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Features

• Complete programmability within the Genie™ family
• Utilizes the CANBERRA Instrument Control Bus (ICB)
• 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
• Secure computer operation without conflicting front panel controls 1.

Description

The CANBERRA Model 9635 Analog-to-Digital Converter is a single-width NIM family member of the ICB line of programmable front end electronics and has been designed primarily for use in high count rate applications. This highly linear, 8K ADC contributes no system dead time to spectroscopy systems using traditional Gaussian or Triangular Shaping amplifiers.

The Model 9635 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 the spectroscopy system.

Programmable Gain, Range and 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 programmed for Automatic or Delayed operation. Automatic operation uses an internal constant-fraction peak detector operating on the trailing edge of the input pulse to initiate a conversion. Delayed operation waits up to 100 ìs after the leading edge of the input pulse passes the LLD before initiating a conversion. This delay time is ADJustable on the front panel with help from the adjacent Linear Gate signal INSPection test point. Conversions may be enabled/disabled by a Gate input applied at any time during the Linear Gate Interval. Coincidence or Anticoincidence operation is programmable.

Conversion for the Sample Voltage Analysis (SVA) mode is initiated by the falling edge of a Gate pulse applied in the Coincidence mode. The same LLD and ULD limits are used for acceptance of the peak input during the positive gate time.

The Model 9635 provides the connections required for use with current CANBERRA 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 9635 accepts programming information over an 8-bit wide CANBERRA bus standard called the Instrument Control Bus (ICB). ICB NIMs connect to this bus via a host module such as the Model 556A Acquisition Interface Module (AIM) as part of a hierarchy of networked acquisition and control managed by a Genie Family computing platform.

Adjustments are made through the Graphics User Interface of the Genie software environments. Equivalent batch procedure commands are also available in the environments. All ICB NIM parameters are stored in the single data file structure of the Genie Family, allowing verification of correct set up from one experiment to the next.

All ICB NIMs feature a characteristic READY LED to indicate operational status.

The 9635 ADC is fully compatible with CANBERRA's Model 8233 Digital Stabilizer and Model 8224 Analog Multiplexer.

*U.S. Patent 4,476,384.

**G. P. Westphal, Nuclear Intruments and Methods, 163 (1979) 189-196.