We have been busy in the second half of 2018 with, amongst other projects, several large simulator builds. Our Unisim Compact range of small, close-match solar simulators continue to also prove popular and our last system in stock has just shipped to the University of New South Wales.
We are continuing to work on the application of LED technology to our close-match simulators and have some interesting R&D work coming up in 2019 which will take our N-Zone solar simulator design to large area applications.
2018 has been very busy for our thermal vacuum chambers TVAC#1 and TVAC#2 as we have conducted bakeout and TVAC cycling work for a range of customers, including quite a lot of components for the ESA Solar Orbiter mission.
We are currently designing a full IR heat shroud for TVAC#2 to be fitted in 2019. We had hoped to complete in late 2018 but demand for the chamber has meant maintenance time has been limited.
We are excited to announce that we will be expanding our lab capabilities to include FTIR analysis via transmission and ATR in early 2019. This facility will primarily be used for analysing molecular witness plates for contamination control during vacuum bakeouts. However, we will also be offering FTIR analysis of condensables collected from our standard outgassing test. There will be further announcements via this news page and our main test facilities page when this becomes available.
We are making our in-house Unisim Compact available for demonstration and testing. You are also welcome, without any obligation, to use our house Compact for a half-day to measure any of the cells on which you are currently working.
TS-Space Systems is proud to have supplied a Unisim Solar Simulator to NEC Space Technologies, LTD. a world leader in the manufacture and testing of satellite equipment.
The Unisim close match solar simulator provides a world leading close spectral match to the standard AM0 spectrum via multiple discrete wavebands which is vital for accurately characterising the multijunction solar cells used for space applications.
"We are very pleased to work with NEC Space Technologies LTD again", said Dr Bill Williams, Director at TS-Space Systems, "We are proud to add NEC Space Technologies LTD. to the long list of leading PV research and manufacturing groups who have selected our solar simulators for their work".
We are busy finishing several large simulator builds at the moment, but we are still planning new additions to our products and services for 2016.
We have new LED boost options for our Unisim Compact solar simulators and we will be launching our in-house simulator demo service in 2016. Customers will be able to book a day on our in-house Unisim Compact solar simulator and try it out for themselves. Tea and biscuits included!
2015 has been an incredibly busy year for our outgassing rig. If you are interested in outgassing or any of our in-house test services, the sooner you contact us the more likely we are to fit you in to our test schedule.
We value product support very highly at TS-Space Systems which is why we offer extensive support via phone and email for the full lifetime of every TS-Space Systems product. Training is also provided at our premises where customers can take advantage of one-on-one tuition with the product designers to learn how to operate and maintain their solar simulators and other tools.
If you have a question or information you'd like to see included in an FAQ, post it in the relevant section and we'll add it in.
"A solar simulator (also artificial sun) is a device that provides illumination approximating natural sunlight. The purpose of the solar simulator is to provide a controllable indoor test facility under laboratory conditions, used for the testing of solar cells, sun screen, plastics, and other materials and devices." 
"A solar simulator usually consists of three major components: (1) light source(s) and associated power supply; (2) any optics and filters required to modify the output beam to meet the classification requirements" 
Thus we need to select a light source that approximates the solar spectrum we want to simulate, be it AM0 for space applications of AM1.5 for terrestrial, and appropriate power supply. We also need to be able to manipulate the beam via an optical system such that the spectrum and spatial uniformity of irradiance can be optimised for the required application.
There are four commonly used light sources used in solar simulators:
Xenon Arc Lamps - These have been commonly used in most simulators since the very first 1960's designs due to the raw output having a fairly approximate match to the AM0 spectrum. There are, however, large infra-red "spikes" which must be attenuated to achieve a close spectral match. Even so, a single source solar simulator consisting of an IR filtered xenon arc source will provide a crude match to AM0/AM1.5, which is acceptable if you are testing single-junction devices or biological tests where an exact spectral match is not necessary. They are expensive compared to other arc sources, primarily due to the increasing demand for a limited global supply of xenon.
Metal Halide Arc Lamps (HMI) - Commonly used in film and television lighting where a close match to daylight is required along with a high temporal stability for filming, metal halide arc lamps provide an alternative to xenon which are more stable, give better temporal stability, are low-pressure, easier to maintain and cheaper. The spectral perturbations in the infra-red are much reduced from xenon, meaning they are excellent basis for both Class "A" and advanced solar simulators (see relevant section above). For reference, an unfiltered metal halide arc lamp will produce a B class spectral match.
For more information on this see our previous article on close spectral match solar simulators or our new LED-hybrid solar simulator.
Quartz Tungsten Halogen Lamps (QTH) - These provide an excellent black-body match in the infra-red but very poor across the visible range. As such they are more commonly used in more advanced multi-source solar simulators. See our previous post for more information on advanced solar simulators.
These are typically dictated by the light source used. For example, arc lamp power supplies are typically highly complex devices that have to manage a high voltage ignition stage in order to establish the arc. QTH lamps will require a comparatively more simple DC source with a compatible power output.
The optical layout of a solar simulator varies greatly depending on a multitude of variables including: the type and number of light sources used, the area of illumination generated, the spectral output generated etc. For basic solar simulators there are perhaps greater areas of commonality between manufacturers: a parabolic reflector, mixing mirror, IR clipping filter and 90 degree "down" mirror are generally found in single source xenon Class "A" systems.
Generally, major concerns for the optical system of a solar system (beyond achieving its required classification) is the ease of use/adjustment and maintenance. If a specific vertical or horizontal beam orientation is required then this should also be considered.
A simplified version of this simulator is now offered. This is based on our standard, spectrally close-matched simulators, but uses LED boost zones in place of the traditional arc and tungsten lamps, up to 1100nm. These are much more compact than our simulator zones, are extremely stable and perform well within the international standards for spatial uniformity of +/-2%.
The basic technique, assuming that illumination levels above and below AM0 are required, is to reduce the overall level of illumination of the simulator so as to be, say, 10% below AM0, but maintaining the AM0 spectral distribution (Figure 1).
Selected LED's are then used to provide the correct illumination for each junction at AM0 (Figure 2). By varying the output of these LED's, the current in any selected junction may be increased or decreased as required. In this way, any junction may be investigated independently of any other junction. Please note that alternative LED wavelengths to the ones demonstrated here are available.
control of an individual LED as well as groups of LED's with the same wavelength. LED output configurations of the simulator can be saved and recalled.
The software automatically detects the LED units installed at start-up which allows the user to replace individual LED's or even install an alternative wavelength LED with minimal disruption to the control system. Thus any later changes to simulator wavelength requirements can be accommodated with minimal cost and downtime.
Please feel free to contact us for more information and pricing.
The term 'close-match' to describe a solar simulator that attempted to move beyond a single-source design and accurately reproduce the solar reference spectrum was first used in 1997 by Dr Williams from 'TS-Space Systems LTD' when the results from the first ever close-match solar simulator were presented. The research compared the results of testing multi-junction solar cells using a close-match spectrum to the results from using another, basic solar simulator and showed measurement variations of up to 20% in some cases.
The importance of a good spectral match or 'close-match' solar simulator for accurately measuring and investigating multi-junction solar cells was clear and has since been thoroughly demonstrated in the research literature:
"The photovoltaic characterization of triple-junction InGaP2/GaAs/Ge solar cells is presented. Measurements made using a single light source solar simulator are compared with other measurements made using a multi-light source solar simulator that provides a close match to the air mass zero (AM0) solar spectrum. The output spectrum of the solar simulators has been measured, and two methods for calibrating the simulator output intensity haven been employed. The spectral response of the solar cells has been characterized through quantum efficiency measurements. These data are analyzed to determine the effect of the simulator spectrum on the measured photovoltaic response, and in particular, areas where spectral mismatch between the simulator and AM0 can lead to inaccurate performance predictions are highlighted."
Figure from  comparing a basic spectral match and the new 'close-match' solar simulator presented in . The deviation at 2200nm onwards is due to the spectrometer calibration.
 "Solar Cell Calibration and Measurement Techniques" NASA Technical Memorandum 113155 November 1997 IECEC–97534
 Jeffrey H. Warner ; Robert J. Walters ; Scott R. Messenger ; Justin R. Lorentzen ; Geoffrey P. Summers, et al."Measurement and characterization of triple junction solar cells using a close matched multizone solar simulator", Proc. SPIE 5520, Organic Photovoltaics V, 45 (November 3, 2004); doi:10.1117/12.559734; http://dx.doi.org/10.1117/12.559734
Spectral irradiance comparison between AM0 standard (ASTM E-490) and TS-Space Unisim: (a) irradiance from each of four lamps indicated by “zone” numbers and vertical blue markers indicate band gaps of typical IMM four junction solar cell; (b) percent of total irradiance for each of six wavelength regions as specified by IEC 60904-9.
At TS-Space Systems, when we made the worlds first multi-source close match solar simulator back in 1997 , we also made the world's first multi zone solar simulator by definition. What is a "zone" when it comes to solar simulators? It's a good question and one we get asked quite a lot of the time.
Modern multi-source solar simulators follow a general pattern of combining an arc lamp (traditionally Xenon) with one or more incandescent lamps. At TS-Space Systems we've lead the way by adopting Metal Halide arc lamps for our latest range of solar simulators which are cheaper and much more stable than Xenon sources without using feedback controllers.
But where our solar simulators really excel is their division of the spectrum into independently controllable wavebands. We call these spectral "zones". As an example, the measured spectrum of a TS-Space Systems Unisim, quad-source (four zone) solar simulator is shown to the left.
The intensity of each "zone" can be adjusted independently in a TS-Space Systems Unisim solar simulator. Being able to adjust discrete portions of the spectrum while a device is under test allows for specific sub-cells to be limited or saturated with their appropriate wavelength of light. Thus the behaviour and characteristcs of the device can be fully investigated.
A further distincition can therefore be drawn between advanced solar simulators which provide a close-match and those which not only provide a close-match, but divide the spectrum into controllable "zones" which are suited to the spectral response of each band gap within the solar cell.
What happens when you need more than four "zones"? That's where our Unisim N-Zone comes in.
 Wilkinson, V. A.; Goodbody, C.; Williams, W. G., "Measurement of multijunction cells under close-match conditions," Photovoltaic Specialists Conference, 1997., Conference Record of the Twenty-Sixth IEEE , vol., no., pp.947,950, 29 Sep-3 Oct 1997
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