Model 8715 - Analog-to-Digital Converter

Features

• 900 ns Fixed Dead Time ADC
• 8K channel resolution
• Digital offset in 128 channel increments
• Exceptional linearity (differential <±0.9%, integral <±0.025%)
• Pulse Height Analysis using either automatic peak detection or delayed triggering
• Analog Sample Voltage Analysis
• Pulse pileup rejection and live time correction interfaces
• Compatible with Loss Free Counting Systems1

Description

The Model 8715 Analog-to-Digital Converter (ADC) is an ultra- fast 900 ns, Fixed Dead Time, analog-to-digital-converter for high count rate nuclear spectroscopy. This highly linear, 8K ADC contributes no system dead time to spectroscopy systems using traditional Gaussian or Triangular Shaping amplifiers.

The Model 8715 boasts differential and integral linearity performance that until now was only possible with Wilkinson ADCs. Its exceptional linearity improves peak shape and resolution, thereby improving the overall performance of your spectroscopy system. It requires a single NIM width.

Concentric Gain and Range controls together with Digital Offset allow the user to maximize the use of limited MCA memory by selecting only the specific energy range of interest. This can be particularly useful for multi-input applications such as alpha spectroscopy, thus eliminating the need for older biased amplifiers. These digital controls accomplish the same end, more accurately and repeatably.

Conversion for the Pulse Height Analysis (PHA) mode can be initiated AUTOmatically using an internal peak detector operating on the input pulse, or can be DELAYED up to 100 ìs after the leading edge of the input pulse passes the input threshold. A front panel INSPEct test point is provided so that the user can monitor the Linear Gate (LG) time between LLD crossing and the beginning of conversion for either mode. Conversions may be enabled/disabled by COINCidence/ANTIcoincidence gating applied at any time during the Linear Gate interval.

Voltage sampling and subsequent conversion for the Sampled Voltage Analysis (SVA) mode is initiated by the leading and trailing edges, respectively, of a Gate pulse applied in the Coincidence mode. The same Lower and Upper Level Discriminators (LLD/ULD) limits are used for acceptance of the peak input during the positive gate time. The Model 8715 provides front panel, screwdriver adjustable, multi-turn potentiometers for the control of the LLD/ ULD, as well as the ADC Zero.

The Model 8715 provides the connections required for use with current CANBERR A amplifiers that perform pileup rejection and live time correction (PUR/LTC). These ADC/amplifier interfaces are also required to use the Westphal Loss Free Counting or Precision Live Time techniques.2

The Model 8715 ADC is fully compatible with all current CANBERRA MCAs (with external ADC interface options such as the Model 556A), Digital Stabilizer and Analog Multiplexers.