Resolution, silicon photodiode

A 100-W immersion heater (such as VWR Scientific Inc. 33897-140 a 200-W to 300-W tea/coffee immersion heater can also be used), controlled by a Variac magnetic stirrer and stir bar 1000-mL beaker thermometer with a resolution of 0.02 K (platinum resistance thermometer or calibrated thermistor such as Vernier model TMP-BTA) 1- to 5-mW He-Ne laser (633 nm) or a red (545 mn) or green (532 nm) laser — a battery-operated laser pointer is suitable, but a module with a separate 3-volt power supply, available from Z-Bolt and other sources, will give better power stability for long rans two Polaroid sheets in rotation holders photodetector such as photomultiplier tube or Thorlabs model 201/579-7227 silicon photodiode analog-to-digital data collection system such as Vernier LabPro. 

We employ method B to study effects of this type. In this mode, our apparatus yields relative high-resolution fluorescence spectra at different time windows after excitation of the sample by the 355 nm pulse. The spectra are acquired by the upconversion method. The upconverted fluorescence spectrum is recorded simultaneously at all monitored wavelengths by an optical multichannel analyzer. It is constructed from a poly-chromator (HR320 Instruments SA) and an intensified silicon photodiode array detector (Princeton Applied Research Model 1412). The detector is interfaced to our Cromemco computer. 

We have coupled both PIN and APD silicon photodiodes to CsI(Tl) scintillators and studied their energy resolutions, stabilities, and low energy... 

For detection in the UV-visible region, photomultipliers or other photoelectric devices are used. Some instruments may use a multi-channel diode array detector. An array of typically 300 silicon photodiodes detects all the wavelengths simultaneously with a resolution of about 1 nm. This provides a great saving in time and an improved signal/noise ratio. 

Figure 7 shows the photon spectrum from Cs and sources. They were obtained with a 1 cm pure Csl crystal at 117 K coupled to the photodiode with optical silicon grease. The light output was 26,000 photons/MeV, leading to an r.m.s energy resolution of less than 6 % for 511 keV photons. To our knowledge such a performance as not been achieved so far. 

Semiconductor silicon diodes, called photodiodes, with special conductance properties are generally used in diode array spectrophotometers. Photodiodes are very useful because scan times of the order of a few milliseconds and thus many scans may be obtained in a very short time. In addition, the data obtained, being digital, can be further processed to generate spectra with a very high degree of resolution and accuracy. 

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