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Description

Si(Li) detectors, which cover the energy range from a few hundred eV to 50 keV or so, are used in a wide variety of applications including x-ray fluorescence, x-ray microanalysis, PIXE, EXAFS, x-ray diffraction, and M�ssbauer.

The finest in semiconductor technology and cryogenics, combined with advanced signal processing electronics give CANBERRA Si(Li) detectors solid performance and reliability. Unlike early Si(Li) detectors and unlike those manufactured by some companies today, CANBERRA Si(Li) detectors are stable at room temperature so they can be shipped and stored without LN₂.

CANBERRA Si(Li) detectors are available in two versions. The standard detector uses conventional geometry and a gold surface barrier entrance window. The Super Si(Li) uses a proprietary geometry and entrance window. This, along with a special shaping amplifier, improves resolution by at least 10 eV (FWHM) and increases the peak/background by about ten-fold to greater than 10,000:1.

CANBERRA offers a full complement of signal processing and data acquisition electronics. The detector includes a low-noise preamplifier of the pulsed-optical feedback type. This pre-amplifier employs a specially fabricated FET which is cooled along with the detector in a cryostat.

Transmission curves for various types and thickness of windows. The polymer window curve does not show the effect of the support grid on overall efficiency.

The Model 2026 amplifier employs active filters and a gated baseline restorer to minimize both high and low frequency noise in the spectrum. Selectable time constants allow the user to optimize resolution vs. throughput rate. A pileup rejector prevents the MCA from storing pulses which are distorted due to pile up in the main amplifier and a live-time corrector extends the acquisition time to compensate for rejected counts. These functions demand a compatible MCA, such as those manufactured by CANBERRA. A special version of the 2026, the Model 2026X-2, must be used with Super Si(Li) Detectors.

Si(Li) energy resolution, including intrinsic and electronic noise effect, as a function of energy.

The 1786 liquid nitrogen monitor protects the detector and frontend electronics from damage due to warm-up. Both audible and visual alarms warn of LN 2 depletion, and automatic bias shutdown occurs after 30 minutes should conditions persist.