Difference between revisions of "MainPage:Nuclear:NPS:APDStudies:ADCSpectrum"
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==Setup Description== | ==Setup Description== | ||
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The amplifier and a PbWO_4 crystal remain inside an aluminum box which shields the system in order to increase the signal/noise ratio. In one of the ends of the Crystal an LED is placed. The control over the amount of light emitted by the source is done by adjusting the voltage that is applied at the terminals of the LED. In the other end of the crystal the APD can be found, it has been glued to the crystal. The APD is followed by a preamplifier/amplifier system which allows to apply the high voltage and to get a signal out of the APD. The trigger system works with the LED: every time the LED is turned on it creates a pulse which goes to a Quad Gate generator. The signal coming from the amplifier goes first into a CAEN Dual Delay module N108A in order to get the signal and the gate synchronized before they reach the ADC (CAEN 16 Channel Dual Range Multievent QDC V965). | The amplifier and a PbWO_4 crystal remain inside an aluminum box which shields the system in order to increase the signal/noise ratio. In one of the ends of the Crystal an LED is placed. The control over the amount of light emitted by the source is done by adjusting the voltage that is applied at the terminals of the LED. In the other end of the crystal the APD can be found, it has been glued to the crystal. The APD is followed by a preamplifier/amplifier system which allows to apply the high voltage and to get a signal out of the APD. The trigger system works with the LED: every time the LED is turned on it creates a pulse which goes to a Quad Gate generator. The signal coming from the amplifier goes first into a CAEN Dual Delay module N108A in order to get the signal and the gate synchronized before they reach the ADC (CAEN 16 Channel Dual Range Multievent QDC V965). | ||
Revision as of 18:05, 16 May 2017
ADC Spectrum characterization
Motivation
Photomultipliers (or PMTs) are sensors tipically used for light collection on the experimental branch of Nuclear Physics. However, it has been shown that PMTs are highly sensitive when it comes to the presence of strong magnetic fields. In addition to PMTs, Avalanche Photo Diodes (APDs) can also be used with the additional advantage of insensitiveness to magnetic fields (up to 7T or better). APDs also offer another advantage over PMTs like compactness, a higher quantum eficiency, and Low voltage operation (~400V compared with 1.5KV required for PMTs Devices). APDs are not perfect though, these devices are more sensible to noise than PMTs are, have a larger temperature gain-dependence, and the sensitive area is smaller (Usually it is being circumvented designing a device that acts as a lens -such an acrylic light guide- to focus the light coming from the crystal into the sensitive area of the APD.). This scenario contributes with another variable to the experiment and it is how the light guide that is being used affects the light collection process.
The APDs are the sucesors of the first Silicon-based photo sensors called PIN Photodiodes. As photons reach the PN-Junction it creates a current by impact ionization. This current is proportional to the amount of photons reaching the depletion layer and therefore can be used to establish the intensity of the light reaching the sensitive area of the APDs.
Setup Description
The amplifier and a PbWO_4 crystal remain inside an aluminum box which shields the system in order to increase the signal/noise ratio. In one of the ends of the Crystal an LED is placed. The control over the amount of light emitted by the source is done by adjusting the voltage that is applied at the terminals of the LED. In the other end of the crystal the APD can be found, it has been glued to the crystal. The APD is followed by a preamplifier/amplifier system which allows to apply the high voltage and to get a signal out of the APD. The trigger system works with the LED: every time the LED is turned on it creates a pulse which goes to a Quad Gate generator. The signal coming from the amplifier goes first into a CAEN Dual Delay module N108A in order to get the signal and the gate synchronized before they reach the ADC (CAEN 16 Channel Dual Range Multievent QDC V965).
Stability of the source
In order to compare different properties of the APD response to light collection, the stability of the source must be assured. In this case, an stable pulse sent to the LED will provide stability of the amount of light sent to the APD (reassuring reproducibility of the results).
