921E High-Rate Multichannel Buffer

• High-speed MCA in a two-wide NIM

• Integral Ethernet connection for instant integration into CONNECTIONS spectroscopy networks

• Ultra-fast, 16k-channel <1.5 µs conversion time ADC

• 16k-channel data memory, 2³¹–1 (2 billion) counts per channel

• Digital spectrum stabilizer

• Sample changer control port

The ORTEC Model 921E is a member of the EtherNIM family of multichannel buffers. Combined with appropriate computer hardware, ORTEC signal-processing electronics and ORTEC CONNECTIONS applications software running under Windows® 2000/XP, EtherNIM multichannel buffers are the ideal data acquisition hardware for a wide variety of applications in pulse-amplitude spectrometry.

The Model 921E provides the following functions (see Fig. 1):

1. Fast, 16k-channel, successive-approximation ADC, with fixed conversion time of <1.5 µs

2. Digital Spectrum Stabilizer

3. Nonvolatile data memory: 16k channels, 2³¹–1 (2 billion) counts per channel

The 921E is simply connected into an Ethernet environment under Windows 2000/XP. It may be integrated easily into existing networks. Control and spectral display is achieved by the use of a suitable ORTEC CONNECTIONS-32 applications package such as MAESTRO-32, GammaVision-32, ScintiVision-32, or Renaissance.

The two-wide NIM 921E employs a dual Direct Memory Access (DMA) architecture to maximize system throughput. It provides the very best in throughput performance for ultra-high-rate spectrometry with a germanium detector. Figure 2 shows some actual performance data taken with a Model 921E used in conjunction with its companion product, the Model 973U Ultra-High Count-Rate Amplifier. The upper curve shows the throughput to memory when the integration time of the 973U is at its lower setting, 1.5 µs. The lower curve depicts the throughput to memory when the integration time of the 973U is at its higher setting of 3 µs. In both cases the pile-up rejection circuitry of the 973U and 921 were enabled. The maximum throughput to memory is almost 100k counts/sec. At this maximum throughput, the accuracy of the livetime clock is ±3%.

The high pile-up-free throughput and highly accurate deadtime correction make the 921E EtherNIM MCB the instrument of choice for ultra-high count-rate spectrometry with germanium detectors.

The communications protocol used by the 921E is the “traditional” NIM digital bus NIM/488¹ per DOE/ER-0457T (formerly NIM/GPIB) method used for several years in all ORTEC MCB products.²

For the “do-it-yourself” programmer, software toolkits are available to simplify the task of making a user-written application communicate with the 921E.

¹Please refer to “Standard NIM Digital Bus (NIM/488),” DOE/ER-0457T, U.S. NIM committee, May 1990; Standard NIM Instrumentation System, NTIS, U.S. Department of Commerce, Springfield, Virginia 22161.

²The 921E also provides the ORTEC Dual-Port Memory connector on the rear panel. DPM communications are still supported by ORTEC applications packages for historical reasons, but Ethernet communications are recommended in most cases as more convenient (especially over large distances) and, in most cases, less expensive to implement. An RS-232-C port is also provided for diagnostic purposes.

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