| Spectral Emission, Excitation and Lifetime Measurement of Phosphors and Scintillators
|
 |
The McPherson Phosphor Test System is a vacuum ultraviolet spectrophotometer with design optimized for test of phosphor emission and luminescence. It delivers vacuum ultraviolet (VUV) excitation wavelengths to samples and in turn measures radiative emission. This is a useful system for quality control of optical properties, fundamental research and development of emitting materials. Customers are engaged in the search for materials that exhibit photon cascade emission (PCE) a process where quantum yield is greater than unity. This would be a tremendous boon for large industries involved with commercial lighting. More efficient fluorescent lamps that utilize means other than low pressure Mercury discharge for excitation are sought. Phosphor emitters that efficiently use VUV excitation are used in many type of flat panel displays too. Lower power requirements, better and stronger colors as well as improved efficiency are all desired.
The McPherson Phosphor Test System is ideal in situations where phosphors, scintillators and other luminescent materials require accurate characterization in terms of emission wavelength and lifetime. The McPherson system can deliver VUV excitation wavelengths at 146 nm, 173 nm and more either by using a vacuum monochromator to select discrete excitation bands from a broadband Deuterium source, by using filters, or in some cases Excimer discharge lamps. Excitation wavelengths are focused to the samples. The (phosphor) samples may be exchanged while maintaining the vacuum required for high-energy excitation. Phosphor emission is collected and delivered to a McPherson spectrometer for analysis. The emission spectrometer is equipped with a CCD for quick determination of the phosphor emission wavelength (color.) In single channel mode the phosphor samples may be analyzed in more detail, especially regarding lifetime (to nanosecond time scales.)
Overall, the system has a usable wavelength range of 115 nm to 930 nm. This can be expanded into the deep, windowless UV or into more simply into the IR with additional sources/detectors. Interchangeable sample holders accommodate 25mm diameter samples or sample cups. Samples are oriented horizontally to simply handling powder and other loose granular sample types. Up to 20 samples can be installed and samples can be indexed under vacuum. The optical and pumping systems are built into a support table equipped with castors and leveling legs for easy transport and set up. The electrical components are built in. A control computer sits on a separate table. Complete, ready to use systems are available.
Specifications
| Excitation Wavelength(s) | < 1nm FWHM discrete bands selectable from 120 to 400nm Vacuum monochromator Model 234/302 Filters and Excimer sources - optional |
| Emission Wavelength(s) | < 1nm FWHM discrete bands measured from 200 to 900nm PMT used for lifetime and scanning CCD for Color and survey work - optional |
| Sample Size | 20 ambient temperature 25mm diameter sample cups horizontal mounting |
| Sample Environment | Ambient / Room temperature Cryogenically cooled (single sample) - optional Heated (to 400deg C) (single sample) - optional |
Time Resolved Spectra / Lifetime
| Application Example: Set the vacuum ultraviolet spectrometer set to desired Excitation wavelength. Set the Emission monochromator to 525 nm. Select a (green) phosphor sample. Enter 525nm in the GO TO parameter field of the software and then press GO TO. The monochromator will proceed to 525 nm and data acquisition will commence. The McPherson systems uses a SR430 Multi-Channel Scalar for measurement of phosphor lifetime / decay. The function generator DS335 is set to produce a trigger pulse. The trigger pulse from the DS335 function generator closes a shutter and starts acquisition by the SR430 Multi-Channel Scalar. The screen will remain dormant until the preset number of scans have accumulated. When finished, the spectra will appear. The DONE button will appear. Press the DONE button to obtain the file save prompt. |  |
Spectral Emission, Excitation Measurement
 | Application Example: Set the vacuum ultraviolet spectrometer set to desired Excitation wavelength. Set the Emission monochromator to SCAN from 350 to 600nm. Select a (green) phosphor sample. The McPherson systems uses a SR430 Multi-Channel Scalar for measurements during Emission wavelength scans. This mode will take the mean data value and record one data point per wavelength increment. Enter the desired BEGIN, END and INCREMENT values in software and then SCAN. The monochromator scan will commence and data acquisition will begin. The screen will update until all wavelength increments have been recorded. |
 |
 |