Sahara II Silicon Drift X-ray Detector

Silicon Drift Detector - Overview

The Sahara II Silicon Drift Detector (SDD) is PGT's latest addition to our extensive line of X-ray detectors. Evolving from the original Sahara SDD, introduced in 2001, Sahara II features high performance with no liquid nitrogen, no moving parts, no vibration and no maintenance. Sahara II is the ideal solution for people looking to relieve the burden and cost of liquid nitrogen and still maintain excellent X-ray performance. And because it's vibration-free, the Sahara is the best choice when working at high magnifications (>50,000X.)

Compatible with all types of electron microscopes, Sahara detectors are available with PGT's exclusive Variable Z interface, which guarantees optimum geometry regardless of the microscope's configuration or application. Sahara's high count rate performance and ability to maintain resolution and calibration over an extremely wide count rate range makes it the perfect solution for rapid collection on electron tolerant samples (metals, ceramics, composites, etc.), and excellent efficiency on all samples. Environmental and low vacuum SEMS, FESEMs and TEMs benefit from the excellent low-end sensitivity and trouble free operation of these detectors.

How it Works

Unlike a conventional Si(Li) detector, the SDD design features a unique electrical field shape and signal path, low capacitance relative to the active surface area, and a small anode and integral FET on the surface of the device (fig 1). This design results in optimum signal shaping and resolution specification at 1 ms, compared to 10 ms or longer for a conventional Si(Li). And the short shaping time yields another advantage - exceptional high-count rate performance with little compromise in energy resolution.

The Sahara detector is operated at -15°C and cools in less than 30 seconds utilizing air-cooled Peltier cooling, eliminating the need for liquid nitrogen or noisy coolant circulators. Si(Li) detectors require operation at near liquid nitrogen temperature. To reach this temperature, mechanically (or Peltier) cooled Si(Li) detectors require compressors, water chillers and other mechanical moving parts that cause vibration, require maintenance, and ultimately wear out. Cool down time for such a detector is measured in hours.

Performance

The Sahara II brings low energy performance into the realm once occupied only by Si(Li) detectors. Couple this with ultra-high count rates, and the Sahara II is clearly the performance leader. Featuring our proprietary thin window technology, the Sahara provides the best low energy sensitivity available - down to Boron with the 129 eV resolution Sahara and down to Carbon with the 138 eV resolution Sahara.

Stability

In an EDS system, the detector is the most critical component affecting long-term performance and accuracy. In addition to excellent resolution and high count rates, peak stability directly affects the absolute accuracy of your measurements. The Sahara II detector delivers unprecedented stability over the entire count rate range. The result - reproducible results, time after time.

Versatility

Variable Z (VZ) is a unique feature on PGT detectors that allows tilting the detector in the vertical direction while under vacuum. This lets you optimize count rate regardless of the microscope and sample geometry. Whether you need to make measurements at short working distances for low vacuum work, or longer working distances for lower magnification and large samples, Variable Z puts you in control. Doing EDS under variable pressure on a sample at 5mm working distance one moment, then EDS/EBSD at 20mm the next moment…Try that with a fixed-geometry detector.

    Sahara II SDD VS. Mechanically/Peltier Cooled Si(Li)

  • 30 Second Cool Down vs. Hours
  • Operating Temperature -15 C vs. -200 C
  • No Moving Parts vs. Mechanical compressors or water chillers
  • NO Vibration vs. transfer of mechanical vibration to the electron column

Convenience

While other detectors use Peltier cooling, they often require the addition of fluid circulators to remove the excess heat from the system, adding noise, vibration, and yet another device to maintain. Not the Sahara II. By utilizing the unique properties of the SDD, the Sahara is able to achieve peak performance at a temperature of -15° C, with a temperature cycle time of less than 30 seconds. Turn it on when you need it, off when you don't - it's that simple. Ideal for use in clean rooms and other environments where LN2 is unavailable, the Sahara offers long-term cost savings, convenience and safety benefits as well.

Silicon Drift Detector Applications:

  • SEM & TEM X-ray Microanalysis
  • X-ray Fluorescence analysis
  • Accelerators:
    • Induced X-ray Excitation
  • Synchrotrons:
    • Absorption Edge Spectroscopy