Introduction
In addition to the necessary high-voltage supply, the operation of a channel electron multiplier requires a preamplifier and an electronic counter (see Introduction/Principle). The dead time of the preamplifier and the threshold of the discriminator must be adjustable in order to adapt to the experimental conditions.
Additionally in many applications, the simultaneous use of two or more channel electron multipliers is necessary, either as single detectors or as an array of detectors with a common high-voltage power supply. Each detector requires a high-voltage (positive oder negative) that is adjusted to the measurement and every signal line requires its own preamplifier/discriminator with an adjustable dead time and discriminator threshold. In addition, these parameters of the measurement must be specified and the measuring values read out and made available for data processing.
| Fig. 5 MEASARplus for the operation of 5 CEMs at positive high voltage |
The MEASAR measuring system enables up to 28 channel electron multipliers with positive high voltage (MEASARplus, measurement of electrons) or negative high-voltage (MEASARminus, measurements of ions) to be operated from a PC or laptop at the same time. Since the anode lies approximately on ground potential in operation with negative high-voltage, at positive high-voltage but at high positive potential, which requires its own coupling condensator for each signal line, two measuring systems are offered.
The required plug-in units differ depending on whether a CEM array should be operated in which all CEMs receive the same high-voltage power supply or several CEMs must be supplied with separate high-voltages.
The MEASAR measuring system was developed to provide experimenter a computer-supported unit that can take over all necessary tasks in connection with the operation of channel electron multipliers or micro channel plate detectors.
| Fig. 6 Operation of several CEMs with MEASAR |
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