument for narrow band imaging with high spatial and spectral resolution. This report is written with a clear goal of deploying the FP based spectrometer on the NLST as one of the back-end instruments for solar observations. It is also assumed that the NLST project will have fully functioning adaptive optics system and also the post-processing capabilities like speckle, destreching etc. The projected FOV may not be available all the time at the full spatial resolution (due to the
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Let us know when your receive great advice so we can thank our lawyers and point others with similar questions in the right direction.Got it!
My fiancee's ex-wife hacked into his email and yahoo messenger and had an ex girlfriend send him naughty pictures and what not. She has also hacked into other things such as my email, or facebook. I am 3 months pregnant and I know that she is trying to make me loose the baby from stress. I have all the proof that she is the one doing this. She also constantly sends me messages on my cell phone, email, and what not harassing me about my relationship and who i am and everything. She is causing me great physical and mental distress. Is there anything I can do in addition to getting a restraining order against her?
You are on the right track with the first item. You'll probably want to get an antiharassment order, which you can file at the Maleng Regional Justice Center down there in Kent. After you file, there will be a hearing with all parties and witnesses present. I know it sounds silly, but it helps you legally to make it explicit that neither of you want to hear from her again, that all contact is unwanted contact.
Second, there is a cause of action in Washington for intentional infliction of emotional distress, but it's a very difficult one to prove harm for because your only harm is emotional, as opposed to physical injuries, which are more easily quantifiable. Additionally, the defendant's conduct must be extreme and outrageous. Though this is understandably traumatic and troubling for your family, it may not be enough for this cause of action. With more details on your case, an attorney could more easily determine if you have a case that is worth your time to pursue.Ask a similar question
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Open questions: Zombie projects, translational research, and the real secret of the inside of the cell
It may be a sign of incipient old age, but I find myself increasingly convinced that the key question in biology these days is philosophical, not scientific. It is the question of what balance should exist, given that the financial pie is not only finite but likely to be shrinking for some time, between large-scale, top-down, 'big science' projects that are primarily aimed at information gathering, and hypothesis-driven, individual-investigator initiated 'little science' projects. The seesaw has tilted pretty heavily in favor of the big stuff lately. I have nothing against such programs in principle, but it seems to me that in practice there are too many of dubious merit and low benefit-to-cost ratio. They are never pitted against small science projects when they are reviewed, and because they are attractive to administrators - they produce lots of data that can be shown proudly to superiors, politicians and citizens - they become very difficult to kill, even if the data are not very useful or the original mission has been fulfilled, because too many influential reputations and comfortable livelihoods are vested in their continuation. As I see it, there is a danger that these 'zombie programs' will take over biology, and investigator-initiated research, which is where most breakthroughs come from, is already getting short shrift as a consequence. It's time we stop letting that happen by default, and ask how priorities in biomedical research should be set, and by whom.
Two other, interrelated philosophical questions are: (1) whether biological research should focus predominantly on mammalian cells and organisms - the direction it seems to be heading - or whether there is, as I firmly believe, still a large place for work in model organisms; and (2) whether the distinction between 'basic' and 'translational' research is, as I have asserted elsewhere
Lest you think this is all too metaphysical, I do have a key scientific question to offer. I think one of the most important unsolved problems in biology is what the interior of the cell really looks like. This holds for both prokaryotic and eukaryotic cells. We've all seen those beautiful cartoons of the crowded environment inside a bacterium, and have watched mesmerizing videos like The Inner Life of the Cell
Herding CATS


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hey, i bet y'all know im a pretty bad artist, so i had an idea. what if i had someone else draw for me? i will put forth a few descriptions of some fanfic characters of your request and whoever had the best rendition will have it posted on my profile.
please send all submitted art to this email adress ======> email@example.com
remember, ypou have to request a character, so plz respond as fast as possible!
thanks to all and God bless Ariyh, Scriptor mirifice 21:26, March 28, 2011 (UTC)


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Case Conclusion Date: 06.25.2012
Practice Area: DUI and DWI
Outcome: Not Guilty both counts.
Description: Following an accident, Dudley police investigated a suspect. Since this was a 4th offense we opted for a jury trial. My client attended a Patriots game and on his way home he was involved in a motor vehicle accident. Following an investigation, the officer testified that he observed a strong odor of alcohol on my client's breath, slurred speech and bloodshot eyes. My client had admitted to drinking at the game. The jury deliberated for approximately 25 minutes and found my client not guilty. Result: Not Guilty Both Counts.


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Skip to main content
1 Definitions
1.1 "ibtm arabia" means the event for the Arabia meetings, events, incentives and business travel industry to be held at the Jumeirah at Etihad Towers, Abu Dhabi 7th-9th February 2017. It is a trade exhibition owned and organised by Reed Travel Exhibitions, a division of Reed Exhibitions Limited, of Gateway House, 28 The Quadrant, Richmond, Surrey TW9 1DN.
1.2 "Exhibitors" means exhibitors who have contracted with Reed Exhibitions Limited to take stand space at ibtm arabia.
1.3 "Hosted Buyer" means the meetings and business travel trade professional, who has been registered as a Hosted Buyer and has agreed to these Terms and Conditions and has been accepted by Reed Exhibitions Limited to attend ibtm arabia as a buyer of meetings, events, incentives and business travel products where accommodation, transfers and flights are provided by Reed Exhibitions Limited.
1.4 "Pre- Scheduled Appointment Programme" means the appointment programme operated by Reed Exhibitions Limited to co-ordinate the appointments of the Hosted Buyer with Exhibitors during ibtm arabia and "Pre-Scheduled Appointments" shall be construed accordingly.
1.5 "Show Team" means Reed Exhibitions Limited and ibtm arabia event personnel at Gateway House, 28 The Quadrant, Richmond, Surrey TW9 1DN, UK.
1.6 "Published fare" means a flight ticket that has been booked directly on an airline's own fare tariff, therefore carrying its own restrictive conditions pertaining to amendment and cancellation fees that will need to be applied.
2 Registration
2.1 As part of your acceptance onto the Hosted Buyer Programme you will receive: • Return flights from selected ports to Abu Dhabi according to the event dates and dependent on flight schedules• Accommodation for the duration of your stay at the Jumeirah at Etihad Towers, Abu Dhabi according to the ibtm arabia dates, unless otherwise agreed in writing• Transfers to and from the Jumeirah at Etihad Towers, Abu Dhabi and networking functions• Access to the Welcome Evening and Gala Evening• Pre-Scheduled Appointments with Exhibitors based on your highlighted preferences • Professional education with experts in their field• Refreshments including lunch and dinner
ALL other costs and incidental expenses are the responsibility of each attendee. Examples include: • Private transfers • Food and beverage • Flight upgrades • Hotel upgrades • Additional nights' accommodation • Personal extras• Travel vaccinations• Visa costs• Travel insurance
2.2 Completion of the online application form does not automatically guarantee you a place on the ibtm arabia Hosted Buyer Programme. You will be notified if your application is successful. The Show Team's decision shall be final.
2.3 The Show Team will only accept one application per participant. In the event that multiple applications per participant are received, only the first application will be considered.
2.4 All sections of the application form must be fully completed including the provision of valid credit card details of which a non-refundable $5 USD validation fee will be charged. Failure to do so will result in the form not being processed.
3 AttendanceAs a Hosted Buyer we ask you to commit to the entire programme (6th – 8th February 2018) due to the exclusivity of ibtm arabia.
3.2 The Show Team is responsible for co-ordinating your participation as a Hosted Buyer at ibtm arabia including accommodation, transfers and appointment setting. Flights will be provided over the period of ibtm arabia only. Flights are booked by the Show Team and therefore all queries should be directed to the Show Team.
Hosted Buyers are requested not to contact the ibtm arabia travel suppliers (i.e., agents, airlines and hotels) directly unless instructed by the Show Team otherwise.
3.3 If a Hosted Buyer wishes to make his/her own travel arrangements please inform the Show Team directly using the email address firstname.lastname@example.com and ensure that you travel according to the ibtm arabia dates and schedule.
3.4 Hosted Buyers agree to settle all expenses with the hotel prior to departure and will indemnify Reed Exhibitions Limited for any failure to do so.
3.5 Hosted Buyers who do not complete their Pre-Scheduled Appointments Programme selection by the agreed date will be liable for the "No Show" fee. Hosted Buyers must actively participate in the Pre-Scheduled Appointments Programme, i.e. selecting the required number of appointment preferences within a specified timeframe and partake in up to thirty (30) Pre-Scheduled Appointments during their attendance at ibtm arabia.
3.6 Hosted Buyers who are unable to honour an appointment on site, should contact the Exhibitor directly to arrange a more convenient appointment time.
3.7 If one or more persons from the same organisation each attend ibtm arabia as a Hosted Buyer then those persons must conduct their Pre-Scheduled Appointments individually.
3.8 Please note that attendance at Pre-Scheduled Appointments will be monitored and non attendance shall constitute a breach of these Terms and Conditions.
3.9 Hosted Buyers, by applying for Hosted Buyer status, are consenting to their contact details being made available to all Exhibitors at ibtm arabia for the purposes of arranging additional appointments.
3.10 Hosted Buyers shall wear business attire as a condition of entry to ibtm arabia.
4 Travel
4.1 Your invitation is non-transferable. Should a circumstance arise whereby you have to cancel your participation, you may request to substitute another person from your organisation. The Show Team must first accept and qualify that substitute person. Should that person meet the qualifications and the substitution be made on or prior to 2nd January 2018, cancellation charges will not apply.
4.2 Due to airline restrictions changes to travel plans after 2nd January 2018 will be considered on a case by case basis, but Reed Exhibitions Limited reserves the right to make charges for such changes. Such charges shall be notified to you and shall be debited from the credit card detailed in your application.
4.3 Any unused flight tickets must be returned directly to the Show Team.
4.4 VISAS. Please note that participants from certain countries may require a Visa to enter Abu Dhabi. It is the responsibility of each participant to organise their own individual visa.
4.5 Travel Vaccinations. Please note that travel vaccinations are the responsibility of each individual Hosted Buyer. Please contact your local doctor for further information.
4.6 Travel Insurance. Please note that Travel Insurance is the responsibility of each individual Hosted Buyer and the Show Team have not and will not affect travel insurance for Hosted Buyers. Travel insurance must be in effect from the day of departure up to and including the day you arrive back at your home country.
4.7 Excess baggage, customs fines and the like are the responsibility of each individual Hosted Buyer. ibtm arabia does not endorse or approve of the export of gifts given to Hosted Buyers by Exhibitors. It is the responsibility of each attendee to ensure that such gifts may be both legally removed from Abu Dhabi and imported into your home country.
5. Post-event toursPost-Event Tours are offered by the respective host destinations. If you are accepted as a Hosted Buyer by the Show Team and if you have indicated your interest in a Post-Event Tour, the respective host destinations you selected will be notified of your interest by the Show Team. Should you be approved for a Post-Event Tour, the following Terms and Conditions will apply:
5.1 Hosted Buyers are accepted for Post-Event Tours by the host destinations based on whether they meet the host destinations' criteria, as determined at the sole discretion of the respective host destinations. The host destinations' decisions are final.
5.2 Travel to and from ibtm arabia and Post-Event Tours is co-ordinated by the Show Team but is provided solely by the host destinations.
5.3 Accommodation during Post-Event Tours is the sole responsibility of the host destinations.
5.4 Cancellation: In the event you cannot participate in a Post-Event Tour for which you were selected, you must notify the Show Team by an email to firstname.lastname@example.com as soon as practicable.
5.5 A cancellation received by the Show Team on or prior to 2nd January 2018 will not incur a cancellation fee unless Post-Event Tour travel arrangements have already been agreed and confirmed by the Show Team and host destination. If such travel arrangements have been confirmed by the Show Team and host destination, the cost thereof will be charged to the Hosted Buyer.
5.6 A cancellation received by the Show Team after 2nd January 2018 shall incur a cancellation fee payable to the host destination to cover the travel and accommodation costs incurred by it up to the date of cancellation, and the Hosted Buyer will be advised.
5.7 Regardless of when a cancellation is received by the Show Team: if a Post-Event Tour cancellation by Hosted Buyer requires flights to or transfers from ibtm arabia to be revised by the Show Team to accommodate the Hosted Buyer's new plans, all costs of such flight and transfer revisions shall be the sole responsibility of Hosted Buyer and shall be charged to the Hosted Buyer by Reed Exhibitions Limited as an additional cancellation fee.
6 Cancellations and no shows6.1 Cancellation fees for Hosted Buyers
If you need to cancel your participation in the show, you must provide written notice by email to firstname.lastname@example.com. The cancellation will not be effective until you have received a written acknowledgement from the Show Team.
In the event of cancellation, the following fees will apply;
• Cancellations received on or before 2nd January 2018 will not incur a fee unless the flight has been agreed and confirmed. If the flight has been confirmed or is a published fare flight, the cost of the flight or relevant cancellation fee will be charged.
• Cancellations received after 2nd January 2018 will incur a fee of:
- $1500 USD for International Hosted Buyers - $1250 USD for Middle East Hosted Buyers (excluding Abu Dhabi & Dubai)- $750 USD for Abu Dhabi & Dubai based Hosted Buyers
6.2 No Show fees for Hosted Buyers
"No Show" fees for Hosted Buyers will be applied in the following circumstances:
• If you do not make the required number of Exhibitor selections and/or Pre-Scheduled Appointments prior to the close of the Pre-Scheduled Appointment Programme diary
• You are reported onsite as a "No Show"
• You are unable to attend ibtm arabia and do not advise the Show Team in writing prior to close of business on 4th February 2017.
• If you miss two or more Pre-Scheduled Appointments at ibtm arabiaIn the event of a "No Show ", the following fees will apply;
- $1600 USD for International Hosted Buyers - $1400 USD for Middle East Hosted Buyers (excluding Abu Dhabi & Dubai)- $850 USD Abu Dhabi & Dubai based Hosted Buyers
No Show fees will be charged to Hosted Buyers if confirmed accommodation and transportation arrangements have been provided by ibtm arabia.
Hosted Buyers participation and attendance are monitored by the Show Team and Exhibitors.
6.3 Cancellation and No Show charges
The Hosted Buyer agrees that the above charges are a reasonable pre-estimate of the loss suffered by Reed Exhibitions Limited in the event of the Hosted Buyer breaching these Terms and Conditions.
7 Exclusion of liability7.1 Reed Exhibitions Limited takes no responsibility:
7.1.1 for Hosted Buyers who miss their ibtm arabia flights;
7.1.2 for the insolvency or failure of any airline company or hotel or ground handling company or other supplier;
7.1.3 for flight cancellation or delay;
7.1.4 if the Hosted Buyer is refused permission to board the aircraft or is refused entry to Abu Dhabi;
7.1.5 for any delay or loss of baggage or excess baggage charges - any subsequent dispute shall be directly between the Hosted Buyer and the airline).
Any replacement flights and other costs incurred in relation to the above will be at the expense of the Hosted Buyer or airline, where appropriate.
7.2 The Hosted Buyer must obtain adequate travel insurance coverage for their stay and it is recommended in particular that Hosted Buyers take out adequate cancellation insurance to cover the instances referred to in paragraph 4.6 & 4.7 for baggage and medical insurance.
7.3 Individual visa requirements, travel permits, other licences and inoculations will be the sole responsibility of the Hosted Buyer including any necessary costs incurred.
7.4 Reed Exhibitions Limited, its agents, its employees, and its subcontractors shall not be liable for loss, damage or delay resulting from acts or threats of war, hijack, terrorist activity, civil commotion, industrial disputes, fuel shortages, natural disasters or adverse weather conditions, strikes or lockouts intervention or regulation, military activity, epidemics or any other circumstances outside Reed Exhibitions Limited's or its subcontractor's control which shall make it impossible or inadvisable for Reed Exhibitions Limited to hold ibtm arabia at the time and place provided or makes it impossible to get the Hosted Buyers to ibtm arabia or to provide flights, hotels, transfer appointments, events or other services to Hosted Buyers. Reed Exhibitions Limited reserves the right to re-schedule ibtm arabia on another date and/or at an alternative site.
7.5 Reed Exhibitions Limited shall not be liable to the Hosted Buyer, in contract, tort or otherwise for any loss of profit, loss of business or revenue, loss of anticipated savings or any indirect or consequential loss or damage, costs or expenses arising out of or in connection with the Hosted Buyers attendance at ibtm arabia
7.6 Reed Exhibitions Limited shall not be liable for the death or personal injury of any Hosted Buyer save where such liability can not be excluded under English Law.
7.7 Reed Exhibitions Limited's liability to the Hosted Buyer in respect of their attendance at ibtm arabia under these Terms and Conditions whether in contract, tort or otherwise shall not exceed $1600 USD.
8.2 Persons (such as spouses, family) accompanying the Hosted Buyers are not included in any offers regarding the Hosted Buyer programme.
8.3 By agreeing to these Terms and Conditions, Hosted Buyers are consenting under all relevant data protection legislation to Reed Exhibitions Limited communicating with you by telephone, fax, email and by post and using Hosted Buyer's personal information for internal processing and for disclosure to third parties such as ibtm arabia Exhibitors, travel agents, airlines, hotels and transport providers in connection with the Hosted Buyer's attendance at ibtm arabia (including, without limitation, for processing your credit card for additional travel and accommodation charges, cancellation or No Show fees). In addition, we may use Hosted Buyer details to invite Hosted Buyers to other events organised by Reed Exhibitions Limited or its group or to offer other relevant products and services supplied by Reed Exhibition Limited's group or third parties (other than those you have consented to above in connection with your attendance at ibtm arabia). Please use the Data Protection Act opt-out section at the end of the registration form to indicate your preferences.
8.4 These Terms and Conditions, and any dispute, controversy, proceedings or claim of whatever nature arising out of or in any way relating to these Terms and Conditions, the validity and performance hereof or their formation (including any non-contractual disputes or claims), shall be governed by and construed in accordance with English law (save that the conflicts of law principles will be expressly excluded). The parties hereby irrevocably acknowledge and agree that the English courts shall have exclusive jurisdiction in respect hereof.
8.5 "ibtm" is a registered trade mark of Reed Elsevier Properties SA and is used by Reed Exhibitions Limited under licence.
8.6 We request that you provide contact details for the person whom you would like to use as a contact in the case of an emergency during the Event. This information will remain confidential and will not be used for any other purpose. By providing this information, you are confirming that the named contact has agreed that his/her details may be supplied to us for this purpose.
We use cookies to operate this website and to improve its usability. Full details of what cookies are, why we use them and how you can manage them can be found by reading our Privacy & Cookies page. Please note that by using this site you are consenting to the use of cookies.


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How to reload/refresh a page using JavaScript and jQuery
Labels: JavaScript , JQuery
Is it possible to have an abstract method in a final class?
This is one of the interesting core Java questions which was asked to one of my readers recently during a telephonic interview for Java developer job interview. Even though he knows that you cannot make an abstract class final in Java, he got confused by the wording of the methods. The answer is simple, No, it's not possible to have an abstract method in a final class in Java. Why? because as soon as you declare an abstract method in a Java class, the class automatically becomes an abstract class and you cannot make an abstract class final in Java as discussed before, hence it's not possible to have an abstract method in a final class in Java.
Labels: abstract modifier , core java , core java interview question , final modifier
Does Spring Certification help in Job and Career? Why become Pivotal Certified Spring Professional?
One of the frequently asked question among Java and Spring developer is whether Spring certification is valuable? or does Spring Certification help you in Job and Career? These questions are not very different from what Java developer ask about Oracle's Java certification (see here). The short answer to these question is Yes, Spring Certifications are very valuable and it not only provides Industry recognition for your knowledge, experience, and skill but also set you apart from the millions of Java and Spring developer who are not certified. Of course, as with any certification, the most valuable part, apart from recognition is the learning process and this is true for Spring certifications as well.
Labels: IT Certifications , spring , Spring certification
2 Ways to check if A String is rotation of other in Java?
Write a program to check if one String is a rotation of another String is a common coding problem you will see on programming job interviews. A String is said to be a rotation of another String, if it has the same length, contains same characters, and they were rotated around one of the characters. For example, String"bcda" is a rotation of "abcd" but "bdca" is not a rotation of String "abcd". One of the simplest solutions to this interesting problem is first to check if two String has the same length, if not then one String cannot be the rotation of another. If they are of the same length then just create another String by concatenating first String with itself, now check if second String is a substring of this concatenated String or not, if yes, then second String is a rotation of first.
Posted by Javin Paul 8 comments
OCAJP 8 FAQ - Oracle Certified Associate Java Programmer I Certification (1Z0–808) Frequently asked Questions
The Oracle Certifications is one of the most repeated, industry recognized certifications. It also provides Java certifications like Oracle Certified Associate Java Programmer, also known as OCAJP and Oracle Certified Professional Java Programmer, also known as OCPJP. These two are most popular Java certification and there are many benefits of passing them e.g. better chance to get a Java development job, improved performance on Java interviews, better salary rise, and promotions, and better opportunity for moving abroad.
Labels: Java Certification OCPJP SCJP , OCAJP
Amazon Prime Day, Good opportunity to Buy Books and Gadgets
Most of my friends and colleagues used to wait until November to buy books, gadgets, and other computer items to get the huge discount offered on Black Friday deals, but you don't need to. Amazon is bringing Black Friday to the summer with their annual Prime Day offers. The Amazon Prime day is nothing but a one-day shopping extravaganza, where you get huge discounts on thousands of Amazon products including books, gadgets and other computer and electronics items. So, if you are looking to buy a new laptop, a new smartphone or want to track your fitness, you can buy Fitbit and other such gadgets at a much cheaper price on Amazon prime day.
Labels: general
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